M3 Digital LCR Meter
Contents
1. TEST FIXTURE FOR EXTERNAL DC BIAS Or Battery Internal Resistance Measurement HS C2 device 1M 10GnF under test C1 O a oe eae 470uF 63V pate kes Hp O oft R2 390 1W 49R9 b swt apen far boitery megsurement IN4 604 aes aS VR 1GGnF VBIAS lt 40V oO HR 262. low capacitance use cables that are shielded all O the Open Short Compensation Before making any measurements the LCR meter must be zeroed each time it is turned on Zeroing must also be performed each time the test fixture is changed This open short compensation when properly performed is important in subtracting out effects of residual impedance and stray admittance caused by test cables Open Short compensation is one of the most important steps to insure accuracy in measurement Through this process each residual parameter value can be measured and the value of a component under test automatically corrected The model of the measurement circuit is given in the figures below NORMAL MEASUREMENT MODE Ym Virtual admittance Zx Measured impedance Zss Residual impedance Rss Residual resistance Lss Residual inductance Ypp Stray admittance Gpp Stray conductance Cpp Stray capacitance 11 OPEN zero mode SHORT zero model One of the most important things to remember is to make a concerted effort to achieve consistency in measurement techniques and fixturing Of equal importance when performing open short compensation is the test clips must be positioned exactly as the device under test expects to see them In other words position the clips the same distance apart as they will be when connected to the DUT There are two methods of zeroing the meter The first method is to zero at the selected test frequency To perfo
3. Inductance and A value for toroid core C D Capacitance and Dissipation R Q DC Resistance and Quality Z Absolute impedance and phase angle R X Resistance and Reactance G B Conductance and Susceptance n Vs M This key selects the transformer measurement mode Pressing this key steps through and permits the selection of the desired function N 6 1 N 6 Vs Vp M 6 N 6 Turns ratio and phase angle 1 N 6 reciprocal turns ratio and phase angle Vst Vp Secondary and Primary Voltage M 0 Mutual Inductance and phase angle FRE The Freq key selects one of the following test frequencies 100 Hz 120 Hz 250 Hz 500 Hz 1 kHz 2 5 kHz 5 kHz 7 8125 kHz 12 5 kHz and 15 625 kHz The selected frequency is indicated just above this key Pressing this key for longer than two seconds sets the LCR meter to use the default parameters The default frequency is 1KHz AUTO HOLD The Auto Hold key selects the impedance range of measurement appropriate for the device under test Pressing this key holds the unit in its current measurement range Repeated pressing of this key changes the measurement impedance range 1 6 Pressing this key for longer than two seconds returns the unit to auto ranging or normal mode The range is displayed in the top right corner of the display The A character behind the Range number indicates that the instrument is in Auto Range mode In Manual or Hold
4. change to the measurement mode A failure to calibrate at any level other than OPEN and SHORT may require that the default resistor values be modified The calibration routine compares the value entered against the measured value of the calibration resistor If the measured value falls outside the program tolerance the calibration will fail In this case adjust the value of the resistor that has failed in the PARAMETER setup as outlined above e Turn the LCR meter OFF and then ON If the instrument failed any of the calibration steps above the instrument will indicate this failure and the point of failure at power up Successful calibration will place the instrument into measurement mode Accuracy e Basic accuracy is 0 2 for frequencies up to 1K Hz with impedances between 15Q to 600KQ range 2 to 5 e Accuracy for frequencies between 1KHz and 10 KHz and a second area between 100Hz and 10 KHz and between 0 3Q and 3 MQ is 0 3 e Accuracy for range 1 and 6 is lower because there are two resistors for the X10 amplifiers that introduce additional drift 0 1 additional e Accuracy is 0 8 for impedances between 0 and 0 3Q for frequencies above 10 KHz and for impedances above 3 MQ Accuracy specifications are valid when the open short calibration is performed and with appropriate Kelvin clips See chart below for graphical analysis of accuracy 100M 3M 600k eordrsva 070 J3 15 0 2 100Hz 1k 10k 25k Freque
5. from becoming negative The schematic for a simple test fixture to apply DC bias is provided at Appendix 1 Inductors Inductors are measured in Henries An inductor is a device for storing energy in a magnetic field which is the opposite of a capacitor that is a device for storing energy in an electric field An inductor consists of wire wound around a core material Air is the simplest core material for inductors because it is constant but for physical efficiency magnetic materials such as iron and ferrites are commonly used The core material of the inductor its length and number of turns directly affect the inductor s value e Model and frequency An inductor can be graphically represented as in the figure below 14 Cp The series resistance Rs represents the resistive losses in the windings The parallel capacitance Cp is the equivalent capacitive effect between the turns of the coil and the parallel resistance Rp is the sum of all losses in the core Open flux inductors are more sensitive to metallic materials that are in close proximity because such materials modify the magnetic field Toroidal inductors keep the flux inside the core and are less sensitive to external conductors in close proximity Inductor measurements can be made in either the series or parallel model Where the inductance is large the reactance at a given frequency is relatively large so the parallel resistance becomes more significant
6. meter has a basic accuracy of 0 2 and has 10 test frequencies The LCR meter is controlled by a high speed microcontroller with embedded logic that controls the display and keypad as well as setting measurement conditions and performing calculations SPECIFICATIONS Measurement Modes Auto L Q C D R Q Z 0 R X G B N 0 N 0 Vs Vp M L AL C Vr varactor option Equivalent Circuit Series or parallel Parameters Displayed Value Deviation Deviation Measurement Display Range L Q C D R Q Z 0 R X G B N 0 N 6 SDZOZWAXMXPPROAVINOY VstVp Vs Vp M M L A L AL 0 01 uH 99 99 H 0 001 100 0 001 pF 99999 uF 0 001 10 1 mQ 99 9 MQ 0 001 100 1 mQ 99 9 MQ 180 00 180 00 1 mQ 99 9 MQ 1 mQ 99 9 MQ 1 9999 180 00 180 00 0 0001 1 180 00 180 00 230V N or 115V N 0 01V resolution 115V or 230V 0 01 uH 99 99 H 0 01 uH 99 99 H L N N set by user from 1 to 999 With varactor option C Vr C Vr TEST CONDITIONS Test frequency 0 001 pF 99999 uF 0 00 5 0V or 0 0 30 0V 100 Hz 120 Hz 250 Hz 500 Hz 1 kHz 2 5 kHz 5 kHz 7 8125 kHz 12 5 kHz 15 625 kHz 2 measurements per second Drive Voltage 0 5 Vrms 5 Measurement Rate Ranging Auto or Manual ACCURACY Conditions At least 15 minutes warm up 23 C 5 C Basic Accuracy 0 2 See the accuracy section for detailed accu
