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820 User Manual

1. sss B 2 Daisy Chain Addressing cccccccccccsesescsteesssesnsneeseseseeescseeeeenesesesnaeneaeees B 3 Commtarids eame ebbe itia te e Fe iere dig etas B 3 History Oriented Commands Mode Commiarids rene bene eee niei B 4 Read Variables ette e eget tenere etie B 5 Other Read Commands siensia ieni tiere B 11 Group Read Programming ecencoconcnononnnncnrnenennnnnnnannanenarnnnnnnnnrarnrnenaranararnanass B 11 Setting Parameters ep menai reete e Eie RaR EE eE eene nennen B 12 Numeric Parameters eise ei ni aeaeaei opene doc ho rai n sia B 13 Indexed Parameters eme tret eed B 13 Character String Parameters sss B 14 Template Parameters sie ene de ege e a e E recen B 14 Query Parameters c cccccsesesseseseeseseescecesesescsnesneseseseeseseseececesesssesnsaneneaes B 15 Histogram Reports sse entente nennen B 19 Tailored Report iet EUER RRBHER MOUNTS B 19 Miscellaneous ite senem eem B 20 Error Checking TDi rana B 22 Flistory Records 2o siento ette nedum ai abeo eee B 23 Types of History ite i ras te tente delete T nd tete B 23 eo NAE Oe asinis DEI a e Edu eei A iones B 24 BACKUP 1 5 oie Aeterna en e er caster Sts B 24 Find esos eisai MUN MIRO RD RUE UR UA B 24 History Data Variables s sse B 25 Exceedance History Variables sss B 25 Interval History Variables sss B 26 Daily History Variables D1 D102
2. information related to that occur rence The Peak and Unweighted Peak are displayed here Note that even in the stop mode the Model 820 continues to display the detected values on the upper right hand side of the screen The numbers on the left are the highest during the measurement and the values on the right are the current Peak and Unweighted Peak The Leg values are shown here to be 85 5 dB C weighted the measure ment ran for nearly four minutes Should one of four letters OVLD flash intermittently with the stick figure an Overload has occurred in this measurement see Chapter 7 The SEL level using 3dB exchange rate is 109 1 dB and the duration of the measurement is given The Alarm can be set to begin a measurement at a designated time The here indicates the next measurement has not been chosen The current internal tem perature as measured by the Model 820 is shown in the lower portion of the screen 10 1 97 Performing a Measurement Reading the Data 5 3 Step 8 The property controlling the final screen in this series is built into the Model 820 to conserve power Press the v key Now that you are more familiar with the information available in the displays above lets take a closer look at the parameters that affect these readings Step 1 To access these parameters turn the Model 820 on by pressing Next press 3 9 Or press 5 and the fol lowing sc
3. I9 5 current record is 17 RMS Exceedance count in record 12 Example I9 5 current record is 17 RMS Exceedance count in record 22 I1 Date and Time of Occur rence ddmmmyy hh mm ss UnWeighted Peak Excd Count nnn I2 Duration hh mm ss mm ss ss 13 Lint nnn n dB 14 SEL nnn n dB 15 Lmin nnn n dB I6 Lmax nnn n dB I7 Lpeak nnn n dB I8 UnWeighted Peak nnn n dB I9 RMS Exceedance Count nnn I10 Peak Exceedance Count nnn B 26 Model 820 User Manual 9 26 97 112 Overload Counts nnn 113 nn 1 Lnn 114 Ln 1 nnn n dB 121 nn 5 Lnn 122 Ln 5 nnn n dB 123 nn 6 Lnn 124 Ln 6 nnn n dB 1101 Intv Variables 1 24 Macro Daily History Variables D1 D102 Brackets in the syntax indicate optional characters and operands Syntax Response Dfailylvar_no hour daily_var Example D5 5 hourly noise level for hour 5 to 5 59 59 a m D1 Date ddd ddmmmyyyy D2 Daily Leq nnn n dB D3 Daily LDN nnn n dB D4 Daily CNEL nnn n dB D 5 hn HNL for hour 0 23 nnn n dB D 6 hn HNL partial hour indica c tor D7 Daily Lmin nnn n dB D8 Daily Lmax nnn n dB 9 26 97 B 27 D9 Daily Lpeak nnn n dB D 10 Daily Luwpk nnn n dB D 11 Daily Run Time hh mm ss mm ss ss D 12 Daily Avg Wind Spe
4. These parameters define the sound level meter charac teristics Most changes will require a SHIFT if mem ory holds previous data No Prompt 39 Detector Entry Slow Fast Impl Comment Slow exponential avg 1 second constant Fast exponential avg 1 8 sec ond constant Impl impulse response 40 Frequency Weighting A A16 C C 16 Aand C weightings meet Type 1 specifications Note A16 and C16 not applicable to the Model 820 41 AC Out Weighting Flat Wght F 20 W 20 F 20 Flat Level with 20 dB gain W 20 Weighted with 20 dB gain 42 Unweighted Peak Flat C 9 30 97 Parameters 8 11 43 Mic Polarization O 28 200 This selects the polarization Voltage voltage for the microphone Chose 28 or 200 V for con denser type microphones and O V for pre polarized micro phones electret 44 Reference Level O to 255 dB measured level reference level relative level used in some functions 45 CurrantExchange 3dB 4dB 5dB 6dB Exchange rate for currant TWA Rate 1 or Dose readings For OSHA use 5dB 46 Current 0 to 255 dB Levels above threshold are inte Threshold 1 grated into currant TWA or Dose readings For OSHA use 80 dB 47 Currant 0 to 255 dB 10096 dose if this level is main Criterion 1 tained for full dose period For OSHA use 90 dB 48 Overall 3dB 4dB 5dB 6dB Exc
5. Accessories The Model 820 is delivered with the following standard accessories The standard Model 820 Precision Sound Level Meter including a Model 2541 or 2560 1 2 inch precision air condenser microphone and Model 828 preamplifier Alkaline battery 9 volts IEC GLR61 or NEDA ANSI 1604A A good quality alkaline cell should provide more than 16 hours of Model 820 operation Since most rechargeable cells have less capacity expect shorter use User manual Soft carrying case belt pouch Le D part CCS009 WS001 a 3 1 2 inch windscreen Wind noise can adversely affect measurements Using the windscreen on the microphone reduces wind noise and protects the element from dust and bumps SWW_SLM_UTIL software Utility software package allowing data retrieval and translation of binary files generated by the Model 820 to ASCII File Format via RS 232 connection and is capable of editing and storing instrument setup parameter to the PC or loaded directly to sound level meter 1 12 Model 820 User Manual 10 1 97 Optional Equipment The following optional equipment is also available e ADP005 BNC to preamp thread adapter to input direct signal through preamp Includes equivalent capacitance and shorting connector for noise floor testing e ADP012 Adapter for direct signal input to the Model 820 Must be used only with DC coupled sources 1200 ohms or less e CBL033 Printer cable for direct printout to se
6. cccccccsesesseesessesssescececesescseensneseseseenesesescecenesesssnananeness 5 1 SDN Stasi pa eH QI ADAE MER nA UTD ape nese cases se Lund MPG rH 52 AAA S ER UB e eid 5 5 I Chapter 6 Chapter 7 Chapter 8 Maria M 5 8 RE 5 9 I9osezL DE A RR e ta en E pes 5 9 BAT TERN A pede eter esta aS anp aA TEES e eat esietato 5 13 MEMORY ide no em eed i teet eite 5 14 Stopping the Measurement mmcccocononenennnnnnnnnnnnrnrannnnonnnnnenenacananonnnnnrarannnnnnananans 5 15 Timed Measurement 6 1 Using the Timer for Unattended Readings sess 6 1 Using the Time Key Functions sss 6 5 Setting the Password Lock to Protect Settings sss 6 5 History Functions 7 1 Setting and Viewing Advanced Functions sess 7 1 AA esee eed 7 2 Time History Data nennen tnter tenete 7 4 Og PSI axe eo aN eta Ie en RUN cw e e b ed RS Lee 7 4 Interval USO etre RR 7 5 Exceedatce scs eee be heise tribe dicen in iaa 7 8 Setting PassBy Functions erener nineties iinis iori iassa 7 12 Ovetload rin ne Ae ei se tatu E RA S 7 14 Setting the Daily History Parameter coooocinoncncnnnnnnncnnonnenracannnnnnannrararnnnnnanananos 7 14 Parameters 8 1 Parameter Key Access Review ssssseseeeeee eene en eene 8 1 Entering and Exiting the Setup Menu sss 8 1 Locating Parameters sss tete Sk rasek aeeai 8 2 Changing Parameters Enter Modify sss 8 3 Error Messages us
7. 0 1 second resolution e Format hhhhh mm ss s Maximum gt 4 years Standards Met e ANSI 1 4 1983 Type 1 e ANSIS1 25 1991 Type 1 e IEC 651 Type 1 IEC 804 Type 1 e Directive 86 188 EEC e Directive IEC TC 29 Power Supply Internal 9 V battery typically 20 hour operation actual run times vary depending on operating con ditions e External 7 to 16 VDC 30 mA current drain A 10 Model 820 User Manual 9 25 97 Battery life indication selected from keyboard or computer program Dimensions Weight with Microphone Preamplifier and Battery e Width 3in 7 6 cm Length 13 in 33 cm Depth 1 0 in 2 5 cm Weight 13 oz 370 gm Weight w o preamp amp microphone 11 oz 310 gm Shipping weight 3 lbs 1 4 kg 9 25 97 A 11 A 12 Model 820 User Manual 9 25 97 APPENDIX Serial Port Interface Remote Control The Model 820 is fully controllable remotely via Serial Port interface Setup items and operational mode can be altered Data can also be dumped to or queried by the controlling computer The Model 820 may be connected to the computer directly or through a modem A network of many instru ments can be formed all controlled by one computer by using the address ability mode This chapter will describe the Serial Port interfacing of the Model 820 and the various interface commands with their syntax Modem control is also covered These com mands are a subset of the L
8. 59 Lin 5 Percent O to 99 60 Lyn 6 Percent 0 to 99 9 30 97 Parameters 8 13 Exceedance Levels 61 65 These parameters define noise threshold levels to be used when counting the number of exceedances during a measurement viewed in MAX b and c displays for rms PEAK b UWPK b for peak exceedance and trig gering the exceedance history see parameter 66 No Prompt Entry Comment 61 RMS Excd Lvl 1 0 255 dB First rms detector exceedance level 62 RMS Excd Lvl 2 0 255 dB Set above Level 1 63 Peak Excd Level 0 255 dB Weighted peak exceedance level 64 Uwpk Excd Level 0 255 dB Unweighted peak exceedance level 65 Excd Hysteresis O 9 This sets the amount once an exceedance occurs that the level must drop below the exceedance level before the Exceedance event ends and a new exceedance can occur Normally set this level to 2 or 3 dB This prevents multiple exceedances for a single event if the level flickers around the threshold Exceedance History 66 70 161 163 These parameters select and define what data are to be saved in memory during an exceedance No Prompt Entry Comment 8 14 Model 820 User Manual 9 30 97 66 Excd Enable No Yes Yes Exceedance report will be stored in memory when exceedance conditions above are met 67 Excd Exchange 3dB 4dB 5dB 6dB Used to calculate exceedance integrated level Normally this is set to 3dB
9. R A not applicable to the Model P A 820 R P A I A R I A P I A R P I A R S Run Stop 15 Output 1 Timer enter time There are 2 modes to the Logic Output Time now If the time is set to 5 sec or less it is assumed to be a minimum time and the output will be asserted for a minimum of the time selected If the time is programmed to be greater than 5 sec then the time is consid ered to be the maximum dura tion that the pulse should last and the output will be asserted for a minimum of 5 sec and a maximum of the time pro grammed 8 8 Model 820 User Manual 9 30 97 20 Power Save Auto Off Manual Off Audio Off Auto Off If in the Stop mode and if no keys are pressed or commands given for 12 min the Model 820 will turn off automatically Manual Off The Model 820 will not turn off until the OFF key is pressed a computer OFF command is given or the bat teries become low Audio Off Not available on the Model 812 Timer 21 27 GHIFT These parameters are used when Start and Stop of measurements are to be controlled by the clock Entry Comment 21 Timer Mode Off Block 1 day Block Run Time 1 on Run 2 day Date to Stop Time 1 on Stop Date 1 day Run Time 1 to Stop Time 1 each day from Run Date to Stop Date 2 day Run Time 1 to Stop Time 1 and Run Time 2 to Stop Time 2 each day from Run date to Stop Date 22 Timer Run Date dd mm yy
10. R6 _O STIME OverAll Start Date and Time ddmmmyy hh mm ss R7 _C RTIME Current Runtime hhhhh mm ss s R8 C STIME Current Start Date and Time ddmmmyy hh mm ss R9 _O TWA Overall TWA Time Wght Avg nnn n dB R10 O XR Overall Exchange Rate Text cecce Rll _C TWA Current TWA Time Wght Avg nnn n dB R12 _C XR Current Exchange Rate Text cecce R13 _O SEL Overall SEL nnn n dB R14 _C SEL Current SEL nnn n dB R15 _O LMIN OverAll Minimum Level nnn n dB R16 _O TMIN OverAll Lmin Date and Time ddmmmyy hh mm ss R17 _C LMIN Current Minimum Level nnn n dB R18 _C TMIN Current Lmin Date and Time ddmmmyy hh mm ss R19 _O LMAX OverAll Maximum Level nnn n dB R20 _O TMAX OverAll Lmax Date and Time ddmmmyy hh mm ss R21 _C LMAX Current Maximum Level nnn n dB R 22 _C TMAX Current Lmax Date and Time ddmmmyy hh mm ss R23 _O LPEAK OverAll Peak Level nnn n dB R24 _O TPEAK OverAll Lpeak Date and Time ddmmmyy hh mm ss R25 _C LPEAK Current Peak Level nnn n dB B 6 Model 820 User Manual 9 26 97 R26 _C TPEAK Current Lpeak Date and Time ddmmmyy hh mm ss R27 _O LUWPK OverAll UWPk Level nnn n dB R28 O TUWPK OverAll Luwpk Date and Time ddmmmyy hh mm ss R29 C LUWPK Current UWPk Level nnn n dB R30 _C TUWPK Current Luwpk Date and Time ddmmmyy hh mm ss R 31 _RMSCNT OverAll RMS Exceedances 1 nnnnn R32 _RMSCNT2 OverAll RMS Exceedances 2 nnnnn R33 _PEAKCNT OverAll Peak E
11. Signal 5 Pin configurations for the INT002 follow 820 5 pin Connector End Computer DB 9 ERN UN Pin1 Shield i 1 Pin 2 Red Pin3 Yellow Pin4 Blue Pin 5 White B 2 Pin 2 Yellow Pin 4 Blue Pin 6 White Pin 8 White Model 820 User Manual 9 26 97 Daisy Chain Addressing A network of instruments may be interconnected to one computer using the appropriate cabling such as the CBL040 and each may be controlled individually Each is given a unique address parameter or item 10 The addresses are sent as a single byte ranging in value from 129 to 255 representing address 1 to 127 respectively address plus 128 Whenever an address byte is received only the corresponding instrument is enabled to receive commands A broadcast command can be sent By sending an address of zero CHR 128 all units on the chain will become addressed and accept the commands that follow Only the device with an address of 1 will respond to the commands if data transfer is required This will allow all units to be started at the same moment or to have the same parameter sent to all devices with one command i e set all clocks to the same time These devices cannot be just paralleled together That would short outputs together and damage the instru ments Use the designated cables Commands The commands are a series of ASCII characters with an alpha command and one or two numeric operands fol lowed by a charge return ASCII 13 The co
12. The F is the check character for the S205 0 command A detailed description of the protocol is available from Larson Davis and the latest revisions of software utilize the protocol Q 206 Q TBLMODE Ln table mode Q 207 Q NFLVL NOISE FLOOR LEVEL Overall Daily This parameter is set to the noise floor of the instrument so that it can properly indicate Near Noise Floor mes sages when within 10dB of the noise floor It is also used with NF Compensate Q208 which will place the Model 820 in an extended Linearity Range Mode The true noise floor of the entire system must be measured and entered in Q207 This will vary with the selected input weighting or microphone sensitivity An equivalent microphone capacitance can be used after calibration to determine the noise floor It may also be possible to remove the microphone bias to obtain this value When properly set up the linearity range can be increased by 10dB NOTE The mode is always turned off with a CAL Change Q 208 Q NFMODE NOISE FLOOR COMP MODE Q 209 Q 875MD 875 RTA MODE None Excd Intv Dual unused Q 210 Q CNTLREG AUX CONTROL REG Q211 Q EXREC EXCD RECORD NUMBER Q212 Q IVREC INTV RECORD NUMBER Q 213 Q HSTREC HIST RECORD NUMBER Q214 Q LOGREC RUN LOG RECORD NUMBER B 22 Model 820 User Manual 9 26 97 Q215 Q DYREC DAILY RECORD NUMBER Q216 Q CALREC CALIBRATION RECORD NU
13. 10 1 97 L The average RMS level the L R is displayed by pressing eq Dose LDL DOSE the noise exposure may be calculated with three different sets of parameters e Current LDL Log Data Logic Overall Parameters 45 54 are used with the calculation to arrive at the current dose from the current data and sets the exchange rate threshold level and criteria level for the current measurement These can be set differently from the overall in order to give different dose readings To protect the measurement the OVERALL Dose set tings parameters 48 50 may not be modified once the measurement has started without a reset However OVERALL CRITERION may be changed at any time If you wish to look at dose with different exchange and threshold values LDL may be used by modifying the LDL settings parameters 52 54 Note that the run time for LDL and OVERALL is always the same D9 The average RMS level in this reading is 68 2 dB slow average for the 12 minute and 14 9 second measurement period Parameter 51 Full Dose Period or Criterion Time applies to Current Overall and LDL 10 1 97 Performing a Measurement Reading the Data 5 9 A new measurement may be started at any time without effecting the Overall Dose using the Current Dose set tings by modifying the CURRENT exchange rate and threshold settings An automatic reset occurs when CURRENT settings are modified creating a new CUR RENT d
14. AC DC power adapter 220 Vac to 9Vdc 50 60 Hz for use with INTO002 e 820 OPTO1 Modification of the Model 820 for use in outdoor noise monitoring system using the Model PRM2101 Outdoor Preamplifier Includes addition of a second connection to the 820 for control of the elec trostatic actuator Also includes environmental test ing and certification as follows Separate testing of 820 and PRM2101 in a computer controlled environ mental chamber Note Figure 14 or call LarsoneDavis for additional information on these and other accessories 1 14 Model 820 User Manual 10 1 97 5 i wso01 WS005 Windscreen R i 8 8 with birdspikes il e Rainhat with Tm m m NUUS A electrostatic actuator 1 2 inch Microphone o o o A t Ire st wo Ire Ie i ADP008 U N N N N mm mm E E ADP011 PRM2101 820 SYSTEM 2105 i PRM828 Note Those items marked with are standard included accessories L J T r EXCXXX 20 Max 20 AC Out black CBLO42 6 Ut black DC Out red CCS009 Soft Case eeoe 4 Conductor S Oe c Shielded Battery to CBLO035 4 power 820 m alligator clips CBLO38 1 5 PSA005 AC DC Ad ol aptor Battery 2 T CBLO39 1 5 Battery i INTOO2 12 C3 E To next SLM CBL040 12 CBL009 020 820 OPTO1 required Battery powers 2101 heater and EA PSA001 PSA001 CBL077 6 optional C CBL033 6
15. D will appear in succession The measurement should be retaken The Interval Report on the printout will indicate which inter val had the OVERLOAD Setting the Daily History Parameter The Model 820 automatically calculates daily sound sta tistics including Leg 24 Lan CNEL Lpeaky Luwpkr Ens Lmax and Emin and for each hour of the day the hourly Leq the hourly EXCD Leg and the resultant Background Leg Step 1 To access item 88 Daily Enable press SHIFT and z Yes No Daily Noise History can only be viewed in the Daily Noise History printout or downloaded to a computer 7 14 Model 820 User Manual Six L percentiles optional see parameter 206 Choose Yes if you wish this option enables 9 24 97 C HAPTER Parameters As we have seen in previous chapters the Model 820 owes its versatility in great part to a flexible setup More than 160 parameters and options can be selected to tailor the Model 820 to any measurement Four prepro grammed setups for standard applications are in mem ory One may use these as blueprints for modifications It is also possible to store up to 11 other setups in memory for later recall Along with downloadable setups from software this truly makes the Model 820 a myriad of instruments in one In this chapter we will review the following Parameter access keys ite Modify Enter Cancel Learn to store and retrieve complete setups from
16. Le 4dB gives L DOD 5dB gives LOSHA 6dB gives L Avg 68 Ex Min Duration 0 255 Exceedance must last at least this many seconds to be logged 69 Excd Time Hist No Yes Exceedance time history is saved if set to Yes 70 Excd Hist Per 0 255 Exceedance time history sam ple period in 1 32 s Ten sam ples before and after the exceedances are normally stored up to a maximum of 255 samples 161 Timed EXCD Per mm ss Exceedance Time history is recorded from 10 samples before exceedance to 10 sam ples after this period 162 Excd Trigger Level Bypass Bypass Enables a variable threshold 163 EXCD Time Start Max Start The exceedance will be measured at the beginning Max The exceedance will be measured at the maximum Interval History 72 79 ree em e o Intv Enable No Yes Interval report will be stored in memory if Yes is entered 9 30 97 Parameters 8 15 73 Intv Exchange 3dB 4dB 5dB Used to calculate interval inte 6dB grated level Normally this is set to 3 dB L 4 dB gives L DOD 5 dB LOSHA 6 dB L Avg 74 Intv Threshold 0 to 255 dB Levels above threshold are integrated during each inter val normally O dB for Leq For noise hygiene interval TWA set to dose threshold 75 Intv Period hh mm This sets the period for the interval history from 1 minute up to 99 59 A 1 second inter val may also be selected by ent
17. Prms po10 t 0 where p is the reference sound pressure of 20 uPa The square of the sound pressure is a power like quantity that can be expressed in the original form of the level definition 2 P rms p 2 A L 10 L eeu a Prms Po10 Po Sound Pressure Level can be converted to sound pressure as follows If the sound pressure is 1 Pascal then the sound pressure level is L 20108 20108 50000 20 4 699 94 04B 20 107 Calibrators often use a level of 94 dB so they generate a sound pressure of 1 Pascal If the sound pressure level 76 3 dB then the sound pres sure is Pa 20 10 102 20 1958576 20 e 197255 20 0 0065 0 13 Energy Average Leg The value of a steady sound measured over a fixed time period that has the same sound energy as the actual time varying sound over the same period This descriptor is widely used It is a fixed average See Sound Pressure Impulse The value of an impulsive sound The reading will depend on the time weighting applied Unweighted Peak The peak value of a sound with a meter that Model 820 User Manual 10 14 97 Sound Power W has flat frequency weighting and a peak detector Weighted Peak The peak value of a sound with a meter that has a frequency weighting other than flat and a peak detec tor The sound power emitted by a sound source It is measured in Watts Sound Power Level PWL L The logarithmic form of sound p
18. See Timer Mode comment 23 Timer Stop Date dd mm yy See Timer Mode comment 24 Timer Run Time 1 hh mm ss See Timer Mode comment 25 Timer Stop Time 1 hh mm ss See Timer Mode comment 26 Timer Run Time 2 hh mm ss See Timer Mode comment 27 Timer Stop Time 2 hh mm ss See Timer Mode comment 9 30 97 Parameters 8 9 Lock 28 34 These parameters limit access of certain functions to those with the correct password Step 1 After setting password and lock options exit For complete instruction on set the setup and press SHIFT to lock ting the Lock parameters see chap ter 6 Step 2 To unlock press SHIFT S amp then Modify and enter the password No Prompt Entry Comment 28 Lock Password 8 characters Enter your password 29 Lock R S Key No Yes Lock mode change 30 Lock Setup No Yes 31 Lock Function No Yes 32 Lock Reset No RES ALL Cur All 33 Lock ON Key No Yes 34 Lock I O No Yes 8 10 Model 820 User Manual 9 30 97 Calibration 35 38 GHIFT CAL SLM Prompt Entry Comment CAL Level 114 00 Enter the sound pressure level 0 255 dB of your calibrator Calibrator S N to 8 char Calibrator serial no will be printed Auto Cal Mode No Yes unused Auto Cal Time 00 00 hh mm Sound Level Meter 39 50 Allows automatic daily calibra tion check with LDL electro static actuator available at later date
19. Step 4 Step 5 Step 6 4 2 With the Model 820 on press and the fol lowing screen appears To access parameters using numeric values press To access the Current Time press 0 and then 6 The number 6 is assigned to the Current Time parameter Press to prepare the screen for changes in the Current Time Notice the flashing f changes to n Using numeric keys make changes and press Enter or if the time is correct just press Enter To exit the setup mode press Model 820 User Manual A complete list of parameters and their assigned numbers is found in chapter 8 You have already visited parameter 43 Microphone Polar ization and found it preset to 200 Notice that the flashing f has been replaced by a flashing m indicating the numeric key access The flashing parenthesis indicate this field is ready to receive numeric input Entering 0 before the new num ber will remove any prior parame ter settings The third way to access Current Time parameter press SHIFT GE Remember press to change or correct the field and press Enter 9 10 97 Setting Parameters Using Numbers and Other Characters The Model 820 has the ability to show 3 lines for your Company Name and one line for the Measurement Title which is used on the reports These parameters are entered from the keyboard Through the keyboard you can enter all of the capital l
20. Use a tripod whenever possible 2 Measure the influence of other sources by measuring the background sound level without the source of interest You may have to correct for the background There are two types of near fields the acoustic near field and the geometric near field Acoustic Near Field The distance from a source of sound is less than an acoustic wavelength In the near field the effect of the type of sound source is significant Since the wave length varies with frequency See the definition of Wave length the distance will vary with frequency The most common example of a near field is driving an automobile with an open window As you move your ear to the plane of the window the sound pressure level builds up rapidly wind noise since most of the pressure changes are to move the air and very little of it compresses the air to create sound Persons not far way can hardly hear what you hear The acoustic near field is characterized by pressures that do not create sound that can be measured in the far field Therefore measurements made here are not useful in predicting the sound levels far way or the sound power of the source Geometric Near Field The distance from a source of sound is less than the largest dimension of the sound source In the near field effect of source geometry is significant Sound C 11 Noise Noise Dose D C 12 sources often have a variety of specific sources within them such as exh
