LOM-DO7 Manual
Contents
1. 9 4 1 Calibration Process eee 9 4 2 Equipment Required esee 9 4 37 Preparation uen ener eere e 9 4 4 Calibration Using MTS2 Standard 10 4 5 Calibration Using Discrete Resistance Standards 10 Chapter 5 MAINTENANCE 12 3 T General s nite herede tec tege oe 12 5 2 Battery Charging eee ii ent neal 12 5 3 Battery Replacement essere 13 Figures Figure 3 1 Description of Controls eee 3 Figure 3 2 Combined current and potential probes Kelvin clips 5 Figure 3 3 Connections for resistance measurements with various DUT Configurations saose renaire tria e ae der edere 6 Figure 3 4 Remote Start Socket viewed from panel 7 Figure 3 5 Printer Output Connections eese 8 9 Figure 4 2 Full Scale calibration setup Ne 11 Figure 4 3 Zero calibration setup sese 11 LOM DO7 LOM DO7 N WARNING AN OBSERVE ALL SAFETY RULES WHEN WORKING WITH HIGH VOLTAGES OR LINE VOLTAGES ELECTRICAL SHOCK HAZARD DO NOT OPEN CASE REFER SERVICING TO QUALIFIED PERSONNEL HIGH VOLTAGE MAY BE PRESENT WITH HIGH VOLTAGE OPTIONS WHENEVER HAZARDOUS VOLTAGES 45 V ARE USED TAKE ALL MEASURES TO AVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BAR2. Charging is automatically controlled with built in protection circuits eliminating the possibility of overcharging The display will go blank when the battery voltage is too low to allow accurate measurements The battery will recharge in ap proximately six hours leave the LOM DO7 lid open to permit maximum ventilation IMPORTANT Always connect the unit to ac power after use to charge the battery It should be stored with batteries fully charged when the instrument is stored or not used for long peri ods the batteries should be recharged monthly If the batteries become deeply discharged due to being left uncharged for long periods the in ternal charger will automatically sense the bat tery state and will trickle charge with a very low current to restore the batteries before automati cally switching to fast charge This low current charge may take up to 20 hours to restore the batteries Maintenance Continuous charging will not damage the batter ies and is recommended in order to keep them in the best condition IBATTERY CAUTIONS The internal battery is the sealed lead acid type When disposal is required be sure to do so in accordance with local regulations Do not attempt to incinerate the battery Do not short circuit the battery terminals Do not crush puncture open dismantle etc the battery NOTE If a battery is stored for long periods it should be fully recharged every six months 5 3 Batte
3. 3 4 1 Ohmmeter Connections The LOM DO7 employs a four wire method of measurement i e four connections to the resis tor under test are required The unit is supplied with four leads two voltage leads to be placed across the exact measurement points and two current leads to be placed outside the measure ment points The Kelvin clips shown in Figure 3 2 place voltage and current connections at the same point a Connect the black leads to the C and P terminals and the red leads to terminals C and P b Clip the test leads onto the resistor under test Cleanliness is important if the DUT is not clean clean it with fine emery cloth or steel wool to remove oxides C Itis not always possible to use the combined current and potential Kelvin clips in which case test leads with spade lugs or a special test fix ture may have to be made for a particular ap plication d Fig 3 3 illustrates connections to various types of test resistors e When measuring 4 terminal resistance stan dards the Kelvin clips may not be usable be cause of terminal geometry Make four separate connections to the current and potential termi nals 3 4 2 Start up When the LOM DO7 is first switched on an in ternal self test is automatically performed The display indicates 8888 followed by PASS then performs an automatic zero sequence and finally sets to the following default start up conditions Operation LOM DO7 Fi
