AC Signal Analysis Using Models 2015, 2015
Contents
1. peak max speak next speak right peak left Will reset the instrument to default set tings Should be done here unless don above while setting up unit to output sine wave Turns off continuous trigger this is re quired for peak measurements Sets a single trigger Sets the measurement function to distortion Sets frequency to 20Hz which is required for peak measurements Triggers a reading akes sure trigger is complete Returns the frequency and amplitude of the peak Returns the frequency and amplitude of the next highest peak Returns the frequency and amplitude of the highest peak to the right of the current spectral component Returns the frequency and amplitude dBV of the highest peak to the left of the cur rent spectral component Using Models 2015 2015 P and 2016 THD Multimeters 35 Measuring differences between two peaks The commands below for the Model 2015 P measure a peak spectral component and a delta value between two spectral components In this example the peak is found then it is compared with the magnitude of the spectral component at 1200Hz The difference in frequency and amplitude between the reference marker and the present location is returned in dBV units rst sinit cont off strig coun 1 sens func dist sens dist freq 20 finite opc sens dist peak max sens dist peak sref sens dist peak sfr 1202. Returns frequency and amplitude For this example values 3000 14 would be returned 14dBV 3kHz The frequency pointer is now at 3kHz Finally this command can be used again to search for the frequency that has the third high est amplitude SENS DIST PEAK NEXT Finds frequency having the next highest amplitude Returns frequency and amplitude For this example values 600 20 would be returned 20dBV 600Hz 22 Using Models 2015 2015 P and 2016 THD Multimeters Delta function The delta function returns the difference in frequency and amplitude between two frequency pointer positions Delta is calculated as follows delta frequency reference frequency frequency at present location delta amplitude reference amplitude amplitude at present location Acquiring reference frequency and amplitude Typically delta readings are referenced to the frequency that has the highest magnitude The following commands are used to acquire these reference points SENS DIST PEAK MAX Move frequency pointer to frequency that has the highest magnitude SENS DIST PEAK SREF Acquire frequency and amplitude values The example in Figure 6 shows how to use the delta function In Figure 6A the MAX com mand moves the frequency pointer to 1000Hz The SREF command then acquires the max readings 1000Hz 12dBV as the reference points for the delt
3. Selects appropriate range based on value lt n gt 0 to 757 5 volts SENS VOLT AC RANG AUTO ON OFF Turns Autorange on or off SENS FREQ THR VOLT RANG lt n gt Selects frequency input range lt n gt 0 to 1010 volts 3 Setting the integration rate not used for FREQ Front panel Press RATE display will indicate FAST 1 NPLC MED 1 NPLC or SLOW 10 NPLC Remote command SENS VOLT AC NPLC lt n gt Sets integration rate which is based on the specified number of power line cycles lt n gt 0 01 to 10 Using Models 2015 2015 P and 2016 THD Multimeters 4 Setting the number of displayed digits Front Panel Press DIGITS to cycle through the number of digits 4 to 7 Remote commands Changing the displayed number of digits does not affect bus reading resolution Sl ENS VOLT AC DI G lt n gt ui SENS FREQ DIG lt n gt 1 Sets number of digits to display for ACV lt n gt 4 to 7 Sets number of digits to display for FREQ lt n gt 4 to 7 5 Using the digital filter not used for FREQ The Model 2015 2015 P 2016 has a digital averaging filter to stabilize readings The Repeating filter takes the set number of readings averages them then updates the display The Moving filter throws out the oldest reading takes a new reading averages them then updates the display The Moving filter updates the display faster but takes longer for read
4. delta frequency 1000Hz 3000Hz 2000Hz delta amplitude 12dBV 14dBV 2dBV Frequency list analysis A specified list of frequencies up to 50 can be analyzed using the PEAK LIST commands Creating frequency list The following command is used to specify the list frequencies in Hz to be analyzed SENS DIST PEAK LIST lt freqlist gt Creates frequency list lt freqlist gt Up to 50 frequencies from 20 to 20480 Hz Each listed frequency must be separated by a comma Example The following command creates a 3 point frequency list 1kHz 2kHz and 3kHz SENS DIST PEAK LIST 1e3 2e3 3e3 Retuming amplitudes for listed frequencies Using Models 2015 2015 P and 2016 THD Multimeters 25 The following command is used to return the amplitudes for the frequencies in the frequency list SI ENS DIST PEAK LIST DATA Requests frequency list amplitudes The order of the returned list of amplitude values in dBV corresponds to the order that the frequencies are listed in the lt freqlist gt For the Creating frequency list assume amplitudes of 8dBV 1kHz 9dBV 2kHz and 10dBV 3kHz The LIST DATA command will return the following values 8 The Model 2015 P can only analyze frequencies that are a multiple of 20 If a listed fre 9 10 quency is not a multiple of 20 the frequency that will be analyzed is the next lowest multiple of 20 For