21. ssssssssssee B 27 Model 820 User Manual 10 1 97 App C 10 1 97 Run Log Variables B 28 Calibration History Variables esses B 28 Time History Variables sss B 29 Histogram Table Variables B 29 Print Commands trennen nennen B 30 Error Messages and Warnings sss B 31 Modem Control Mode sccesceccsesceessesescenesesssesnsnesseseeceeseseeceenesesesnaneneneess B 33 Modem Mode Afora taei eaaa nnne nennen nennen B 33 Dial Out Mode luminarias B 33 Monitor Numiber iiianeaesieneienideeie i ei e rides B 34 820 Phone Dialing Procedure B 34 Model 820 Answering Procedure sss B 35 Glossary C 1 vi Model 820 User Manual 10 1 97 Introduction Welcome to the LarsoneDavis Model 820 Your new hand held Model 820 from Larson Davis is a combina tion Type 1 precision integrating sound level meter and a statistical data logger that exceeds all worldwide accu racy requirements for the measurement of noise The Model 820 measures sound with the ease of opera tion of a point and shoot sound level meter The latest advances in surface mount technology air condenser microphones and internal firmware have been com bined in a rugged lightweight yet extremely versatile unit Many sound level meters in the market can create signif icant measurement errors because of their limited dynamic range pulse range and crest factor The Model 8
22. through the display a key name is indi cated for each one If there is a fol lowing the key name then the options function will be invoked after selecting that key otherwise the particular report will be printed immediately STR A permanent storage register for parameters and calibration data in EEPROM type memory that is not lost when all power is lost There are 10 RAM registers to store data SETUP Enables the setting of desired SETUP parameters each accessed by using the up and down arrow keys RCL The EEPROM register and the RAM register may be recalled by pressing the RCL key scrolling to the desired register and pressing ENTER 10 1 97 Overview to Model 820 2 3 Functions R S This key starts and stops measure ments RESET Restarts a measurement by eras ing the values just measured This func tion can be used whether a measurement is in the run or stop mode Enter used to enter new parameters selected by the user SHIFT Allows access to the blue letter functions on the keypad EXCD The Exceedance History is a record of noise events which exceed a programmed level for a time greater than a programmed minimum time period See parameters 66 70 LOCK The lock functions protect instru ment data and configuration The level of security is configured in Setup INTV The Interval History provides a history of a number of measurement val ues for a moderate size tim
23. when an illegal exceedance is logged into memory An illegal exceedance is when Excd Lmax RMS Excd Level 2 parameter 62 The phone will also be dialed if the memory is low 9 26 97 B 33 e Phone The valid characters in Phone are those rec ognized by the modem to which the Model 820 is attached and generally include W will wait for another dial tone P selects pulse dialing T selects tone dialing will pause dialing for 2 s space or used to make the number more readable Example T9W 1 412 555 1212 indicates to use tone dial ing dial 9 for an outside line wait until the dial tone is detected and then dial the number Monitor Number The monitor number is used to specifically address the monitor 820 Phone Dialing Procedure The Model 820 dialing process is as follows Step 1 The Model 820 recognizes an exceedance or low memory condition Step 2 The Model 820 asks the modem to dial the Example 820 ATDT 1 555 phone number 1234 Enter Step 3 The modem informs the Model 820 that a con Modem 10 Enter nection has been made The Model 820 modi fies its baud rate to that of the connected modem If the connection is unsuccessful the procedure is retried in 4 min Step 4 The Model 820 sends the following announce ment 820 820A0123 001 2 enter where 0123 is the Model 820 s serial number 001 is the monitor number entered and 2 is a flag 1 Alarm 2 Exceedance 4 Low Memory More th
24. 0 0 10000 0 5 50 0 2 800 0 0 12500 0 8 63 0 1 1000 0 0 16000 0 9 80 0 0 1250 0 0 20000 1 2 100 0 0 1600 0 0 125 0 0 2000 0 0 AC Output FLAT Frequency Response Nominal AC Output FLAT Nominal AC Output FLAT Nominal AC Output FLAT Frequency Hz Weighting dB Frequency Hz Weighting dB Frequency Hz Weighting dB 10 7 6 160 0 1 2500 0 0 12 5 6 2 200 0 1 3150 0 0 16 4 7 250 0 1 4000 0 0 20 3 5 315 0 0 5000 0 0 25 2 5 400 0 0 6300 0 0 31 5 1 7 500 0 0 8000 0 1 40 due 630 0 0 10000 0 1 50 0 9 800 0 0 12500 0 2 63 0 6 1000 0 0 16000 0 3 80 0 3 1250 0 0 20000 0 5 100 0 3 1600 0 0 125 0 2 2000 0 0 9 25 97 A 5 Detector Time Weightings The available RMS detector time weightings are FAST SLOW and IMPULSE There are also two available PEAK detectors Weighted Peak Unweighted Peak Weighted Peak Detector Rise Time 60 us Unweighted Peak Detector Rise Time 30 us Effects of Temperature The SPL level varies lt 0 5 dB when the complete instru ment is tested over the 10 C to 50 C temperature range The reference reading for this test is taken at 20 C and 36 relative humidity RH the input signal is at 1000 Hz Effects of Humidly The SPL level varies lt 0 5 dB when the complete instru ment is tested over the 30 to 90 RH range This test is performed at 40 C with an input signal of 1000 Hz Limits of Temperature and Humidity Permanent damage can occur when stored
25. 152 154 161 8 20 changing 8 3 Lmax Lmin 5 5 locating 8 2 Model 820 Chapter 8 8 1 time history 7 2 Passby 7 13 diagram 7 12 setting functions 7 12 PEAK 5 7 Peak 8 17 key 2 5 Phone Dialing B 34 Pin B 2 Pin configurations B 2 Polarization 5 5 Power ac dc output 4 8 connecting 1 15 external 1 15 internal 1 15 to 1 16 Model 820 1 17 specifications A 10 Power Save 8 9 Preamp connecting 1 17 Preamplifier C 13 Print 2 3 8 18 Chapter 10 1 2 commands B 30 daily report 8 20 normal printout parameters 10 1 Printing a Report 10 1 real time 10 4 reports 10 2 R RAM registers 8 5 Real time printing 10 4 Reference Direction specifications A 2 Reference Level 8 12 specifications A 4 Register RAM 8 5 Register EEPROM 8 5 Remote control Serial Port 1 2 Report printing 10 1 Reports printing 10 2 Reset key 2 4 RESET ALL 8 1 RS 232 1 6 data communications A 9 RS 232 Address 8 7 RS 232 interface B 1 Run Log Variables B 28 Run Stop key 2 4 Index 5 S Screen Symbols 2 8 SEL key 2 6 Serial number 1 12 Serial Port App C 1 2 Setup enter and exit 8 1 key 2 3 recalling 8 5 storing 8 4 Setup Parameters 8 6 Shift 2 3 key 2 4 SLM 5 2 key 2 5 SLM Sound Level Meter 8 11 Sound average level lavg C 1 day night average level C 3 energy average Leq C 16 exposure C 14 exposure level C 14 fixed average C 15 glossary C 13 impulse C 16 instantaneous C 16 intensity l C 17 moving average C 15
26. 24 97 63 Peak Excd Level Weighted peak exceedance level e 64 Uwpk Excd Level Unweighted peak exceedance level e 65 Excd Hysteresis 0 9 The Exceedance History parameters items 66 70 allow you to select and define what data are to be saved in memory during an exceedance Each exceedance indicates the time it started durations symmetry Leg SEL Lmax Peak and Time History if desired eq Step 1 Press and to access item 66 from the previous field or press and Enter Here is a brief explanation of each parameter e 66 Excd Enable Yes No e 67 Excd Exchange 3dB 4dB 5dB 6dB e 68 Ex Min Duration 0 255 e 69 Excd Time Hist Yes No 9 24 97 History Functions After an exceedance the level must drop this amount below the exceed ance threshold before a new exceed ance is logged This prevents multiple exceedance for a single event if level fluctuates about the threshold Yes would insure the exceedance report will be stored in memory when exceedance conditions 61 65 are met Used to calculate exceedance inte grated level and normally set at 3 dB Leg 4 dB gives Lpop 5 dB gives Losa 6 dB gives Lave This parameter sets the minimum duration in seconds of exceedance records With this item set to Yes a time history is saved only during the time an exceedance event occurs 7 9 70 Excd Hist Per n 32 0 255 Use the v key to s
27. HIGH RECORD n Q 110 Q PRN HIST REPORT x Q111 Q PRN HIST REPORT LOW RECORD n Q 112 Q PRN HIST REPORT HIGH RECORD n Q 113 Q PRN DAILY NOISE REPORT x Q 114 RESERVED PARAMETER 18 24 respectively 120 Q 121 150 Reserved Miscellaneous Q 151 Q AUTOLEQ AUTO SEND HISTORY LEQ TO PRN unused Q 152 Q EAON ELECTROSTATIC ACTUATOR OFF ON Q 153 Q HEATER HEATER LINE OFF ON unused Q 154 Q MDMMD MODEM MODE x Q 155 Q DIAL MODEM DIAL OUT MODE x Q 156 Q PHONE MODEM PHONE NUMBER 30 char Q 157 Q MONNUM 20 20 Q 158 Q MDMI MODEM INIT STRING 30 char Q 159 Q PWRMD POWER MODE Normall Ext CO Q 160 Q PWRCO EXTERNAL POWER CUT OFF VOLTAGE Q 161 Q TMEXPR TIMED EXCD PERIOD Special Functions Advanced use only Remaining commands are not available on SETUP menu B 20 Model 820 User Manual Q 162 Q NI18 23 RESERVED PARAMETER 18 23 167 Q 168 Q RTEXCD REAL TIME EXCD REPORT x Q 169 Q RTINTV REAL TIME INTV REPORT x Q 170 Q RTHIST REAL TIME HIST REPORT x Q 171 Q RTLOG REAL TIME RUN LOG RPT x Q 172 Q RTDAY REAL TIME DAILY REPORT x Q 173 Q RTCAL REAL TIME CAL REPORT x Q 174 Q RTFRMT UNFORMATTED REPORTS x 9 26 97 Q 175 Q RPTBEG Begin Printing x Q 176 Q PTYPE PRINTER TYPE x Q 177 Q RPT DATA REPORT x Q 178 Q RPT R S AND CAL LOG x Q 179 Q RP
28. Power On Fault Cause Character c D Data Checksum Corrupt E EEPROM Checksum Corrupt K Key Reset 4 RESET 4 On P Parameter Checksum Corrupt O Opcode Error R RAM Setup Register Corrupt T Test Memory Corrupt W Watchdog Reset An indicator has been added to the ON display on the top line of the 820 s display to show faults that were detected by the power on test procedure The R151 command will display the fault character to a computer The indicators are R 152 _INRMS Internal RMS detector level nnn nn dB R153 _INPEAK Internal PEAK detector level nnn nn dB R 154 _INUWPK Internal UwPk detector level nnn nn dB R155 _KEYCNT Free Bytes in Keyboard Stack nnn R 156 _BGTIM Background Leq Time hhhhh mm ss ss R 157 _CALSTAT Calibration Status lt lt UnStable gt gt R 158 _MEMSIZ Total number of bytes for histories nnnnnnn R159 _MEMUSE Memory Available in percent nnn nn R 160 _O OVLD OVERALL OVERLOAD FLAG c R 161 unused unused variable R 162 O SE Overall Sound Exposure nnnnn n PH B 10 Model 820 User Manual 9 26 97 a The number of keys in the keyboard stack is available with the R155 command This is used with keyboard simulation to prevent the loss of keys Other Read Commands Sound Exposure E is calculated and displayed in pascal squared hours as needed in some of the European Coun tries This value is read with the R162 command and is available in the top line
29. SPL for the overall mea surement UWPK PEAK PEAK The highest weighted Peak Detec tor output level Lpk Date and time of the occurrence of the Lpk is also shown The number of times the weighted peak level exceeds a programmed threshold is also counted and displayed b window UWPK The highest UnWeighted Peak Detector output level Luwpx The date and time of the occurrence of the Lyywpk is also shown The number of times the weighted peak level exceeds a pro grammed threshold is also counted and displayed b window 10 1 97 Overview to Model 820 2 5 Keys Functions BATT LN Ly The L values represent the SPL exceeded n of the run time All values from 1 to 99 are available four or six of these are displayed at a time and can be changed even while running BATT This key gives the percentage of power remaining in the 9 V battery or external supply BATT b Gives Model 820 revision num ber and date TIME LEQ Leg The Equivalent Level or Leg is a Time Weighted Average based on an exchange rate of 3dB true energy mea sure with no threshold Time The date and time of last reset or measurement start are available from the Time a display The current date and time are shown with the Time b display TIMER SEL SEL The Single Event Level or Sound Exposure Level is an energy reading in decibels It is the TWA level plus 10 times the log of measurement time in second
30. a exponen tial decay factor so that when the time of integration is near the current time t it is essentially undiminished For times older less than the current time the value is diminished and so becomes less important The rate at which older data are made less influential is expressed by the constant T The larger is it the slower the decay factor reduces and the slower the response of the system to rapid changes These are stan dardized into three values called Time Weighting See the values below Fixed Average The averaging process is over a fixed time period The equation for it is T 1 2 Poen c G Ti The sound pressure is squared and averaged over a fixed time period Unlike the moving average the sound pressures in all time intervals are equally weighted Sound Pressure Level SPL L The logarithmic form of sound pressure It is also expressed 10 14 97 by attachment of the word decibel to the number The loga rithm is taken of the ratio of the actual sound pressure to a reference sound pressure which is 20 MicroPascals u Pa There are various descriptors attached to this level depend ing on how the actual sound pressure is processed in the meter Instantaneous The time varying reading on a meter face on in a meter output due to changes in the sound pressure The reading will depend on the time weighting applied The fundamental relationship between the two is logarith mic rms L 20 L 20108
31. able memory Normally all data is taken with 0 1 dB resolution 2 bytes level To save memory this option allows storage of history in 1 0 dB resolu tion This option allows saving the weighted peak Peak unweighted Peak UWPK or Max RMS level Lmax with each RMS history sample See the following step These options select the history period length as determined by the value set in parameter 83 times 9 24 97 Step 9 Use the and to select the value you want for this field Step 10 Press the v to item 85 Hist Base The setting range is 0 255 dB Step 11 To enter a value press the value Enter Step 12 Press the v to item 86 Hist Base Mode Off RMS Peak Step 13 To change the field press Modify i and Enter Step 14 Press the v to item 87 Histogram Resolution for these options 1 8 1 2 1 0 2 0 5 0 10 Step 15 Select the value you want Press M to the proper setting and then press Enter 9 24 97 History Functions the units set in parameter 84 For example selecting a period of 180 and a unit of 10 seconds would give 1800 seconds or 30 minutes for l each Leg history period A period of 2 and a unit of 1 32 sec ond would result in a history stored every 1 16 second Setting Item 83 to 0 is equivalent to set ting it to 256 This is for editing purposes only All history is stored regardless of this base level However only data above the base level
32. are displayed This parameter controls the stored data which the preceding base level operates For example if this was set to Peak and the base level set to 100 dB only peaks 100 dB and above would be displayed The Model 820 provides an ampli tude distribution that can be printed If the resolution is not sat isfactory a different one may be selected and the amplitude distri bution re displayed or printed This is possible because all data is stored to the nearest 1 8 dB 7 3 Time History Data Chapter 5 explained how to perform a measurement To examine the Time History of that measurement take the following steps Step 1 To access Time History press and a screen similar to the following will appear Step 2 Press the key to sequence through the stored history data Log The Log key function is a Run Stop log It indicates how many times the measurement was started and stopped and at what time Once a measurement is in progress information can be examined as follows 7 4 Model 820 User Manual The Time History is used to view the data that was acquired with the settings discussed in the previous section In this example we are viewing the Leq and Peak data that was gathered during the history period This display contains History information about the measure ment It was started by a key stroke Press the v key to view other readings 9 24 97 Step 1 Press GHIF
33. circuit and thereby to create a signal For high sensitivity this device has a voltage applied across the diaphragm from an internal source Electret A microphone that uses the motion of a thin dia phragm caused by the sound to change the capacitance of an electrical circuit and thereby to create a signal The voltage across the diaphragm is caused by the charge embedded in the electret material so no internal source is needed Microphone Uses The frequency response of microphones can be adjusted to be used in specific applications Among those used are Frontal incidence Free Field The microphone has been adjusted to have an essentially flat frequency response when in a space relatively free of reflections and when pointed at the source of the sound Random incidence The microphone has been adjusted to have an essentially flat frequency response for sound waves impinging on the microphone from all directions Pressure The microphone has not been adjusted to have an essentially flat frequency response for sound waves imping ing on the microphone from all directions C 9 What a microphone measures A microphone detects more than just sound The motion of a microphone diaphragm is in Microphone Guidelines cont response to a force acting on it The force can be caused by a C 10 number of sources only one of which are we interested sound Non sound forces are 1 direct physical contact such as that with a finger or a r
34. log B 28 time history B 29 Vibration C 18 W Warnings error messages B 31 Warranty 1 6 Wavelength l glossary C 18 Wavenumber glossary C 19 Weighted 8 hour time weighted average sound level C 5 Weighting 8 11 frequency C 7 slow 5 4 time C 18 Weightings A and C 5 4 Index 7
35. name field Q Enter set one of four custom instrument name screens which will appears each time you turn the instrument pl on Step 2 Press Modify Notice the parentheses begin to flash and the f changes to n and the L is underscored Larson Davis You may now enter the SE Pare Tae appropriate letters here by using SO aot EPI the Alpha Character Keyboard Entry shown above Step 3 Press GHIFT The flashing n is replaced by S and will remain for five seconds At this time you may select any in character from the S table press mami ppg oM e that key and it will replace the let E ade amet 2S ter at the cursor _ The cursor then moves to the next letter Step 4 Press SHIFT twice The n is replaced by 2 for five seconds Letters from the 2 panel are available for entry 9 10 97 Quick Start 4 5 Step 5 Press SHIFT three times Example To enter the company name of Lar son Davis in the first line follow these steps a To access the Name Display turn on the meter Press Ei oA b Press to place the cursor at the begin ning or use the 4 or to position the cursor c To clear the field if necessary press SHIFT twice and the 4 key d The letter L is on the S field Press SHIFT e The letter A is on the S field Press SHIFT again f The R S O keys are in the 2 field Press SHIFT twice to access the 2 field g To C
36. the sum of all set flags The Model 820 awaits a response code which should be 820A0123 11111111 enter where 0123 is the Model 820 s serial number and 11111111 is the Lock Combination parameter 28 which is required whether or not the Model 820 is currently locked If the response is incor rect the announcement is resent Four chances are given to respond correctly A 3 cr sequence will cause the Model 820 to hang up B 35 Step 6 When a correct response is received the Model 820 indicates it is ready to send data when requested with 820 Ready enter B 36 Model 820 User Manual 9 26 97 APPENDIX Glossary This appendix contains technical definitions of key acoustical and vibration terms commonly used with Larson Davis instruments The reader is referred to American National Standards Institute document S1 1 1994 for additional definitions Specific use of the terms defined are in the main body of the text Allowed Exposure Time Tj It is the allowed time of exposure to sound of a constant A weighted sound level given a chosen Criterion Level Crite rion Duration and Exchange Rate The equation for it is T T Tice tle ii E i Uag YQ lays 178 where L is the Criterion Level T is the Criterion Duration Q is the Exchange Rate K is the Exchange Rate Factor and Lavg is the Average Sound Level Example If L 90 T 8 Q 3 and L 95 then 8 EE 5 656 5 hours and 39 minut
37. through the following equation where is the wavelength c is the sound speed f is the fre quency in Hz and o is the radian frequency It has the dimensions of inverse length Yearly Average Sound Level YDNL Lyan The Day Night Average Sound Level for each 10 14 97 day is averaged over the entire year It is calculated as fol lows 1 365 E ap Ldn 10 Las USE 10 i l C 20 Model 820 User Manual 10 14 97 Index A AC output specifications A 7 AC DC Output 4 8 Accessories 1 12 American National Standards Institute see ANSI 1 4 ANSI standards met A 10 Answering Procedure B 35 Appendix A Specifications 1 2 Appendix C Serial Port Interface Remote Control 1 2 Arrows key 2 7 B Battery 5 13 directions for checking voltage 2 10 internal life of 1 15 key 2 6 Baud Rate 8 7 Block 1 9 Block diagram Model 820 1 9 C Calendar real time A 10 Calibration 1 5 8 11 C 1 Chapter 3 3 1 glossary C 2 key 2 5 Model 820 1 2 3 1 Character Parameters B 14 Clock real time A 10 run time A 10 Commands status B 5 Conventions formatting 1 3 Criterion 8 12 C 2 sound level C 3 D Daily History 8 18 setting parameters 7 14 variables B 27 Data determine storable 9 1 time history 7 4 Data Reading Chapter 5 5 1 Date 8 7 De output specifications A 7 Decibel C 3 Department of Defense level C 5 Detector 8 11 C 5 Diagram exceedance 7 10 passby 7 12 Dial Out Mode B 33 Dialing Procedure B 34 D
38. used to detect events over 65dBA and there is expected 20 events per hour or 240 per day 20 events hour time 12 hours day assuming that the plant operations will be reduced during the night Statistics based on hourly intervals and a one minute time history are desired to identify disturbance pattern The follow ing completed work sheet shows the calculations for this example 9 9 97 Memory Usage 9 3 Exceedance Memory Estimation Bytes needed Basic Exceedance Record 32 Excd Time Hist 21 n n estimated of samples 129 bytes max 20sec Excd TOTAL Bytes Excd sumlines1 4 gt gt gt gt gt gt Anticipated Excd Day Enter Number gt gt gt gt gt gt TOTAL Excd Bytes Day ee lines gt gt gt gt gt gt Interval Memory Estimation Bytes needed Basic Interval Record 34 Intv Save Ln s Yes Prm 77 18 Intv Save Ln Table 384 TOTAL Bytes Intv sum lines 6 8 gt gt gt gt gt gt Anticipated Intv Day Enter Number gt gt gt gt gt gt TOTAL Excd Bytes Day UT lines gt gt gt gt gt gt Daily History Memory Calculation Bytes needed Basic Daily Record Daily Save 6 Ln Values 18 Daily Save Ln Table 440 TOTAL Daily Bytes Day oo Te 12 gt gt gt gt gt gt ru Time History Memory Calculation Hist Resolution Hist Save Peak 16 1 04B No 1 9 4 Model 820 User Manual 9 9 97 Time History Memory Calculatio
39. will be displayed here in the order they happen They are accessed by either the 4 and M keys or the a and 8 keys which will scroll only the warning messages This screen shows the percentage of memory left of the total avail able 248837 divided by 250793 99 21 10 1 97 Step 2 Press the M key to access the next screen Total Exceedances were 27 total Intervals were 3 and 1Daily Histo ries Step 3 The third screen gives additional information This display indicates there are 8 Press the hi key to examine this screen Histories in memory 3 Logs and 0 Calibrations Hs is the number of time history samples Lg is the number of RUN STOPs made and CL is the number of calibra tion check records Stopping the Measurement Press to stop the measurement The stick figure will return to the resting position To view any of the previ ous measurement data simply press the appropriate key and the information will appear 10 1 97 Performing a Measurement Reading the Data 5 15 5 16 Model 820 User Manual 10 1 97 C HAPTER Timed Measurement The ability to take a measurement at a specific time and date is one of the unique qualities of the Model 820 This feature allows you to take unattended measurements Accessed through the TIMER key this flexible system has modes to permit one or two measurements a day between two dates or a single block measurement from a start dat
40. 01 _REPORT Report Number nnnnn R 102 _PAGE Page Number nnnnn R 103 _PRNLINE Printer Line Number nnn R 104 _CALTIME Calibration Date Time ddmmmyy hh mm ss R 105 _CHKTIME Cal Check Date Time ddmmmyy hh mm ss R 106 _OFFSET Cal Offset nnn n R 107 _CHKLVL Cal check Level nnn n OFFSET R 108 _RMSEX RMS Exceedance Flag 1 R 109 _RMSEX2 RMS Exceedance Flag 2 R110 _PKEX PEAK Exceedance Flag R111 _UWPKEX UWPK Exceedance Flag R112 _OVLD System Overload Flag bi R 113 _EXXR Excd Exchange Rate Text ceecee R114 _IVXR Intv Exchange Rate Text cecce R115 _AUTOADV Auto Advance History Ind R 116 131 _unused unused variable R 132 _DYMIN Today s Minimum Level nnn n dB R 133 _DYMAX Today s Maximum Level nnn n dB R 134 DYPEAK Today s Peak Level nnn n dB R 135 DYUWPK Today s UWPk Level nnn n dB R 136 _DYRNTIM Today s Runtime hh mm ss mm ss ss R 137 _ALMTIM Next Alarm Time hh mm 9 26 97 B 9 R 138 IVTIME Interval Date and Time of Occurrence ddmmmyy hh mm ss R 139 _IVDUR Interval Duration hh mm ss mm ss ss R 140 IVLINT Interval Lint nnn n dB R 141 _IVSEL Interval SEL nnn n dB R 142 IVMAX Interval Lmin nnn n dB R 1438 _IVMIN Interval Lmax nnn n dB R 144 _IVPEAK Interval Lpeak nnn n dB R 145 _IVUWPK Interval UnWeighted Peak nnn n dB R 146 _HISTLEQ AUTO SEND HISTORY LEQ nnn n dB R 147 149 _unused unused variable R 150 _RUNCNT Number of RUNS amp CONTINUES nnnnn R 151 _POFAULT