4. 4 Set the MTS2 to FS and wait for the reading to stabilize The reading should be 40 00 1 digit 5 Set the DO7 to VE and wait for the reading to stabilize The reading should be 40 00 1 digit 6 Set the DO7 to AVE and wait for the reading to stabilize The reading should be 40 00 1 digit 7 Reset the DO7 to VE Set the MTS2 to 4 Q FS and wait for the reading to stabilize The reading should be 4 00 1 digit 8 Set the MTS2 to 400 mW FS and wait for the reading to settle The reading should be 0 40 1 digit 9 Set the MTS2 to 40 mo FS and wait for the reading to settle The reading should be 0 04 1 digit 10 Repeat steps 2 through 10 for the remaining ranges Setting the MTS2 appropriately 11 Turn the DO7 power OFF and remove the test 12 Document the results in accordance with company policies and procedures 4 5 Calibration Using Discrete Resistance Standards 4 5 1 Discrete 4 terminal resistance standards may be used in place of the IET Calibration Standard The standards must have an uncertainty better than 0 01 if the full calibration accuracy is to be achieved Full consideration of the LOM DO7 Calibration measuring current must also be taken into ac count when selecting the standards The LOM DO7 can be calibrated to standards between 1000 and 6000 digits for each range using the KYB entry However full accuracy will only be achieved if standards of
5. 4000 to 6000 digits are used The following nominal standards are rec ommended 400 Q 40 Q 4 Q 400 40 mQ and 4 4 5 2 In all measurements the P1 and P2 terminals are conventionally connected Bear in mind that ther mal emf s may be present The LOM DO7 is par ticularly sensitive to these on the 6 mQ range LOM DO7 4 5 3 For FS measurements connect the C1 or 11 and C2 or 12 leads in the conventional manner see Fig 4 2 4 5 4 For ZERO measurements connect the C1 or I1 and C2 or 12 leads to the C2 terminal of the standard see Fig 4 3 4 5 5 Using the above described connections for ZERO and FS Full Scale measurements per form steps 4 through 10 of the above procedure which uses the MTS2 standard to complete the calibration DO7 STANDARD RESISTOR P1 P2 LEADS PURE COPPER MULTI STRANDED C1 C2 LEADS 10A RATING 55 0 15mm Figure 4 2 Full Scale calibration setup P1 P2 C2 DO7 STANDARD RESISTOR P1 P2 LEADS PURE COPPER MULTI STRANDED C1 C2 LEADS 10A RATING 55 0 15mm Figure 4 3 Zero calibration setup Calibration 11 12 LOM DO7 Chapter 5 MAINTENANCE 5 1 General Normally no maintenance is required other than cleaning with a moist cloth Avoid strong deter gents or solvents If a failure occurs or if the unit cannot be cali brated it should be returned to IET or to an IET representative Contact IET for an RMA numbe
6. 4 PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT LOM DO7 SERIES Digital Micro ohmmeter User and Service Manual l ET LAB 5 l N C www ietlabs com IET 534 Main Street Westbury NY 11590 TEL 516 334 5959 800 899 8438 FAX 516 334 5988 4 PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT LOM DO7 SERIES Digital Micro ohmmeter User and Service Manual Copyright 2005 IET Labs Inc LOM DO7 im December 2005 0 EPIS INC wren 534 Main Street Westbury NY 11590 TEL 516 334 5959 800 899 8438 FAX 516 334 5988 4 PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT EPIS INC s m 534 Main Street Westbury NY 11590 TEL 516 334 5959 800 899 8438 FAX 516 334 5988 LOM DO7 WARRANTY We warrant that this product is free from defects in material and workmanship and when properly used will perform in accordance with applicable IET specifications If within one year after original shipment it is found not to meet this standard it will be repaired or at the option of IET replaced at no charge when returned to IET Changes in this product not approved by IET or application of voltages or currents greater than those allowed by the specifications shall void this warranty IET shall not be liable for any indirect special or consequential damages even if notice has been given to the possibility of such damages THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INC
7. E C1 C2 LEADS 10A RATING 55 0 15mm Figure 4 1 Preferred calibration setup Calibration LOM DO7 10 4 3 6 Let the setup stabilize for a few minutes 4 4 Calibration Using MTS2 Standard 4 4 1 Calibration 1 Turn the panel switch to the CAL position The CAL LED should light 2 Set the LOM DO7 to the 60Q range VE and press the LOCK and ON switches at the same time hold them down until you hear a beep 3 When the reading stabilizes press the KYB switch The display should show 0 4 Press the OK switch The OK LED should light for about 3 seconds 5 The display should now show 0 00 1 digit If not repeat steps 3 and 4 6 Set the MTS2 to FS 7 When the reading has stabilized press the KYB switch 8 Enter the value 40 using the keypad and then press OK The OK LED should light for three seconds 9 The display should now show 40 00 1 digit If it does not repeat steps 10 Repeat steps 2 through 9 for the remaining ranges in each case setting the MTS2 to the appropriate value 11 Turn the panel switch to RUN and remove the key 4 2 2 Verification 1 Verify that the panel switch is set to RUN and the calibration key is removed 2 Set the MTS2 to 40 Ohm Zero 3 Set the DO7 to the 60 range VE and press LOCK ON Wait for the reading to stabilize The reading should be 0 00 1 digit Record this reading and subsequent readings if required
