20024 man_GB - pedranti elio
Contents
1. Current Terminals These terminals provide the measuring current With the current circuit open the voltage present at the output is between 2V and 2 4V depending on the state of the battery and the presence or absence of the mains voltage V V Voltage Terminals Through these terminals is detected the voltage drop across the unknow resistor with a sensitivity that reaches 10nV on the range of 32uQ GND Ground Terminal Located at the rear of the instrument is a standard bushing with hole 4mm in diameter electrically connected to the housing Can be used to improve the rejection to environmental disturbance by connecting the instrument to the ground Alternatively or in combination the same bushing can be used to connect a shield of voltage cable as shown in Fig 2 or Fig 3 on page 7 to page 18 LINE Power Socket Located at the rear of the instrument is the power plug from the mains 230V 10 48 66Hz and 5x20mm fuse holder with fuse 200mA delayed COM Communication Port Located at the rear of the instrument allows to communicate with a PC via an optically isolated connection You can read the data and setup of the instrument and modify the setup 13 96 DIGITAL 20024 AUXILIARY INFORMATIONS In the five areas of the lower part of the display the status line provides many auxiliary information summarized in the table below Infor2. 0 6 3200 0 0 5 0 6 32010 0 6 0 7 OK 0 7 TEST NOISE 4 i OK TEST EMC TEST BURN IN OK MANUAL CABLES SOFTWARE i OK This is to certify that the instrument conforms to the technical specifications relating thereto as stated in the technical specifications Date The Verifier The Operator DECLARATION OF CONFORMITY The company PEDRANTI ELIO Via Cesare Battisti 33 B Cardano al Campo Varese Italia declare under our sole responsibility that the instrument 20024 to which this declaration relates is in conformity with the rules laid down in directive CEE89 336 Cardano al Campo 07 07 08 Pedranti Elio 33
3. Pressing the button briefly is recall the saved configuration range filtering current automatic manual backlight and function displays the main measurement or measure temperature compensated Button pressed gt 1 sec Save configuration Pressing the button for longer than a second you save the current configuration HOLD Freezing of the measure Toggle on off the hold mode of the measure During the Hold mode does not work any button with the exception of the buttons backlight BKL and filter FLT If the instrument is in hold mode Hold text is displayed flashing in the status line at the bottom right of the screen 10 96 DIGITAL 20024 36 Name button A AUTO FUNC A Z In the table below are summarized the operation the mode of activation and the type of signaling in function of time for which a button is pressed Action Acoustic short Operation warning long short long short If in Autorange mode Exit from auto range remaining short in the selected range If in Manual mode If it has not reached the range short 3200 passes to the upper range Do not execute the command if it long is on the range 3200 In the lower part of the screen appear the range activates and the text Man short If in Autorange mode Exit from auto range remaining short in the selected range If in Manual mode If it has not reached the range of short 32
4. respectively For the range of 32 0 the word depends on the last setting made If the measurement is in Do not execute the command Overload If the measurement is valid Measurements are made using direct and reversed polarity and is represented the average The measure goes on hold and you have the flashing of the word on the bottom screen Exits from Bipolar measurement Each time the button is pressed you select a different filter value in the sequence 1 2 4 8 16 32 64 1 2 4 Turns on off the backlight of the display Given the high consumption of the backlight is recommended in case of battery operation turning it on only when absolutely necessary Switch from direct to reverse polarity measurement and vice versa At the bottom of the screen appears Dir or Inv Recall the saved configuration range filtering current automatic manual measure compensated and backlight Save the current configuration of the instrument If the measurement is not in Block the measure and you have Hold the flashing of word Hold in bottom of the screen Remain active only FLT BKL and CFG buttons If the measurement is in Hold Exits from block of the measure 12 96 DIGITAL 20024 36 INPUTS On the front panel there are only four test sockets which are essential if you want to measure resistances of low and very low value with the Kelvin method
5. 256 byte12 absolute value Is a read only variable byte 13 Serial number Is the instrument serial number Is a read only variable byte 14 Checksum Is the algebrical sum of thirteen bytes of data truncated to the lower byte If hypothetically the sum of the byte corresponds to 07A2H 07A2 value in hexadecimal notation this byte is A2H Is a read only variable WRITING SETUP The whole setup of the instrument is written at one time by sending the command byte 08H following it by the same first five bytes received while reading amended as necessary to reflect the new desired setup It is reiterated that regardless of how many and which bytes have been modified is absolutely indispensable send all five bytes represented in the table below after the command byte 08H adding as the seventh and last byte the checksum byte You should definitely consider when you want to change the setup first perform a read so you have the updated position at the last moment of the state and of the setup of the instrument 28 96 DIGITAL 20024 36 WRITE COMMAND 08H a Type of Read byte Definition data Write 08 command code for writing write upper byte of room temperature compensation lower byte of room temperature compensation range read and write filter read and write statel read and write checksum write read and write Below you will specify in detail