7. reference square waves signals have no particular phase relationship to the measured analog signals and because the current through Zx is not controlled The AC signal voltage from the phase sensitive detector is integrated during an integer test signal period that is near 20ms 50Hz operation or 16 67ms 60Hz operation together with a DC offset This ensures that the final result is always the same sign The value of the voltage is obtained by timing the discharge of the capacitor with a 17 bit counter inside the controller TRANSFORMER PARAMETER MEASUREMENT This function measures transformer parameters through an IC switch permitting the measurement of the High Sense voltage for the secondary side or High Drive for the primary side of the transformer The Low Drive and Low Source terminals are connected to ground through a virtual ground In Mutual Inductance measurement mode the instrument measures the primary current and the secondary voltage to compute the mutual inductance Secondary Source Resistor Primary G D L Figure 1 3 Basic Transformer Measurement Setup 21 DIAGNOSTICS AND CALIBRATION SCREENS DIAGNOSTIC MODE Pressing and holding the MODEL key during power up permits access to one of two modes Diagnostic mode and Calibration mode The instrument displays the following screen Select diagnostic mode by pressing L C R Z key You
8. than any series resistance therefore the parallel model should be used For very large inductance values a lower measurement frequency will yield better accuracy For low value inductors the reactance becomes relatively low so the series resistance is more significant and the series model is the appropriate choice For very small inductance values a higher measurement frequency will yield better accuracy All inductors have a maximum allowable current Above this value the core saturates the magnetic field remains constant and the inductance decreases to near zero The maximum current is dependent on the core material A core material with high permeability gives a higher inductance for the same number of turns as a core of low permeability The drawback is that the core saturates at a much lower current Note Inductors with a Q less than 1 will not be automatically detected The LCR meter will default to the Rs mode Increasing the test frequency to where the inductor Q is greater than 1 will then switch the major parameter to L If at the highest test frequency the Q does not raise above 1 manually selecting the L mode will give the value of the inductor Resistors The unit of measurement for resistance is the Ohm Of the three basic circuit components resistors cause the fewest measurement problems This is true because it is practical to measure resistors by applying a dc signal or relatively low ac frequencies Resistors are usual
9. M Digital LCR Meter M Digital LCR Meter Model Auto Frequency L C R Z nlVsIM Freg Hold Range Model Menu Disp Zero User s Manual Copyright September 2006 M Cubed Electronix Inc All rights reserved M Cubed Electronix Inc reserves the right to modify alter or change functions and specifications without notice Table of Contents Page 1 General Information Specifications 3 2 Symbols and Terms 4 3 Display and Controls 5 4 Initial Calibration 8 5 Operation 11 Connecting to the DUT 11 Open Short Compensation 11 Measurement 13 Capacitors 13 Inductors 14 Resistors 15 Q and D Factors 15 Transformer Measurement 16 Sorting 17 Ar Value 18 6 Theory of Operation 20 7 Diagnostics and Calibration 22 8 Appendix 1 DC Bias Test Fixture 26 A special thanks to the following individuals for their contributions in the development and realization of the M Digital LCR Meter and documentation Michel Waleczek Sarcelles France www mwinstruments com designer programmer engineer Field Testers Robert Hughes Columbus OH Robert Cerreto Amherst OH Robert Finch Albuquerque NM James Larsen Anchorage AK Monty Northrup Austin TX Bruce Stough Saint Louis Park MN GENERAL INFORMATION The M DIGITAL LCR Meter is a multi frequency impedance measuring instrument capable of measuring resistance capacitance inductance or transformer parameters from 1 mQ to 100 MQ The M DIGITAL LCR
10. S clips together using another short piece of wire Turn the LCR meter off e Hold down the Model key and apply power to the LCR meter Release the Model key when the DIAG CAL screen appears e Press the key under CAL n Vs M e Press the key under PARAM L C R Z e Press the key under NEXT L C R Z until the display shows Mains Frq 60 Hz on the first line and NEXT 50HZ 60Hz on the second line Press the key under 60Hz Freq e Press the key under NEXT If you are NOT going to adjust the default values for the calibration resistors proceed to the next step If you want to change the default resistors values first review the Calibration Mode page 21 and continue as follows Press the NEXT key The display will show the calibration resistor value of RCAL1 which is 10 0000 ohms Pressing the NEXT key will step through the value of all six resistors To edit the value of any of the calibration resistor values more precisely press the key under EDIT when the appropriate resistor is shown A cursor will appear under the first digit Pressing the key under CHANGE will increment this digit When the correct number is displayed pressing the key under NEXT will step to the next digit Continue to adjust the numbers until the value of your calibration resistor is displayed As an example assume that the 10 ohm calibration resistor measures 9 995 ohms using an ACCURATE ohmmeter To enter this value select EDIT for the 10 0000 ohms resistor The cursor
11. This step calibrates the LCR meter for an OPEN state Press the key under OK Freq The calibration routine will calibrate the OPEN state for each of the 10 test frequencies There will be a progress indicator bar displayed on the second line of the display As each frequency is successfully calibrated the instrument will step to the next frequency If the calibration process fails at any frequency the progress bar will stop and FAIL will be displayed on the second line There will also be an audible alert long tone The calibration process will stop and the instrument will return to the starting screen for the failed step Upon successful calibration of the OPEN state the instrument will proceed to step 2 The display will show STP2 SHORT CAL Remove the short between the HD and HS clips Remove the short between the LD and LS clips Using a short piece of wire short all 4 clips together with the separation between the HS and LS clips the same distance as they will be when connected across one of the precision calibration resistors The HD and LD clips should be placed to the outside of the HS and LS clips This step calibrates the instrument fora SHORTED state Press the key under OK Freq The calibration process will again step through each of the 10 test frequencies The process is identical to the OPEN calibration procedure above Upon successful completion of the SHORT calibration the instrument will continue to step 3 The instrument wi