41. 20 does not have these limitations Furthermore its internal firmware is designed to accom modate changing regulations and to overcome sound measurement problems While the Model 820 is the size of a dosimeter it is also a complete environmental noise monitor offering features which will ensure quality mea surements for many years We invite you to read this manual to get the most out of your new Larson Davis sound level meter About This Manual This manual has 10 chapters and 3 appendices covering the following topics 1 1 10 1 97 Introduction Chapter 1 Introduction Overview of this user manual and the Model 820 s functions and measurement capabilities Chapter 2 Overview to Model 820 Understanding the keyboard and screen turning the instrument on and off and checking the battery voltage Chapter 3 Calibration Using a reference to calibrate the instrument and its importance Chapter 4 Quick Start Setting parameters using function keys and using numbers and other charac ters Chapter 5 Performing a Measurement Reading the Data taking a measurement and becoming familiar with the function keys Chapter 6 Timed Measurement Using the timer for unattended readings setting additional parameters and using the password lock Chapter 7 History Functions Setting parameters for exceedance levels history interval time history and daily history Chapter 8 Parameters A complete listing o
42. 24 hour military time clock where afternoon hours are denoted by adding 12 hours e g 3 45 p m 15 45 hrs Modify this parameter as follows Step 1 With the Model 820 on press SHIFT Step 2 Step 3 Step 4 Step 5 9 10 97 Press the key and use the numeric keys to enter correct time and then press Enter The Current Date is the next field Press the v to the next display The Day of the Week is in the next field Press v to access that field To exit the setup mode press Quick Start The current time is displayed If it is incorrect enter the correct time The current date will appear If it is incorrect press to access the field enter the correct date using the corresponding number keys and press Enter If the day is incorrect press and 1 or Q4 to the correct day Press Enter 4 7 AC DC Output AC and DC is accessed by the use of the optional CBL042 or by using a stereo miniphone plug as shown in figure 4 5 The DC output provides a voltage from the RMS detector that is proportional to the sound level The scale is 20 3 mV dB The output voltage is 0 3 volts with an output impedance of 6002 The AC output gives an AC signal proportional to input signal and can be Flat or A and C weighted It is used to record input signal to the Model 820 note Appendix A for more details CBL042 AC Output black DC Output ring AC Output tip e EL Groun
43. 3 0 630 19 0 1 0 800 0 8 0 0 1000 1000 0 0 0 1250 0 6 0 0 1600 1 0 0 0 1 2000 2000 12 0 1 0 2 2500 13 0 2 0 3 3150 12 0 4 0 5 4000 4000 1 0 0 7 0 8 5000 0 5 1 2 1 3 6300 0 1 1 9 2 0 8000 8000 1 1 29 3 0 10000 25 4 3 4 4 12500 4 3 6 1 6 2 16000 16000 6 6 8 4 8 5 20000 9 3 11 1 11 2 Model 820 User Manual 10 14 97 Leg Level dB Measurement Duration T Microphone Guidelines 10 14 97 See Energy Equivalent Sound Level Sound Level Energy Average and Time Weighted Average A descriptor of a measured physical quantity typically used in sound and vibration measurements It is attached to the name of the physical quantity to denote that it is a logarith mic measure of the quantity and not the quantity itself The word decibel is often added after the number to express the same thing When frequency weighting is used the annota tion is often expressed as dB A or dB B The time period of measurement It applies to hearing dam age risk and is generally expressed in hours Standard ANSI 12 19 Microphone Types A device for detecting the presence of sound Most often it converts the changing pressure associ ated with sound into an electrical voltage that duplicates the changes It can be composed of one of the following types Capacitor Condenser A microphone that uses the motion of a thin diaphragm caused by the sound to change the capaci tance of an electrical
44. 4 O cr terminates group command programming After programming this group read list the response to G0 is 59 5 38 6 102 2 the SPL Lmin and Lmax Setting Parameters All commands begin with S See Chapter 8 for a list of all the parameters and their settings Note that the parame ter numbers are for both Set 5 and Query Q com mands There are four types of parameters e Numeric Indexed Character strings Template Brackets indicate optional characters and operands cr carriage return lf line feed _ space B 12 Model 820 User Manual 9 26 97 Numeric Parameters Syntax Response S et item number parameter valuecr If Example S62 120 sets RMS Excd Level 2 to 120 Indexed Parameters Indexed parameters can be set in two ways a index number and b actual indexed parameter value a Index Number Syntax Response S et item number index number cr lf Example S9 3 sets parameter 9 Baud Rate to third possible value of 2400 S66 1 sets Excd History Enable to Yes S84 O sets Hist Period Units to 1 32s S84 1 sets Hist Period Units to _1 0s b Index Parameter Text Indexed parameter texts must be preceded by a semico lon and enclosed by brackets Indexed parameter texts must include the maximum number of characters including spaces which are indicated below with __ This command may be us
45. 5 date parameters 4 7 day parameters 4 7 DOSE 2 7 Dose 8 12 Enter 2 4 EXCD 24 8 10 functions of 2 3 HIST 2 4 INTV 2 4 8 15 LDL 2 7 LDN 2 7 Leq 2 6 8 9 Lmax 2 5 Lmin 2 5 Lmin Lmax 8 14 Ln 2 6 8 13 LOCK 8 10 Lock 2 4 log 2 4 memory 2 4 5 14 Modify 2 7 numeric 4 3 parameter 4 1 PEAK 2 5 Print 8 18 R S 8 6 RCL 8 6 RESET 8 6 Reset 2 4 Run Stop 2 4 SEL 2 6 SETUP 8 6 Setup 2 3 SHIFT 8 9 Shift 2 3 to 2 4 SLM 2 5 8 11 T A 2 7 TIME 2 6 8 9 Time 8 9 Time History 8 16 Time key functions 6 5 time parameters 4 7 TIMER 2 6 Timer mode 8 9 Timer run 8 9 Timer stop 8 9 UWPK 2 5 White 2 3 Key Leq 8 9 L LDL 5 9 key 2 7 Ldn Key 2 7 Leq 5 9 glossary C 5 Leq Eqivalent Level 1 5 Leq Equivalent Level Key 2 6 Level C 9 Dept of Defense C 5 Lmax key 2 5 parameters 5 5 Lmin key 2 5 parameters 5 5 LN LM Statistical Levels 8 13 Ln 5 8 key 2 6 LN Statistical Levels 8 13 Lock 8 10 key 2 4 Log key 2 4 Logged Dated Logic see LDL 2 7 Measurement Chapter 5 5 1 Index 3 Performing a 5 1 stopping 5 15 Measurement Timed Chapter 6 6 1 Memory 8 4 estimating usage 9 3 key 2 4 5 14 setup 8 4 store and retrieve 8 4 usage Chapter 9 9 1 Memory Usage Chapter 9 1 2 Messages error messages and warnings B 31 Microphone 1 5 connecting 1 17 guidelines C 9 reference number 1 12 what it measures C 10 Microphone Extension Cables specifications A 6 Microphones capacitor C 9 electrit C 9 u
46. 7 APPENDIX Specifications This Appendix contains the specifications for the Model 820 in the following order Type Reference Direction Measurement Ranges Reference Level Frequency Weighting Detector Time Weightings Effects of Temperature Effects of Humidity Limits of Temperature and Humidity Microphone Extension Cables Positioning of Instrument and Observer for Best Mea surements ACand DC Outputs Reference Frequency Stabilization Time Microphone Electrical Impedance Functions Measured DataStorage 9 25 97 A 1 Data Communications Digital Display Digital Display Resolution Display Bargraph Real time Clock Calendar e Run time Clock Typical Noise Floors e Standards Met Power Supply Dimensions Weight with Microphone Preampli fier and Battery Type The LarsoneDavis Model 820 with attached PRM 828 preamp and Model 2541 microphone is a combination Type 1 precision integrating sound level meter and sta tistical data logger The Model 820 can also be used with any of the LarsoneDavis 1 2 condenser microphones They may also be used with any LarsoneDavis 1 4 or 1 microphones provided they are used with an ADPO11 1 4 to 1 2 preamp adapter or an ADP008 1 to1 2 preamp adapter attached to the PRM 828 The Model 820 polarization voltage can be set to either 200V or 28V Reference Direction The reference direction is perpendicular to t
47. 820 Block Diagram Microphone RMS Slow Fast Impl 0 28 200 V Bias Supply Indicates parameter number Figure 1 3 Block Diagram The block diagram above shows how the Model 820 sound level meter merges state of the art analog cir cuitry a powerful microcomputer controller and a large amount of usable data memory The signal from the precision air condenser micro phone preamplifier is input directly to the linear peak detector and through the selected A or C weighting fil ter to the root mean square rms and weighted peak detectors Analog to digital conversion is performed maintaining a full 110 dB range for the RMS signal The numeric data is then analyzed by the Model 820 s dedi cated digital processor With system programming residing in PROMs pro grammable read only memory upgrades or future changes in regulations can easily be accommodated Measurement modes are selected and shown in informa tive screens on the 32 character liquid crystal diode LCD display The custom keypad provides direct access to the needed data or setup item An accurate built in Quartz clock calendar and timer are ideal for unattended measurements and time stamping of events 1 10 Model 820 User Manual 5 pin Connector 10 1 97 The 256 kB memory can be used to store time exceed ance or interval data as selected by the user All can be printed or transferred to an external computer via the serial port even during
48. 97 PEAK is a weighted value and rep resents a true Peak SPL from the on board Peak Detector In this example the PEAK is 116 2 dB and occurred at the time and date shown on the screen Parameter 63 sets the level above which the read ings must go to be recorded by the Model 820 Parameter 63 controls the setting for this measurement Here the set ting is 74 dB C weighted and in this measurement was equal to or exceeded 46 times The umweighted Peak value is the unfiltered no A or C weighting signal from the Peak Detector Performing a Measurement Reading the Data 5 7 Step 2 For the second screen press the bi key Ln L values are determined by parameters 55 60 and should be examined next in our current measurement Step 1 Access L by pressing the key and a screen similar to the following will appear Step 2 Pressthe M key to access the second screen of three 5 8 Model 820 User Manual The value for the UWPK is set in parameter 64 and is 85 dB This value was reached 30 times Parameters 55 56 in this example were set to 5 and 10 respectively This screen shows their values in this measurement These indicate the sound pressure levels that were exceeded 5 and 10 of the mea surement duration Parameters 57 58 were set at the given values shown in the screen and their readings are apparent Press the i key to see the third screen and the values recorded there
49. ENTER 142 Invalid Numeric Entry 143 OPEN 144 Already Open 145 No History Yet 146 At End of History 147 At Start of History 148 History Format Error 149 Unknown I O Command 150 I O Operand Invalid 151 Unable to Calibrate 152 EEPROM Write Error 153 Memory was Lost Data Reset 154 RECALL Not Found 155 Function Not Implemented B 32 Model 820 User Manual 9 26 97 156 System Locked 157 A D Stack Full 158 A D Over Run Serial Port Framing Serial Port Line Noisy Serial Port Over Run Wait for Stabilization Power Turned Off Time Date Not Set 165 Printer Already BUSY 166 Lithium Battery Low 167 Timer ON Pending Modem Control Mode The modem control mode enables the Model 820 to auto matically dial out upon an exceedance or a low memory condition This mode also enables the Model 820 to answer the phone so that instructions can be received The modem must be Hayes TM compatible and set to respond to commands using numeric codes non ver boses Setup parameters 154 to 157 control this feature Modem Mode 154 If the Modem Mode is Yes the Model 820 will dial the Phone on the events selected by the Dial Out Mode defined below Dial Out Mode 155 None The Model 820 will not dial a computer for any reason e Excd The Model 820 will dial a computer to report
50. Easy one step reset of measurement Battery level indication Standard 9V internal alkaline battery life of more than 16 hours or external power using LeD cable CBLOS35 for longer measurements RS 232 computer and modem interface standard All functions fully programmable Comes complete with PC SWW_SLM_UTIL software for data retrieval and translate binary files to ASCII format Other PC soft ware also available Large two line 32 character high contrast LCD dis play Small 33cm x 7 5cm x 2 5cm 13 H x 3 W x 1 D and lightweight 370g 13 oz including microphone and battery Rugged ABS case with EMI and RFI protection Environmental enclosures available for system secu rity and protection from inclement weather Durable membrane keypad Two year warranty see warranty statement on the copyright page at the front of this manual 1 6 Model 820 User Manual 10 1 97 Model 820 Components A layout of the Model 820 is shown below C lt _____ __ Microphone LCD Display TARSONDAVIS MODEL 820 Connector AC DC out Keypad f Connector Cal Heater Port Optional 88 Connector Figure 1 1 Model 820 The Model 820 is a convenient hand held sound level meter with a simple user interface As can be seen the standard Model 820 includes the fol lowing e Model PRM828 is a 5 1 2 inch
51. GRAM TABLE RESOLUTION Q 88 Q DYENB ENABLE DAILY LDN HISTORY Q 89 Q PRNRPT DATA REPORT x Q 90 Q PRNLOG R S AND CAL LOG x Q91 Q PRN SETUP REPORT x Histogram Reports The RMS Peak and UWPk histogram reports have been implemented with this revision The unformatted reports have also been developed and the format is the level of the first bin followed by the number of samples in each bin in hex 0 9 amp a There are 1024 RMS bins and 128 Peak and UWPk bins this corresponds to 1 8th dB resolution for RMS and 1dB resolution for the peak tables Q 92 Q PRN RMS HISTOGRAM TABLE x Q 93 Q PRN RMS HISTOGRAM TABLE LOW VALUE n Q 94 Q PRN RMS HISTOGRAM TABLE HI VALUE n Q 95 Q PRN RMS HISTOGRAM TABLE RESOLUTION x Q 96 Q PRN PEAK HISTOGRAM TABLE x Q 97 Q PRN PEAK HISTOGRAM TABLE LOW VALUE n Q 98 Q PRN PEAK HISTOGRAM TABLE HI VALUE n Q 99 Q PRN PEAK HISTOGRAM TABLE RESOL x Q 100 Q PRN UWPK HISTOGRAM TABLE x Q 101 Q PRN UWPK HISTOGRAM TABLE LOW VALUE n Q 102 Q PRN UWPK HISTOGRAM TABLE HI VALUE n Q 103 Q PRN UWPK HISTOGRAM TABLE RESOL x Tailored Report Q 104 Q PRN EXCD REPORT x Q 105 Q PRN EXCD REPORT LOW RECORD n Q 106 Q PRN EXCD REPORT HIGH RECORD n Q 107 Q PRN INTV REPORT x 9 26 97 B 19 Q 108 Q PRN INTV REPORT LOW RECORD n Q 109 Q PRN INTV REPORT
52. IMPROVE ACCURACY Refer to the specifications or device specific perfor mance results for the accuracy of the system M 10 Lock 820 leave 820 s power on M 11 Lock 820 and Power Off To unlock the unit and send the lock combination to the unlock parameter with the S230 cccccccc command where cccccccc is the correct combination entered before lock ing M 12 Disconnect Modem M 1000 Non destructive memory test walking bit M 1001 Destructive memory test pattern test amp amp 33 E Read Variables Syntax Variable Description Response R1 _DEVTYPE Device manf and model String R2 _DT TM Current Date and Time ddd ddmmmyyyy hh mm ss R3 _STAT Status RUN PAUSE STOP RESET C RESET O LOCKED A short form of the status command is R3 1 which has a 5 character response 9 26 97 B 5 The first is an s when stabilizing or a space when stable The second is the current mode S for Stopped R for Running P for Paused C for Calibrating V for View mode O for stopped with overall data reset and C for stopped with Current data set reset The third character is the Lock Status and is either an L or a U The fourth character is the Halt Line Status and is a 1 if high and a 0 if low The fifth or last character will be an a if an Alarm has been detected R4 _C SPL Current SPL nnn nn dB R5 _O RTIME OverAll Runtime hhhhh mm ss s
53. L DLe M 1 CBLO77 6 optional M EPS012 Environmental Case EPS013 Environmental Case w Battery Software SWW SLM UTIL SWW SLM LINK SWW ENV SWW REM SWW NMS SWW ACS E Larson Davis WEB Page Desktop Computer EA Laptop Computer Serial Printer Modem Figure 1 4 820 System Diagram Connecting Internal or External Power To insert the 9 volt battery in the Model 820 slide the battery cover at the bottom of the instrument away from the 5 pin connector see Figure 1 4 Gently pull on the connector board and connect the cell by first connecting one terminal then the other This prevents contact bounce which could scramble the Model 820 power up sequence Internal battery life is approximately 16 hours Refer to the description in Chapter 2 of this manual for additional battery information 10 1 97 external 1 GND mA and A Introduction Alternatively you may use an power source via pin and pin 4 of the 5 pin connector To do this order cable CBL035 from Larson Davis The Model 820 accepts 7 16 Vdc 30 is internally fused at 0 5 1 15 Figure 1 5 Internal Battery Source Environmental Considerations The Model 820 sound level meter can be both used and stored in a wide range of temperatures free of moisture and non condensing humidity conditions Moisture will cause the breakdown of an
54. Larson Davis Model 820 Sound Level Meter User Manual Larson Davis Incorporated 1681 West 820 North Provo UT 84601 1341 801 375 0177 www lardav com Model 820 User Manual 3 11 98 MODEL 820 USER MANUAL Copyright Copyright O 1997 by Larson Davis Incorporated This manual and the hardware described in it are copyrighted with all rights reserved The manual may not be copied in whole or in part for any use without prior written consent of Larsone Davis Incorporated Disclaimer The following paragraph does not apply in any state or country where such statements are not agreeable with local law Even though Larson Davis Incorporated has reviewed its documentation Larsone Davis Incorporated provides this publication as is without warranty of any kind express or implied including but not limited to the implied warranties of merchantability or fitness for a particular purpose This documentation is subject to change without notice and should not be construed as a commitment or representation by Larson Davis Incorpo rated This publication may contain inaccuracies or typographical errors Larson Davis Incor porated will periodically update the material for inclusion in new editions Changes and improvements to the products and or programs described in this manual may be made at any time Warranty Larsone Davis Incorporated warrants this product to be free from defects in material and workmanship for two years f
55. M Init Modem Initialization Sequence 8 20 Model 820 User Manual 9 30 97 159 Power Mode Normal Ext CO Normal meter uses internal battery unless greater exter nal voltage is also applied Ext CO external cutoff when external power falls below 10 5 V meter turns off to prevent battery damage 161 Timed EXCD Per mm ss Exceedance Time history is recorded from 10 samples before exceedance to 10 sam ples after this period 162 EXCD Trigger Level Bypass Bypass Enables a variable threshold 163 EXCD Time Start Max Start The exceedance will be measured at the beginning Max The exceedance will be measured at the maximum 168 Rt EXCD Report No Yes Print exceedance report in real time 169 Rt INTV Report No Yes Print interval report in real time 170 Rt HIST Report No Yes Print history report in real time 171 Rt RUN LOG No Yes Print run log history 172 Rt Daily Report No Yes Print daily report 173 Rt CAL Report No Yes Print cal report 206 Daily Save Lj s Yes No Enables L table for daily his tory 9 30 97 Parameters 8 21 8 22 Model 820 User Manual 9 30 97 C HAPTER Memory Usage Each of the Model 820 s History Functions use space out of a common memory The amount each record takes is bas
56. MBER Q217 Q TBLLVL LOCATE HISTOGRAM TABLE LEVEL Q NI42 RESERVED PARAMETER 42 49 respectively Q N149 Q OVLDLVL OVERLOAD LEVEL Q 227 Q RMSOS RMS CALIBRATION OFFSET Q 228 Q PKOS PEAK TO RMS CAL OFFSET Q 229 Q UWPKOS UwPk TO RMS CAL OFFSET Q 230 Q NI51 RESERVED PARAMETER 51 52 231 Q N152 Q 232 Q TEMP ENTER CURRENT TEMPERATURE Q 233 Q SERNUM ENTER SERIAL NUMBER History Records The various histories of the Model 820 are accessed in a similar fashion After using a direct index to the correct record one can advance or back up a certain number of records to the new value to be read Brackets in the syntax indicate optional characters and operands cr carriage return lf line feed Types of History Denoted in syntax by history_no 1 Exceedance E 2 Interval I 3 Daily D 4 Run Log L 5 Calibration C 6 Time H 7 Histogram Table T 9 26 97 B 23 Advance Advance a number of records from present record num ber If no num record number of records is provided 1 is assumed Syntax Response A dvance num record history no cr lf Example A9 5 current record is 17 calibration history s record 26 17 9 is located Backup Backup a number of records from present record num ber Syntax Response Backup num record history no cr 1f If no num_record number of records is provided 1 is assumed Example B9 5 cur
57. Maximum passby duration will be reduced if exceedance is reduced Step 1 To enable the Passby function turn on the Model 820 and then press s 000 and The screen will show either of two options Level PassBy Step 2 Press and then press bi to PassBy and then press Passby s Max Start of Exceedance Occurrence Figure 7 2 Passby Diagram 7 12 Model 820 User Manual When the Exceedance History and Passby parameter 66 and 162 is enabled a Passby record will be created whenever a delta 10dB event is detected See Figure 7 2 The occurrence time or Maximum Level must be equal to or greater than the RMS EXCD LVL 1 parameter 61 9 24 97 After taking a reading with Passby enabled you may wish to examine the Passby events You may also look at this while the instrument is running To do this follow this step Step 1 Press Exceedance which is now Passby and using the or keys scroll through the events Use the 4 or keys to look at infor mation about this event a EXCD a Time PassBy record and date b EXCD b Duration and record number of PassBy event c EXCD c SEL and Leg of PassBy event d EXCD d Max RMS level and Symmetry of PassBy record e EXCD e Peak PassBy level and UWPK of PassBy record Step 2 To examine the Maximum PassBy of all those collected press SHIFT and the 0 key Use the 4 and di keys to access the following data windo
58. RRENT THRESHOLD Q 47 Q CCRIT CURRENT CRITERION Q 48 Q OXRATE OVERALL EXCHANGE RATE Q 49 Q OTHOLD OVERALL THRESHOLD Q 50 Q OCRIT OVERALL CRITERION Q51 Q DOSET DOSE PERIOD Q 52 Q LDLXRATE LDL EXCHANGE RATE Q 53 Q LDLTHOLD LDL THRESHOLD Q 54 Q LDLCRIT LDL CRITERION 9 26 97 Q 55 Q LNN1 Lnn 1 PERCENT Q 56 Q LNN2 Lnn 2 PERCENT Q 57 Q LNN3 Lnn 3 PERCENT Q 58 Q LNN4 Lnn 4 PERCENT Q 59 Q LNN5 Lnn 5 PERCENT Q 60 Q LNN6 Lnn 6 PERCENT Q61 Q RMSTH1 RMS EXCD LEVEL 1 Q 62 Q RMSTH2 RMS EXCD LEVEL 2 Q 63 Q PKTH PEAK EXCD LEVEL Q 64 Q UWTH UWPK EXCD LEVEL Q 65 Q HYST EXCD HYSTERESIS Q 66 Q EXENB ENABLE EXCD HISTORY Q 67 Q EXXRT EXCD EXCHANGE RATE Q 68 Q EXMIN EXCD MINIMUM DURATION Q 69 Q EXHENB EXCD TIME HIST ENABLE Q 70 Q EXPER EXCD TIME HIST PERIOD Q71 Q EXADEN EXCD SAVE A D ENABLE unused Q 72 Q IVENB ENABLE INTV HISTORY Q73 Q IVXRT INTV EXCHANGE RATE Q 74 Q IVTHOLD INTV THRESHOLD Q 75 Q IVPER INTV PERIOD Q 76 Q IVSYNC INTV TIME SYNC Q 77 Q IVLN INTV SAVE Ln S Q 78 Q IVADEN INTV SAVE A D unused Q 79 Q IVSTOP INTV AUTO STOP Q 80 Q HSTENB ENABLE TIME HIST Q81 Q HSTRES HIST RESOLUTION Q 82 Q HSTPK HIST SAVE PEAK Q 83 Q HSTPER HIST PERIOD Q 84 Q HSTUNIT HIST PERIOD UNITS Q 85 Q HSTBASE HIST BASE B 18 Model 820 User Manual 9 26 97 Q 86 Q HSTMODE HIST BASE MODE Q87 Q HGRES HISTO
59. T SETUP REPORT x Q 180 Q RPT RMS HISTOGRAM TABLE x Q 181 Q RMSLO RMS HISTOGRAM TABLE LOW VALUE n Q 182 Q RMSHI RMS HISTOGRAM TABLE HI VALUE n Q 183 Q RMSRS RMS HISTOGRAM TABLE RESOLUTION x Q 184 Q RPT PEAK HISTOGRAM TABLE x Q 185 Q RPT PEAK HISTOGRAM TABLE LOW VALUE n Q 186 Q RPT PEAK HISTOGRAM TABLE HI VALUE n Q 187 Q RPT PEAK HISTOGRAM TABLE RESOL x Q 188 Q RPT UWPK HISTOGRAM TABLE x Q 189 Q RPT UWPK HISTOGRAM TABLE LOW VALUE n Q 190 Q RPT UWPK HISTOGRAM TABLE HI VALUE n Q 191 Q RPT UWPK HISTOGRAM TABLE RESOL x Q 192 Q RPT EXCD REPORT x Q 193 Q RPT EXCD REPORT LOW RECORD n Q 194 Q RPT EXCD REPORT HIGH RECORD n Q 195 Q RPT INTV REPORT x Q 196 Q RPT INTV REPORT LOW RECORD n Q 197 Q RPT INTV REPORT HIGH RECORD n Q 198 Q RPT HIST REPORT x Q 199 Q RPT HIST REPORT LOW RECORD n Q 200 Q RPT HIST REPORT HIGH RECORD n Q 201 Q RPTEND DAILY NOISE REPORT x Q 202 Q CALMODE CALIBRATION MODE Q 203 Q ULCOMB UNLOCK COMBINATION cccccccc Q 204 Q IONAME I O FILENAME cccccccc Q 205 Q ERCHK ENABLE ERROR CHECKING I O 9 26 97 B 21 Error Checking I O The error checking I O protocol verifies that commands and data are transferred without errors e To enable error checking the command or 205 1 command is used To disable error checking two CR characters in a row may be sent if not in the Modem Mode or the S205 OF command is sent
60. T and Two screens are available using the 9 key A N BATTERY In Chapter 2 we accessed the Battery information to check the amount or voltage remaining in our battery This function has additional screens available The first two indicate the amount of voltage remaining and the second shows the information related to the last revi sion 10 1 97 Performing a Measurement Reading the Data Ldn is the noise descriptor that applies a 5 dB weighting factor between the hours of 10 00 PM and 6 00 AM when calculating the Time Weighted average CNEL adds an additional 5 dB between the hours of 8 00 PM and 10 00 PM Ex in the second screen takes all exceedance records and aver ages them together BkGnd is the overall Leg of all samples that were not an event 5 13 Step 1 Access the Battery display by pressing SHIFT and 4 Press the di key to access the second screen Step 2 Press the 3 key and a screen similar to the fol lowing will appear MEMORY Memory will be addressed in Chapter 9 but it would be well to examine the key functions here Standard memory size is 250 KBytes Three screens are available from this function Step 1 Press GHIFT and EY A screen similar to the fol lowing will appear 5 14 Model 820 User Manual The Revision date is shown Eight additional screens are avail able from this function Warning or Error messages encountered during normal operation