6. noise byte 6 Statel Being a set of flags each bit can be changed independently of any other Binary Meaning Value Measure represented 0 main measure bargraph 1 main measure bargraph absolute and relative percentage 2 setting room temperature 3 measurement with temperature compensation main measure room temperature Measuring current 0 low current 1 high current Backlight display 0 off l on Measurement direct reverse 0 measured by direct current 1 measured by reverse current Select range manual automatic 0 manual 1 automatic Measurement active in hold 0 no request 1 are asked to hold the measure Measurement active in zeroing 0 no request 1 asked the zeroing of the instrument byte 7 Checksum Is the sum of the six bytes of data including command byte truncated to the lower byte If hypothetically the sum of the previous byte corresponds to 02 02 value in hexadecimal notation this byte is FBH 30 31 32 5 INSTRUMENT MODEL 20024 SERIAL NUMBER INSTRUMENT BATTERY OK USB PORT I TEMPERATURE of CALIBRATION RANGE RESISTANCE OF MEASURED VALUE RESULT REFERENCE 3200 0 5 0 6 320 0 5 0 6 3200mO 0 5 0 6 OK 320 0 5 0 6 OK 32 0 5
7. the number of readings to be performed to obtain the average the value of which is set by FLT button Button pressed gt 1 sec__ Lead current compensation The second function of this button is activated if this is pressed over a second and allows to compensate the voltage drop on the current cables in a better way than does the procedure of auto zeroing In fact despite the high common mode rejection of the input amplifier when current cables have high voltage drop due to the measurement currents of 1 10A or the section of these is insufficient or they are too long the amplifier is not able to fully compensate for the common mode voltage variation that it comes to have between the normal operating conditions with the current circulating in the cables and that of auto zeroing when current is interrupted momentarily 96 DIGITAL 20024 36 Although specifically designed for the compensation described above and then especially in the presence of measurement currents of 1A and 10A this possibility is active on all ranges since also allows zeroing the measurement if it appears that connected to the terminals as shown in Fig 2 the main measure is not of zero value Fig 2 Connection to be made during the compensation of the voltage drop on the current cables By its nature the compensation is different for each range and depends on the measuring current used Compensation is therefore only valid for
8. the range and for the current measurement For this reason the instrument saves the particular compensation in the memory cell corresponding to that range and the current so as to recall it when they are selected again The compensation is saved in non volatile memory at power down Since the saved values are highly dependent on the measurement conditions length and cross section of cable current potential thermoelectric and internal temperature of instrument as well as elapsed time from power on of the latter it may happen that the next time you turn on the instrument the compensation is no longer valid Selecting the Current Measurement Toggles the current measuring low or high The nominal current measurement is indicated by the word cur or CUR depending on whether low or high respectively For the range of 32uQ where the current is only 10A the writing depends on the last selection made Procedure of Bipolar Measure Multifunction button Button pressed lt 1 sec Activation bipolar measurement Do not execute this command if the measure is overloaded 96 DIGITAL 20024 36 If the instrument is performing the measurement with reverse current change it to direct current then wait for a time dependent on the number of readings to be performed to obtain the average the value of which is set by pressing the FLT button The bipolar measurement procedure consist to run the number of measurements s
9. write byte 5 Status1 This byte is a set of seven fields where is summarized the state of the instrument Is a variable both read and write Status1 Binary Meaning Value Measure represented 0 main measure bargraph 1 main measure bargraph absolute and relative percentage 2 setting room temperature 3 measurement with temperature compensation main measure room temperature Measuring current 0 low current 1 high current Backlight display 0 off l on Measurement direct reverse 0 measured by direct current 1 measured by reverse current Select range manual automatic 0 manual 1 automatic Measurement active in hold 0 active 1 in hold Measurement active in zeroing 0 active 1 zeroing 26 96 DIGITAL 20024 36 byte 6 Status2 This byte is a set of 6 fields which complement the state of the instrument Is a read only variable Binary Meaning Value Bipolar measurement 0 measurement not bipolar 1 bipolar measurement 2 bipolar measurement in hold 3 not used Overload measurement 0 overload 1 positive overload 2 negative overload 3 not used Sign of the main measurement 0 positive polarity 1 negative polarity Sign of the relative measurement 0 positive polarity 1 negative polarity not used not used byte 7 8 Main measu
10. 6 32 64 measures Maximum inductive value 35 Henry 150 ohm Working temperature 0 50 C Storage temperature 20 60 C Weight 4770 gr approximately Dimension 243x89x285mm WxHxD 15 96 DIGITAL 20024 36 The table below shows the values of resolution measuring current and maximum power dissipated by the unknown resistance depending on the selected full scale RESOLUTION AND MEASURING CURRENT Range Resolution Resolution Voltage Current Maximum resistance voltage of f s low high power 320 0 10 0 108 Q 10 100nV 0 32 3 2mV 1 10A 320u W 32mW 20 1 Summary table of the resolutions sensitivity measuring current and maximum power dissipation of the unknown resistance as a function of the selected range To prevent which excessive heating inside of the instrument may cause drifts in the measure particularly so on the two lower ranges and when is used a high measurement current the battery charge current is about 1A when the instrument is turned on and 2A current when it is off Consequently the full charge when switched off involves approximately 20 hours of time while if the instrument is on and always working with measuring current the charging time can vary greatly depending on the selected range and the state of the backlight For measuring current of 1A and backlight on you have a slight discharge of the battery whi