12. alue LCRZ 3 30 1023 823 667 538 DISP 1 23 323 220 117 Buzzer test This test is used to test the operation of the audible alert feature menu Complex i v This diagnostic mode gives access to the in phase and quadrature measurements that are used to compute the final value The instrument determines two complex vectors one for the current and one for the voltage Each vector has an in phase real component and a quadrature imaginary component The coordinates of these vectors are relative to the reference range resistors These values must be multiplied by the current range resistor value to get the actual vectors In this mode the range and the frequency can be changed The LCRZ key permits toggling between the Voltage coordinates and the Current coordinates The screens below show the results when a 1uF capacitor is connected to the instrument at 1kHz frequency The theoretical absolute value of the capacitor impedance is 159Q at 1kHz We will select the range 2 to get optimum signal noise ratio Range resistor is 100Q typical for range 2 The coordinates of the Voltage vector are 55 7Q for the real part and 34 7Q for the imaginary part Press L C RZ key to get the Current vector coordinates The coordinates of the Current vector are 21 9Q for the real part and 35 1Q for the imaginary part We can now draw a complex graphic to show the final result ee ari It is possible to calculate the absolute impeda
13. can now select one of the four diagnostic modes by selecting NEXT Press CHE to access the keypad diagnostic mode Press I T to return to the main menu Press HET to access next diagnostic function Press H to access the buzzer test Press Et 1 T to return to the main menu Press HET to access next diagnostic function Press CHE to access complex voltage current measurement Press E f T to return to the main menu Press HEF to access next diagnostic function Press HE to access analog digital converter results Press E31 T to return to the main menu Press E T to return to the keypad diagnostic function Keypad test This test is useful to test the operations of keypad circuits The keypad delivers a voltage that is read by the micro controller The result of the conversion is displayed in the top right of the screen An X is also displayed according to key pressed The X remains in the display after the key is released You can exit this mode only when all 8 keys have been pressed This is the first screen when entering the keypad diagnostic mode This screen is displayed when the L C R Z key is pressed This screen is displayed when the n Vs M key is pressed Compare the results with the table below Alternatively measure the voltage across R70 resistor on the keypad assembly Actual values can differ by a small percent due to resistors tolerances 22 Voltage R70 Displayed V v
14. ce Rs has little significance in this case the parallel circuit model should be used to more closely represent the effective value The opposite is true when C has a large value In this case the Series Resistance Rs is more significant than Rp thus the series circuit model becomes appropriate Mid range values of C require a more precise reactance to resistance comparison but the logic remains the same The rule of thumb for selecting the most appropriate model should be based on the impedance Z of the capacitor Above approximately 10 KQ use parallel model Below approximately 10Q use series model Between these values follow the manufacturers recommendation e Frequency Generally high value capacitors should be measured at lower test frequencies because the impedance of the component will be very low Low value capacitors should be measured at higher frequencies Electrolytic Capacitors The accurate measurement of electrolytic capacitors particularly large value caps can present unique requirements The M LCR meter applies an AC signal to the DUT To test some polarized components such as electrolytic and tantalum capacitors it may be preferable to use only positive voltages During normal operation the AC current source swings negative 50 of the time which results in an inverse polarization of the capacitor under test To prevent this inverse polarization a DC bias can be applied to prevent the voltage across the part
15. curate ohmmeter 0 01 accuracy or better you can measure the value of the six calibration resistors and adjust the precise values within the calibration routine Measure and note the value of each resistor Remember the accuracy of the measurements made by the LCR meter will be dependent on the accuracy of the initial calibration If you are NOT sure of the accuracy of your ohmmeter accept the default values In this case add 0 1 to the basic accuracy value of the instrument Calibration also requires the 4 clip cable provided with the kit or a true Kelvin clip cable with HD HS High Drive High Source terminals connected to one clip LD LS Low Drive Low Source terminals connected to the second clip and the cable shields connected to ground at the plug end The calibration sequence only needs to be performed once The values derived during the calibration routine are stored in non volatile memory and will remain stored in the instrument until the calibration routine is performed again left 4 wire test cable right Kelvin Clip cable Turn on the M3 Digital LCR meter and allow it to warm up for at least 15 minutes to stabilize prior to calibration For a detailed explanation of the Calibration and Diagnostics options see DIAGNOSTICS AND CALIBRATION SCREENS starting on page 19 To begin calibration connect the test cable to the DIN socket on the LCR meter Short the HD and HS clips together using a short piece of wire Short the LD and L
16. e correct number of turns has been entered press the key under fF Press the Menu key and select YES to save this configuration Connect the toroid inductor to the LCR meter and the A value will be displayed on the second line of the LCD where by the example used here A 561nH Assume that an inductance of 100uH is needed To determine the number of turns required N using the formula presented above L 100uUH or 0001H A 561nH or 000000561H N V 0001H 000000561H V 178 13 so 13 turns would be required on this core for an inductance of 100 uH press the Menu key and select E to save the current configuration THEORY OF OPERATION The M3 DIGITAL LCR meter uses an auto balancing bridge technique to measure unknown impedance by measuring the voltage across the device under test DUT and the current through it Figure 1 1 is the basic block diagram of the M3 DIGITAL LCR meter and shows how the instrument measures unknown impedances The output of a signal source is applied through a source resistor Rs which varies according to the measurement range to the unknown device ZX and range resistor Rr The effect of amplifier A is to cause the same current Ir that flows through the unknown device to flow through Ra and as a result to drive the junction of the unknown device and Rp to zero volt virtual ground Across Re there is a voltage V2 Jr x Rr Voltages V1 and V2 across the unknown device and across Rp respectively are co