61. T and amp to access Log screens Step 2 View the start and stop times and date by press ing the 0 key Step 3 Go back to LOG a by pressing the M key Tog gle through the record logs by pressing v Step 4 The a and 3 keys may be used to look at additional records Press the M to look at asso ciated dates and times This screen gives you information about the most current readings This measurement was started by a key stroke If it had been started by preset alarm Key would have been replaced with Alm The Log information indicates that the measurement was stopped by keystroke If a low battery had been the reason for the measurement stopping BATT would have appeared To retain data already gathered the Model 820 will ter minate the measurement when battery power becomes low Interval History The Interval History Parameters allow you to select and define the interval size and determine what data are to be saved Each interval gives you Leg SEL Min Max Peak UWPK Exceedance count and if you turn this feature on L s Listed below is each parameter and a brief explanation of its function 9 24 97 7 5 History Functions Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 7 6 To access the Interval History parameters press You may also use numeric values With this item set to Yes the Interval Time History ITH is ie 2 Enter T
62. UTPUT 1 HOLD TIME unused Q LOGIC2 OUTPUT 2 LOGIC Q17M Q OUT2TI OUTPUT 2 HOLD TIME unused Q 18 Q HALT HALT LINE MODE Halt Line Mode Q18 has a None state available This allows systems with intrusion alarm hardware to be disabled during servicing The choices are None Pause Toggle Level Alarm The Model 820 dials out when in the Modem Mode and remaining mem ory gets below 5000 bytes It now uses RMS Threshold 2 to dial out on EXCD events Q 19 Q BEEP BEEP WHILE RUNNING unused Q 20 Q PWRSV POWER SAVE OPTIONS Q21 Q TIMMD TIMER MODE Q 22 Q RUND TIMER RUN DATE Q 23 Q STOPD TIMER STOP DATE B 16 Model 820 User Manual 9 26 97 Q24 Q RUNTI TIMER RUN TIME 1 Q25 Q STOPT1 TIMER STOP TIME 1 Q 26 Q RUNT2 TIMER RUN TIME 2 Q 27 Q STOPT2 TIMER STOP TIME 2 Q 28 Q LKCOMB LOCK COMBINATION Q 29 Q LKRS LOCK R S KEY Q 30 Q LKSU LOCK SETUP Q31 Q LKFN LOCK FUNCTION Q 32 Q LKRES LOCK RESET Q 33 Q LKPWR LOCK THE ON KEY Q 34 Q LKIO LOCK I O Q 35 Q CALLVL CAL LEVEL Q 36 Q CALSN CALIBRATOR S N Q 37 Q AUTOCAL AUTO CALIBRATION MODE Q 38 Q CALTIM AUTO CAL TIME Q 39 Q DETC DETECTOR Q 40 Q WGHT FREQUENCY WEIGHTING Q 41 Q HPASS HIGH PASS FILTER unused Q 42 Q LPASS LOW PASS FILTER unused Q 43 Q MICV MIC POLARIZATION unused Q 44 Q REFLVL RELATIVE LEVEL REFERANCE Q 45 Q CXRATE CURRENT EXCHANGE RATE Q 46 Q CTHOLD CU
63. aindrop 2 those caused by the movement of air over the diaphragm such as environmental wind or blowing 3 those caused by vibration of the micro phone housing and 4 those caused by strong electrostatic fields Rules 1 Do not permit any solid or liquid to touch the microphone diaphragm Keep a protective grid over the diaphragm 2 Do not blow on a microphone and use a wind screen over the microphone to reduce the effect of wind noise 3 Mount microphones so their body is not subject to vibra tion particularly in direction at right angles to the plane of the diaphragm 4 Keep microphones away from strong electrical fields A microphone measures forces not pressures We would like the microphone to measure sound pressure force per unit area instead of sound force If the pressure is applied uniformly over the microphone diaphragm a simple constant the dia phragm area relates the two but if the pressure varies across the diaphragm the relationship is more complex For exam ple if a negative pressure is applied on one half the dia phragm and an equal positive pressure is applied to the other half the net force is zero and essentially no motion of the diaphragm occurs This occurs at high frequencies and for specific orientations of the microphone Rules 1 Do not use a microphone at frequencies higher than speci fied by the manufacturer to increase the frequency response choose smaller microphones 2 Choose a micr
64. air condenser microphone Some precautions should be taken For example allow the Model 820 ample time to adjust to abrupt tempera ture changes Condensation may form inside a cold Model 820 if it is brought into a warm room or vehicle and may persist long after the outside case has adjusted to the ambient temperature Also temperatures inside closed vehicles can reach excessive levels Therefore do not leave the instrument in direct sunlight in a vehicle A simple safeguard is to keep the instrument inside a sealed foam insulated case or bag with desiccant silica gel available at photographic equipment stores or from Larson Davis 1 16 Model 820 User Manual 10 1 97 Preparing to Use the Model 820 Connecting the Mic Preamp Before powering the SLM carefully thread the micro phone on the preamplifier The microphone bias voltage is not dangerous but installing or removing the micro phone with the instrument on may damage the electron ics Insert the 828 in the nose cone or extension cable by lining up the latch button with the channel in the mating connector The small black dot should click and protrude at the base of the 828 after insertion It must be depressed completely to remove the preamplifier from the mating connector 10 1 97 Introduction Model 820 User Manual 10 1 97 Overview to Model 820 Once your Model 820 is unpacked and connected to a battery or external power supply you can turn it on and tak
65. aling with OVERLOAD Setting the Daily History Parameter Setting and Viewing Advanced Functions The Model 820 has a variety of advanced functions that allow for gathering and storing great amounts of data with any given measurement In this section you will learn how to access the parameters choose the proper settings and view some of the data collected 9 24 97 History Functions 7 1 Time History Time History records include the rms integrated level and if selected Peak Unweighted Peak or Lmax Param eters 80 87 allow you to select the period for the history and what data are to be saved Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 7 2 Turn the Model 820 on and access Time History parameters Press The following screen item 80 Time history Enable appears To enable the Time History press M to Yes and Enter Press the v to item 81 History Resolution 1 0 d B 0 1 dB To change this setting press 0 To access item 82 Hist Save Peak press v No Peak UWPK Lmax You may press and make your selection with di and then press Enter Press the v to item 83 Hist Period 0 255 units Press the v to item 84 Hist Period Units 1 32s 1 0s 10 0s 60 0s Model 820 User Manual Yes With this item set to Yes the time history function is enabled Despite Model 820 s large memory ensure X anticipated requirements do not exceed avail
66. an one of these can be set at a time in which case x is the sum of all set flags B 34 Model 820 User Manual 9 26 97 Step 5 Step 6 The Model 820 awaits a response code which should be 820 A0123 11111111 enter where 0123 is the Model 820 s serial number and 11111111 is the Lock Combination parameter 28 which is required whether or not the Model 820 is currently locked If the response is incor rect the announcement is resent Four chances are given to respond correctly A 3 cr sequence will cause the Model 820 to hang up When a correct response is received the Model 820 indicates it is ready to send data when requested with 820 Ready enter Model 820 Answering Procedure Step 1 Step 2 Step 3 Step 4 Step 5 9 26 97 The modem informs the Model 820 that a con Modem 2 enter nection has been requested thatis the phone is ringing The Model 820 answers the phone 820 ATA enter The modem informs the Model 820 that a con Modem 10 enter nection has been made The Model 820 modi fies its baud rate to that of the connected modem If the connection is unsuccessful the procedure is retried in 4 min The Model 820 sends the following announce ment 820 820A0123 001 0 enter where 0123 is the Model 820 s serial number 001 is the monitor number entered and 0 is a flag 1 Alarm 2 Exceedance 4 Low Memory More than one of these can be set at a time in which case x is
67. ance d Parameter 64 UWPK Exceedance e Parameter 112 Overload current f Parameter 160 O OVLD overall overload This instrument can store a great variety of measurements in mem ory depending on the current parameter setup Nevertheless current measurements are always easily available from the keypad The display now reads a C weighted slow average reading of 84 5 dBC re 20 uPa The level is also shown on a semi analog bar graph Parameters 39 43 affect these values and parameters 45 47 effect the Current SLM The Lmin and Lmax for the current reading at the current time are dis played in the first screen Notice that the current sound pressure level continues to read in the upper left corner and fluctuates Note that even in the stop mode the Model 820 continues to monitor SPL while in this window The space beneath 88 4 in this screen where the are located is a field where six items of information are available Respec tively with the controlling param eter these are listed to the left If these parameter values have been triggered the will appear to indicate that the record contains Model 820 User Manual 10 1 97 Step 4 Press the v key again for the second screen Step 5 Press the v key for the third screen Step 6 Step 7 The next screen addresses the Alarm time and current temperature Press the v key and the fifth screen will appear
68. anenees 1 3 Formatting Conventions sse eren nennen 1 3 Eeatutesa x salo gite O ATAR 1 4 Model 820 Components sse nennen 1 7 Block Diagrantc acu eon te tei tee n eer esie eed potes tede 1 9 Getting Started cometa iunt dan etes 1 11 Unpacking and Inspection sse 1 11 ACC SSOFIOS E E gione T IO nasa 1 12 Optional Equipment tinneis notie tenente 1 13 Connecting Internal or External Power esses 1 15 Environmental Considerati0NS icicionononiononnnonnonoconinnonencnnoninnacincanonincncnoss 1 16 Preparing to Use the Model 820 Connecting the Mic Preamp 1 17 Overview to Model 820 2 1 Understanding the Model 820 Keypad 2 1 Getting to Know Screen Symbols sss 2 8 Understanding the Model 820 Screen cococcnconononononnnnnennnrncannnnnnnrnrornrnnnararananoos 2 9 Turning On the Model 820 2 9 Checking the Battery Voltage sse 2 10 Turning Off the Model 820 isinir aea ae ena ae o a A EEan 2 11 Calibration 3 1 Calibrating the Model 820 seen 3 1 Quick Start 4 1 Setting Parameters Using Function Keys sess 4 1 Setting Parameters Using Numbers and Other Characters 4 3 Setting Time Date and Day parameters s esses 4 7 AC DC Output 5 52 n npeunec epe ene eremi a erae 4 8 Performing a Measurement Reading the Data 5 1 Taking a Measurement
69. anging Parameters Enter Modify Parameters may consist of numerical values character fields or selected choices Numerical or character fields are shown between parentheses Another parameter type is the template entry parameter These prompt for specific data entry For example For both types follow these simple steps Step 1 Press Modify Step 2 Enter a value from the numerical keypad Use the SHIFT key for alphabetical input Step3 Confirm any change with Enter Step 4 Cancel any change by pressing before Enter Parameters whose value is selected from a few possible choices are displayed with the current setting inside square brackets To make a selection Step 1 Press and then the and di keys 9 30 97 Parameters This one has rounded brackets that mean this is an entry parameter Type the number or character desired see Chapter 4 If there is an angle bracket gt then the entry field is too big to fit the screen and will scroll with the M key For complete coverage of numeri cal and alpha entry see chapter 4 8 3 Step2 Confirm change with Enter Step 3 Cancel change by pressing before Enter Error Messages Entry errors will be noted by a warning message For example Verify the correct entry format Learning to Store and Retrieve Setup Memory The current setup parameters can be stored internally in two ways for late
70. arameter be incor rect the Model 820 will not calibrate correctly 3 1 9 30 97 Calibration Step 1 Step 2 Step 3 Step 4 Step 5 3 2 Check the microphone polarization by looking at setup parameter 43 To do this turn on the Model 820 press and 8 and Enter The following display will appear Should the brackets contain a value other than 200 e g 28 or 0 press the amp until the value 200 appears and then press Enter If you are using a pre polarized microphone this parame ter should be set to 0 Press Cancel to return to the main screen To begin the calibration process check or insert the new calibration level given in parameter 35 To do this press 8 and 5 then Enter The following screen will appear Press then enter the SPL value of your calibrator if other than 114 0 including any corrections for pressure etc Model 820 User Manuall The flashing f the Keyboard Sta tus Indicator displays which key functions are active This indicates that the function keys are used for different purpose in current func tion In this screen the value 200 is selected from three options 200 28 0 The Larson Davis Model CAL200 calibrator outputs 114 dB or 94 dB re20 uPa Note that the Model 820 automatically uses the C weight ing while calibrating This ensures a correct reading at typical calibra tion frequencies of 250 H
71. arsone Davis Model 870 com mands In this chapter we will cover the following items e Model INT002 Interface Cable sess 2 e Daisy Chain Addressing 3 Commniahds sien ete o ERE E CUR RENS BS Uie Group Read Programming e Setting Parameters nee Query Parameters eso deett 15 e History Records uppii a p a 23 e History Data Variables sse 25 e Print Commands niit ee dee etie edes 30 e Error Messages and Warnings sse 31 Modem Control Mode sss 36 9 26 97 B 1 Model INT002 Interface Cable The Serial Port communication is made through the 5 pin connector at the base of the Model 820 Interface interface signals usually need to be converted for proper communication with desktop computers The Model INT002 Cable level converter is required for this pur pose Its electronic circuits provide the correct signal lev els and polarities When used with the AC DC adapter the INT002 also powers the units externally minimizing battery depletion which can be substantial during Serial Port transfers Step 1 With the instrument turned off insert the cable connector in the 5 pin port Step 2 Connect the cable to the of the computer using Baud rate Serial Port address and the supplied 9 25 pin adapter if necessary handshaking protocol are selected using parameters 9 10 and 12 Unless using addressing set the address to 0
72. at you do is shown in the left column and the rationale why you do it with other cautions and comments are shown in the right column For example 10 1 97 Introduction 1 3 Microphone Polarization Voltage is preset by Lar son Davis at 200 volts Should this parameter be incor rect the Model 820 will not calibrate correctly Step 1 Check the microphone polarization To do this The flashing f the Keyboard Sta turn on the Model 820 press A and tus Indicator displays which key 8 and Enter The following display will functions are active This indicates appear that the function keys are used for different purpose in current func tion Step 2 Should the brackets contain a value other than In this screen the value 200 is 200 e g 28 0 press the amp until the value selected from three options 200 200 appears and then press Enter 28 0 Especially important information is shown in italics for example To access items 48 50 Overall Exchange Rate Overall Threshold Overall Criterion press the v key Features The Larsone Davis Model 820 meets the requirements of the American National Standards Institute ANSI 1 4 International Electrotechnical Commission IEC 651 and 804 1985 standards for Type 1 accuracy and offers the following features Dynamic range of more than 100 dB for error free measurements Impulse measuring range greater than 100 dB 1 4 Mo
73. aust and intake noise When in the near field the sound of a weaker but close source can be louder than that of a more distant but stronger source Therefore measure ments made here can be used to separate the various sources of sound but are not useful in predicting the sound levels and sound spectrum far from the source Typically it is unwanted sound This word adds the response of humans to the physical phenomenon of sound The descriptor should be used only when negative effects on people are known to occur Unfortunately this word is used also to describe sounds with no tonal content random Ambient The all encompassing sound at a given location caused by all sources of sound It is generally random but need not be Background The all encompassing sound at a given location caused by all sources of sound but excluding the source to be measured It is essentially the sound that interferes with a measurement Pink It is a random sound that maintains constant energy per octave Pink light is similar to pink noise in that it has a higher level at the lower frequencies red end of the spec trum White It is a random sound that contains equal energy at each frequency In this respect it is similar to white light It is the percentage of time a person is exposed to noise that is potentially damaging to hearing Zero represents no expo sure and 100 or more represents complete exposure It is cal culated by dividing the ac
74. ber of printout 107 INTV Report No Short Long Prints interval report 108 Lowest Rec O 65535 Starting interval record num ber of printout 109 Highest Rec 0 65535 Ending interval record number of printout 110 HIST Report No Yes Prints time history report 111 Lowest Rec 0 gt 999999 Starting history record num ber of printout 9 30 97 Parameters 8 19 Highest Rec 0 gt 999999 Ending history record number of printout 113 Daily Report No Short Long Prints daily report NOTE Parameters 168 173 for additional printing options Additional System Functions 152 154 161 The functions below apply to the LDL Model 820 when used in remote applications such as in airport or perime ter noise monitoring systems Requires Model 820 option 01 These parameters are for control in Model 2101 No Prompt Entry Comment 152 E A Cal Tone No Yes Automatic electrostatic actua tor calibration tone control 820 OPT 01 must be installed 153 Heater On Yes No 154 Modem Mode No Yes Select if Model 820 s RS 232 port is connected to modem 155 Deal Out Mode None EXCD Instrument automatically ALRM Both dials out if EXCD RMS Exceedance level 2 is Exceeded ALRM Enclosure intruder alarm is triggered or Both 156 Phone 157 Monitor Number 0 127 Monitor Identification number 158
75. connect to external power Also con sider the safety of the instrument during the test period Finally verify that the current time and date are set correctly in the internal clock of the 820 The following section covers setting the time and date The Model 820 will turn itself on and begin measurement at the appropriate time 6 4 Model 820 User Manual 9 24 97 Using the Time Key Functions In Chapter 5 we learned to take a measurement and examine some of the data gathered during that reading The TIME key functions as a record of when the last measurement started Two screens are available in this function Step 1 Press SHIFT and to access this information Current time day and day of week are controlled by parameter 6 8 This screen displays the time and date the current or last measure ment began The second display shows the cur rent date day and time Step 3 Press to return to the main screen Setting the Password Lock to Protect Settings The Model 820 SLM can insure that your settings will not be disturbed by providing a Lock Password parame ter items 28 34 9 24 97 Timed Measurement 6 5 Step 1 From the previous field press 3 or from the main screen press i Modify 2 B Enter You can also press SHIFT ES Step 2 Press and enter your personal combina Refer to Chapter 4 to review enter tion of numbers or letters from 1 8 characters ing number
76. croll through the fields Use the Modify M and Enter keys to make any changes desired within each field End of Start of Exceedance Exceedance Tstart Hysteresis Figure 7 1 Exceedance diagram The diagram above is an example of an exceedance with markings of explanation It should be noted here that additional parameter set tings have been added out of numerical sequence to sat isfy additional needs found in the field These will now be explained e 161 Timed EXCD Per mm ss 162 Excd Trigger Level PassBy 163 Excd Time Start Max 7 10 Model 820 User Manual The exceedance time history sam ple period is in 1 32 seconds Ten samples before and after the exceedance are normally stored up to a maximum of 255 samples Exceedance Time history is recorded from 10 samples before exceedance to 10 samples after this period Must be in Level Passby treated later Start This setting will begin the exceedance measurement as it occurs 9 24 97 Occurrence Time Tstart if set to Start Occurrence Time Tmax if set to Max max T start Symmetry y y duration Lmax Must be gt rms Level 1 Only events that are longer than the minimum duration set and having Lmax greater than the RMS Exceedance Level 1 parameter 61 will be recorded It is also impor tant to set the Excd Time History Period to 0 5 or 1 sec ond by entering a 16 or 32 for pa
77. d sleeve DC Output red Figure 4 5 AC DC Output Connector 4 8 Model 820 User Manual 9 10 97 Performing a Measurement Reading the Data With the basic parameters set and the instrument cali brated as discussed in Chapters 3 and 4 you are ready to take a measurement and examine the readings from the data collected Taking an actual measurement with the Model 820 only requires pressing the or RUN STOP key In this chapter we will e Take a measurement Examine and briefly explain the function keys associ ated with the measurement i e MENESES O MD and 5 Stopping the measurement Taking a Measurement This section will address measurements and the infor mation available during and after the measurement has been taken The most basic function of the Model 820 is to measure sound pressure Follow these steps to exam ine the SLM function key 10 1 97 Performing a Measurement Reading the Data 5 1 SLM Step 1 Step 2 Step 3 5 2 Turn the Model 820 on and wait for the unit to become stable Press 2 The stick figure in the upper right corner will appear to be running With the instrument in RUN mode press 5 The current sound pressure level is displayed An additional six screens are available from this display Press the 3 key to access the first a Parameter 61 RMS Exceedance b Parameter 62 RMS Exceedance 2 c Parameter 63 Peak Exceed
78. data gathering LeD PC compat ible software employs a binary data dump method for even faster data transfer External battery or DC power may be supplied through the same five pin connector Getting Started This section outlines the steps you need to follow when you first receive and unpack the Model 820 The follow ing topics are covered Unpacking and Inspection Accessories and Optional Equipment Connecting Internal or External Power Environmental Considerations Preparing to use the Model 820 Connecting the Microphone to the Preamp You will then be ready to use the Model 820 for actual measurements as described later in Chapter 4 of this manual Unpacking and Inspection Your Model 820 has been shipped in protective packag ing Please verify the package contents with the follow ing list Accessories and Optional Equipment and retain the shipping containers for safe shipment at a future date Report any damage or shortage immediately to Larsone Davis Inc at 801 375 0177 10 1 97 Introduction If you have not already done so please record at the beginning of this manual see the copyright page your instrument s serial number located on the label on the back of the Model 820 the microphone serial number located inside the micro phone the preamp serial number and the purchase date You will be asked to give this information in any future communi cations you may have with Larsone Davis Inc
79. del 820 User Manual 10 1 97 Standard microphone allows measurements typically between 30 and 140 db A in one range Optional microphones allow measurements as low as 20 dB or as high as 190 dB A Mic bias is user selectable 0 28 and 200 V Selectable A and C frequency weightings for hearing protector applications Multiple detectors provide simultaneous RMS and PEAK measurements Leq integrated level duration ranging from 1 second to 99 hours manually controlled Measures FAST SLOW Unweighted PEAK Weighted PEAK Impulse Leg Lpop Losna Dose Projected Dose TWA Sel Lae Lmax Lmin Six user defined Las Lan CNEL and more User selectable dose exchange rate criterion thresh old and reference duration Measures and stores more than 40 000 different DOSE combinations in a single measurement Allows com parisons of different DOSE standards using the same data Complete data logging capabilities with 256 kB stan dard memory Passby event data such as time duration Lmax L SEL integrated about 10 dB of the maximum eq Selectively logs Exceedance when signal level rises above a user set threshold for a time longer than a user set period Time history sampling periods are user selectable from 32 samples second up to one sample every 255 minutes Quartz clock calendar system for data annotation Calibration from front panel using an appropriate calibration source 10 1 97 Introduction
80. dge History Oriented Commands E xceedance variable number relative recO variable value E xceedance variable number time hist num variable value I nterval variable number relative rect variable value D aily variable number hour num L og variable number relative recO variable value variable value C alibration variable number variable value H istory variable number relative rect variable value T ables variable number table variable value A dvance range history number acknowledge B ackup range history number acknowledge Flind record number history number acknowledge P rint report number acknowledge B 4 Model 820 User Manual 9 26 97 Mode Commands Format for the Mode Commands is Command Description MI Power On clear error message list and reset display functions to a windows M2 Power Off M3 Run M4 Stop M5 View M6 Mark M7 Reset Current Data use S1 1 for Reset All M8 Reset Histories Only M9 High Resolution Levels to I O channel only Increased resolution I O is possible by using the M9 1 command All sound levels are then sent with an additional fractional character nnn nn giving 1 100th dB resolution The Model 820 acquires noise data with 1 32 dB resolution Greater resolution is achieved through averaging HOWEVER THIS DOES NOT