8. E CONDUCTORS REMOVE POWER WHEN HANDLING UNIT POST WARNING SIGNS AND KEEP PERSONNEL SAFELY AWAY N CAUTION N DO NOT APPLY ANY VOLTAGES OR CURRENTS TO THE TERMINALS OF THIS INSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON THE FRONT PANEL OR THE OPERATING GUIDE LABEL vi LOM DO7 Chapter 1 INTRODUCTION 1 1 General Description The LOM DO7 is an accurate bench portable Digital Ohmmeter for the measurement of resis tance in the range 0 1 uQ to 60Q It utilizes the four terminal Kelvin resistance measurement method to eliminate the effects of lead resistance The measured values are displayed on a 4 digit 6000 count LED display there is also an over flow indicator Simple push button selection of the range re quired makes the LOM DO7 easy to use Error and status warnings are illuminated when appro priate The unit will withstand accidental appli cation of line voltage to the measuring terminals 1 2 Theory of Operation The measurement is true 4 terminal using the Kelvin principle A stable current is produced across the resistance to be measured via the C terminals and the voltage drop across the un known resistance Rx is measured at the P ter minals This potential drop is then compared against the voltage drop across internal stan dards The ratio of these is then converted to the resistance value of Rx and displayed in ohms on the digital display Use of specially selected components assures hig
9. LUD ING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTIBILITY OR FITNESS FOR ANY PARTICULAR PURPOSE LOM DO7 Contents WARRANTY itte EH he lii 0 lur NOE iv WARNING dee pinu eeu CAUTION nce ae Chapter 1 INTRODUGC ELIO Ni sii Fh FERE PESE 1 1 1 General Description 7 1 1 2 Theory 0100 1 1 3 Case Design nime 0 Ede 1 1 4 Available Accessories ii essen 1 Chapter 2 SPECIFICATIONS 2 2 2 2 22 Me s reinient ien Ee be etu be Let o p tiat 2 Chapter 3 OPERATION 3 3 1 Initial SE eee tnde 4 3 2 Safety 1e ee Rer e RR et et aet 4 3 9 Eeat tes nac pee ee e m este 4 3 3 1 Measurement Polarity pp 4 3 3 2 Range Selection 6p irent tenete 4 3 3 3 Error amp Status Lamps eene 4 5 5 2 E 5 REED eee 5 34 4 Current Modeni e Hen e cuite 6 34 5 Over Ringene ucc oe eei 6 3 4 6 Open Circuit Lead essere 7 3 4 7 Low Battery and AC 7 34 6 CONNECTIONS ai dee 7 3 5 Remote Operation and Printer 7 3 5 1 Remote Operation esee 7 3 52 Printer AA tees 7 3 6 PrOteetloti re tegere Per eR eie rt oda 8 Chapter 4 CALIBRATION
10. T gt lt Remote Start gt Socket Battery Status Indicator o RangeSwitches RS232 Printer Socket On Off Power Switch Calibration Lock Figure 3 1 Description of Controls Operation 3 LOM DO7 3 1 Initial Inspection After unpacking inspect unit for shipping dam age and report any problem immediately to the carrier retaining packaging materials for inspec tion 3 2 Safety This unit is designated Safety Class as defined in the IEC Publication 1010 1 Amendment 1 This unit has been designed and tested in ac cordance with IEC Publication 348 entitled Safety Requirements for Electronic Measuring Apparatus and has been supplied in a safe con dition The present instruction manual contains some information and warnings which should be followed by the user to ensure safe operation and to keep the unit in safe condition Before switching on the unit make sure that it is set to the correct line voltage and that the cor rect fuse for that voltage has been installed See the table in Chapter 6 The unit must be plugged in to a grounded outlet only and any extension cord used must be the 3 wire grounding type 3 3 Features 3 3 1 Measurement Polarity The measuring current polarity can be selected from the front panel The display will indicate ei ther or to show the direction of current flow This is particularly useful when evaluating circuits with thermal emf or