11. DIGITAL NANO OHMMETER 32000 points In Q 320 0 mod 20024 USER MANUAL PROFESSIONAL MEASURING INSTRUMENTS 20024 MAN_GB DOC JUNE 2015 26 DIGITAL 20024 INDEX INTRODUCTION DESCRIPTION AUTO HOLD DEFINITION BUTTONS AND INPUTS BUTTONS INPUTS AUXILIARY INFORMATIONS TECHNICAL SPECIFICATIONS TIPS ON THE MEASUREMENT EXECUTION POTENTIAL OF CONTACT USING THE METHOD OF BIPOLAR MEASURING MEASUREMENT ON RANGE 32 0 ELECTROMAGNETIC FIELS CURRENT CABLES OF INSUFFUCIENT SECTION SLOW OF MEASUREMENT MEASUREMENT OF ELEMENTS HIGHLY INDUCTIVE PROTECTION FROM OVERVOLTAGE AND OVERCURRENT COMMUNICATION PORT GENERALITY READING DATA WRITING SETUP 14 15 18 18 20 20 21 22 22 22 23 24 24 24 28 DIGITAL 20024 96 DIGITAL 20024 36 INTRODUCTION The digital nano ohmmeter mod 20024 is a instrument with performance absolutely unique although size and weight are extremely low provides resolutions and features never present together so far 32000 measuring points 5 measurements per second 8 ranges from 320 Ohm to 32 uOhm from 10 mOhm to 1 nOhm of resolution current measurement can be selected choice of automatic or manual range measurement graphic display bar graph relative measure both absolute and percentage simultaneously of the main measurement temperature compensatio
12. absolute and relative percentage setting the room temperature measurement with temperature compensation main measure room temperature each time you press the button main measure bargraph absolute and relative percentage Pressing the button when are displayed only the main measure and the bargraph will displayed also the relative measure expressed as a percentage and absolute both with sign The percentage value is calculated with the formula percentage 100 actual_value initial_value initial_value where with the initial value and actual value are respectively indicated the value read from the instrument at a time when you pressed the button and the last acquired value obtained from an average of readings equal to the value reported by The minimum and maximum values represented are respectively 100 0 to 6550 0 When the percentage value in absolute terms equals or exceeds 100 the resolution automatically changes from 0 01 to 0 1 In absolute representation you have the resolution of the range at that moment on while the value is expressed as absolute actuale_value initial_value 96 DIGITAL 20024 36 setting the room temperature By pressing the button you have disappearance of the main measure of the bar graphs and relative measures while displaying only the temperature compensation of the resistance denoted by Ta ie ambient temperature This is be
13. ange of scale switch to range higher gt 31999 points switch to range lower lt 3000 points Resolution and measuring current view Tab 1 RESOLUTION AND MEASURING CURRENT Measurement accuracy 20 C range 320Q 3200uQ high current 0 05 0 001 C 2 digit Measurement accuracy 20 C range 320Q 3200p low current 0 06 0 001 C 3 digit Measurement accuracy 20 C range 320uQ high current 0 06 0 001 C 3 digit Measurement accuracy 20 C range 320uQ low current 0 07 0 001 C 5 digit Measurement accuracy 20 C range 3240 0 07 0 001 C 5 digit Noise referred to input from 0 01Hz to 0 1Hz 200nV with filter 16 FLT 16 Compensation current cable Zeroing compensation of emf of voltage circuit and the offset of the instrument up to 1000 digits Heating time after the power up about 15 minutes within a tolerance of 0 3 Compensation range of the measure with the room temperature Ta 0 0 C a 50 0 C in steps of 0 1 C Coefficient of temperature compensation copper according to standard CEI EN 60228 2005 10 Temperature at which the measurement is reported 20 0 C according to standard CEI EN 60228 2005 10 Open circuit voltage A A current circuit open 2 20 Vmax battery operation 2 40 Vmax mains operation Filter average on 1 2 4 8 1
14. bsolute value certainly modest generally a few tenths of microvolts but unfortunately they are more than detectable by instruments of similar sensitivity That s why it is essential to take some basic and essential precautions to have a good quality of the measurement The main but not the only ones are Clean the surfaces of the terminals of the unknown resistance and measuring cables from oil water oxides etc If the section of the current cables is less than or equal to 4mm2 these must be of equal cross section to avoid that a different heating by Joule effect causes a drift of the measurement over time In any case it is strongly recommended that you use cables of not less than 6mm2 when using the lower ranges of 320040 320uQ and 32 0 Wait for the cooling of the object to be measured Avoid heating cooling even slightly and in whatever way a terminal of the resistor to be measured relative to each other Avoid concatenate the measurement cables with varying magnetic fields that can cause a bad reading Always perform an auto zeroing and possibly a compensation of test lead to the first measure and wait at least 10 minutes after the power on before you use the instrument if you want good accuracy and stability of the measurement Always perform auto zeroing when you are on the range 3200uQ 320uQ 32uQ or the test leads are connected to another resistance Do not change the measurement poin
15. cause that temperature is that at which the measurement is taken of the unknown resistance In this screen the temperature is varied using the buttons A and respectively for increasing and decreasing the temperature value displayed on the right of the screen with a resolution of 0 1 C in a range between 0 0 C and 50 0 C The new value is automatically saved in non volatile memory of the instrument when you switch to the measure compensated measurement with temperature compensation main measure room temperature Pressing another once the button you have the representation of the compensated measurement at the top while in the central area is the actual measurement of resistance indicated by Ra and performed at room temperature and the set room temperature Ta The compensated measure refers to a standard temperature of 20 0 C according to CEI EN 60228 2005 10 If you press the CFG button to save the configuration when you are on this screen recalling the saved configuration or switching on the instrument is called this screen main measure bargraph Pressing the button disappears the screen with the compensated measure and appears the main measure and the bargraph If you press the CFG button to save the configuration when you are on this screen recalling the saved configuration or switching on the instrument is called this screen 96 DIGITAL 20024 36 Interpr