5. wave Sets the measurement function to distortion sens func dist ssens dist freg auto on By default the instrument is set to or measure the input signal frequency ssens dist freq 2000 continuously for maximum accuracy or The user may preset the incoming ssens dist freqg acg frequency or program the instrument to measure the frequency once and hold that value sens dist rang auto on Sets the input voltage range to auto or The user can also set a manual input esens dist rang 1 voltage range th xample command pro grams the instrument to the 100mV range init Triggers readings opc Makes sure trigger is complete sens dist bnois Query Background noise measurement Th measurement is returned in VRMS Using Models 2015 2015 P and 2016 THD Multimeters 31 Fast frequency sweep RMS voltage measurements Below are the commands needed to set up the instrument to sweep three individual output frequencies For this example the frequencies are 500 1000 and 1500HZ However the sweep can test up to 50 different points The instrument will output a frequency then take a measure ment then change frequency and take another measurement This process will continue for all points in the sweep ASC Will reset the instrument to default settings Sets the measurement function to distortion sens func dist sens dist rang auto on Sets the input voltage range to auto or The
6. Addenda associated with the previous Revision of the manual are incorporated into the new Revision of the manual Each new Revision includes a revised copy of this print history page Revision A Document Number 2015 903 01 cccccscceseessessesseeseeseeeeeeeeseeeseeaeenee December 2001 All Keithley product names are trademarks or registered trademarks of Keithley Instruments Inc Other brand names are trademarks or registered trademarks of their respective holders KESI Safety Precautions The following safety precautions should be observed before using this product and any associated instrumentation Although some instruments and accessories would normally be used with non hazardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury Read and follow all installation operation and maintenance information carefully before us ing the product Refer to the manual for complete product specifications If the product is used in a manner not specified the protection provided by the product may be impaired The types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensuring that the equip ment is operated within its specifications and operating limits and for ensuring that operator
7. The following command is typically used to establish the initial position for the frequency pointer SENS DIST PEAK MAX Sets frequency pointer to 1kHz 3 Acquire reference points for delta calculation SENS DIST PEAK SREF Acquire frequency amplitude values at 1000Hz For this example the values 1000Hz 12dBV are acquired as the reference points for the delta calculations 24 Using Models 2015 2015 P and 2016 THD Multimeters 4 Move frequency pointer to 600Hz SENS DIST PEAK SFR 600 Move frequency pointer to 600Hz Note that the frequency amplitude values at this frequency are 600Hz 20dBV The values will be used in the delta calculations next step 5 Send DELTA command to calculate delta 600Hz referenced to 1K Hz SENS DIST PEAK DELTA Return results of delta calculations Delta at 600Hz which is referenced to 1000Hz is calculated as follows delta frequency 1000Hz 600Hz 400Hz delta amplitude 12dBV 20dBV 8dBV 6 Move frequency pointer to 3000Hz SENS DIST PEAK SFR 3e3 Move frequency pointer to 3000Hz Note that the frequency amplitude values at this frequency are 3000Hz 14dBV 7 Send DELTA command to calculate delta 3kHz referenced to 1kHz SENS DIST PEAK DELTA Return results of delta calculations Delta at 3000Hz which is also referenced to 1000Hz is calculated as follows