11. The LED bar graph display indicates the state of charge of the battery Batteries must be fully charged for proper operation on the lowest two ranges due to the high current required The other ranges may be used during battery charging ac operation however an additional error of up to eight digits will be introduced 3 4 8 Connections To make the most accurate possible measure ments ensure that all test leads are in good con dition and have less than 0 20 resistance Some spade lugs and crocodile clips especially nickel plated brass types can produce high thermal emfs when heated This can sometimes cause problems for example when connecting to hot motor windings Avoid such problems by using plain copper or brass connections and keeping them clean and oxide free The heavy duty binding posts used are designed to accept standard banana plugs in the top socket and bare wires and spade lugs may be clamped when inserted from the side Operation LOM DO7 3 5 Remote Operation and Printer Output Nd E Figure 3 4 Remote Start Socket viewed from panel 3 5 1 Remote Operation If a normally open switch such as a footswitch test leads with a start button or some other type of contact closure is connected to pins 1 and 2 of the REMOTE socket it will mimic the function of the ON key when activated See Fig ure 3 4 3 5 2 Printer Output The print format will be as follows Sign Value Units Mode 600 0
12. ccess to the calibration process which is keylock pro tected 4 2 Equipment Required IET Calibration Standard MTS2 or equivalent 4 terminal standard s Set of 2 low thermal emf leads Set of 2 general purpose leads 10 A rating 4 3 Preparation 4 3 1 Ensure that the unit is completely as sembled Place itin a temperature controlled en I ii P1 c2 P2 vironment 20 C 5 C for a minimum of 4 hours Ensure that the batteries are fully charged 4 3 2 Connect each of the four LOM DO7 termi nals to the equivalent terminals on the calibra tion standard It is essential that low thermal emf leads are used for the P1 and P2 leads See Fig ure 4 1 for the preferred setup 4 3 3 An internal battery powers the LOM DO7 and this should be fully charged before calibra tion The ac charger can be left connected if desired 4 3 4 Set the calibration standard to 40 Ohm Zero 4 3 5 Turn the LOM DO7 ON by pressing the ON OFF switch If the HELP message is dis played perform a special CAL RESET opera tion as follows 1 Insert the Calibration Key into the panel Switch and turn it to the CAL position The CAL LED should light 2 Press the CLE Switch Its LED should light for one second The HELP message should now be replaced by a normal display 3 Turn the panel switch back to the RUN position Pam LE T J 2 CALIBRATION STANDARD MTS2 P1 P2 LEADS PURE COPPER MULTI STRANDE
13. circuits where di ode effects can influence the measurement For measurements where thermal emf can cause a large zero error there is an automatic average AVE button When it is pressed the measur ing current will automatically be reversed and the average value displayed thus eliminating the need for external computations This averaging feature also adjusts the measurement time au tomatically giving the fastest possible measure ment even for inductive circuits The VE and VE lamps will light to indicate that the current polarity is changing For very unstable values where the average mode is unable to establish a stable reading the averaging will be aborted after approximately 25 seconds and the display will show A new AVE cycle will be started automatically 3 3 2 Range Selection Any of the six measuring ranges can be selected manually by simply pressing the desired RANGE button The selected range is indicated by an lit LED Over range is indicated by the display read ing 3 3 3 Error amp Status Lamps The following LEDs will light to indicate the in strument status LINE ac power is connected to the instrument O C One of the measuring leads is open LEAD Open circuited too high a resistance or not connected to the test sample cor rectly or the internal protection fuse is open This lamp will always be lit in the STBY Standby mode Operation 3 4 Making Measurements
14. elative Polarity humidity of 8096 Selectable positive or negative current Storage temperature flow plus an average mode which 20 C to 50 C automatically displays the average AC power value of the positive and negative 103 127 V or 207 253 V 47 63 Hz polarity measurements Power consumption lt 40 VA Dimensions 343 x 327 x 152 mm 13 5 x 12 9 x 6 0 Weight 8 3 kg 18 3 Ib Ranges and Accuracies Range Resolution Typical Uncertainty Temperature Current At 20 C 5 C 1 Year Co efficient C 60 10 mQ 1 mA 0 15 Rdg 0 05 FS 40 ppm Rdg 30 ppm FS 6 Q 1 10 mA 0 15 Rdg 0 05 FS 40 ppm Rdg 30 ppm FS 600 mQ 100 uQ 100 mA 0 15 Rdg 0 05 FS 40 ppm Rdg 30 ppm FS 60 mQ 10 1 Amp 0 15 Rdg 0 05 FS 40 ppm Rdg 30 ppm FS 6 ma 1 10 Amp 0 2 Rdg 0 1 FS 40 ppm Rdg 30 ppm FS 600 uQ 0 1 10 Amp 0 2 Rdg 0 2 FS 40 ppm Rdg 250 ppm FS NOTE Add temperature coefficient specification value to uncertainty specification value when operating outside the 15 C to 25 C temperature range NOTE Measurements on the lowest range 600 uW may have an additional zero offset of up to 0 counts if the measuring current is applied repeatedly for long periods This offset can be eliminated by using the average measuring mode Specifications LOM DO7 Chapter 3 OPERATION Ue ipe Measuring Terminals AC Power Input k U