16. ch if the measured current increases to 10A is discharged about in one hour The following is the graph of autonomy of the battery as a function of the selected range and the switching on off the backlight of the display 16 96 DIGITAL 20024 36 Battery autonomy Owith backlight high current 32 uohm D 320 3200 uohm D 32 320 3200 32 320 ohm open circuit 150 200 250 300 350 Hours Tab 2 Graph representing the autonomy of battery as a function the selected range and status of the backlight 17 96 DIGITAL 20024 36 TIPS ON THE MEASUREMENT EXECUTION POTENTIALS OF CONTACT After switching on the instrument before taking any measurements it would be advisable to wait at least 10 minutes This allows the necessary thermal settling of the components of the nanoohmmeter In carrying out the measure is essential in order to obtain the best results follow the connection diagram of the terminals of measurement shown in Fig 3 In this way it is avoided that in the circuit voltage there are the contact resistances of the current terminals with a macroscopic alteration of the measurement results With cables of Kelvin type this problem does not exist since the two tweezers placed to end are connected in such a way as to avoid that the contact resistances adversely affect the measurement Ot
17. es of the voltage and current and that are not wobbly or vibrate 21 96 DIGITAL 20024 36 even in proximity to static magnetic fields this will cause the occurrence of induced voltages of amplitude and frequency dependent on the movement CURRENT CABLES OF INSUFFICIENT SECTION Another cause of error even if in this case decidedly modest and found only on the ranges from 3200UQ 32000 32 0 is due to the limited section of the current leads If in fact the section is less than 6 mm2 and the cable is proportionally too long it has between zeroing and measurement a difference in the voltage drop on the cable that the measuring amplifier is no longer able to properly compensate by introducing a error with the cables supplied usually not more than 2 to 4 digits The remedy is to use on the lower range cables of elevated section and as short as possible If there is any cables that provide high falls and compensation is necessary to reduce the error see the instructions on page 7 relating to paragraph Zeroing procedure SLOW OF MEASUREMENT This is certainly not a cause of the error but it may seem sometimes that the instrument is too slow or even stop it the reason is due to the value that has been set in the filter The higher this value the longer the time that the instrument takes to make a series of measurements on the unknown resistance MEASUREMENT OF ELEMENTS HIGHLY INDUCTIVE The nano
18. et by the FLT with the direct current and the same with the reverse current and perform the average then returning in direct current mode During the procedure appear the words BIPOLAR flashing and the bar timepiece At the end of the procedure the measurement is displayed and flashes at the bottom of the screen A further bipolar measurement can be started by pressing again the BIP button Button pressed gt 1 sec Deactivation bipolar measurement Pressing the button for longer than a second the instrument leaves the bipolar measurement mode and disappears written at the bottom of the screen FLT Selecting Filter Each time the button is pressed you select a different filter value in the sequence 1 2 4 8 16 32 64 1 2 4 The number which is also displayed at the bottom of the screen after the word Flt indicates the number of acquisitions used to calculate the average which is the main measure represented This is particularly useful especially on the range of 32uQ or when using the measuring current low where the instrument has a maximum sensitivity voltage The greater the number of measurements over which the average is performed and more slowly responds the instrument While maintaining a frequency of update of the measurement on the display of 5 Hertz has the advantage of better stability of the representation It may happen that switching to a following filter value the main measure proves unreliable temp
19. etation of the operation of the bargraph The bar graph under the main measure shows graphically the value between 1040 0mQ and 1049 9mQ In the picture the bar graph is set to value of 1040 0mQ 7 1mQ 71 pixels The bar graph has a total of 100 pixels and graphically displays the small variations of the main measurement For example if the primary measure is 264 15uQ the value to the left under the bar graph would be 264 00uQ and the bar graph would be 15 pixels long 0 15uQ Zeroing procedure Multifunction button Button pressed lt 1 sec This multifunction button allows the auto zeroing the instrument without the need to disconnect the terminals of current or voltage and short circuit them This procedure on instruments of high sensitivity such as this if not done properly could make it completely unreliable the measurement With the automatic procedure is also obtained compensation of the various thermoelectric effects in the contact points between the terminal voltage and the unknown resistance as well as all along the measuring cable up inside the instrument for each contact of different metal materials During execution of auto zeroing is obtained also the elimination of the drift of the measuring amplifier Pressing the button for less than 1 second appear the words AUTOZERO flashing and the bar timepiece until the completion of the procedure the duration of which is variable depending on
20. he terminal voltage V with V this does not result dangerous to the instrument but does not guarantee the validity of the measure because the amplifier is optimized for positive signs AUTO HOLD The instrument has an Auto Hold function ie the ability to freeze the display when the test leads or the pliers are disconnected from the element under test In particular this happens when you have the interruption of the circuit by disconnecting at least one of the current terminal It is given to reporting on the status line at the bottom right of the screen with the flashing CAUTION This function is automatically activated only when the instrument is in Manual mode This allows you to maintain the auto ranging function for automatic selection of the most suitable range to measure 96 DIGITAL 20024 36 DEFINITION BUTTONS AND INPUTS BUTTONS The instrument has 12 buttons whose functions and modes of operation are detailed below and summarized in a table below Through them you can directly select all the functionality of the instrument without resorting to menus or keystrokes Four buttons are dual function and the selection of the function is based on the time in which they are pressed short if less than one second or long if greater than said time The two functions refer to the same mode As an example consider the BIP button Pressing it briefly activates the bipolar measu