81. e and time to a stop date and time In this chapter we will discuss Using the Timer for Unattended Readings Using the Time Key Functions Setting the Password Lock to Protect Settings Using the Timer for Unattended Readings Examine the capabilities by looking at the parame ter fields Step 1 Turn the Model 820 on press i followed by The Timer parameters 21 27 EE SHIFT and The following display begin with this screen parameter will appear 21 D 9 24 97 Timed Measurement 6 1 Step 2 Press to access the cursor in brackets With the brackets flashing use the gt to select one of four possibilities Off Block 1 Day or 2 Day Example Suppose we want to measure a given area near a large machine in a factory for 5 days 2 periods each day Step 3 To do this choose 2 Day and press Enter Step 4 To continue press the to access the next parameter screen To continue our example we want to start 26 September at 8 30 A M and end at 12 00 noon begin again at 1 00 P M and end at 4 30 P M each day for 5 days Step 5 Press to change the date and enter 0 0 06006 Press Thenew Timer Run Date is now 26 Sep 1996 Step 6 To access Timer Stop press the v A Previously entered date will appear 6 2 Model 820 User Manual Block Run Time 1 on Run Date to Stop Time 1 on Stop Date 1 Day Run Time 1 to Stop Time 1 each day from Run Date to St
82. e e a ran an aran a s A 3 RMS Detecta Ai A A 3 Other Detectors 5 mee tuere ida A 3 Reference Leyel nate tete tet use dite iuis A 4 Frequency Weighting Sirro nenei ipsios kei re E ETS na tenete A 4 Detector Time Weighting Stirs hrei anaes e Terrae O Eee Sanasi A 6 Effects of Temperature soist piion ere A EERE ESE NEEE RER E iR A 6 Effects of Hunmudly eee eere ree eripe pres A 6 Limits of Temperature and Humidity sess A 6 Microphone Extension Cables sssssssssseeeseeerneen A 6 Positioning of Instrument and Observer for Best Measurements A 7 AC and DC Outputs AA A nana nennen A 7 AC Output otii e temi diede tees A 7 DC Outp t i nente tet eee dee eri bin idad A 7 SS AAA A 8 Stabilization AAA Re eee tenere A 8 Microphone Electrical Impedance sss A 8 Functions Measured eias eme tm t met e reed t ees A 8 iii App B Data Storage xiu ite cian ta A rs A 9 Data Comimunications ttt nem rete reete A 9 Digital Display ivan eene tas ere PET PERCHE ERE A 9 Digital Display Resolutions sson ee e EE E nennen A 9 Display Batgraphes AAA A 9 Real time Clock Calendar eese nennen nennt A 10 Run time Clock airs igi niin nied SA A 10 Standards Meteo en eundem deae A 10 Powersupply odit as A 10 Dimensions Weight with Microphone Preamplifier and Battery A 11 Serial Port Interface Remote Control B 1 Model INT002 Interface Cable
83. e interval 1 minute to larger than 99 hours in one minute or greater steps It is pro grammed by parameters 72 79 MEM Memory use in percent bytes free and total byte available are provided as well as a count of all of the History Records stored in memory 2 4 HIST The Time History function is a record of short interval Leq reading and optionally a Peak UWPK or Ln ax read ing The interval can vary from 1 second to 255 minutes History period is set by parameters 183 84 LOG The Run Stop Log is a time record of all the actions which start or stop the data taking process of the Model 820 Model 820 User Manual 10 1 97 Keys Functions CAL SLM CAL Calibration information and con trol Initially in the CAL a display the current calibration offset is displayed with a flashing prompt to press either the a key to check the calibration or press the x key to change the calibration SLM The Sound Level Meter function displays the current Sound Pressure Level SPL while the instrument is in the Run Mode or the SPL at the instant it was last stopped LMAX Lmax The maximum SPL or L max is the largest sampled SPL for the overall mea surement period displayed with the date and time of its occurrence Two addi tional screens accessed by pressing the left or right arrows show the number of times the SPL exceeded two fixed levels Lyn The minimum SPL or Lmin is the lowest sampled
84. e simple measurements In this chapter we dis cuss the following Understanding the Model 820 Keypad Understanding the Model 820 Screen Getting to Know Screen Symbols Turning on the Model 820 Checking the Battery Voltage Turning off the Model 820 Understanding the Model 820 Keypad The keypad for the Model 820 has 20 keys as seen in the following figure Figure 2 1 10 1 97 Overview to Model 820 2 1 ls LARSON DAVIS MODEL 820 Modify lt 7 8 9 TIME TIMER LDN LDL LEQ SEL T A DOSE 4 5 6 CAL LMIN WPKY BATT SLM LMAX PEAK LN 1 2 3 LOC MEM LOG SHIFT excepi INTV HIST Cancel Enter Ga EN EN R ES Ga EN EN ES TYPE 1 INTEGRATING SOUND LEVEL METER Figure 2 1 Model 820 Keypad 2 2 Model 820 User Manual 10 1 97 These keys perform the following functions This infor mation is covered in more detail in chapter 4 of this manual Keys Functions White White functions are accessed by pushing buttons directly Blue Blue functions are accessed by first press ing the key The smaller letters numbers above the keys are accessed by the adjoining key at the appropriate time to be explained later OFF ON Turns on the Model 820 ON Cancel When the Model 820 is on this button serves to return to a previous menu or Cancel the present function OFF SHIFT OFF turns off the Model 820 after it has been stopped PRINT Access to a list of reports scrolled PRINT
85. ed nnn n or nnnnn unused D 13 Daily Gust nnn n or nnnnn unused D 14 Daily Gust Direction ccc unused D 15 Daily Gust Time hh mm ss unused D 16 Daily Wind Excd Count nnnnn unused D 17 Daily Windy Percentage nnn unused D 18 n Daily Direction n 1 8 cccnnn unused D 19 Daily Ln Table in hexa hhhhhh hhhhhh hhhhhh decimal ih D 101 Daily Variables 1 4 7 11 Macro D 102 Daily HNLs 5 0 23 6 0 Macro 23 D 103 Daily Wind 12 17 18 1 8 Macro unused Run Log Variables Brackets in the syntax indicate optional characters and operands Syntax L og var nolog var Response Example L1 Run Stop number L1 Run Stop Number nnnnn L2 Run Stop Type RUN STOP CONT PAUSE MARK L3 Cause TIMER KEY A D n HALT INTV BATT L4 Day Date and Time ddd ddmmmyyyy hh mm ss L101 Run Log Variables L1 L4 all variable values Calibration History Variables Brackets in the syntax indicate optional characters B 28 Model 820 User Manual 9 26 97 Syntax Response C alibration var no cal var Example C1 checked level C1 Checked Level nnn n C2 Day Date and Time ddd ddmmmyyyy hh mm ss C3 Calibration Mode Manual Auto C4 Cal Status OK Bad C 101 Cal Variables 1 4 all variable values Time History Variables Brackets in the syntax indicate optional characters and operands Syn
86. ed on the options selected In this chapter we will provide information that will assist you to Determine the amount of storable data considering the given options Estimate memory usage by giving an example of a test reading and an associated chart to determine the memory needed to complete the reading Determine Storable Data The following tables indicate the amount of memory used for each type of record Exceedance Records Excd History Enable z Yes Prm66 Options add bytes shown if enabled Bytes Basic Exceedance Record 32 Excd Time Hist Yes Prm 69 1 plus number of samples 129 bytes max Save full accumulator and Count in Binary Aux Cntl Reg bit value 16 Prm 210 9 9 97 Memory Usage 9 1 Interval Records Intv History Enable Yes Prm 72 Options add bytes shown if enabled Basic Interval Record Intv Save Ln s Yes Prm 77 Intv Ln Table Aux Cntl Reg Bit Value 1 Prm 210 Daily Records Daily History Enable Yes Prm 88 Options add bytes shown if enabled Bytes Basic Daily Record 175 Save Daily Ln s Yes Prm 206 18 Daily Ln Table Aux Cntl Reg Bit Value 1 440 Prm 210 Time History Records Time History Enable Yes Prm 80 Options Hist Resolution Prm 81 Hist Save Peak Prm 82 Bytes 1 0dB No 0 1dB No 1 0dB Peak UwPk Max Wind 0 1dB Peak UwPk Max Wind Other Histories and Memory U
87. ed with flag 2 of the query command which automatically encloses the parameter and required spaces in brackets Syntax Response S et item_number indexed_parameter_text cr lf Examples 9 26 97 B 13 S9 2400 sets Baud Rate to 2400 S66 Yes sets Excd History Enable to Yes S84 1 32s sets Hist Period Units to 1 32s S84 1 0s sets Hist Period Units to 1 0s Character String Parameters To include leading spaces in a character string parame HH ter precede the character string with a gle quote or grave accent ASCII 9610 or 6016 leading sin Syntax S et litem number character string cr Response lf Example S2 ABC Acoustics sets Name to ABC Acoustics Template Parameters Date The month day and year are entered in that order and are separated by month abbreviated and year in that order Syntax The display shows day Response S et litem number mm dd yy cr If Example 22 05 23 89 sets Timer Run Date to 23May1989 _Time The hour minutes and seconds are entered in that order and are separated by Military 24 hour clock time is used i e add 12 to afternoon hours Syntax Response B 14 Model 820 User Manual 9 26 97 S et item number hh mm ss cr If Example S24 14 25 33 se
88. eighting which has the values listed here Choose one by pressing Flat Whgt F 20 W 20 Item 42 UwPk Weighting press the v again Chose from the values listed with gt Flat C Item 43 Mic Polarization was touched upon earlier Press to exit setup mode Lmax E min We have already looked at the L and Lmin in a previ ous screen These values are also available directly from display keys They can be accessed while the unit is tak ing a measurement or in the stop mode Only when the unit is running is the data recorded These measure ments are usually read after they have been taken and the measurement is stopped Here we will examine them while a measurement is being taken 10 1 97 unfiltered A16 C16 and Flat do not apply to the Model 820 F 20 means Flat plus 20 dB of level added W 20 means Weighted with 20 dB of level added Flat record all sound and C weighting simulates the human hearing at higher sound levels This selects the polarization volt age for the microphone Choose 28 or 200 V typically 200 V is cho sen for condenser type micro phones and 0 V for pre polarized microphones electret Performing a Measurement Reading the Data 5 5 Step 1 Step 2 Step 3 The same key Ex finds the Lmin values in conjunction Press Gis to display the greatest RMS SPL value since the beginning of the measurement Press the key and examine the second scre
89. en available in this series with the SHIFT key Step 1 5 6 Examine these values press these keys together and the following display will appear Model 820 User Manual The highest RMS level occurred at 9 19 hrs and was 99 2 dBA on the given date Additional screens are available here recording the num ber of times the current reading has reached predetermined levels selected in parameters 61 62 In this example parameter 61 was set to 55 dB and C weighted parameter 40 In this measure ment the RMS has topped this level 11 times The display shows that parameter 62 was set to 65 dB and is C weighted This measurement topped this level 6 times The current measurement Lmin occurred on November 27 1996 at 9 21 A M Remember the Model 820 used military time to desig nate between A M and P M That Lmin Value was 51 5 dB There are no other screens avail able from this display 10 1 97 PEAK UWPK The Model 820 also has a peak level detector Its values during the measurement or when stopped are found by pressing the key Step 1 Access Peak values Press ER Step 2 The second display available from this function is accessed by pressing the bi key Unweighted Peak UWPK has two screens available as well and are accessed with the GHIFT and keys Step 1 Press SHIFT and and examine these values for the current reading 10 1
90. ence Level The reference level is 114 0 dB SPL Frequency Weightings The available frequency weightings for the Models 820 are described in the table below Detector A Weight C Weight Flat NE RMS Vv yV Weighted Peak v Vv Unweighted Peak y vV AC Output V Vv Y DC Output V y NOTES 1 The RMS frequency weighting is selected via parame ter 40 Frequency Weighting The Weighted Peak Detector and DC Output frequency weighting always matches the RMS Detector frequency weighting 2 The Unweighted Peak Detector frequency weighting is selected via parameter 42 UWPK Weighting there fore it can be set independent of the RMS Detector fre quency weighting The Unweighted Peak Detector s typical FLAT frequency response is shown in the table below A 4 Model 820 User Manual 9 25 97 3 The AC Output frequency weighting is selected via parameter 41 AC Out Weighting It can be set to Flat weighting or it can be set to match the RMS Detector fre quency weighting The AC output s FLAT frequency response is shown in the table below Unweighted Peak FLAT Frequency Response Unweighted Peak Unweighted Peak Unweighted Peak E Nie Hz FLATWelgnting priis fe FLAT Weighting p DD Hz FLAT Weighting 10 3 4 160 0 0 2500 0 0 12 5 2 5 200 0 0 3150 0 1 16 1 7 250 0 0 4000 0 2 20 1 2 315 0 0 5000 0 2 25 0 8 400 0 0 6300 0 3 31 5 0 5 500 0 0 8000 0 4 40 0 3 630
91. ering 00 00 76 Intv Time Sync No Yes Synchronizes start of interval with clock and daily history report If Yes is entered the interval report will be started or restarted if already running at the start of each hour or minute depending on Intv duration 77 Intv Save L s No Yes Selects whether interval L s are stored The L s stored are those in effect items 55 60 at end of interval 79 Intv Auto Stop No Yes If yes automatically stops instrument at the end of each interval for precise timing of series of manual measure ments Use R S key to restart Time History 80 87 This third type of history is the most conventional The rms integrated level and if selected a maximum reading are stored in memory at the end of each time history period 8 16 Model 820 User Manual 9 30 97 Prompt HIST Enable Entry No Yes Comment Time history report will be stored if Yes is entered Despite the Model 820 s large memory ensure anticipated require ments do not exceed available memory 81 Hist Resolution 0 1dB 1 0dB Normally all data is taken with 0 1 dB resolution 2bytes level Allows storage of history with 1 dB resolution to con serve memory 1byte level 82 Hist Save Peak No Peak UWPk Lmax This option allows saving the history period s highest weighted Peak unweighted Peak UWPk or rms level Lax with each RMS
92. es y CE ERES MES i qoG5 90 10 4095 90 This means that if a person is in this area for 5 hours and 39 minutes he will have accumulated a Noise Dose of 10096 Standard ANSI 12 19 Average Sound Level L yg Itis the logarithmic average of the sound during a Measure ment Duration specific time period using the chosen Exchange Rate Factor Exposure to this sound level over the period would result in the same noise dose and the actual DI ez Calibration unsteady sound levels If the Measurement Duration is the same as the Criterion Duration then Layg LTwA LC T L 4 Lavg qLogio J 2e dt T where the Measurement Duration specified time period is T T 5 T4 and q is the Exchange Rate Factor Only sound lev els above the Threshold Level are included in the integral Standard ANSI 12 19 Adjustment of a sound or vibration measurement system so that it agrees with a reference sound or vibration source It should be done before each set of measurements Community Noise Equivalent Level CNEL Lg A rating of community noise exposure to all sources of sound that differentiates between daytime evening and nighttime noise exposure The equation for it is 0700 1900 2200 2400 Lj 10 10 L 10 Lj 5 10 Lj 10 10 L 10log 10 10 10 10 den 10 Criterion Duration T 0000 0700 1900 2200 The continuous equivalent sound level is generally calcu lated on an hourly basis and is sh
93. etters from A to Z the digits 0 to 9 and some punctua tion characters There are three levels of functions when in the Alpha Parameter Modify Mode The charts below Figures 4 1 to 4 4 show the charac ters that are available They are listed according to the number of times you consecutively press the key The shift indicator in the lower right corner of the instru ment s display will show the number of times the key has been pressed by showing the letter n and S then 2 and 3 respectively for 0 to 3 presses Figure 4 1 Standard Alpha Numeric Keyboard Layout 9 10 97 Quick Start This panel is available without pressing the shift key or the equiv alent of 0 presses 4 3 This panel is accessed by pressing the shift key one time The S will appear in the lower right corner of the display indicating this panel is accessed This panel is accessed by pressing the shift key two times The num ber 2 appears in the lower right corner of the display indicating this panel is accessed This final panel is accessed by pressing the shift key three times The number 3 appears in the lower right corner of the display indicating this panel is accessed Figure 4 4 3 Shift Level 3 Alpha numeric Keyboard 4 4 Model 820 User Manual 9 10 97 Step 1 To enter a name for example turn the Model All but the last of these screens you 820 on and press these keys to access the first have seen before This display is to
94. evel or press y enter the desired dB numerically and press Enter The Current Dose is often used as a second Dose mea surement The collected data is available on the printout The Overall Dose parameters have the same available set tings as the current settings and are accessed in the same way Step 4 To access items 48 50 Overall Exchange Rate Overall Threshold Overall Criterion press the v key Full Dose Hours item 51 has a range of 0 to 99 hours but is normally set to an 8 hour workday Step 5 To access Full Dose Hours press the E key Parameters 52 54 are a second set used to calculate over all dose from the overall data Data already in memory is recalculated with new parameters using LDL log Data Logic Step 6 To look at DOSE press 58 Step 7 To look at Projected Dose press to the PROJ b screen Step8 If you wish to alter the LDL Exchange Thresh old or Criterion settings press enter the desired values and press Enter Step 9 To look at LDL press SHIFT and 48 10 1 97 Damage to hearing normally occurs with lengthy exposure to sound at 90 dB and above For this reason the Criterion is generally set at 90 dB Changes can be made in any dis play by pressing Modify entering desired values and pressing Enter The overall criterion level set in item 50 and the dose hours set in item 51 determine what is 100 dose OSHA criterion is 90 dB Thresh old i
95. f all parameter items and an explanation of their basic functions Chapter 9 Memory Usage Sizing parameter needs to insure adequate memory for any given measurement Chapter 10 Printing a Report Turning gathered data into a printed report Appendix A Specifications A listing of acoustic elec tronic environmental and physical characteristics of the Model 820 Appendix B Model 820 Serial Port Interface Remote Con trol Setting interface commands with their syntax Appendix C Glossary Definitions of key terms and concepts used in this manual 1 2 Model 820 User Manual 10 1 97 e Appendix D Index Alphabetical listing of all major components of this manual About This Chapter Specifically this introductory chapter covers the follow ing topics e Formatting Conventions Explanation of the fonts and other formatting conventions used in this manual e Model 820 Features A listing of the featured character istic and capabilities of the Model 820 e Model 820 Components Description and diagrams of the Model 820 external parts e Getting Started Instructions for unpacking a listing of accessories and optional equipment and initial setup Formatting Conventions This manual uses the following formatting conventions Functions accessed by pressing a key on the Model 820 keypad are shown with an icon for example Press and then press In step by step directions the process wh
96. from normal setup parameters P1 Data Report P2 Data amp Histograms Short Full Report Histories with SHORT option Long Full Report Histories with LONG option All Report Enables Turned OFF Begin Printing a Report Begin Printing using RXD as Hardware Handshake flow control X 100 Abort Printing XMODEM Begin Printing same as P100 except through the XMODEM communication protocol X X CANcel transfer mode 2 in a row ASCII CAN or CHR 24 Error Messages and Warnings The code listed is the number provided by R98 All error messages begin with CHR 7 ERROR Error Code Message COUNT OVERFLOW EXPONENTIAL OVERFLOW RTX TASK SELECT ILLEGAL EXCHANGE RATE UNKNOWN INTERRUPT WATCHDOG RESET OPCODE ERROR All warning messages begin with CHR 7 WARN ING 9 26 97 B 31 Add 128 to these numbers to get the actual warning number Warning Message Code 128 Out of Memory 129 Battery Low 130 POWER FAILURE 131 DIVISION BY ZERO 132 Operand 1 Range 133 Operand 2 Range 134 DPC Format 135 Key Has No Effect 136 Stop Required 137 Key Has No Effect In VIEW 138 Parameter Entered Wrong 139 RESET ALL Required 140 Use ARROWS ON to Exit 141 Use NEXT PREV or
97. hange rate for overall TWA Exchange Rate 2 or Dose readings 49 Overall O to 255 dB Levels above threshold are inte Threshold 2 grated into overall TWA or Dose readings 50 Overall O to 255 dB 100 dose if this level is main Criterion 2 tained for full dose period Dose 51 The noise exposure Dose may be calculated with three different set of parameters CURRENT OVERALL and LDL See section on occupational noise for additional information The dose displayed with the DOSE key is Dose 2 No Prompt Entry 8 12 Model 820 User Manual Comment 9 30 97 51 Full Dose Hours 0 99 This is normally set to 8 for an 8 hour workday It is used with the criterion level to determine a 10096 projected dose 52 LDL Exchange 3dB 4dB 5dB 6dB Use LDL function to reevaluate stored data with new dose parameters 53 LDL Threshold 0 255 dB 54 LDL Criterion 0 255 dB L Statistical Levels 55 60 Lan is the rms noise level which was exceeded nn of the time The L s are computed from the overall level distribution histogram or each interval s level histogram see item 77 The measured and displayed Lan may be changed during the measurement The six nn are auto matically listed in increasing order No Prompt Entry Comment 55 Lin 1 Percent O to 99 56 Lin 2 Percent O to 99 57 Lin 3 Percent 0 to 99 58 Lin 4 Percent 0 to 99
98. he choices are enabled Note Be sure that total Yes No Press the 3 to access the next parameter 73 Into Exchange Rate for these choices 3dB 4dB 5dB 6dB Press the Y to item 74 Into Threshold You may find 80 dB preset but you may enter another value 0 255 Press the 3 to item 75 Into Period Press and the numeric values for the interval period desired and then press Enter hh mm Press the v to Into Time Sync item 76 for these choices Yes No Press the v to item 77 Intv Save L s The Choices are Yes No Model 820 User Manual memory requirements do not exceed available memory This parameter is the exchange rate used for each interval Set this to 3 dB for community noise and 5 dB for OSHA studies This sets the TWA threshold for the interval time history For hear ing conservation purposes 80 dB is recommended For most commu nity noise purposes set this parameter to 0 or slightly above the noise floor This sets the period for the interval history A 1 second Interval may be selected by entering 00 00 The Model 820 allows synchroniz ing the interval report with the Daily History Report If Yes is entered the Interval Report will be started or restarted if already run ning at the start of each hour For this to work properly the Interval Time should be one hour or some multiples of hours The benefit of synchronizing the hourly levels and the inter
99. he plane of the microphone diaphragm when using a free field microphone e g 2540 or 2541 in a free field The micro phone should be pointed directly at the source A 2 Model 820 User Manual 9 25 97 When using a random incident microphone in a free field the microphone should be pointed 80 degrees off axis of the source of the sound When in a random sound field a random incident microphone 2559 or 2560 may be pointed in any direc tion Measurement Ranges RMS Detector Dynamic Range gt 110 0 dB Primary Indicator Range gt 105 0 dB The instrument will have a different Noise Floor Lower Limit and Overload Level depending on the sensitivity of the microphone used Some typical values for 2 dif ferent Larson Davis microphones are listed in the table below The data in the above table was obtained by electrically testing a number of instruments For all electrical tests the microphone was replaced with an equivalent electri cal impedance LarsoneDavis ADP005 microphone adapter Other Detectors Weighted Peak Detector 85 0 dB 9 25 97 Max Level for A Weight C Weight moe Overload Pulses of Microphone Noise Floor Noise Floor Cower Dimis Level L hen eU Crest Factor dBSPL dBSPL dBSPL 10 dBSPL 2541 17 5 16 5 23 5 130 0 133 0 112 0 2559 29 0 28 0 35 0 141 5 144 5 123 5 A 3 Unweighted Peak Detector 38 0 dB e AC Output 88 0 dB e DC Output 105 0 dB Refer
100. herefore you should verify that the remaining battery capacity is sufficient before you make an especially critical or lengthy mea surement 2 10 Model 820 User Manual This screen will remain until the user inputs other commands The flashing uppercase S indicates system initiation and will con tinue 10 45 seconds When the system initiation is com plete a stick figure in the upper right corner of the display will appear seated indicating the Model 820 is in STOP mode Do not press the key during a measurement since it will pause the measurement while pressed 10 1 97 Step 1 To manually check battery voltage simply press the SHIFT keys Information similar to the following will display Turning Off the Model 820 To turn off the Model 820 simply press the GHIFT 9 key 10 1 97 Overview to Model 820 Remember pushing a button can produce small low level noises which can affect your readings In addition the Model 820 momen tarily pauses the current measure ment whenever a key is pressed in order to interpret the keyboard event Therefore where possible do not press the key during a valid event you wish to measure The first screen a displays the percentage of power left in the bat tery an internal power source INT or indicates external power is being used EXTV The second screen b gives revi sion number and date The instrument will not allow itself to be turned off