17. e signal is generated using a square wave filtered by a 5 order switched capacitor elliptic filter LPF 7 The cut off frequency is determined by the frequency of the filter clock signal and is set to 1 28 times the test signal frequency The output of the filter is a x 100 over sampled signal and a first order low pass filter LPF 2 removes most unwanted harmonics Total harmonic distortion is approximately 0 05 The LPF2 filter is followed by a buffer and a source resistor selector Reference Signal Buffer Source Resistor Clock Signal Figure 1 2 Signal Source Section Block Diagram 20 PHASE DETECTOR AND A D CONVERTER Phase and absolute value of the unknown impedance is obtained by multiplying the unknown AC voltage with a square wave that is coherent with the stimulus The mean value of the multiplier output is proportional to the in phase or quadrature component of the unknown voltage A total of four such measurements in which the phase of the square wave is advanced by 90 resolves the unknown voltage into orthogonal components This process is applied for both the voltage and the current Therefore eight measurements are needed for the final calculation Anti phase components are substrated 0 with 180 and 90 with 270 consequently eliminating all common offsets and reducing noise Each of these voltages measurements is meaningless by itself because the
18. e the short from the 4 test clips The meter is now ready to perform measurements same _ spacing as_ DUT Bare Wire Short note correct sequence HS and LS to the inside The second method will zero the meter at all ten test frequencies at one time Use this option when measuring several different type components at different frequencies To perform this function connect the clips leads as above for performing an OPEN zeroing Press and hold the Zero Range key for two seconds or longer The LCD will display OPEN SHORT Exit Notice that the Open and Short options are capitalized Press the key under OPEN and the instrument will zero the meter at each of the 10 frequencies Connect the clips as above fora SHORT Press and hold the Zero Range key for two or more seconds The LCD will again display OPEN SHORT Exit with the functions in capital letters Press the key under SHORT and the instrument will zero at each of the 10 test frequencies Measurement The M Digital LCR meter defaults to Auto detect Auto model operation at power up with a test frequency of 1kHz When a capacitor inductor or resistor is properly connected to the test clips the device will be recognized automatically within limitations as defined below To measure a device connect the HD and HS clips to one lead of the DUT and connect the LD and LS clips to the other device lead Do not hold the clip leads while the DUT is being measured T
19. efore any ESR or D measurement Range Auto Hold In order to measure both low and high impedance values several measurement ranges are provided in the M LCR meter Ranging is usually done automatically and selected depending on the impedance of the DUT Note that these ranges are impedance ranges not inductance or capacitance ranges Range depends of the component value and the test frequency Allowing the LCR meter to automatically select the correct range helps maintain the maximum signal level and highest signal to noise ratio for best measurement accuracy The process keeps the measured impedance close to full scale for any given range again for best accuracy Range holding rather than auto ranging is a feature most applicable for repetitive testing of similar value components Range holding can reduce test time Another use of Range Hold would be when measuring components whose value falls within the overlap area of two adjacent ranges Impedance Ranges Range 1 0 001Q to 15Q Range 2 15Q to 300Q Range 3 300Q to 3 kQ Range 4 3 KQ to 30 KQ Range 5 30 kQ to 600 kQ Range 6 600 kQ to 99 9 MQ ranges 1 and 6 are extended ranges respectively using the reference resistor of range 2 and 6 Extended ranges use voltage amplification range 1 or current amplification range 6 Transformer Measurements The M LCR meter has a special function to determine the turns ratio between the primary and secondary windings of a t
20. fault value is OFF Set this feature to ON to compensate for random noise that is apparent when measuring some components There are seven selectable step rates from 2 to 8 Each step adds approximately 25 seconds to the sampling refresh rate of the LCD display At measurement default value is OFF Set this feature to ON to measure the A value of an unknown toroid core Press the forward arrow key to enter the number of turns on the inductor To enter the number of turns select EDIT A cursor will be displayed under the last digit on the LCD Pressing the Change key will step the value of the digit over the cursor Pressing the NEXT key will move the cursor to the far left position When the number of turns has been entered press the OK key For accuracy a minimum of 10 evenly distributed turns on the core is recommended 1 Pressing the Menu key and saving the current configuration will place the LCR meter in L Ar mode The A value will be displayed on the second line of the display 2 To return to normal measurements press the Menu key and step backward or forward using the appropriate arrow key to the A display option Select OFF and press the Menu key again Save the current configuration DISP The Disp key selects the manner that the value of a component will be displayed If the Sorting mode is disabled pressing Disp cycles through the following display types e The value being measured e The deviation of the val
21. gnostic mode and Calibration mode The instrument displays the following screen Select calibration mode by pressing the n Vs M key The instrument now displays two setup modes Parameters or Calibration The FHEEIM mode allows selection of 50Hz or 60Hz operation and adjustment to set the precise values of the calibration resistors The FL mode provides the calibration routine the LCR meter Select the Parameter mode by pressing the LCRZ key The instrument now displays the following screen Calibration resistor values are 10 100 1K 10K 100K 1M ohms Pressing the n Vs M key will allow editing the precise values of the currently displayed resistor Pressing the LCRZ key will step to the next resistor Stepping past the 6 calibration resistors values the instrument will display the Mains Frequency option This option must be set prior to adjusting any resistor values 24 Select the appropriate frequency for the region where the LCR meter will be used In the United States select 60 Hz by pressing the Freq key Select the HET option by pressing the LCRZ key This will bring up the option to SHWE the edited parameters by pressing the n Vs M key Selecting MET by pressing the LCRZ key will return the display to the RCALI screen and pressing the Freq key will Ef T the Parameters setup without saving any entered values Selecting FILIE will force the entered parameters to be stored in memory overwriting the default