15. g 3 2 Combined current and potential probes Kelvin clips 60Q range and STBY Standby mode The unit is now ready to make measurements The dis play will blank after approximately 25 seconds of inactivity If the internal checks indicate an error the dis play will read HELP Contact our Service De partment or your IET Representative for assis tance 3 4 3 Measurement Connect the resistance to be measured to the measuring terminals in accordance with the dia gram on the instrument panel and using the most appropriate connection technique for the un known See Figs 3 1 and 3 2 Select the range required and the current measurement mode i e or AVE LEDs will light to indicate which functions are active To initialize the measure ment press the ON switch A single measure ment will be taken and the value held on the dis play for approximately 25 seconds After 25 sec onds the display will go blank and only the RANGE LED will remain lit The last measured value can be recalled by pressing the ON switch To make another measurement the ON switch should be pressed again To take continuous readings press and hold the LOCK and ON switches until a beep is heard this will activate a continuous reading mode LOM DO7 Connections to Stud Terminals Connections to Cable Joint Connections to Current Shunt Fig 3 3 Connections for resistance measurements with various DUT configurations Measurements
16. h accuracy and long term stability 1 3 Case Design The case is ruggedly constructed from a safety yellow ABS polycarbonate composite A strong internal sub frame ensures that the LOM DO7 will withstand the harshest environments The Calibration front panel is a reverse printed polycarbonate overlay with clear and unambiguous text 1 4 Available Accessories Supplied 1 Set of test leads 1 Power cord 1 Operation Manual Optional Lead Sets HSO1 Kelvin Clip Set with 3 meter leads HSO1 RS Similar to HSO1 but includes remote start button HSO2 Kelvin Clip Set with 3 meter and 15 meter leads HSO2 RS Similar to HSO2 but includes remote start button LSO3 Large Kelvin clips with 3 meter leads accept cables and bars up to 38 mm in diameter LSO4 Similar to LSO3 but with 3 meter and 15 meter leads Other Optional Accessories FSO1 Foot Switch for remote actuation 601 1 Meter Cable Test Fixture Wood Base CO2 1 Meter Cable Test Fixture Metal Base CBO2 Accessory Pouch attaches to cover MTS2 Calibration Standard PRO2 Portable Thermal Printer RS101 RS232 Cable LOM DO7 Chapter 2 SPECIFICATIONS 2 1 General 2 2 Measurement Digital Display Resistance 4 digit 0 8 high LED 6000 count with True four terminal measurement with automatic decimal point and error fixed dc measuring currents warning lamps Measuring time Operating temperature range Approximately 0 5 seconds 0 to 40 C with maximum r
17. mQ VE 600 0 mo 600 0 AVE The value printed will be followed by a line feed and carriage return If the DO7 displays an over range condition it will print as For cable connection details see page 8 Print All All measured values will be sent to the printer RS232 when the PRINT ALL switch is ON as indicated by the LED on the switch This key toggles ON OFF LOM DO7 Print Last The last measured value only will be sent to the printer This is defined as the last value mea sured when switching from ON to STBY This key toggles ON OFF Baud Rate This key will display the currently set Baud Rate when pressed To change the value press CLE and then use the keyboard to enter the new value finishing with OK If the newly entered value is valid it will be stored in non volatile RAM If itis invalid a long beep will sound and the existing rate will be retained The valid Baud Rates are 75 110 150 300 600 1200 2400 4800 9600 19200 The format is fixed at 8 bit data 1 start bit 1 stop bit and no parity 3 6 Protection This instrument is protected against voltages hon Ji Hve being applied inadvertently to the terminals A high interrupting capacity fuse is installed inter nally in the current circuit and a gas discharge tube GDT is installed across the current termi nals If voltages above 90 V are applied to the measuring terminals the GDT will strike effec ti