101. history sample 83 Hist Period 1 255 units Multiplier of units of time in parameter 84 sets rate at which history samples are stored Ex 1 x 60 0s for minute by minute history 16 x 1 32s for 0 5 second history 84 Hist Per Units 1 32s 1 0s 10 0s 60 0s Note The rms detector is sam pled 32 times s These sam ples are averaged into an integrated sound level Leq stored every time history period 85 Hist Base 0 255 dB This is for editing purposes only All history is stored regardless of this base level However only noise data above the base level are displayed on the screen 86 Hist Base Mode Off RMS Peak Type of noise data used by the base mode 9 30 97 Parameters 8 17 87 Hist Resolution 1 8 1 2 1 0 2 0 Selects the interval in dB of the 5 0 10 overall time level amplitude distribution 88 Daily Enable No Yes Yes to store daily data such as Lan CNEL Leg and back ground level This option pro vides the storage of 24 hourly noise levels for each one of these quantities when interval duration is 1 hour and Intv Time Sync Yes Print Options 89 112 These parameters allow for tailored reports of LDL Model 820 data during or after the measurement They can be accessed from outside the SETUP by pressing air then 7 for printer type and options Refer to section on printouts for samples of informat
102. ia phragm is covered by a protective grid which should not be removed in normal use Rain droplets or other foreign matter on the dia phragm may alter the micro phones s response Please use a windscreen whenever possible Using cable CBL038 or INT002 and related software the 5 pin connector is used both for external power and for the remote interface 10 1 97 Block Diagram All the standard functions of a precision sound level meter are provided instantaneous level Leg SEL Lmax Lmin dose projected dose etc In addition many valu able parameters can be stored time history interval data such as L s and Leg exceedance and exceedance time history etc Level calibration is performed in a few key strokes and every change or check is entered in a cali bration log The Model 820 s large data memory relieves the user from the concern of data loss caused by memory limita tions Furthermore measurements can be printed or transmitted at up to 19 2 K baud via RS 232 for further manipulation or archiving Despite its numerous functions the Model 820 is easy to use Annotated displays indicate units and measurement mode The single setup menu lets the user scroll through and program parameters or use an index key to modify specific information Multiple measurement setups can be stored in memory for later recall And of course com plete setups can also be transferred from a computer 10 1 97 Introduction 1 9
103. ic time period The Sound Pressure C 14 equation for it is T 2 f p t dt SEL 10Log 0 ua Pol The sound pressure is squared and integrated over a specific period of time T2 T this is called the sound exposure and has the units Pascal squared seconds or Pascal squared hours PO is the reference pressure of 20 uPa and T is the ref erence time of 1 second It is then put into logarithmic form It is important to note that it is not an average since the refer ence time is not the same as the integration time The physical characteristic of sound that can be detected by microphones Not all pressure signals detected by a micro phone are sound e g wind noise It is the amplitude of the oscillating sound pressure and is measured in Pascals Pa Newtons per square meter which is a metric equivalent of pounds per square inch To measure sound the oscillating pressure must be separated from the steady barometric pressure with a detector The detector takes out the steady pressure so only the oscillating pressure remains It then squares the pressure takes the time average and then takes Model 820 User Manual 10 14 97 the square root this is called rms for root mean square There are several ways this can be done Moving Average The averaging process is continually accept ing new data so it is similar to an exponential moving aver age The equation for it is The sound pressure is squared and multiplied by
104. inting Normal Printout Parameters Before proceeding with printing baud rate needs to be determined and entered Set parameter 9 to proper baud rate determined by type of printer used If after starting printing bad information is printed baud rate or printer type is probably set incorrectly To cancel printing hit SHIFT and E Normal printouts can be accessed from outside the SETUP mode by following these steps Step 1 Turn the Model 820 on and press air The fol lowing display will appear briefly and then scroll automatically through several options ae 9 25 97 Printing a Report 10 1 Step2 To tailor your report and select the printer type and options press 7 and the following screen will appear There are several options here which include HPJet HPLzr ASCII Epson IBM Step 3 You can change the printer selection by press ing the key and then Q to the printer you will use and press Enter Step 4 Press the v key to the next display item 89 duplicated here as item 177 the beginning of the parameters that manage printouts Step 5 Scroll through these parameters with the 3 key and make your selections Press to access the appropriate choice and press Enter Printing Reports Printing reports is easy as connecting your Model 820 to a printer and pressing a key Using the CBL033 serial printer cable connect your serial printer to the Model 820 at
105. ion found on each printout No Prompt Entry Comment 89 Prn Data Report No Yes Prints quick data report 90 R S and Cal Log No Yes Prints Run Stop and calibra tion log report 91 Setup Report No Yes Prints list of current setup parameters 92 RMS Histogram No Yes Prints histogram of overall rms levels 93 Lowest Level 0 255 RMS Histogram lowest printed level 94 Highest Level 0 255 RMS Histogram highest printed level 95 Histogram Resl 1 8 1 2 Spacing in dB between histo 1 0 2 0 5 0 10 gram entries 8 18 Model 820 User Manual 9 30 97 96 Peak Histogram No Yes Prints histogram of overall peak levels 97 Lowest Level 0 255 Peak Histogram lowest printed level 98 Highest Level 0 255 Peak Histogram highest printed level 99 Histogram Resl 1 0 2 0 5 0 10 Spacing in dB between histo gram entries 100 UwPk Histogram No Yes Prints histogram of overall unweighted peak levels 101 Lowest Level 0 255 UWPk Histogram lowest printed level 102 Highest Level 0 255 UWPk Histogram highest printed level 103 Histogram Resl 1 0 2 0 5 0 10 Spacing in dB between histo gram entries 104 EXCD Report No Short Long Prints exceedance report 105 Lowest Rec 0 65535 Starting exceedance record number of printout 106 Highest Rec O 65535 Ending exceedance record num
106. is not possible to directly add or sub C 3 tract physical quantities when expressed in decibel form The word level is always attached to a physical quantity when it is expressed in decibels for example L represents the sound pressure level The table below shows the actual value of a specific item such as sound pressure for which the level is to be determined First the value is put into expo nential form in powers of ten the exponent is the Bel The exponent is then multiplied by ten to yield the decibel This procedure converts multiplication into addition every time 10 is added to the level the value is multiplied by 10 When the value is not a even multiple of ten the exponent is more com plicated as shown in the table Every time the level increases by 3 dB the value is multiplied by 2 doubled These two rules are worth remembering Linear form Level form Exponential Form 10 Exponent Ration of Value to Reference of Ratio 1 10 0 10 10 10 100 10 20 200 10 23 1000 10 30 10000 10 40 100000 10 50 1000000 10 60 The definition of decibel is intended for power like quanti ties W Sometimes power is represented by the square of a measured quantity and this results in a different form of the equation See Sound Pressure Level L 10 pe loLogo y W W10 0 The value of the item in the table is not the value of the quan tity itself but the ratio of that quantity to a reference qua
107. isplay digital A 9 Dose 5 9 key 2 7 projected 5 13 DSP80 Index 1 Components 1 7 Duration measurement C 9 Dynamic range 1 4 E EEPROM 8 6 Register 8 5 Enter changing parameters 8 3 key 2 4 Environment 1 16 effects of Temperature A 6 Equivalent Level See Leq 2 6 Error B 31 messages and warnings 8 4 B 31 Error Checking I O B22 Exceedance 8 14 diagram 7 10 key 2 4 parameters 7 8 Exceedance History 8 14 Exchange Rate 8 12 glossary C 5 Exchange Rate Factor glossary C 5 Exposure Factor glossary C 5 F Far Field C 6 acoustic C 6 geometric C 6 Features 1 4 Model 820 1 4 Formatting 1 3 conventions 1 3 Free field C 6 Frequency band pass filter C 7 glossary C 6 Hz rad sec C 7 Frequency Weightings Index 2 specifications A 4 Frequency weightings 1 5 Functions additional system 8 20 history 7 1 setting and viewing 7 1 time history 7 2 Functons passby 7 12 G Glossary App D 1 2 H Histogram variables B 29 Histogram Reports B 19 History commands B 4 Exceedance 8 14 History Functions Chapter 7 7 1 Interval 8 15 key 2 4 records B 23 Time 8 16 History Functions Model 820 1 2 Hysteresis 8 14 I O Error Checking B 22 Impulse 5 4 indexed B 13 Indexed Parameters B 13 Interal key 2 4 interface 8 6 International Electrotechnical Commission IEC 1 4 Interval History 8 15 parameter settings 7 5 Interval Variables B 26 Intrusion alarm B 16 arrows 2 7 BATT 2 6 Blue 2 3 CAL 2
108. its bottom port Let s look at the print options again 10 2 Model 820 User Manual Items 89 113 allow you to select the reports which are to be printed and how the output data are to be configured Items 89 113 are copied sequen tially into items 177 201 for print ing tailored reports and may be edited directly for one printing and then they will revert to set tings entered in parameters 89 113 For a complete list of Print Options see Chapter 8 page 21 9 25 97 Step 1 Turn the Model 820 on and press air The dis play will begin to scroll through the various print options available Here are some of the Screens You will notice that the scroll is quite rapid To slow it down so you can study the options use the a or x keys and the display will remain for five seconds before returning to automatic scroll This option allows you to access the printer setup status This option will return you to the Printout Parameters and will start with the printer type selection The v key will access item 89 of the Printout Parameters This option allows you to tailor your own report changing the set tings of parameter items 89 113 but imputting the entries in items 177 201 After the printout is complete the values will revert back to factory settings Step 2 Press the key until you find the Exceedance History report screen The brackets contain the command that will
109. ives peak and unweighted peak levels INTV f h gives statistical infor mation 7 7 Exceedance Exceedance is defined as an acoustic event characterized by the sound level going above or exceeding a predeter mined level An exceedance event requires the following to occur The SPL must be above the RMS EXCD LVL 1 parameter 61 or the weighted peak level must be above the PEAK EXCD LEVEL parameter 63 or the unweighted peak level must be above the UWPK EXCD LEVEL parameter 64 and must be true for longer than the minimum duration parameter 68 An exceedance count on the other hand is obtained whenever the level goes above RMS EXCD LVL 1 RMS EXCD LVL 2 PEAK EXCD LVEL and UWPK EXCD LEVEL and are indicated on the printout respectively This count has nothing to do with duration but only indicates the number of times the level went above the various exceedance levels Exceedance Level parameters are used to define the noise threshold levels to be used when counting the number of Exceedance during a measurement The num ber of times the four levels were exceeded will be given in the data report To find the Exceedance parameters items 61 65 turn the Model 820 on and follow these steps Step 1 Press the Notice the available settings 0 to 255 dB for items 61 64 e 61 RMS Excd Lvl 1 First RMS detector exceedance level e 62 RMS Excd Lvl 2 Set above Level 1 7 8 Model 820 User Manual 9
110. lear the field press SHIFT twice to access the 2 chart and press the Clear key h To replace a character with a Space press SHIFT twice to access the 2 field and press the Space key Step 6 When the first line is completed press the v to go to the next field the second line Step 7 Press and select the appropriate chart by pressing GHIFT and the desired character key Step 8 When the second line is complete press the to go to the next field the third line and repeat the process Step 9 The fourth line is for the Measurement Title Press the v key Step 10 To exit the setup mode press 4 6 Model 820 User Manual A 3 will appear for five seconds The letters from the 3 panel are available for entry The display in Step 1 above will appear If you change your mind about clearing the field hit to return to the original title Repeat a and b in Step 5 to return to this point Enter the L key second from the lower left The cursor will auto matically move to the next letter Enter the A key Enter the R S O keys consecu tively or one at a time Complete the rest of the entries in the same fashion Three lines are available for entry i e company address telephone The first fourth lines appear on screen when the 820 is turned on 9 10 97 Setting Time Date and Day parameters Once you have set the parameters you can now enter the correct time and date The Model 820 has a
111. mand When the Model 820 is RUNNING the Valid condition will remain in effect for 1 second The LDLVALID Read Command provides three responses LDL Valid Calculating and LDL Invalid NOTE The exceedance Leq R68 and exceedance time R69 include data from qualified events that are stored in the EXCD History If an event is discarded because it was shorter than the minimum duration then it will not be included in these values R70 _BGLEQ Background Leq nnn n dB R 71 85 unused unused variable R86 _BATT Battery Level nnn R87 _BATTSRC Battery Source INT EXT ccc R88 TEMP Temperature nnn n R89 _SERNUM Serial Number cecce R 90 _REVNUM Software Rev amp Rev Date n nnn ddmmmyyyy R91 _FREEMEM Free Memory nnnnnnn R92 _RECLOG Number of RUN STOP Records nnnnn R93 _RECEXCD Number of EXCD Records nnnnn B 8 Model 820 User Manual 9 26 97 R94 _RECINTV Number of INTV Records nnnnn R95 _RECHIST Number of HIST Records nnnnn R 96 _RECDALY Number of Daily Records nnnnn R97 RECCAL Number of Daily Records nnnnn R 98 n _ERRMSG Error Message List ececececececececececee n is the error list number 1 8 1 being latest error or nnn nnn nnn if n 0 or omitted then the 8 error codes are output as number R99 _LOGIC1 Logic Output 1 State On Off unused R 100 _LOGIC2 Logic Output 2 State On Off unused R 1
112. me up to 30 charac ters Place any message you desire in these 3 lines The 3 lines of name are savable only in EEPROM Title up to 30 charac ters Used to describe a measure ment or setup Current Time hh mm ss also accessed w SHIFT Current Date mm dd yy Leap years are considered For years less than the year manu factured the 21st century is assumed 2000 2092 other wise the 20th century is used 1993 1999 Day of Week Sun Sat Baud Rate 300 19200 Baud rate of the serial inter face Serial printer or com puter rate should be the same 10 RS 232 Address 0 127 Enables addressed communi cation mode for a network of LeD SLMs Each must have a unique address Normally only one Model 820 is used thus the address should be set to O to disable 12 COM Ports Hand shaking Register None Hdwr XOFF Both Serial handshaking protocol Model 820 SW1 uses None Note To conserve power the Model 820 turns off the serial port after 255 sec of nor use To keep unit on and connected an external power supply must be used 9 30 97 8 7 Parameters 14 Output 1 Logic Off True takes it to 5 volts When set to Off DTR is DTR RMS R PEAK P R P INTV D Indication that Interval started and will stay on time set in parameter 15 R I P I R P I A D Logic control including A are
113. mmands may be spelled out though only the first character is sig nificant ie READ 123 may be abbreviated to R123 Every command has a response to acknowledge that it was received correctly and to provide data requested For high reliability systems there is an error checking protocol that is added to ensure proper command data transferal See Error Checking Protocol on page 34 The following tables summarize all of the commands and are listed in this order mode control commands first parameter commands next data extraction com mand and report data download command last 9 26 97 The following instruments are compatible on a common network Models 712 720 812 820 870 and TAC100 Future instruments may also be compatible with this network B 3 Square brackets indicate optional characters or operands Syntax Response R ead variable number 0 operand 2 variable value S et parameter number parameter value acknowledge S et parameter number fixed parameter index acknowledge S et parameter number fixed parameter prompt Thursday acknowledge i e Set 8 Thu will set day of week to Qluery parameter number 0 option flags parameter value Option flags may be added for combined effect 32 Index Number 8 Tab over response 2 print in braces 1 Print parameter name K ey key simulation string acknowledge M ode mode number acknowle
114. n Bytes 0 1dB No 1 0dB Peak UwPk Max Wind 0 1dB Peak UwPk Max Wind TOTAL bytes Hist Record Select the appropriate of bytes from lines 16 19 Hist Records Day 24 hours divided by Hist Period in hours Enter Number Calculate i e 24 60 sec 3600 sec per hour 1440 TOTAL Hist Bytes Day Memory Use per Day Calculation Exceedance History bytes day Multiply lines 23 and 24 copy copy to 29 from line 5 Interval History bytes day from line 11 Daily History bytes day Time History bytes day from line 15 from line 22 Run Log bytes day n number of Run Log records day 2 nx20 X 20 n x 20 bytes record Calibration Log bytes day Setup RAM Registers bytes used n number of registers stored day 1 nx17 X 17 nx 17 bytes record 0 nx506 n x 506 bytes record TOTAL bytes used day Sum lines 23 29 20898 Model 820 s Memory Size 252661 See SYSTEM b 251 805 TOTAL Run Time in days until out of memory Divide line 34 by 33 Memory Usage 12 05 9 5 9 6 Model 820 User Manual 9 9 97 C HAPTER Printing a Report The Model 820 allows for tailored reports of data during and after measurements In this chapter we will access the printing option parameters for the following topics Normal Printouts Printing Reports Real time Pr
115. nd over the Criterion Duration that contains the same sound energy as the actual unsteady sound over a specific period The period is gener ally shorter so the sound energy is spread out over the Crite rion Duration period Example If the Criterion Duration 8 hours and the specific period is 4 hours and the average level during the 4 hours is 86 dB then the Lgp 4 83 dB Day Night Average Sound Level DNL Lan A rating of community noise exposure to all Decibel dB 10 14 97 sources of sound that differentiates between daytime and nighttime noise exposure The equation for it is 0700 2200 2400 L 10 10 L 10 L 10 10 Lj WL08 49 10 10 10 0000 0700 2200 The continuous equivalent sound level See definition is generally calculated on an hourly basis and is shown in the equation as L The values for the hourly periods from mid night to 7 a m have 10 added to them to represent less toler ance for noise during sleeping hours The same occurs from 10 p m to midnight They are energy summed and con verted to an average noise exposure rating A logarithmic form of any measured physical quantity typi cally used in sound and vibration measurements Whenever the word level is used it implies this logarithmic form The relationship is relatively simple but the mathematics can become complex It is widely used and was developed so that the very wide range of any quantity could be repre sented more simply It
116. ng the Model 820 Screen The operating screen for the Model 820 has several fields which vary according to the keys pressed on the keypad The most pertinent information is generally at the top and center to left and instructions are generally on the bottom center to left Several characters are consistent in their appearance We will now turn the Model 820 on and examine a variety of possible screens Turning On the Model 820 Step 1 Press to power the Model 820 and initiate a self test Step2 The next display automatically appears 10 1 97 Overview to Model 820 Three successive displays will appear while the meter stabilizes for 10 45 seconds The first display has copyright information and appears only 1 to 2 seconds The second display shows the pro duction date and the serial number uniquely assigned to your Model 820 This message appears for only 1 or 2 seconds 2 9 Step 3 The third screen automatically appears The third screen appears almost immediately showing the title information for the current or last reading and is programmable by the operator At this point you can change the parameters and begin taking actual measurements Checking the Battery Voltage The Model 820 continuously monitors its battery voltage to ensure accurate measurements It has a battery life of about sixteen hours It will turn off automatically when the voltage falls below 5 7 volts T
117. ntity So for every level in decibels there must be a reference quan tity When the quantity equals the reference quantity the level is zero To keep the values above zero the reference is generally set to be the lowest value of the quantity Department of Defense Level Lpop The Average Sound Level calculated in accordance with Department of Defense Exchange Rate and Threshold Level See Average Sound Level C 4 Model 820 User Manual 10 14 97 Dose See Noise Dose Detector The part of a sound level meter that converts the actual fluc tuating sound or vibration signal from the microphone to one that indicates its amplitude It first squares the signal then averages it in accordance with the time weighting char acteristic and then takes the square root This results in an amplitude described as rms root mean square Eight Hour Time Weighted Average Sound Level L ya s It is the constant sound level that would expose a person to the same Noise Dose as the actual unsteady sound levels The equation for it is D Lrwacs Let gL0810 755 NOTE This definition applies only for a Criterion Duration of 8 hours Standard ANSI 12 19 Energy Equivalent Sound Level Leg The level of a constant sound over a specific time period that has the same sound energy as the actual unsteady sound over the same period fr oat E 1 Lo 10Lo03 19 gt e 2 DT where p is the sound pressure and the Measurement Dura tion s
118. of the DOSE a display The for mula used is E T 10 Leq 10 20uPa where E is the Exposure T is the elapsed time in hours and 20uPa is the reference sound pressure 20 micro pas cal squared R 163 _TAKTS Takt Maximal 3 Second nnn n dB R 164 _TAKT5 Takt Maximal 5 Second nnn n dB Group Read Programming Code Description Response O1 Read SLM data nnn n nnn n nnn n nnn n lt CR gt lt LF gt R 4 SPL R 11 TWA R 17 Lmin R 21 Lmax lt CR gt lt LF gt O2 unused unused variable o3 Read Group of R variables pro grammed by G n r O4 Read 820 s LCD Display each line separated by lt LF gt The group read command G0 and the Olther 3 com mand return the values of a list of up to 8 read variables previously defined by the programmer Syntax Response GO or 03 cr values of variables separated by commas 9 26 97 In order to define the variables read by group read com mands use the following command for each desired read variable G roup n var no cr If Syntax Response Where n is from 1 to 8 indicating the group list index and var no is the number of the R variable associated with the index Use var no of 0 to define the last group list index when n lt 8 Example Gl 4cr assigns the current SPL to the first group index G2 15 cr assigns Lmin to the second index G3 19 cr assigns Lmax to the third index G
119. op Date 2 Day Run Time 1 to Stop Time1 and Run Time 2 to Stop Time 2 each day from Run Date to Stop Date If the date is incorrect simply press and enter the correct data then press Enter 9 24 97 Step 7 To change the date press and enter the 5 day ending date i e October 1 i e 01 MO 06 and the following display will appear The five day block is now set Next we will set the time periods each day within the block Step 8 Press the v to Run Time 1 and press Modify Our start up time is 8 30 A M so press 08 BO and Enter and the display should look like this Step 9 Press the to Stop Time 1 Press to enter the numbers 12 OO and then press Enter Step 10 Press the v to Run Time 2 Press to enter Notice that military time is used D 8 00 our afternoon start time Press 0 01 24 00 to avoid confusion Enter A M to P M Step 11 Press the v to Stop Time 2 Press to enter 106 O and Enter 9 24 97 Timed Measurement 6 3 Step 12 To check your Timer setup press This will return you to the main screen Press SHIFT and the following screen should appear Step 13 If you press the V key it will give you the morning time run If you press the M again it will give you the afternoon time run settings The Model 820 can now be turned off by pressing and placed in the test area Make sure to check the battery Chapter 2 or