22. he LCR meter will automatically select the correct Range for the detected device as well as the most appropriate Model series or parallel Pressing the L C R Z key will manually step through the measured major and minor parameters for the DUT Pressing the Model key will manually switch between Series and Parallel equivalent circuits To return to the Auto detection mode press the L C R Z key for two seconds or more To return to the Auto Model mode press and hold the Model key for two seconds or longer Temperature can have a large impact on the DUT impedance Usually capacitors have large temperature coefficients except for ceramic COG capacitors which can exhibit only a 0 003 C variation Inductors especially those with non air cores may vary largely with temperature Ambient and DUT temperature drifts may introduce error into the measurement Control ambient temperature changes to reduce errors Capacitors Capacitors are measured in Farads The basic construction of a capacitor is a dielectric material between two electrodes The many different types of capacitors available are classed according to their dielectric types The figure below shows the range of generic capacitance values for standard types Aluminum Electrolytic Tantalum Electrolytic Mica Sey ee ee 1uF imF A capacitor can be modeled as a pure capacitor C with some parasitic elements see the figure below RS is the actual series resistance comprised of
23. ll display STP3 100 ohm CAL Pay particular attention to the value displayed here This is 100 ohms The 100 ohm level must be calibrated before the 10 ohm process This is NOT an error Remove the short from the 4 test clips Connect the HS clip to one side of the 100 ohm resistor close to the resistor body Connect the LS clip to the other side close to the resistor body Connect the HD clip to the same lead as the HS clip and connect the LD clip to the opposite side with the LS clip Press the key under OK to begin the calibration process The calibration routine will calibrate the instrument at all ten test frequencies The calibration process is the same as above Successful completion of the 100 ohm calibration will move the routine to step 4 The instrument will display STP4 10 ohm CAL Connect the 10 ohm calibration resistor to the 4 test clips in the same manner as in the 100 ohm calibration step Press the key under OK The calibration routine will begin with the same process as in the previous steps As each calibration step is completed the routine will move to the next step Step 5 requires the 1K calibration resistor Step 6 requires the 10K calibration resistor Step 7 requires the 100K resistor and Step 8 requires the 1M resistor Upon successful calibration of all 6 values the instrument will then allow you to save the calibration values The display will show STP8 SAVE Press the key under OK The instrument will display PASSED and
24. ly measured at dc or low frequency ac where Ohm s Law gives the true value under the assumption that loss factors are accounted for e Model For low values of resistors below 1kQ the choice usually becomes a low frequency measurement in a series equivalent mode Series because the reactive component most likely to be present in a low value resistor is series inductance which has no effect on the measurement of series R For high values of resistors greater than several MQ the choice usually becomes a low frequency measurement in a parallel equivalent mode Parallel because the reactive component most likely to be present in a high value resistor is shunt capacitance which has no effect on the measurement of parallel R Dissipation Factor D or Quality Factor Q D and Q are useful as measures of the purity of a component that is how close it is to being ideal or containing only resistance or reactance D the dissipation factor is the ratio of the real part of impedance or resistance to the imaginary part reactance D is commonly used when describing capacitors of all types A low D indicates a nearly pure capacitor Q the quality factor is the reciprocal of this ratio For inductors a high Q 15 indicates a more reactively pure component The importance of D or Q is the fact that they represent the ratio of resistance to reactance or vice versa In order to achieve reliable measurement results a short zeroing must be performed b
25. n WER LG condition In this case pressing the Auto Hold key will return the meter to Range 1 The second special transformer measurement function is the ability to calculate the secondary winding voltage of a power transformer With either a low voltage or high voltage transformer correctly connected as above press the n Vs M key until the Vs and Vp parameters are displayed The default primary voltage is 230V To change the primary voltage to 115V press the Menu key The bottom line of the display will present the primary voltage options Press the key under i 1 to select this as the primary Em LT to display the correct secondary voltage The display now reflects the calculated secondary voltage based on the turns ratio with the designated primary voltage The third transformer measurement option is the calculation of the Mutual Inductance between the primary and secondary windings With the transformer connected as above press the n Vs M key until the Mutual Inductance value is displayed on the display lt O gt gq o 4 a gt oO g 2 fe B eF a E 5 lt lt ct rm ple ferete 4 oO na a oma oO QO lt Q Q To calculate the Mutual Inductance the meter measures the primary winding inductance as normal inductance but the voltage measured is the secondary winding voltage This automatic measurement can introduce some errors due to parasitic capacitance between the windi
26. nce of the capacitor Z 100 x v i 100 x 65 62 41 36 158 6Q Note that this value is close to the theoretical value 159Q Zv Sig oe ea 23 A D results This diagnostic mode gives access to the primary measurements that are used to compute the in phase and quadrature values The values displayed correspond to the phase detector output signal mean value measured by the A D converter The phase detector is a multiplier The input of the multiplier is either the Voltage or the Current signal One can switch between these two signals using the L C R Z key The 1 gain is driven by a square wave signal that has the same frequency as the test signal The phase of this signal can be shifted from 0 to 270 with 90 step with the n Vs M key Press LCRZ key to select Voltage measurement then n Vs M key to select 0 phase angle Press Auto Hold and set the Range to 2 The display shows the result of the A D conversion Pressing the N VS M key permits the measurement of this voltage with 90 180 and 270 phase angle Subtracting anti phase values gives the quadrature voltage value here Vq 0 344 0 6909 0 34690 Subtracting anti phase values gives the in phase voltage value here Vi 0 79745 0 23967 0 55778 Perform the same tests with the current measurement by pressing the LCRZ key Calibration Mode Pressing and holding the MODEL key during power up permits access to one of two modes Dia