8. are equivalent to the original component Note that selected parts should be purchased only through Keithley Instruments to maintain accuracy and functionality of the product If you are unsure about the applicability of a replacement component call a Keithley Instruments office for information To clean an instrument use a damp cloth or mild water based cleaner Clean the exterior of the instrument only Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument Products that consist of a circuit board with no case or chassis e g data acquisition board for installation into a computer should never require cleaning if handled accord ing to instructions If the board becomes contaminated and operation is affected the board should be returned to the factory for proper cleaning servicing 11 01 Table of Contents PA DOUE THIS SUIS sisina nna aa 1 Measurements OVervieW sc eeeseeseesseeseeseceseceeeeseeeeesesseeeaeeseeeaees 2 Harmonic distortion measurement sseeseeeseeseereresrrererrereees 2 AC volts and frequency measurements ssseeseeeeeeeeeeererereeee 2 Frequency spectrum analysis Model 2015 P only 2 Measuring harmonic distortion 0 00 0 ce eeeeeeeeceeeeeeeseteeeeeeeseeeaees 3 Harmonic distortion calculations 20 0 0 ee eeeseeseeeeeeeeeeeeees 3 THD Total harmonic distortion s s s 3 THD N Total harmonic distortion plus noise 3 SI
9. freq gt Moves frequency pointer lt freq gt 20 to 20480 Hz SENS DIST PEAK LOC Returns frequency and amplitude for present frequency pointer position These two commands are used to acquire the amplitude at a specified frequency As shown in Figure 4 SFR 1000 moves the frequency pointer to 1000Hz and LOC returns the fre quency and amplitude values 1000Hz 12dBV Figure 4 Peak analysis example using SFR and LOC commands Amplitude dBV SFR 1000 LOC returns 1000Hz 12dBV Frequency 1000 1020 1040 1060 Hz Frequency Pointer Using Models 2015 2015 P and 2016 THD Multimeters 19 LEFT and RIGHT commands SENS DIST PEAK LEFT Moves frequency pointer left Returns frequency and amplitude SENS DIST PEAK RIGHT Moves frequency pointer right Returns frequency and amplitude The LEFT and RIGHT commands move the frequency pointer left or right In Figure 5A SFR 1000 moves the pointer to 1000Hz When RIGHT is used the pointer moves right one bin to 1020Hz and the frequency and amplitude values are returned as shown in Figure SB If LEFT is then sent the frequency pointer would move left back to 1000Hz and return those frequency amplitude values Figure 5 Peak analysis example using RIGHT command Amplitude Amplitude dBV dBV p 12 13 13 414 SFR 1040 14 RIGHT returns 1060Hz 15dBV 15 15 Frequency Frequency 1000 1020 1040
10. includes all of the harmonics but also includes any random noise in the signal Since the instrument uses a digital signal processor to perform a Fourier transform on the signal noise can be eliminated from the THD measurement thus providing a true read ing The THD noise feature was included to duplicate what a conventional THD meter would read Mathematically THD noise is expressed as follows dv v3 t vi N THD Noise dB 20 log VI Where N is the RMS level of the noise in the signal THD noise can also be expressed in percent Using Models 2015 2015 P and 2016 THD Multimeters SINAD This is another way of expressing THD noise It is expressed as the ratio of the total signal fundamental noise and harmonics to the total signal minus the fundamental This measure ment is only expressed in dB 2 2 2 are SINAD dB 20 log dvi 2 V3 Vn N V2 V3 Vn N Distortion measurement operations 1 Selecting distortion mode Front panel Press SHIFT and then ACV Remote command SENS FUNC DIST Selects distortion mode 2 Selecting THD measurement type THD THD Noise or SINAD Front panel a Press THD MEAS to display TYPE b Use the right arrow key to highlight the present type selection then use the up or down range keys to select THD THD N or SINAD c Press ENTER then press EXIT Remote command SENS DIST TYPE THD THDN SINAD Selects THD
11. is triggered the reading must become available before starting peak analysis When FETCH is sent the instrument will wait for the reading to be become available before requesting it Another method to wait for the reading to become available is to use SRQ The instrument is programmed such that when bit B5 Reading Available of the Measurement Con dition Register sets SRQ is asserted to allow the program to continue For more information see Section 4 Status Structure of the Model 2015 2015 P 2016 User s Manual Using Models 2015 2015 P and 2016 THD Multimeters 21 7 Perform peak analysis Since most of the peak commands function is relative to frequency pointer position an ini tial position must first be established Typically this is done by finding the frequency with the highest peak magnitude with the following command SENS DIST PEAK MAX Finds frequency having max amplitude Returns frequency and amplitude When the above command is sent the instrument searches for the frequency that has the highest amplitude in dBV For this example this is 12dBV 250mV 1kHz When the Model 2015 P is addressed to talk the values 1000 12 are sent to the computer Note that the frequency pointer is at 1kHz Now the buffer can be searched for the frequency that has the second highest amplitude using the following command SENS DIST PEAK NEXT Finds frequency having the next highest amplitude