21. her sources of error may be the potential of contact that you have when two different metal materials meet To minimize the influence of this physical phenomenon it must try to have the same type of contact between positive and negative terminal voltage and the unknown resistance This contemplates both the state of the surfaces polished oxidized dirty etc that the material other than material of a head of the unknown resistance compared to another as well as the different temperature at which they can be the points of contact of the element under test If the type of contact to the positive terminal is similar to the negative terminal the two effects tend to cancel and at most remains a potential equal to the difference of the two If this effect remains constant over time is sufficient to compensate him once and for all on the contrary should periodically reset by pressing A Z button The change that you mention is mainly due to variations in temperature between the two points where the voltage probes touch the unknown resistance the only Way get a stable Fig Connection diagram for measuring four wires and reliable measure of a resistor of low value is to take every 18 96 DIGITAL 20024 36 precaution to ensure that immediately after an zeroing there are not fluctuations in the temperature difference of the two points of contact All the above said phenomena are in a
22. how to interpret the data to send byte 1 Write command Is a constant value of O8H byte 2 3 Room temperature of compensation It has exactly the same meaning and modes of representation indicated in the section on reading data The validity range of the value is between 0 and 500 inclusive Values that exceed these limits are not considered by the instrument Suppose you want to send a value to an room temperature of 31 2 C it is necessary to consider the value 312 which in hexadecimal is represented as 0138H namely byte2 01H byte3 38H byte 4 Range It has exactly the same meaning and modes of representation shown in the table on the range The validity range of the value is between 0 and 7 inclusive Values that exceed these limits are not considered by the instrument If the new range is different from the previous the instrument is forced into manual mode and exits from eventual representation of the relative measure displaying only the main measure bar graph 29 96 DIGITAL 20024 36 byte 5 Filter It has exactly the same meaning and modes of representation shown in the table for the filter The validity range of the value is between 0 and 6 inclusive Values that exceed these limits are not considered by the instrument On two lower range 320uQ and 32uQ any codes of filter less than 3 are forced to 3 to ensure that an adequate filtering of measurements in the presence of
23. ials of contact is usually due to different causes their drift or noise may be different This can lead to a variation in time of the measurement more pronounced compared to the measurement with symmetric potentials of contact which by definition they cancel each other If there is an asymmetry in the potentials of contact but you continue to use the normal measurement mode not bipolar it should be noted that the correction zeroing which is made may not be constant over time Also considering a asymmetric noise of amplitude and causes different therefore more difficult voidable mutually we recommend using a filter of at least 16 when you run a bipolar measuring it helps to further reduce the variations in the measurement results As can be activated deactivated has already been explained in the section on BIP button MEASUREMENT ON RANGE 32 0 AND 320 0 LOW CURRENT Given that these two ranges have a sensitivity in voltage of only 10nV equal to about 1 1000 of the signal provided by a thermocouple for a change of temperature of 1 C its use must be entrusted to experienced personnel capable of evaluating the multiple phenomena that may incur in making unreliable the measurement It is necessary to be considered very carefully the temperature gradients in both environment and on the resistance being measured You must choose appropriate connection points to the object under test by checking the mechanical strength avoid in any way air fl
24. mation Automatic Manual Direct Reverse Bipolar Battery status Indication 320Q 320 3200mQ 320m2 32mQ 3200 0 320 0 32u O Hold no indication no indication image of a battery with charge level gradually decreasing image of empty flashing battery Selected range Instrument in Autorange mode Instrument in Manual mode The current flows from the positive terminal The current flows from the negative terminal The instrument is performing a bipolar measure Instrument is in Hold mode Instrument is in Auto Hold mode The instrument is not in Hold or Auto Hold mode and even in bipolar measuring Battery OK Battery charge level in gradually decreasing Fully discharged battery Status of the message Permanent on all ranges Permanent Permanent Flashing Flashing Flashing Permanent Flashing 96 DIGITAL 20024 TECHNICAL SPECIFICATIONS Power supply 230V 10 48 66Hz fuse 200mA delayed Power requirement 15 Battery visual indication of charge status battery Battery autonomy view Tab 2 Representation on backlighted graphic display 64x128 pixels 62x44mm Points of measure 32000 Display refresh rate 5 Hz Range 32 0002 320 00u Q 3200 0u Q 32 000m2Q 320 00 3200 0mQ 32 0002 320 002 Range selection automatic manual Automatic ch