27. ncy Operation Connecting to the Device Under Test DUT The M3 Digital LCR meter uses a 4 terminal configuration to connect to the DUT This allows the LCR meter to apply current to the DUT with one pair of terminals High Drive and Low Drive and to measure the voltage across the DUT with the other pair High Sense and Low Sense This configuration increases accuracy for lower impedance measurements For all measurements except transformer measurements and special configurations the two RED clips HD HS terminals will be connected to one lead of the DUT and the two BLACK clips LS LD terminals will connect to the other lead NOTE For low impedance measurement a cable with four independant leads may be used If possible twist the two current leads HD LD and the two voltage leads HS LS separately The sense signals determine the points where the impedance is measured Impedance is measured between these two points way to the test clips This will minimize stray capacitance between the high and low test leads Using the provided 4 terminal test leads shielded coax is recommended If a different test cable is used it should be constructed from coaxial cables Twist the coax e cables and make sure the cables are arranged as shown in the cross sectional view to the right This will minimize errors when performing high impedance measurement The o shorter the cables the less the error When measuring high impedances i e
28. ngs You can compare the result given in this mode to the result given by the method of measuring the opposing and aiding inductance and calculating for M M Laiding Lopposing 4 Sorting The M Digital LCR meter offers the option of measuring like valued components compared against a fixed value The meter will display the difference of each measured component from the fixed value as a percentage The fixed value and tolerance value are user programmable To access the Sorting function press the Menu key For other Menu functions refer to the MENU KEY description on page 6 Press the key under the right arrow n Vs M until the Sorting Option is displayed Press the key under ON Sorting will be activated Press the key under the right arrow To set the percent of tolerance press the key under H xt until the desired tolerance is displayed The selectable tolerances are 1 2 5 10 and 20 Press the key under the right arrow Enter the base value of the component to be compared against To do this press the key under ri i t A cursor will be displayed under the digit to be changed To change the value of this number press the key under HEME The number will increment one number each time the CHEIMISE key is pressed To select the next digit press the key under HET The cursor will move under the active digit Continue to edit the values until the desired base value is entered The multiplier at the end
29. nnected to selector switch S The output of the switch is connected to a differential amplifier 42 Using the same differential amplifier for both the voltage and the voltage measurements ensures that the scaling factor and the offset errors cancel each other during final calculations The real and imaginary components of the voltage and current signals are obtained by multiplying these voltages with a square wave that is coherent with the stimulus Phase Detector An output proportional to the in phase or quadrature component of the voltage is obtained Measurements are performed using a dual slope A D converter that is read by the controller The complex ratio of voltage to current is equal to the complex impedance The measured complex impedance is corrected by calibration factors for both absolute value and phase The other parameters such as L C R Q D are derived mathematically from the corrected impedance value with the model and the test frequency chosen by the user j Rr Source Resistor Hd virduol ground ai Phase Delector Differential Amplifier Figure 1 1 Overall Block Diagram SIGNAL SOURCE The signal source section generates a low distortion sine signal The frequency can be selected from among ten choices 100 120 250 500 1 k 2 5 k 5 k 7 8 k 12 5 k and 15 6 kHz The signal level is 0 5V rms The sin
30. normal functions press the Menu key Press the key under the right arrow until the Sorting Mode is selected Press the key under CIF F Press the Menu key and select YES to save this configuration Ay Value The M Digital LCR meter has the capability of calculating the A value for unknown toroid cores A is defined as the inductance index of a core To calculate the number of turns required for a given inductance the Ar value of the toroid core must be known The formula for calculating the number of turns is N y L At where N is the number of turns L is the desired inductance in Henries and A is the Ax value as determined by the M LCR meter in Henries To determine the A value of an unknown toroid press the Menu key and then press the key under the right arrow Step through the menu options with the right arrow to the A display option Press the key under the H option The AL measurement option is now active Press the key under the right arrow Edit the number of turns on the core by pressing the key under Edit The default value of 10 will be shown the first time this option is accessed Notice the cursor underline under the second digit This indicates the digit to be changed To change this value press the key under CHAIMISE until the correct value is displayed To change to the next digit press the key under HEX 7 The underline cursor will move to the next accuracy a minimum of 10 turns is recommended When th
31. of the value can also be edited The options are p pico n nano u micro m milli blank as displayed K kilo and M Mega When the correct value has been entered press the key under OE The entered value will now appear on the top line of the display Press the key under the right arrow Set the alert notification when a measured component is within the selected tolerance Default is a SHORT beep To change this press the key under Het The options are SHORT LOHE or HOME Press the key under the right arrow This backlight option is for a visual indication when a component is within the specified tolerance Do not confuse this with the Backlight option under the General Settings in the normal Menu The default value is E which means that the LCD backlight will only light when a measured component is within the tolerances entered To disable this function press the key under Hi Press the Menu key To save the current configuration press the key under YES This will save the settings that were entered and place the LCR meter in Sorting Mode The first time that the Sorting Mode is configured and this configuration is saved it will be necessary to turn the power to the LCR meter off and then back on After this initial entry into memory the Sorting mode can be activated or deactivated through the Menu options and it will not be necessary to remove power to the LCR meter To exit the Sorting Mode and return to