12. measurement type 3 Selecting THD frequency type Auto Set or Acquire The THD measurement technique used by the Model 2015 2015 P 2016 requires that the unit know the fundamental frequency of the signal exactly Even a difference of a few hertz will cause large errors The AUTO setting will cause the Model 2015 2015 P 2016 to measure the frequency of a source every time it makes a THD measurement This will slow down the read ing rate but is useful if the source frequency is unknown or unstable SET will prompt the user to manually enter the frequency ACQUIRE is similar to AUTO but only measures the frequency once then uses that fre quency for all subsequent THD measurements The signal source must be applied to the input when ACQUIRE is selected Using Models 2015 2015 P and 2016 THD Multimeters 5 Front panel e Press THD MEAS Press ENTER once The display will show FREQ Using the left right arrow and up down range keys select ACQUIRE AUTO or SET Make sure the signal source is connected and on when ACQUIRE is selected Press ENTER If SET was selected the instrument will prompt the user for the fre quency to be used Use the left right arrow and up down range keys to set the frequency and press ENTER Press EXIT Remote commands nn SENS DIST FREQ AUTO ON OFF Turns AUTO on or off SENS DIST FREQ ACQ Acquires frequency once SENS DIST FREQ lt NRf gt Sets f
13. rst sens func ssens dist or ssens dist or ssens dist sens dist or ssens dist init opc sens dist dist freg auto on freq 2000 freq acq rang auto on rang 1 fft bins 171023 Will reset the instrument to default set tings Should be done here unless don above while setting up unit to output sine wave Sets the measurement function to distortion By default the instrument is set to measure the input signal frequency continuously for maximum accuracy The user may preset the incoming frequency or program the instrument to measure the frequency once and hold that value Sets the input voltage range to auto The user can also set a manual input voltage range th xample command pro grams the instrument to the 100mV range Triggers readings Makes sure trigger is complete This command returns all the values mea sured in the spectrum Using Models 2015 2015 P and 2016 THD Multimeters 33 Measurement of individual harmonics The example below sets the instrument to measure the first 21 harmonics and return the val ues of harmonics 2 through 21 The output is returned in dB relative to the fundamental rst Will reset the instrument to default set tings Should be done here unless don above while setting up unit to output sine wave sens func dist Sets the measurement function to distortion ssens dis
14. them with a comma i e OUTP LIST ELEM DIST AMPL 3 The source delay is from the time the instrument outputs the source value to when the measurement starts This delay occurs for every point in the sweep Typically it is used to allow the source output to settle before performing the measurement 4 The TRIG COUN value must be equal to the number of points in the sweep list see OUTP LIST commana 5 The readings returned depend on the selected data elements see OUTP LIST ELEM command If both distortion and amplitude elements are selected readings are returned in the following format distl ampli dist2 ampl2 10 Using Models 2015 2015 P and 2016 THD Multimeters 6 Each time this command is used up to 50 points can be appended to the sweep list For example assume the original sweep list has 50 points You can use this command three times to append 150 points to the list to result in a 200 point sweep list Make sure to change the trigger count TRIG COUN to match the size of the appended sweep list Example The following command adds two points to the sweep list 0 5V 1 6kHz and 0 5V 1 8kHz SOUTP LIST APP 0 5 1 6e3 0 5 1 8e3 12 Setting high and low cutoff filters remote operation only The instrument includes high and low cutoff filters limiting the range of frequencies used in the distortion measurements These filters can be set anywhere from 20Hz to 50kHz When set ting the low cutoff it must be lowe
15. user can also set a manual input ssens dists rang 1 voltage range th xample command pro grams the instrument to the 100mV range Sets the sine waves output impedance which can be set to 50 ohms 600 ohms or high impedance soutp imp hiz soutp list 1 500 1 1000 1 1500 This sets up the output amplitudes and frequencies to be swept soutp list del 0 This sets source settling time in seconds Zero second setting is the fastest sweep capability soutp list elem ampl Sets the instrument to measur lement of RMS Voltage for each point swept soutp mode list Sets the output mode to output the fre quencies specified trig coun 3 This should equal the number of sweep points you have set in your output list soutp on This turns output sine wave on sinit Triggers readings opc Makes sure trigger is complete Returns list of data measured under RMS Voltage This will return comma separated data outp list data 32 Using Models 2015 2015 P and 2016 THD Multimeters Frequency domain components Below is the command sequence which will output all the components of the Fourier trans form of an input signal Each component of the frequency spectrum is in a frequency bin This command sequence will return all readings in dB in the frequency bins From this data the user can observe the frequency spectrum of the input signal The output is returned in dB rela tive to the fundamental