25. mperature compensation range read and write filter read and write status a read and write status2 a read upper byte of main measure absolute value lower byte of main measure absolute value upper byte of relative value absolute value lower byte of relative value absolute value upper byte of temperature compensated measure lower byte of temperature compensated measure serial number instrument read checksum read read and write 1 2 3 4 5 6 7 8 read read read Below will be explained in detail how to interpret the data received byte 1 2 Room temperature of compensation Represents the value of the temperature used to compensate the measurement and is expressed without a decimal point or equivalently in tenths of a degree if the ambient temperature is set to of 27 4 C the value is equal to 274 To obtain the value perform this calculation temperature_value bytel 256 byte2 Is a value both read and write access byte 3 Range This byte contains a code corresponding to the selected range as indicated in the table opposite Is a variable both read and write 320 0 pa 1 3200UQ S 3 ee 4 3200 25 96 DIGITAL 20024 36 byte 4 Filter This byte contains a code corresponding to the FILTER selected filter as indicated in the table opposite Is a variable both read and
26. n of the measure from 0 0 C to 50 0 C choice of the polarity of measurement automatic measurement in both polarities indicating the average value auto zeringo the instrument compensation of test leads measurement hold choice and display the magnitude of the filtering of the measure backlight on off acoustic signaling of the correct selection line and battery standard operation indication of the state of battery charge save recall of configuration reading data and setting via optocoupled USB only two commands one to read all the data and setup and one to write the new setup Accuracy number of measuring points and resolution as well as reduced size and weight make the instrument certainly unique and suitable for use both in the laboratory as in the field Indeed the presence of internal rechargeable batteries shall release from the necessity of the mains voltage with a autonomy that can reach a maximum of about 350 hours The main measure is also well represented with large characters 10mm high that allow the reading to three meters away The instrument has no menu where you can select the options you want but only and simply the ability to slide four screens in which displays the main measure displays the main measure and the relative and absolute percentage is set the temperature compensation of the measurement displays the measure compensated the main measure and the tempe
27. nsated room temperature for the compensation of the measurement instrument status range filter page view current measurement backlight etc Also you set the room temperature for measure compensation change the setup of the instrument YY All of this means of just two commands a read request with which the instrument provides all the information available to it by sending a string of 13 bytes followed by a fourteenth byte of checksum write command followed by a string of 5 bytes that represent the new setup to which is added a seventh byte of checksum READING DATA Is sent to a single request bytes of 00H value The instrument complies with 13 bytes of data followed by a checksum byte terminal as shown in the following table The first 5 bytes are both read and write or are bytes to be sent to the instrument when requesting any changes to the setup More details will be given in section WRITING SETUP Some data in the form of bytes range filtering and serial number others in the form of words as a set of two bytes the main measurement relative measurement compensated measurement and room temperature for compensation and still others as a set of flags with fields of one or two bits 24 96 DIGITAL 20024 36 READ COMMAND 00H 2 byte Definition data Write upper byte of room temperature compensation lower byte of room te
28. ohmmeter 20024 is able to measure the resistive component also highly inductive elements such as transformers with a power of more than 1 MVA To avoid damage or malfunction of the instrument is advisable to connect in parallel to the unknown resistance a diode as shown in Fig 4 the next page Such protection diode should however put only if actually there is a need and in the presence of inductive loads since on high range the reverse current of the same diode can alter although modestly the measurement To protect the range from 320Q to 320mQ including is sufficient a diode of the type 1N4004 or similar able to withstand currents of 1A For the lower range from 32mQ 32UQ is advisable to use a diode can withstand higher currents Its function is mainly to protect the amperometric circuit The voltage circuit is protected against continuous differential voltages up to 35V and pulse up to 100V for 1 second 22 96 DIGITAL 20024 36 CAUTION The instrument is not able to bear on the bushings of measurement the application of external voltages or currents especially if due to the direct connection with the network line PROTECTION FROM OVERVOLTAGE AND OVERCURRENT The instrument is provided with adequate protection against voltage surges on voltage inputs as specified in the technical specifications but requires in the case of measurement of predominantly inductive elements an external
29. orarily until the buffer of the measures is refilled BKL Backlight Turns on off the backlight of the display In case of battery operation it is recommended to turn on the backlight only when absolutely necessary since the power absorbed by the instrument excluding the measuring current increases from about 120mW to 700mW reducing the operating time of the instrument considerably The autonomy however does not fall below 50 hours with the backlight actived and range 3200mQ or higher 96 DIGITAL 20024 36 POL Measurement Mode Direct or Reverse If the instrument is in Direct mode is brought into Reverse mode and vice versa Allows to determine the direction of the current in the element under test without having to disconnect the terminals to reconnect in the reverse way when a measurement is required with the opposite polarity or to assess the presence of electrical potentials of different nature in the circuit voltage In fact it is not advisable to physically swap the terminals because it may determine different electrical potentials thwarting the measurement made just to determine or to reduce the influence of such potential If possible you should use the higher current for execute the measure In this way minimizes the influence of the potential of contact thanks to a signal voltage ten times greater Save Configuration Multifunction button Button pressed lt 1 Recall saved configuration