18. r before returning the unit directly to IET There is a line fuse in the ac power input socket on the front panel and an input protecting fuse on the circuit board Examine and replace these fuses if necessary before a final decision to re turn the unit for repair CAUTION Disconnect ac power cord and all connecting leads before removing a fuse Re place only with the correct fuse types as shown below Fuse 250 V Voltage IEC 127 Range 5x20mm 104 132 V 1 25 A T sb 191 242 V630 mA T sb Nominal Line Voltage 120 V 220 V Maximum input power 40W The input circuits are protected by a 10 A fuse located in a holder on the main printed circuit board Remove the top cover for access Re place only with the correct fuse type as shown below NFC63210 Altech 10C10x38GI or Cooper Bussman KTK 10 5 2 Battery Charging The LOM DO7 has a built in rechargeable sealed lead acid battery which is fully charged when delivered To ensure good service life from the battery the LOM DO7 incorporates a sophis ticated battery management system Battery condition is indicated by a LED bar graph dis play The battery charger is built in and the instrument may be connected to a 120 or 220 volt ac sup ply The appropriate voltage setting must be se lected on the ac input socket and the correct fuse inserted The LINE LED on the front panel will light to indicate when the unit is connected to ac power
19. ry Replacement Only competent and skilled personnel should carry out battery replacement Be sure to main tain correct polarity of the connecting wires The red wire always goes to the positive battery ter minal Note the blue tag on the red wire does NOT indicate polarity Maintenance LOM DO7 13 IET LABS INC Standards Decades Strobes Sound Level Meters Bridges Formerly manufactured by 534 Main Street Westbury NY 11590 TEL 516 334 5959 800 899 8438 FAX 516 334 5988 Gen Rad www ietlabs com IET LABS INC Standards Decades Strobes Sound Level Meters Bridges Formerly manufactured by 534 Main Street Westbury NY 11590 TEL 516 334 5959 800 899 8438 FAX 516 334 5988 Gen Rad www ietlabs com
20. vely shorting the C or terminals through the protective fuse which will open and interrupt the circuit The voltage terminals are not fused and will withstand up to 460 Volts without damage to the instrument IWARNING To replace the protection fuse the top cover should be removed but only after ac power and all input connections are removed The protec tion fuse is located on the main printed circuit board This fuse has a 40 000 to 200 000 A in terrupting capacity depending on the exact type used Always replace this fuse with one of the same current rating 10 A and atleast a 40 000 A interrupting capacity 8 1 aem NC spt M 3 2 7 Blue ed _ RD O ig inia HR Red lt gt Blue TD es 28 4 HC lt m i 7 5 GND Yellow GND Hc e h e mute NEL AMEN NM 5 CTS Omen Co White VIT oe i G9 ac oe Z5 pin PC 9 Pin Socket Figure 3 5 Printer Output Connections Operation LOM DO7 Chapter 4 CALIBRATION 4 1 Calibration Process This procedure describes the standard calibra tion method for the LOM DO7 Micro ohmmeter using the IET MTS2 Calibration Standard or dis crete resistance standards of the required val ues ICAUTION The LOM DO7 comes factory calibrated to its full accuracy and any recalibration by the user will invalidate this initial calibration The user should therefore be certain that only authorized and competent personnel are permitted a
21. will continue and periodic beeps will be heard until the ON or STBY key is pressed Remember that the current drain on the internal battery can be up to 10 A on the lowest ranges To preserve battery life the unit will au tomatically turn off after 5 minutes of inactivity Note the ON key LED remains lit while mea surements are being made 3 4 4 Current Mode The current mode can be set to or AVE The AVE mode should be selected for all mea surements that are not inductive as this elimi nates errors due to thermal emf in the measure ment circuit or test leads In the AVE mode the LOM DO7 takes readings with the current flow ing in both directions and displays the average of the two readings For measurement of induc tive circuits the measuring current should either be set in 1 or 1 mode 3 4 5 Over Range If the measured value exceeds the upper limit of the range selected the display will indicate Select a higher range Operation 3 4 6 Open Circuit Lead If one of the test leads is open circuited or ex ceeds a preset resistance the O C LEAD LED will light and the display will indicate The C terminals are checked for compliance voltage Measurements cannot be made if this warning message is displayed This warning will also be displayed if the internal protection fuse is open When in STBY mode this LED will always be lit 3 4 7 Low Battery and AC Operation
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