120. ophone for free field or random incidence to minimize the influence of orientation A microphone influences the sound being measured The micro phone measures very small forces low level sound can run about one billionth of a PSI Every measurement instrument changes the thing being measured and for very small forces that effect can be significant When sound impinges directly on a microphone the incident wave must be reflected since it cannot pass through the microphone This results in the extra Model 820 User Manual 10 14 97 Near Field 10 14 97 force required to reflect the sound and a microphone output that is higher than would exist if the microphone were not there This is more important at high frequencies and when the microphone is facing the sound source Rules 1 Do not use a microphone at frequencies higher than speci fied by the manufacturer to increase the frequency response choose smaller microphones 2 Choose a microphone for free field or random incidence to minimize the influence of orientation A microphone measures what is there from any direction Most measurements are intended to measure the sound level of a specific source but most microphones are not directional so they measure whatever is there regardless of source Rules 1 When making hand held measurements keep your body at right angles to the direction of the sound you are inter ested in and hold the meter as far from your body as possi ble
121. or operated above 60 C or below 20 C Condensation of moisture will make readings inaccurate but will be correct when moisture has dissipated Microphone Extension Cables When measuring signals below 20 kHz up to a 12 foot microphone extension cable may be used with the Model 820 A 6 Model 820 User Manual 9 25 97 Positioning of Instrument and Observer for Best Measurements Measurements can be made with the Model 820 held in one hand with the arm extended away from the body however better measurements can be made with the Model 820 placed on a tripod AC and DC Outputs The output impedance is 600 Q for both the AC and DC outputs of the Model 820 For minimal error use instru ments with 100 k input impedance when making AC or DC output readings AC Output Output Impedance 600 Gain 0 dB or 20 dB User Selectable Measurement Range 88 0 dB DC Output Output Impedance 600 Q e Scale 20 mV dB Measurement Range 105 0 dB Voltage Range 0 to 3 volts e Temperature Coefficient 936 uV C 9 25 97 Reference Frequency The reference frequency is 1000 Hz Stabilization Time The Model 820 will not proceed to a running condition until it is allowed to stabilize At power on with the polarization voltage set to 200V or 28V the stabilization time is approximately 45 seconds With the polarization voltage set to OV the stabilization time is approximately 10 seconds A shorter stabiliza
122. ose as the actual unsteady sound over the same period If the Exchange Rate is 3 dB then the TWA is equal to the Leg T 1 Lrwa rc Klo810 FJ T LDK y where T T gt T and K is the Exchange Rate Factor It is used for hearing damage risk assessment Standard ANSI S12 19 The response speed of the detector in a sound level meter There are several speeds used Slow The time constant is 1 second 1000 ms This is the slowest and is commonly used in environmental noise mea surements Fast The time constant is 1 8 second 125 ms This is a less commonly used weighting but will detect changes in sound level more rapidly Impulse The time constant is 35ms for the rise and 1 5 sec onds 1500 ms for the decay The reason for the double con stant is to allow the very short signal to be captured and displayed The oscillatory movement of a mechanical system generally taken to be solid It is used as a broad desciptor of oscilla tions The distance between peaks of a propagating wave with a well defined frequency It is related to the frequency through the following equation h f where c is the sound speed and f is the frequency in Hz It has the dimensions of length Model 820 User Manual 10 14 97 Wavenumber k A number that is related to the wavelength of sound and is used to compare the size of objects relative to the wavelength or the time delay in sound propagation It is related to wave length
123. ose measurement based on data collected from that time on Before we continue with our present measurement take a minute to examine the parameter values available all of which will effect the measurement The Current Exchange Rate parameter item 45 is quickly accessed by following the following steps Press 40 cette Modify and 6 then Enter The choices here are listed below Step 1 3dB 4d B 5dB 6dB The Current Threshold item 46 has a range from 0 to 255 dB Step 2 Press the v key and choose the desired dB level for the Current Threshold Larsone Davis has preset this parameter to 80 dB The Current Criterion is the next parameter item 47 and has been preset to 90 dB in a range of 0 to 255 dB 5 10 Model 820 User Manual The appropriate value for this parameter is established by enforcement authorities in various countries In the USA OSHA mandates a 5 dB exchange rate 3 dB is common in most other coun tries Note that these can be changed without a Reset all The normal Dose setting for threshold is 80 dB which allows the instrument to virtually ignore sound below that level as it does not contribute significantly to the weight of the measurement data sought and saves memory as well If you wish to change this level press Modify enter the desired dB numerically and press Enter 10 1 97 Step 3 Press the v key item 47 Press if you wish to keep the 90 dB l
124. ot stable enough for proper cali bration the Model 820 will exit the calibration mode without changing its calibration level The c indicates the instrument is calibrating The Model 820 will wait until the reading is stable indicator is SsSsSs then adjust the offset for the proper reading CcCcCc An improper calibration offset for instance something greater than 34 0 dB may indicate that the cal ibration tone was shut off before calibration was completed or that polarization was not properly set You may repeat the previous steps or perform a Cal check The display will ask if you want to Reset ALL Data You do 9 30 97 C HAPTER Quick Start Before running a simple measurement it is important to set a few parameters to meet your needs and become familiar with related functions In this chapter we will discuss these items Setting parameters using Xi and Using numbers and other characters e Setting Time Date and Day parameters 8 yp Setting Parameters Using Function Keys The Parameter fields can be accessed in several ways By entering numbers assigned to each parameter the numbers are located above the keys on the keypad and are discussed later in the chapter By scrolling up or down using the A or x keys Byusing any white or blue function keys Follow these steps to access the parameters using numeric values 9 10 97 Quick Start 4 1 Step 1 Step 2 Step 3
125. ower It is also expressed by Sound Speed cj attachment of the word decibel to the number The logarithm is taken of the ratio of the actual sound power to a reference sound power which is 1 pico watt Sound power level can not be measured directly but can only be deduced through measurements of sound intensity or sound pressure around the source The equation for it is W L 10 i 10108 yy W W 10 0 The speed at which sound waves propagate It is measured in meters per second It should not be confused with sound or particle velocity which relates to the physical motion of the medium itself c 20 05 4degC 273 m sec c 49 03 degF 460 ft sec Spectrum Frequency Spectrum The amplitude of sound or vibration at various frequen Threshold Sound Level Lt 10 14 97 cies It is given by a set of numbers that describe the ampli tude at each frequency or band of frequencies It is often prefixed with a descriptor that identifies it such as sound pressure spectrum It is generally expressed as a spectrum level The A weighted sound level below which the sound pro duces little or no Noise Dose accumulation and may be dis regarded It is used for hearing damage risk assessment Standard ANSI 1 25 C 17 Time Weighted Average Sound Level TWA Lrwacrcy It is the level of a constant sound Time Weighting Vibration Wavelength 1 over the Criterion Duration that would expose a person to the same Noise D
126. own in the equation as L The levels for the hourly periods from midnight to 7 a m have 10 added to them to represent less tolerance for noise during sleeping hours The same occurs from 10 p m to mid night The levels for the hourly periods between 7 p m and 10 p m have 5 added to them to represent a lessened toler ance for noise during evening activities They are energy summed and converted to an average noise exposure rating Itis the time required for a constant sound level equal to the Criterion Level to produce a Noise Dose of 100 Criterion Duration is typically 8 hours Example If the Criterion Level 90 dB and the Criterion Duration is 8 hours then a sound level of 90 dB for 8 hours will produce a 100 Noise Dose See Noise Dose Standard ANSI 12 19 Criterion Sound Exposure CSE The product of the Criterion Duration and the mean C 2 square sound pressure associated with the Criterion Sound Model 820 User Manual 10 14 97 Criterion Sound Level Lj Level when adjusted for the Exchange Rate It is expressed in Pascals squared seconds when the exchange rate is 3 dB where q is the Exchange Rate Factor See Exchange Rate L q CSE T 10 Standard ANSI 1 25 It is the sound level which if continually applied for the Cri terion Duration will produce a Noise Dose of 100 The cur rent OSHA Criterion Level is 90 dB Standard ANSI 12 19 Daily Personal Noise Exposure gp It is the level of a constant sou
127. pecific time period T T T4 See Sound Exposure Level Exchange Rate Q Exchange Rate Factor q Exposure Factor k It is defined in ANSI 51 25 as the change in sound level corresponding to a dou bling or halving of the duration of a sound level while a con stant percentage of criterion exposure is maintained The wwe CS Far Field Free Field Frequency Hz rad sec C 6 rate and the factors are given in the table below Standard ANSI 512 19 Exchange Rate O Exchange Rate Exposure Factor k There are two types of far fields the acoustic far field and the geometric far field Acoustic Far Field The distance from a source of sound is greater than an acoustic wavelength In the far field the effect of the type of sound source is negligible Since the wavelength varies with frequency See the definition of Wavelength the distance will vary with frequency To be in the far field for all frequencies measured the lowest fre quency should be chosen for determining the distance For example if the lowest frequency is 20 Hz the wavelength at normal temperatures is near 56 ft 17 m at 1000 Hz the wavelength is near 1 1 ft 1 3 m See the definition of Acoustic Near Field for the advantages of in the acoustic far field Geometric Far Field The distance from a source of sound is greater than the largest dimension of the sound source In the far field the effect of source geometry is negligible Sound sou
128. precision preamplifier using a standard 5 pin SwitchCraft connector and may be extended up to 20 feet with EXCXXX micro phone cable The preamplifier is removed by depress ing the small black latch button with a fingertip while gently pulling it away from the mating connec tor Atwo line 32 character high contrast LCD display 10 1 97 Introduction 1 7 Model 2541 free field or 2560 random incidence 12 inch precision air condenser microphone The micro phones are rugged and reliable but should be kept in their protective case when not in use Avoid unneces sary shock Although an LeD microphone can usu ally survive being dropped it is a delicate precise transducer that should be handled with care A 20 key membrane keypad Model 820 precision hand held Sound Level Meter with integral nose cone Powered internally by 9 volt cell or by an external battery or AC DC adapter WS001 3 1 2 inch windscreen An AC DC mini phone connector with pinout shown on page 4 8 A 5 pin cable connector with the pinout shown in fig ure Figure 1 2 Note that this connector is used to access external power 2 TXD Transmitted Data fm 820 3 RXD Received Data to 820 4 Extemal Battery to 820 5 DTR Data Terminal Ready 1 Ground Figure 1 2 External 5 pin Cable Connector Pinout 1 8 Model 820 User Manual Keep clean and protect from con densing moisture and water The microphone s ultra thin d
129. pressure C 14 sound pressure level SPL Lp C 15 unweighted peak C 16 weighted peak C 17 yearly average level YDNL Lydn C 19 Sound Event Level see SEL 2 6 Sound Level threshold Lt C 17 Sound Level Meter SLM 8 11 Sound Power C 17 level PWL Lw C 17 Sound Pressure Level see Sound C 15 Index 6 Sound Speed C 17 Specifications App A 1 2 frequency weightings A 4 microphone extension cables A 6 reference direction A 2 reference level A 4 temperature A 6 type A 2 Spectrum frequency C 17 Standards ANSI A 10 Status command B 5 Store determine strorable data 9 1 Symbol flashing f 2 8 numeric 2 8 OVLD Overload 2 8 run 2 8 SHIFT 2 8 stop 2 8 Symbols Screen 2 8 stabilizing 2 8 T T A key 2 7 Temperature specifications A 6 template B 14 Template Parameters B 14 Threshold 8 12 Time allowed Exposure time Ti C 1 Key 2 6 weighting C 18 Time History 8 15 data 7 4 Time History see History 2 4 Time Weighted Average see T A 2 7 Timed Measurement Chapter 6 6 1 Timer for unattended readings 6 1 internal 5 4 key 2 6 parameters 8 9 Turning 2 9 Turning Off directions for 2 11 TWA time weighted average sound level TWA LTWA TC C 18 Type specifications A 2 Type 1 Model 820 1 1 1 4 U Unweighted Peak key 2 5 UWPK 5 5 5 7 V Variables calibration history B 28 daily history B 27 exceedance history B 25 histogram B 29 histogram table B 29 interval B 26 interval history B 26 run
130. produce the Exceedance Report i e EXCD 9 25 97 Printing a Report 10 3 Step 3 To generate an Exceedance Report press the key Assuming your reading has Exceed ances the report will contain all recorded occurrences during the test period Real time Printing Another feature of the Model 820 is the ability to print out reports in real time These are called the real time printer parameters or Rt print parameters These param eters are listed in Chapter 8 and duplicated here for your study 168 Rt EXCD Report No Yes 169 Rt INTV Report No Yes Print exceedance report in real time Print interval report in real time 170 Rt HIST Report No Yes Print history report in real time 171 Rt RUN LOG No Yes 172 Rt Daily Report No Yes Print run log history Print daily report 173 Rt CAL Report No Yes Print cal report These reports are automatically printed when you push C As the data is collected it is printed out according to those parameters settings in the Time History 80 87 Interval History 72 79 and the Exceedance History 61 65 For instance if the history period parameter 83 is set to 6 seconds the printer will print a bar graph every 6 sec onds This will continue until you push again These parameters are only available by pressing and entering the parameter numbers directly 10 4 Model 820 User Manual 9 25 9
131. r recall ntwo RAM random access memory registers In one EEPROM register electronically erasable pro grammable read only memory Setups stored in RAM occupy the same memory as the data 256 KB They may be lost if battery power is removed for more than a few minutes One set of param eters at a time can be stored in the EEPROM Parameters in the EEPROM register are secure even if the batteries are disconnected since the EEPROM does not require bias voltage to maintain its state A minimum of 5 000 STORE operations are possible with the EEPROM Storing a Setup The Model 820 must be stopped and memory reset to Remember to reset memory press store to the EEPROM SHIFT 6 Enter 8 4 Model 820 User Manual 9 30 97 Step 1 Press GHIFT The EEPROM register is the default In this instance the title of the measurement is TECH E WRITER Step2 The z keys will scroll through the two RAM registers 0 9 For example press v twice The RAM register 1 is empty Step 3 To store the current setup to the displayed RAM 1 register press Enter STORE RAM 1 TECH WRITER Recalling a Setup Memory must be reset before a recall of setup parame ters can be accomplished Step 1 In the stop mode press SHIFT Enter to reset memory Then press SHIFT 9 30 97 Parameters 8 5 Step 2 The EEPROM is again the default Use v to RAM registers 0
132. rameter 70 since the exceedance time history buffer is used to create this function The max duration of a passby event is 128 sam ples which is 64 or 128 seconds depending on whether 16 or 30 is used in parameter 70 To examine Exceedance data collected follow these steps Step 1 Press 88 The following screen appears with some variation Step 2 Press the M key to access the five screens avail able in the EXCD mode including Duration Leg Lmax Pk UWPK Step 3 To examine the properties of each exceedance record use the 4 or keys to see screens a e Step 4 Press the or a to view the next or previous exceedance 9 24 97 History Functions Max This setting will register the measurement at the Exceedance maximum point Five screens are available Time and Date and the Exceedance number as seen in the screen to the left Duration Leg compari sons Lmay Symmetry Peak and UWPK 7 11 Setting PassBy Functions The PassBy Function is a special exceedance event detec tor that measures the Lmax Leg and SEL of the highest event to raise and lower 10 dB in SPL It is used to cap ture single events such as a vehicle or aircraft passby or other event noises such as blasts or gas getting noise In addition to the levels measured the date and time of the Emax and the duration of the event are recorded The maximum duration of passby event may be 1 or 2 min utes depending on the shape of the event
133. rces often have a variety of specific sources within them such as exhaust and intake noise When in the far field the sources have all merged into one so that measurements made even further away will be no different See the defini tion of Geometric Near Field for the advantages of being in the geometric far field A sound field that is free of reflections This does not mean that the sound is all coming from one direction as is often assumed since the source of sound may be spatially exten sive See the definitions of near and far fields for more detail This definition is often used in conjunction with reverberant field The rate at which an oscillating signal completes a complete cycle by returning to the original value It can be expressed in cycles per second and the value has the unit symbol Hz Model 820 User Manual 10 14 97 Frequency Band Pass Filter Frequency Filter Weighted 10 14 97 Hertz added and the letter f is used for a universal descrip tor It can also be expressed in radians per second which has no symbol and the greek letter w is used for a universal descriptor The two expressions are related through the expression w 2nf The part of certain sound level meters that divides the fre quency spectrum on the sound or vibration into a part that is unchanged and a part that is filtered out It can be composed of one or more of the following types Low Pass A frequency filter that permits signals to pas
134. reen will appear Step 2 The Detector prompt has three possibilities indicated above Press Modity M to access desired setting and Step 3 To set the Frequency Weighting press v to item 40 There are several possibilities here A A16 C C16 Flt 5 4 Model 820 User Manual The Model 820 has been pro grammed to save power whenever it can Each time input is made the internal timer will start at 100 and count downward lf mot pro grammed to do otherwise the Model 820 will turn itself off when this screen reaches 0 just over two minutes Pressing the v key again will scroll loop you back to the SLM original screen Slow exponential avg 1 second constant Fast exponential avg 1 8 second constant Impl impulse response For OSHA measurements this is normally set to Slow For environ mental measurements Fast or Slow may be used Within a given period of time the Fast detector will take more measurements than the Slow Therefore the Fast detec tor is likely to measure more higher and lower levels than the Slow detector The A and C weightings simulate human hearing response and meet Type 1 precision standards for accuracy Flat no weighting allows the signal to pass through 10 1 97 Step 4 Step 5 Step 6 Step 7 Step 8 The Model 820 has been preset at A To change the setting press di to the pre ferred setting and Enter Find item 41 by pressing AC Out W
135. rent record is 17 locates calibration history record 8 17 9 Find Find record number directly Syntax Response Flind rec_no history no cr If Example B 24 Model 820 User Manual 9 26 97 F9 5 locates calibration history record 9 Generally one uses the Find command to get to the first record F1 2 and the Advance command A to move up through the records History Data Variables Exceedance History Variables Brackets in the syntax indicate optional characters and operands Syntax Response E xceedance var no Excd var Example E9 Overload count from current record EI Date and Time of Occur ddmmmyy hh mm ss rence E2 Duration hh mm ss mm ss ss ES3 Lint nnn n dB SEL Lmax Lpeak UnWeighted Peak nnn n dB Peak Exceedance Count Overload Counts nnn Illegal Indication BEEP ILLEGAL Excd Time Hist Samples nnn E 18 lt n gt Excd Time History nnn n dB E 19 lt n gt Excd T H Time SSS SS E 20 lt n gt Excd T H Number nnn E21 n Excd T H Bargraph JES IR ER 9 26 97 B 25 E25 EXCD SYMETRY nnn nn96 E 101 Excd Variables 1 10 Macro E 102 Excd Time Hist 17 18 Macro Interval History Variables Brackets in the syntax indicate optional characters and operands Syntax Response I nterval var noIntv var Example
136. rial printer 6 feet e CBL034 Connects Model 820 to un wired cable end 4 conductor shielded e CBL035 Connects Model 820 and customer supplied external battery e CBL038 Connects Model 820 to battery and RS232 port of most laptop computers CBL077 extension cable or similar recommended if longer length required CBL039 Connects Model 820 to modem Includes capability to use external battery to power Model 820 CBLO77 or similar recommended to extend length e CBL040 Similar to INT002 but allows one to daisy chain an additional Model 820 CBL042 AC DC output of the Model 820 to RCA BNC connectors e CCS002 Custom hard shell airtight watertight case 131 2X127 8X 6 in EPS012 CCS002 weatherproof fiberglass case with custom cut foam interior and desiccant Sealed signal cable feed through Features lock hasp and may be chained through handle for security 10 1 97 Introduction 1 13 e EPS013 Same as EPS012 but with 8 Ah 12 Volt rechargeable battery BAT004 Provides 1 week opera tion in normal conditions Includes CBL038 and bat tery charger EXCXXX Microphone extension cable length XXX feet Epson Printer e INT002 RS 232 cable level converter for data transfer to PC Requires 9 V battery or external AC power supply PSA001 included Note that external supply will also power the Model 820 e PSA001 AC DC power adapter 115 Vac to 9 Vdc 50 60 Hz for use with INTO002 e PSA002
137. rom the date of original purchase During the first year of the warranty period Larson Davis will repair or at its option replace any defective component s without charge for parts or labor During the second year of the warranty period there will be no charge for replacement parts For customers within the continental United States service is provided for instruments returned freight prepaid to an authorized service center The product will be returned freight prepaid For international customers please contact your exclusive Larson Davis representative for details on local service and shipping arrangements The Larsone Davis warranty applies only to products manufactured by Larsone Davis Inc and does not include batteries Accessories and items not manufactured by Lar sone Davis are covered by the warranty of the original equipment manufacturer Product defects caused by misuse accidents or user modification are not covered by this war ranty No other warranties are expressed or implied Larson Davis is not responsible for consequential damages Record of Serial Number and Purchase Date Serial Number Purchase Date Rev Number Mic Number Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 10 1 97 Table of Contents Introduction 1 1 About This Mantal tr em temen te pieni eitis 1 1 About This Chapter ccccccccccccsessssesessssenssescscscesescsnsnssnesesesnesesescecenesesssesn
138. s SEL b Gives exposure in Pa2H which is a linear representation of energy TIMER The ability to take a measure ment at a specific time and date is avail able thus permitting unattended measurements i e one or two measure ments day between two dates or a single block measurement from a start date and time to a stop date and time 2 6 Model 820 User Manual 10 1 97 Functions T A Time Weighted Average SPL TWA and the German Takt Maximal Lev els TAKT are available through the T A key The first display a shows the Over all TWA and Run Time LDN The LDN is a TWA with a 10dB penalty added to the levels measured from 10 pm to 7 am It is used to assess correlate or predict annoyance to noise in residential area noise at night is gener ally less tolerated than noise in daytime hours CNEL is also shown LDN b Shows the average levels of the exceedances and the average levels Bk Gnd of energy not contained in exceed ances DOSE The Dose and Projected Dose sound exposure percentages are dis played in these screens Parameters 48 51 control the Dose measurement LDL Logged Dated Logic allows the user to recalculate TWA SEL DOSE and Pro jected Dose using new Exchange Rate Threshold and Criterion parameters during or after a measurement w o0 10 1 97 Arrows Up Down Left and Right arrows are used to change fields to modify information within a given field and can be u