30. ows partial lighting power which induce localized heating magnetic fields etc It is absolutely advisable to execute the measurement not less than 15 minutes after switching on the instrument this allows to achieve an appropriate balance of thermal components of the instrument itself 20 96 DIGITAL 20024 36 At this point there are two possible strategies of measurement that exploit respectively the thermal inertia and the thermal settling of the components Indeed the passage of a measuring current 10 determines a heating and consequent unwanted thermal drift due to thermal phenomena however that propagate and derive rather slowly stabilizing at about 15 20 minutes Having the possibility of perform a fast measurement is possible to exploit the thermal inertia so as not to give rise to a sufficient heat propagation If is required instead a measurement in time you will have to wait for the thermal settling to have enough stability Please note that thermal drift be as 0 3uV equal to 30 digits with a variation of about 0 5 to 1 5nV sec and it is normal to have variations including noise settling thermal and potential for contact 100 to 200 digits A possible arrangement to minimize the drift and the settling time is to reduce the dissipation of the instrument making it run only on batteries obviously after having loaded well in advance Avoid any case to circulate cooling air
31. protective diode Such a diode as shown in the previous section is fully sufficient to protect the generator current circuit This does not mean however that the instrument is able to withstand electrical stress such as connection to motors or transformers connected to its power supply especially if this is the line network The electric power at stake in this case would be well beyond those Fig 4 Connection diagram of the protection tolerable by the protection diode in parallel with an strongly inductive circuitry internal and external element Note the direction of insertion of the of nanoohmmeter and its diode damage would be certain CAUTION It is important that the protective diode is connected in parallel to inductive element and not between the terminals of current or voltage otherwise it is not able disconnecting current cables to eliminate the strong glitter that is created The spark can also reach voltages of thousands of volts and irreparably damage some electronic circuits of the current generator 23 96 DIGITAL 20024 36 COMMUNICATION PORT GENERALITY The nanoohmmeter 20024 is equipped as standard with a USB interface optically isolated Using the appropriate optional module which looks similar to a plug connector RS232 9 pin you can connect the device to a PC to obtain the following information main measure relative measure measure temperature compe
32. rature 96 DIGITAL 20024 36 DESCRIPTION The instrument is mounted in a aluminum extruded anodized case Of limited weight it has the handles to facilitate transportation and swivel feet in order to better view of the display and accessibility to commands and test sockets The graphic display 64x128 pixel is very large relative to the size of the instrument so as to facilitate the reading even from a distance and in low light Even the arrangement of the information measuring primary and secondary settings and indications has been designed to be easily readable and never create confusion The entire instrument is managed by a 16 bit microprocessor while the technique of measurement is ratiometric four wire otherwise known as Kelvin connection the only one that allows you to get off at accuracies and resolutions so thrusts The amplifier and converter are in a monolithic device so as to have an equivalent input noise with filter 32 of only 100nVpp typical in a minute and drifts lower than typical 300nVpp in 10 minutes On the front there are four bushings A A V V two of which provide for the measuring current and two for the detection of the voltage drop across the resistor The four wire method makes it insensitive the measure from resistance of the wires that carry the current and the various contact resistances in the circuit nanoohmmeter test leads unknown resistance The inpu
33. re Represents the absolute value of the main measure and is expressed without commas or units The correct representation is determined by considering the selected range and bit 4 of State2 If a hypothetical measure is 217 43 mQ range code 4 the value contained in the two bytes considered is of 21743 To obtain the value perform this calculation main_measure_value byte7 256 byte8 absolute value Is a read only variable byte 9 10 Relative measure Represents the absolute value of the relative measure and is expressed without commas or units The correct representation is determined by considering the selected range and bit 5 di Stato2 If a hypothetical measure is 1 09uQ range code 1 the value contained in the two bytes considered is of 109 To obtain the value perform this calculation relative_measure_value byte9 256 byte10 absolute value Is a read only variable 2h 96 DIGITAL 20024 36 byte 11 12 Room temperature of compensation Represents the value of the room temperature used to compensate the measurement and is expressed without comma or units of measure The correct representation is determined by considering the selected range and bit 4 of State2 If a hypothetical measurement 1 1698 2uQ range code 2 the value contained in the two bytes considered is of 16982 To obtain the value perform this calculation temperature_compensated_measure_value byte11