32. parameters Successful completion of storing the saved parameters will be verified with FHSSED displayed on the LCD The instrument will then display the opening Calibration screen as in the first screen of this section Select the Calibration Routine by pressing the n Vs M key The following screen will be displayed Step 1 of the calibration routine calibrates the FEN mode of the instrument To start this routine press the Freq key The display will begin the calibration routine stepping through all ten test frequencies A progress bar will be displayed on the second line of the display Successful completion at each frequency will cause the instrument to proceed to the next frequency Failure to calibrate at a given frequency will be indicated by FHIL being displayed on the LCD and the instrument will return to this step in the menu Successful completion of the OPEN calibration routine will result in the instrument stepping to Step 2 SHORT Calibration Following successful calibration of the HOFT routine the calibration will step through the six resistor values required to calibrate the LCR meter Steps 3 through 8 When the entire calibration routine has been completed the instrument will display the following Save the calibration values into non volatile memory by pressing the Freq key The instrument will acknowledge the completion of this step and the instrument will be placed in to measurement mode 25 Appendix 1
33. racy specifications FEATURES Fixture 4 Wire Kelvin DIN socket Protection Protected up to Joule of stored energy 200 VDC max for charged capacitors Zeroing Open or Short Circuit compensation Compensation Limits Short R lt 20 Q Z lt 50 Q Open Z gt 10 kQ Store and Recall GENERAL Operating Conditions 0 50 C lt 80 relative humidity Power 7 5 13V 200 mA with backlight 100 mA otherwise Dimensions W x H x L 6 125 in X 1 5 in X 3 875 in OPTIONS Varactor Test Fixture Kit SYMBOLS and TERMS JE Ti a X ae ae of Z Conductance Real Part of siemens S Admittance Y Susceptance Imaginary siemens S part of Admittance H Phase angle of Z Degree Mutual Inductance Henry Transformer primary voltage AC Volts V Transformer secondary AC Volts V voltage Dissipation factor none DISPLAY AND CONTROLS Major Parameter Value Range L C R Z G 1 6 Auto ie ee Parameter Mode Auto s Range Auto n t Sees Eer Model Mode mn Model Alito Minor Parameter Value Test Frequency Q D X 6 B DISPLAY The two lines of the LCD show measured values selected parameters instrument status and various messages When making normal measurements the major parameter L C R Z G is shown on the top line and the appropriate minor parameter Q D X 0 B is shown on the bottom line The number of displayed digits and the location of the decimal point are automatically adjus
34. ranging mode this letter becomes a blinking H character Pressing this key for two seconds or longer returns to the Auto mode Impedance Ranges Range 1 0 001Q to 15Q Range 2 15Q to 300Q Range 3 300Q to 3 KQ Range 4 3 KQ to 30 KQ Range 5 30 KQ to 600 KQ Range 6 600 KQ to 99 9 MQ MODEL The MODEL key selects between a series or parallel equivalent circuit model for the device under test Pressing this key for two seconds or longer places the Model selection in Auto mode MENU The MENU key allows access to a series of special configurable parameters Pressing this key displays the programmable options The current state of each option is displayed on the first line of the LCD as that option is selected To move through the Menu press the key under the forward or back arrows displayed on the LCD e Backlight default value is ON The backlight can be set to ON or OFF To turn the backlight off press the key under OFF Sound default value is ON This option turns the audible alert function ON or OFF e Varactor default value is OFF This option requires the Varactor Test Fixture available from M Electronix Turning the Varactor option to ON will place the LCR meter automatically in the Varactor measurement mode upon saving and exiting the Menu To return to normal features select the Menu key and turn the Varactor feature OFF e Sorting default value is OFF Use this feature to measure and sort like val
35. ransformer calculate the secondary voltage for a power transformer and measure the mutual inductance between the primary and secondary winding The use of this option requires the 4 wire cable provided with the LCR meter To enter this mode press the n Vs M key Connect the HD and LD clips to the winding having the greater number of turns and the HS and LS clips to the smaller winding For a low voltage transformer i e 115 VAC primary and 24VAC secondary the primary will be the larger winding and for a high voltage transformer i e 115 VAC primary and 800VAC secondary the secondary winding will be the larger See figure 1 3 page 20 for typical connection LOk condition being displayed Incorrectly connecting the test clips to the transformer will result in an THI on the LCD The first option n will provide the turns ratio between the two windings for a low voltage transformer on the first line of the display The range will default to 1 The phase angle and test frequency will be displayed on the second line Pressing the n Vs M key a second time will select the inverse function HTH Use this function to properly display the turns ratio for a high voltage transformer There are two ranges available for measurement The default setting is Rangel If the turns ratio is very high the display may not be stable at Range 1 Press the Auto Hold key to step the meter to Range 2 Stepping to Range 2 may cause the meter to go in to a
36. rm this function the HD and HS clips must be shorted together and the LD and LS clips must be shorted together Position the two sets of clips as shown below Press the Zero Range key The second line of the LCD will show Open Short Exit Press the key under Open LCRZ The instrument will measure stray admittance parallel resistance and capacitance and use these values to zero the meter at the selected frequency The correctable range is 10 kQ minimum for the absolute impedance An error message will be displayed if the impedance doesn t fit these characteristics same _ spacing as_ DUT Bare Wire Short note correct sequence HS and LS to the inside Short all 4 test clips together spacing the HS and LS clips the same distance apart as the leads on the DUT The HD and LD clips should be placed to the outside of the HS and LS clips Press the Zero Range key and the LCD will again display Open Short Exit on the second line Press the key under Short and the instrument will measure the residual impedance and zero the meter for 0 ohms resistance at the selected frequency The correctable range is 50 Q maximum for the absolute impedance and 20 for the resistance An error message will be displayed if the impedance doesn t fit into these characteristics One possible cause for an error is poor contact between the test clips and the DUT Try to clean the clips and the leads and perform another zero correction Remov