139. s through that have frequencies below a certain fixed fre quency called a cutoff frequency It is used to discriminate against higher frequencies High Pass A frequency filter that permits signals to pass through that have frequencies above a certain fixed fre quency called a cutoff frequency It is used to discriminate against lower frequencies Bandpass A frequency filter that permits signals to pass through that have frequencies above a certain fixed fre quency called a lower cutoff frequency and below a certain fixed frequency called an upper cutoff frequency The differ ence between the two cutoff frequencies is called the band width It is used to discriminate against both lower and higher frequencies so it passes only a band of frequencies Octave band A bandpass frequency filter that permits signals to pass through that have a bandwidth based on octaves An octave is a doubling of frequency so the upper cutoff fre quency is twice the lower cutoff frequency This filter is often further subdivided in 1 3 and 1 12 octaves 8 and 12 bands per octave for finer frequency resolution Instruments with these filters have a sufficient number of them to cover the usual range of frequencies encountered in sound and vibra tion measurements The frequency chosen to describe the band is that of the center frequency Note table in Frequency Filter Frequency Weighting A special frequency filter that adjusts the amplitude of all par
140. s 80 dB Exchange Rate is 5 dB and the Full Dose hours Cri terion Time is 8 dB This step will not work while in the SETUP mode This step will not work while in the SETUP mode either Performing a Measurement Reading the Data 5 11 Dose readings are usually read and have more meaning after the measurement is completed Returning to our recent measurement let s examine the DOSE key and look at the values recorded there Step 1 Press the key where two screens are avail able Press the gt key to access the second screen LDL readings are displayed on four screens We will visit three of these screens using the following steps Step 1 Press the SHIFT and keys 5 12 Model 820 User Manual The measurement ran for nearly four hours and the dose was 0 28 The Projected Dose extrapolates the eight hour dose from dose A which is the current measured dose Notice in the reading the LDL Threshold is set at 80 parameter 49 The Overall Exchange Rate is set at 3 dB parameter 48 The Overall Criterion has been set at 90 parameter 50 Any of these 3 parameters can be modified and a new dose projected dose Leq and SEL will be computed 10 1 97 Step 2 Press the v key to check the LDL d screen PROJ DOSE that is calculated based on the cur rent LDL settings N Lan readings are displayed on two screens Step 3 Access Lg by pressing GHIF
141. s in density pressure motion and temperature as well as other physical quantities Not all rapid changes in the medium are sound wind noise since they do not propagate The auditory sensation evoked by the oscillatory changes Difference between sound and noise Sound is the physical phe nomenon associated with acoustic small pressure waves Use of the word sound provides a neutral description of some acoustic event Generally noise is defined as unwanted sound It can also be defined as sound that causes adverse effects on people such as hearing loss or annoyance It can also be defined as the sound made by other people In every case noise involves the judgment of someone and puts noise in the realm of psychology not physics Rules 1 Use word sound to describe measurements to remove the emotional overtones associated with the word noise Some sound metrics use noise in their name and it is proper to use the name as it is C 13 Sound Exposure SE It is the total sound energy of the actual sound during a spe cific time period It is expressed in Pascals squared seconds T SE p t dt T where pa is the sound pressure and T T is the Measure ment Duration specific time period When applied to hearing damage potential the equation is changed to T SE JAD ar Ti where k is the Exposure Factor See Exchange Rate Standard ANSI 1 25 Sound Exposure Level SEL Lgr The total sound energy in a specif
142. s or letters by using the SHIFT key If you choose to use this feature enter something you won t forget i e a name or birth year and press Enter Step3 Toturnon the Lock press the and DI These setup items control whether keys When Yes appears press Enter or not the lock feature will work for that particular function For example if Yes is entered for Lock Setup then the R S and other function can be used when Setup Lock function is implemented Press v to see other functions that can be locked See chapter 8 parameters 28 34 Step 4 If you should wish to unlock the system for fur Notice that as you enter your code ther input or readings press GHIFT and amp amp only appear to protect then Modity your password Again make the password easy to remember should you wish to use this func tion Enter your password code and press Enter The Model 820 is now unlocked and accessible for additional entries 6 6 Model 820 User Manual 9 24 97 History Functions The process of measuring and recording units of sound and retrieving the data for study and understanding is enhanced by additional functional capabilities of the Model 820 Sound Level Meter This chapter will cover Setting and Viewing Advanced Functions Time History Time History Data Log and Data Interval History Interval History Data Exceedance Setting PassBy functions De
143. sage Run Log History 20 bytes per record Calibration Log History Ram Setup Register REgisters 0 9 Bytes used per register stored 9 2 Model 820 User Manual 17 bytes per record 506 bytes per register 9 9 97 Estimating Memory Usage The easiest way to estimate the memory usage is to work on a time basis such as one day Consider the following Estimate how many Exceedances will occur in a nor mal day Calculate the number of Interval Time History Daily Run Log and Calibration Check records that will be performed in a day Based on the options chosen calculate the number of bytes required for each record type Multiply by the number of records expected per day Sum these values and this is the number of bytes required per day Divide this value into the amount of available mem ory in the Model 820 see GHIFT and this is the number of days the Model 820 can gather data As an example let s assume a job requires monitoring the noise made by trucks coming and going from a fac tory near a residential area From an initial site survey it is discovered that all trucks are over 65dBA at the boundary of the road and residential property and that there seems to be a truck passing the site every 3 min utes The occupants of the residential area want to know how many trucks are traveling this road and why they are disturbed by some more than others The Exceedance Function will be
144. se seed edite te toin Fede ingerere 8 4 Learning to Store and Retrieve Setup Memory sss 8 4 Storing a SetuP ac seemed tet e eoa e E ts 8 4 Recalling a Set p nates deb RR HUY 8 5 Model 820 Setup P rametefSissr riir ae a Ei 8 6 System 1 20 AUS a nd 8 6 Timer 21 27 U T iet Sere nettes nitet ete i hes dH e ties 8 9 Lock 28 34 U L5 ia es 8 10 Calibration 35 38 U Coc ce ccc cece ccc eee ec eee cere nn 8 11 Sound Level Meter 39 50 2 2 cee cece cee cee rece eee C8 11 Model 820 User Manual 10 1 97 Chapter 9 Chapter 10 App A 10 1 97 Dose bDl it Sa ee ee De RR RARE SU T Era eir E8 12 Ln Statistical Levels 55 60 B eee ee eee eee eee 8 13 Exceedance Levels 61 65 V essent 8 14 Exceedance History 66 70 161 163 sss 8 14 Interval History 72 79 M Time History 80 87 eee H8 15 Print Options 89 112 S 1 ccc ccc ccc ccc eee eens 8 18 Additional System Functions 152 154 161 oo sss 8 20 Memory Usage 9 1 Determine Storable Data tefte tede s 9 1 Estimating Memory Usage sse 9 3 Printing a Report 10 1 Normal Printout Parameters sssssssseeeeee eee nnns 10 1 Printing Reports sessssssesesseeeeeeeenenetrernr nennen 10 2 Real time Printing eee eee ti ertet 10 4 Specifications A 1 LV PO ret ie iet seb tee eae m E e teach etie A 2 Reference Direction niet s rete het uad A 2 Measurement Ranges rna a
145. sed in conjunction with other keys to allow other functions Modify Prepares the field for changes while in setup Overview to Model 820 2 7 Getting to Know Screen Symbols Symbols basic to the Model 820 are included below These are generally found to the right of the screen The Operating Mode Indicator upper right character indi cates whether data is being accumulated or not and has the modes indicated by the first four examples The Keyboard Status Indicator displays which key func tions are active The lower four modes are possible and appear in the lower right corner or the display Functionality flashing upper case to lower case Model 820 is stabilizing upon warm up 10 45 sec or SETUP weighting 8s or bias voltage 30s change in stop mode Stop mode no data is being taken Run mode Overload These letters in succession occur alternately with the stick figure with 8 second intervals when an over load has occurred flashing Indicates that the function keys Lmin Dose etc are used for differ ent purpose in the current function Indicates that numeric key input mode is active SHIFT key active secondary function in blue lettering 2 8 Model 820 User Manual 10 1 97 Symbol Functionality SrS If the Model 820 is still stabilizing upon warm up and the R S Run button is pushed r will flash alternately with S Understandi
146. ses C 9 Mode commands B 5 Model 2 1 2 9 Model 820 accessories 1 12 block diagram 1 9 to 1 10 Calibration 1 2 3 1 Components 1 7 features 1 4 Glossary 1 2 Glossary App C C 1 History Functions 1 2 Introduction 1 2 Memory Usage 1 2 9 1 microphone 1 5 Overview 1 2 2 1 parameters 1 2 Performing a Measurement 1 2 Quick Start 1 2 Specifications App A A 1 Index 4 Timed Measurement 1 2 turn on 2 3 Type 1 1 1 Modem answering procedure B 35 control mode B 33 dial out mode B 33 monitor numbers B 34 phone dialing procedure B 34 Modify key 2 7 parameters 8 3 N Near Field acoustic C 11 geometric C 11 glossary C 11 Noise ambient C 12 Background C 12 compensate B 22 Daily History 7 14 daily personal exposure C 3 dose D C 12 exposure C 13 floor B 22 glossary C 2 C 12 pink C 12 projected noise dose C 13 single event exposure level SENEL Lax C 13 white C 12 Numeric Parameters B 13 O Optional 1 13 OSHA level C 13 Overload 7 14 Overview Model 820 2 1 P Parameter B 13 to B 14 character B 14 character strings B 12 Daily History 7 14 DOSE 8 12 Exceedance 7 8 8 14 Exceedance History 8 14 exceedance history 7 9 exceedance level 7 8 indexed B 12 Interval history 7 5 key access 8 1 Model 820 1 2 numeric B 12 to B 13 printout 10 1 query B 15 setting B 12 setting and viewing 7 1 setting keys 4 1 system 1 20 8 6 template B 12 Time History Data 7 4 Timer 8 9 Parameters Additional System Functions
147. tax Response Hlistoryl var no time var Example H2 Peak level in current record H1 RMS Level nnn n dB H2 Peak Level nnn n dB H3 Run Time of Sample calc hhhhh mm hh mm ss mm ss ss H4 HISTORY BARGRAPH ESE Lus Histogram Table Variables Brackets in the syntax indicate optional characters and operands Table 1 RMS 9 26 97 B 29 e 2 Peak e 3 Unweighted Peak Default is last used table or RMS Syntax Response T able var no table table var Example KT RMS current bin level Tln Level of current bin nnn n dB T2 n Count of samples nnnnnc c K or M for Kilo or Mega T3 n Percent of total nnn nn96 T5 n Prints the accumulated timer for the current hhhhh mm ss s level bin The table number is optional a Where n equals the table number 1 RMS 2 Peak amp 3 UnWeighted Peak Print Commands Brackets in the syntax indicate optional characters cr carriage return lf line feed Syntax Response P rint print no cr lf Example Pl cr Example B 30 Model 820 User Manual P9cr 1 sets all report enables in setup to No 177 1cr 2 sets the Data report Run log and EXCD report 178 ler enables short to Yes and S192 ler 3 begins printing to the computer P100cr Syntax Description PO Standard Report Formatted
148. the various memory registers List all parameters with a short explanation Parameter Key Access Review Entering and Exiting the Setup Menu Some setup items may be changed while the Model 820 is running but parameters influencing data integrity require a memory Reset ALL 9 30 97 Parameters 8 1 Step 2 Step 3 Step 4 Enter the setup by pressing The following will appear To exit back to the main screen press Cancel Return to the setup menu Press y Locating Parameters When in the setup menu the arrow keys allow move ment from one parameter to another One may also use a function key or directly index to the appropriate param eters Step 1 Step 2 Step 3 Step 4 Step 5 From the Setup menu press Y to move down the list of parameters one at a time When the arrow keys are used in conjunction with the Shift key SHIFT the Model 820 will take you to the top or bottom of the parameters list Press SHIFT 3 to move to the bottom of the parameter list Press the 5 key Press the SHIFT keys and then 6 f Press NOTE Numbers are entered at the current cursor position Enter leading zeros if necessary 8 2 Model 820 User Manual All items in the list of parameters can be accessed by using the a and v The Model 820 moves you to the rms detector parameters You are now at the beginning of the Exceedance parameters item 61 9 30 97 Ch
149. tion time is also invoked when certain settings Weighting Detector etc are changed Microphone Electrical Impedance The Larson Davis ADP005 should be substituted for the 1 2 microphone when performing electrical tests on the Model 820 The Larson eDavis ADP002 is used in place of a 1 4 microphone and the Larson Davis ADP006 is used in place of the 1 microphones Functions Measured Leg Emaxr Lmin TWA SEL Dose Projected Dose Ln 1 99 e Sound Exposure in pascal squared hours SE in Pa H Time History Histograms Measurement Time Date Duration e Taktmaximal 3 and 5 e Ldn Exceedance Events A 8 Model 820 User Manual 9 25 97 Data Storage e 820 256k byte Memory Typically 3 month memory retention with fresh battery Memory protected during battery change 2 minutes minimum Data Communications Serial interface for computer printer and modem communications Data Rate 19 200 bits per second Digital Display 2line 32 digit 7 segment LCD Full ASCII character set Fully annotated date displays parameter with units Digital Display Resolution dBlevels 0 1 dB Dose 0 0196 Elapsed Time 0 1 second Display Bargraph e 120 dB range 1 dB resolution for SPL 9 25 97 A 9 Real time Clock Calendar 24 hour clock hh mm ss e 1 second resolution 100 year calendar 01JAN1999 Automatic run stop timer with two alarms and four alarm times Run time Clock
150. to 9 and scroll through the ten RAM registers or the pro EEPROM register will recall pre grammed ROM setups viously stored calibration data STORE saves the CAL data so that O nA the calibration for several different iii be u microphones may be stored and recalled as desired For example Register 1 could store the calibra tion for a Model 2560 microphone 2 for a Model 2540 3 for dBuV ROM registers A B and do not affect calibration data Model 820 Setup Parameters Setup parameters of the Model 820 are listed below Modifying some setup parameters such as going from a FAST to a SLOW meter response may not be allowed unless the data is reset This prevents corruption of the overall noise data Parameters are listed below in logical groups with their number and direct index key if available Valid entry formats are listed 0 for numerical 0 for selection Some reserved parameters or selections are not avail able Many of these are active in the Model 870 the Model 820 s big brother System 1 20 S5 SHIFT CER The following parameters define measurement names and determine interface parameters No Prompt Entry Comment 1 Reset ALL Data No Yes This parameter allows a SHIFT RESET without leaving SETUP Note If this parameter is set to Yes a RESET will occur and the parameter will automati cally revert to No 8 6 Model 820 User Manual 9 30 97 2 4 Na
151. ts Timer Run Time 1 to 14 25 33 Query Parameters All these commands begin with Q Brackets indicate optional characters and operands See Chapter on SETUP for a list of all the parameters and their settings cr carriage return lf line feed _ space Syntax Response Qluerylitem_numberl flag Depends on flag Option flags elicit the following responses Flag Response none Current parameter Parameter name and current setting 2 Current parameter setting including spaces in brackets or parentheses 3 Parameter name and current setting including spaces in brackets or parentheses 32 Index number for indexed parameter Flag values may be added together for desired combina tions Example Response 1 066 No 2 066 1 Excd History Enable No 3 966 2 No 4 966 32 0 5 966 3 Excd History Enable No Responses are denoted by x if Yes No or n if numeri cal 9 26 97 B 15 Com Variable Description Comment mand Q RESALL RESET ALL Q2 Q HDG1 HEADING LINE 1 Q3 Q HDG2 HEADING LINE 2 Q4 Q HDG3 HEADING LINE 3 Q TITLE MEASUREMENT TITLE Q TIME CURRENT TIME Q DATE CURRENT DATE Q DAY DAY OF WEEK Q BAUD COMI BAUD RATE Q SADDR COMI ADDRESS Q NI RESERVED PARAMETER Q HS COM PORT HANDSHAKING REGISTER Q NI RESERVED PARAMETER Q LOGIC1 OUTPUT 1 LOGIC unused Q OUTITIM O
152. ts of the frequency spectrum of the sound or vibration unlike band pass filters It can be composed of one or more of the following types C 7 C 8 A Weighting A filter that adjusts the levels of a frequency spectrum in the same way the human ear does when exposed to low levels of sound This weighting is most often used for evaluation of environmental sounds See table below B Weighting A filter that adjusts the levels of a frequency spectrum in the same way the human ear does when exposed to higher levels of sound This weighting is seldom used See table below C Weighting A filter that adjusts the levels of a frequency spectrum in the same way the human ear does when exposed to high levels of sound This weighting is most often used for evaluation of equipment sounds See table below Flat Weighting A filter that does not adjust the levels of a fre quency spectrum It is usually an alternative selection for the frequency weighting selection Center Frequencies Hz Weighting Network Frequency Response 1 3 Octave 1 Octave A 20 504 24 2 6 2 25 44 7 20 4 4 4 31 5 31 5 39 4 17 1 3 0 40 34 6 14 2 2 0 50 30 2 11 6 13 63 63 26 2 93 0 8 80 225 7 4 0 5 100 19 1 5 6 0 3 125 125 16 1 4 2 0 2 160 13 4 3 0 0 1 200 10 9 2 0 0 250 250 8 6 1 3 0 315 6 6 0 8 0 400 4 8 0 5 0 500 500 3 2 0
153. tual time of exposure by the allowed time of exposure The allowed time of exposure is determined by the Criterion Duration and by the sound level the higher the level the shorter the allowed time The sound levels must be measured with A frequency weighting and slow exponential time weighting See Projected Noise Dose T _ 100T g D 100 ppow c where T is the Measurement Duration and T is the Allowed Exposure Time Standard ANSI 12 19 Model 820 User Manual 10 14 97 Noise Exposure OSHA Level Losa Preamplifier Projected Noise Dose See Sound Exposure The Average Sound Level calculated in accordance with the Occupational Safety and Health Administration Exchange Rate and Threshold Level A part of the sound level meter that matches a particular model of microphone to the meter It must be chosen in con junction with a microphone and a cable that connects them It is the Noise Dose expected if the current rate of noise expo sure continues for the full Criterion Duration period Single Event Noise Exposure Level SENEL Lay The total sound energy over a specific Sound 10 14 97 period It is a special form of the Sound Exposure Level where the time period is defined as the start and end times of a noise event such as an aircraft or automobile passby The rapid oscillatory compressional changes in a medium solid liquid or gas that propagate to distant points It is characterized by change
154. until in Stop mode This feature will insure that no important data is lost 2 12 Model 820 User Manual 10 1 97 Calibration Because of variation in microphone sensitivities a sound level meter must be calibrated to a reference sound level for accurate measurements This is easily performed with the Model 820 You will need a calibrator with an appropriate adapter for the Model 820 microphone such as the LarsoneDavis CAL200 This L D calibrator out puts 114 dB or 94 dB with respect to 20 uPa and at a fre quency of 1000 Hz At this frequency the relative response for A and C weightings is the same NOTE A precision calibrator is not necessary for this part of the tutorial but you should make it a regular practice to perform an instrument calibration before and after you take actual measurements in the field However you do not have to recalibrate the Model 820 when you change the settings Please note that if you use a calibrator which uses another frequency some corrections may be required depending on the weighting The output level and the frequency of your calibrator should be listed on its label Use this level with specific environmental and weighting corrections to calibrate the Model 820 level In order to perform calibration the Microphone Polar ization Voltage needs to be properly set Calibrating the Model 820 Microphone Polarization Voltage is preset by Lar son Davis at 200 volts Should this p
155. val reports is that all the statistics Lmax Ly etc are available for the hourly noise levels that make up the daily report Yes This option allows the six L s for the interval report to be stored 9 24 97 Step 7 Press the 3 to item 79 Into Auto Stop The choices are Yes No Step 8 To view Interval Histories after a measurement has been taken press Y A screen similar to the one below will appear Step 9 Examine the data available in each INTV Press gt and scroll to each The 4 will also work and the scroll is a loop Step 10 Press the v or A to view the next or previous Interval respectively 9 24 97 History Functions Yes This option will cause the Model 820 to automatically stop at the end of each interval allowing the precise timing of a series of manual measurements To start a new measurement the key must be pushed No This mode must be off for all automated measurements It is rec ommended that Into Time Sync be set to No to get the full desired period Eight screens are available from the INTV mode The screen at the left gives the Time and Date of a given Interval Duration Leg Linin and Lingx Peak and UWPK and the level setting measurements INTV a gives time interval num ber and date INTV b gives duration and inter val number INTV c gives SEL and Leg INTV d gives min and max level and the number of times level went over RMS exceedance 1 INTV e g
156. ws PSBY a Time and Date of maximum PassBy PSBY b Duration of maximum PassBy PSBY c Leg and SEL of maximum PassBy PSBY d Leg and Max RMS level Step 3 To return to the Exceedance PassBy data screens press SHIFT 4 9 24 97 History Functions If PSBY appears in the screen it means you are in the Max PassBy data screen Hit 4 to get into the Exceedance PassBy screen Five screens are available here by using the M key giving time and date of the occurrence duration and Leg comparisons Symmetry when used in PassBy mode is an indication of where Occurrence Time or Max Level occurs in the event To clarify 25 symmetry would indicate Max Level happened 1 4 of the way into the event in linear time 50 would suggest that the Occurrence Time happened half way into the event and so forth The Single Highest Passby event is accessed by pressing SHIFT and M while in the EXCD Mode 7 13 Overload It should be noted that during any measurement an OVERLOAD may occur Such occurrences happen when input signals exceed internal circuitry limits such as dropping or jarring the instrument Should an OVER LOAD occur during a measurement the data accumu lated during the occurrence will not be accurate The Model 820 registers an OVERLOAD in the upper right corner of the display where the running figure appears The figure takes one step each second At inter vals 8 seconds apart the letters O V L
157. xceedances nnnnn R34 _UWPKCNT OverAll UWPk Exceedances nnnnn R35 _OVLDCNT Overloads nnnnn R36 _PSECNT Number of PAUSES nnnnn R37 _PTIME PAUSE Time OFF not inc hhhhh mm ss R38 LN1 Ln 1 nnn n dB R39 _LN2 Ln 2 nnn n dB R40 _LN3 Ln 3 nnn n dB R 41 _LN4 Ln 4 nnn n dB R 42 _LN5 Ln 5 nnn n dB R 43 LN6 Ln6 nnn n dB R44 _O DOSE Overall Dose nnnnn n R45 _C DOSE Current Dose nnnnn n R46 _O PROJ Overall Projected Dose nnnnn n R47 _C PROJ Current Projected Dose nnnnn n R48 _LDLDOSE LDL Dose nnnnn n R49 _LDLPROJ LDL Projected Dose nnnnn n R50 _LDLLINT LDL Lint nnn n dB R51 _LDLSEL LDL SEL nnn n dB R52 _LDLXR LDL Exchange Rate Text cecce R53 _LDLVALID LDL Valid display see note below cccccc R54 _RELLVL Last Level Relative to REFLVL nnn n R55 _TABLE Display Histogram Selected ccc R56 COUNT Display Overall Count nnnnnk 9 26 97 B 7 R57 _O LEQ Overall Leq nnn n dB R58 _D LEQ Daily Leq nnn n dB R59 _H LEQ Hourly Leq nnn n dB R 60 h _HNL Hourly Leq 0 23 nnn n dB R 61 h _HNLPART Hourly Leq partial indicator nnn n dB R62 _O LDN Overall LDN nnn n dB R63 _D LDN Daily LDN nnn n dB R64 _H LDN Hourly LDN nnn n dB R65 _O CNEL Overall CNEL nnn n dB R66 _D CNEL Daily CNEL nnn n dB R67 _H CNEL Hourly CNEL nnn n dB R68 _EXLEQ Total EXCD Leq nnn n dB R69 _EXTIM Total EXCD Time hhhhh mm ss s NOTE An LDL Logged Data Logic recalculation can be started with a _LDLVALID I O Read Com
158. z to 1 kHz 9 30 97 Step 6 Step 7 Step 8 Step 9 9 30 97 The next setup item allows entry of the calibra tor serial number for record keeping purposes Press the x or Ei Modify 3 and 6 and Press to change the serial number enter the correct numbers and press Enter Seat the microphone fully in the calibrator cav ity If possible both units should be at the same temperature and stationary so that hand vibra tions are not transmitted to the SLM Press to exit calibration setup Then activate the calibrator by pressing the button on its side Press the and on the Model 820 This display indicates the current sensitivity off set and will be blinking between two settings Calibration Refer to the specific instructions accompanying your calibrator for accomplishing this step Pressing the a will check calibra tion pressing the v will change it 3 3 Step 10 Pressing the v key will initiate a calibration change Do that now Step 11 To Reset the Model 820 for re calibration press SHIFT and x Step 12 Press Enter Reset is complete and the instru ment will return to the calibration mode Step 13 To leave the calibration mode press 3 4 Model 820 User Manuall In this screen an error message initially prompted for a reset see step 12 to reset The difference between the current and the last calibration is O dB If the level is n

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