34. ring while pressing for a long time allows you to get out it A suitable acoustic alert if the function or the pressed button is active or not In certain conditions in fact some buttons are disabled and pressing there is a long beep An example is the inability to perform an auto zeroing procedure during a bipolar measure Pressing the A Z button there is a long beep The following lists the buttons and their functions la Selection of the upper range If the instrument is in Automatic mode go to Manual mode If the instrument is in Manual mode selects the range immediately above unless it has already been reached the range of 3200 On the screen relative to the temperature compensation allows increasing this parameter Selection the lower range If the instrument is in Automatic mode go to Manual mode If the instrument is in Manual mode selects the range immediately below unless it has already been reached the range 32 0 On the screen relative to the temperature compensation allows the decrease of this parameter Automatic Manual mode If the instrument is in Automatic mode is brought into Manual mode and vice versa 96 DIGITAL 20024 36 FUNC Main measure Multifunction button Absolute and relative percentage Setting the room temperature Measurement with temperature compensation The button passes successively displaying of main measure bargraph main measure bargraph
35. t after you have performed a auto zeroing Since the potential of contact may vary from point to point is essential to have the best results do not move the points of measurement even if these are assumed to be equipotential current flows and potential of contact different in different points alter the measure This is absolutely valid also if you wanted to run an auto zeroing do not ever alter the electrical connection of the terminal voltage between measurement and the auto zeroing 19 96 DIGITAL 20024 36 USING THE METHOD OF BIPOLAR MEASURING When it is assumed the presence of potential of contact not symmetric on the input terminals which thus can not be eliminated by a simple auto zeroing procedure the solution is the use of the bipolar measurement mode Since for each representation there are more measurements with direct and reverse current and a subsequent stop this measurement system is inherently very slow and therefore is to be used only when needed or for actually to verify that there are asymmetric potentials comparing the result of bipolar measurement which in theory is the correct one with the measurement available after a auto zeroing Do not forget however that a difference of a few digits is possible and normal Is not expected therefore also in case of absence of potential of contact or when these are symmetrical a perfect identity of values Since the asymmetry of the potent
36. t signal is then amplified and compared with the reference internal resistance the result properly prepared and processed by a microprocessor is shown on the LCD The low current used for the measurement reduced to the negligible power dissipation for Joule effect with the consequent very low alteration of the measurement For the same reason the fall of the maximum rated voltage of 32mV which avoids any semiconductor junctions in parallel to the unknown resistance make the measurement invalid With the exception of range 32uQ you can choose between two measurement currents With the current high there is a resolution in 1uV voltage which drops to 0 1uV with the current low If the necessity is to have a minimum dissipation on element under measurement the choice is to use the lower current evidenced by written cur before the value of the current in the lower part of the display Otherwise it is recommended to use higher current shown with the CUR before the value of the current so as to minimize side effects due to potential contact or drifts of the measuring amplifier Important notices in this regard are given in the section TIPS ON THE MEASUREMENT EXECUTION 96 DIGITAL 20024 36 Fig 1 Block diagram of the nanoohmmeter 20024 and the four wire measurement CAUTION The presence of the sign before the value of the measure is only to indicate that they exchanged t
37. that surely would create differences and thermal variations on the cables of voltage measurement that would cause many signal variations Should not be underestimated even the noise both environmental and internal to the instrument The latter is typically contained in approximately 200nV in a period of 1 minute To reduce the variations in the short term it is recommended to use a filtering high 32 or 64 In any case the minimum filtering on 320 and 32 0 is 8 As regards the electromagnetic noise could perform the measurement in a Faraday cage or anechoic connecting the instrument to the earth through the appropriate rear bushing bearing the closer together the tension cables to minimize the area and the noise induced within the coil of the signal If all this seems excessive please note that measurements with resolutions of are definitely very close measurable limits Substantially below 0 1nQ no longer able to go down It is also recommended to put adequate attention to the measurement with low current allowed in all ranges except 32uQ where the resolution of the output voltage is only 0 1 definitely value to be considered low level ELECTROMAGNETIC FIELDS Other causes of instability or failure of the measurement or in zeroing are attributable to the presence of magnetic fields can induce electrical noise can move the level in DC of the signal The best way to mitigate this influence is to keep short the wir
38. uQ passes to the lower range Do not execute the command if it long is on the range of 3210 In the lower part of the screen appear the range activates and the text Man short If in Autorange mode Switch to Manual mode without short changing the range Tf in Manual mode Switch to Autorange mode short selecting the range that is suitable for measurement In the lower part of the screen appear the range activates and the text Aut short Having a complex operation refer to section relative to the FUNC short button to p 5 Measurement of Relative Absolute has the same resolution as the main measure while the measure of Relative Percentage has a resolution of 0 01 up to 99 99 and Dy O TS from OOO cmonwatse se short Perform a auto zeroing the instrument short long If the measurement is in Do not execute the command long Overload If measurement lt 1000 points Captures the value and short treats it as zero If measurement 21000 points not execute the command long DIGITAL 20024 If the measuring current is Switch to low current high and the range are from measurement 3200 to 320 0 If the measuring current is Switch to high current low and the range are from measurement 3200 to 320uQ If the range is 3210 Do not execute the command measuring current fixed to 10A The measuring current is indicated by the word cur or CUR depending on whether low or high
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