37. ted according to the range and resolution The A symbol in front of the major parameter indicates that the measurement is displayed as a relative or absolute deviation from a nominal value A dark arrow present in the top left of the display indicates the unit is in the Auto Parameter mode If a dark arrow is displayed in the bottom left of the LCD the unit is in the Auto Model mode The Range is indicated at the top right of the display The A character behind the Range number indicates that the instrument is in auto range mode In Manual or Hold ranging mode this letter becomes a blinking H character The selected test frequency is displayed on the bottom right of the display L C R Z niVsiM Freg Hold Range SAC aed See Model Menu Disp Zero KEYPAD The keypad is used to select measurement conditions and to enter values All keys have two functions depending on whether the key is pressed momentarily or for two seconds or longer L C R Z This key selects the parameter being measured Pressing the LCRZ key steps through the major parameters to manually select the desired function L Q or L A_ C D R Q Z 0 R X G B When this key is pressed for more than two seconds the instrument goes in Auto Parameter mode In this mode the instrument will select the most appropriate parameter pair and will display the dark arrow at the top left of the display L Q Inductance and Quality L A
38. the lead resistance and the foil resistance RS is generally very low a few mQ RD symbolizes the dielectric loss Its value changes with frequency RD _ C RS Capacitance C dissipation factor D and equivalent series resistance ESR Rs under the major parameters are the parameters usually measured Capacitance is the measure of the quantity of electrical charge that can be held stored between the two electrodes Dissipation factor also known as loss tangent indicates capacitor quality Like most everything else about capacitors it changes with time frequency and temperature ESR is a single resistive value of a capacitor representing all real losses It includes effects of the capacitor s dielectric loss ESR is related to D dissipation by the formula ESR D wC where 27F e Model Measuring a capacitor in series or parallel mode can provide different results The difference can depend on the quality of the device but primarily the capacitor s measured value most closely represents its effective value when the more suitable equivalent circuit series or parallel is used To determine which model is best consider the impedance magnitudes of the capacitive reactance and Rs and Rp Remember that reactance is inversely proportional to C so a small capacitor yields a large reactance This implies that the effect of parallel resistance Rp has a more significant effect than that of Rs Sin
39. ue from the current value The A symbol next to the measured parameter indicates that this function is active The percent of deviation from the current value The A symbol next to the measured parameter indicates that this function is active In Sorting Mode pressing Disp cycles through the following display types e The value being measured The percent of deviation from a stored value The A symbol next to the measured parameter indicates that this function is active In this mode a PASS FAIL message is shown in the second line of the display according to the measured deviation and the selected tolerance Zero Range The Zero Range key allows access to open short compensation Pressing the Zero Range key displays the zeroing options on the second line of the LCD Open Short Exit This option will zero the LCR meter for the currently selected test frequency Pressing the Zero Range for more than two seconds displays the zeroing options OPEN SHORT Exit note that the options are in all capital letters This option performs an open short calibration through the entire range of test frequencies Initial Calibration Before the M Digital LCR Meter can be used for the first time it must be calibrated This is a simple process and requires six precision resistors The calibration resistors provided with the M LCR Meter kit are 0 1 resistors with the following values 10 100 1K 10K 100K 1M ohms If you have an ac
40. ued components 1 Turning the Sorting function ON will allow the user to set the Tolerance between the value of the benchmark component and like components to be measures This Tolerance is selected by pressing the NEXT key 2 When the appropriate tolerance has been selected pressing the key under the left arrow enables the value of the benchmark component to be entered by pressing the Edit key A cursor will appear under the first digit of the value Pressing the NEXT key will move the cursor to the next digit Pressing the Change key will step the value of the selected digit When the desired value has been entered pressing the OK key will record this value 3 Pressing the key under the right arrow will allow the user to set the audible indication when a DUT meets the programmed parameters Default value for the Pass Beep is SHORT Pressing the NEXT key will change the value to LONG or NONE 4 Pressing the key under the right arrow will present the option of turning the backlight on or off when a valid component is measured The default value is YES 5 Pressing the Menu key now will allow you to save the selected configuration and place the LCR meter in the Relative measurement mode 6 To turn the Sorting mode OFF press the Menu key and step backward or forward using the appropriate arrow key until the Sorting option is displayed Press the key under OFF Press the Menu key and save this configuration e Averaging de
41. will appear below the first digit under the number 1 Press the key under change until this value goes to a blank position Press the key under NEXT The cursor will now be under the second digit the number 0 Press the CHANGE key until the number 9 is in this position Press the NEXT key and the cursor will move to the digit to the right of the decimal point Press CHANGE until the 9 appears in this position Press the NEXT key and the cursor will move to the right under the next digit the number 0 Press the CHANGE key until the number 9 is displayed Repeat these steps until 9 995 ohms is displayed To save this value press the key under OK This value will be stored and the display will step to the next calibration resistor When you have entered all of the values you want to change press the NEXT key until SAVE PARAMETERS is displayed Press the key under SAVE n Vs M Continue to the next step Press the key under CAL n Vs M The instrument will display STP1 OPEN CAL on the first line with a left arrow arrow right arrow and OK displayed on the second line Short the HD and HS clips together and short the LD and LS clips together Position the two pair of clips the same distance apart as they will be when connected to the precision calibration resistors It is recommended that the test cable not be moved during the entire calibration process Do not allow the two sets of clips to short together
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