16. 0 sens dist peak delta Will reset the instrument to default set Should be done her above while setting up unit to output sine unless don tings wave Turns off continuous trigger if you do not do this peak commands do not work Sets a single trigger Sets the measurement function to distortion Sets frequency to 20Hz which is required for peak measurements Triggers a reading akes sure trigger is complete Returns the frequency and amplitude of the peak arks peak as referenc frequency and am plitude arks 1200Hz as second reference location Returns the difference in frequency and dBV between th marker and the present location amplitude referenc 36 Using Models 2015 2015 P and 2016 THD Multimeters Specifications are subject to change without notice All Keithley trademarks and trade names are the property of Keithley Instruments Inc All other trademarks and trade names are the property of their respective companies KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland Ohio 44139 e 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 www keithley com BELGIUM Keithley Instruments B V Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 e Fax 02 363 00 64 CHINA Keithley Instruments China Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 6202 2886 Fax 8610 6202 2892 FRANC
17. 1060 Hz 1000 1020 1040 1060 Hz Frequency Frequency Pointer Pointer A SFR 1040 sent B RIGHT sent 20 Using Models 2015 2015 P and 2016 THD Multimeters Peak analysis example The following example shows how to use the MAX and NEXT peak commands to find and measure the frequencies that have the three highest amplitudes Make sure the sine source is connected to the input as shown in Figure 1 1 Set trigger model for single reading mode The Model 2015 P must be in the single trigger state for distortion measurements INIT CONT OFF Disables continuous initiation TRIG COUN 1 Sets trigger count to 1 2 Select distortion function SENS FUNC DIST Selects distortion function 3 Force analysis into 20Hz frequency bins In order to get maximum frequency resolution from the FFT calculation the frequency spec trum must be separated into 20Hz bins using the following command SENS DIST FREQ 20 Set distortion frequency to 20Hz 4 Program output sine wave OUTP FREQ 1000 Sets sine wave frequency to 1000Hz OUTP AMPL 0 25 Sets sine wave amplitude to 0 25VRMS OUTP ON Turns 2015 P source output on 5 Trigger reading With the instrument in the one shot trigger state the following command triggers a single measurement of the input sine wave INIT Trigger a reading 6 Wait for reading to become available FETCH Request the reading After a reading
18. AC Signal Analysis Using M odds 2015 2015 P and 2016 THD M ultimeters Quick Reference Guide A GREATER MEASURE OF CONFIDENCE WARRANTY Keithley Instruments Inc warrants this product to be free from defects in material and workmanship for a period of 3 years from date of shipment Keithley Instruments Inc warrants the following items for 90 days from the date of shipment probes cables rechargeable batteries diskettes and documentation During the warranty period we will at our option either repair or replace any product that proves to be defective To exercise this warranty write or call your local Keithley representative or contact Keithley headquarters in Cleveland Ohio You will be given prompt assistance and return instructions Send the product transportation prepaid to the indicated service facility Repairs will be made and the product returned transportation prepaid Repaired or replaced products are warranted for the balance of the original warranty period or at least 90 days LIMITATION OF WARRANTY This warranty does not apply to defects resulting from product modification without Keithley s express written consent or misuse of any product or part This warranty also does not apply to fuses software non rechargeable batteries damage from battery leakage or problems arising from normal wear or failure to follow instructions THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUD
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21. N 10 i OUTP ON INIT f Wait for SRO to b OUTPUT LIST DATA i Requests the sweep data Read data from 2015 2015 P see NOTE that follows NOTE The actual syntax for these steps depends on the type of GPIB interface used and the type of software used to control the interface For example the WaitSRQ function can be used with a National Instruments interface to wait for the SRQ and the IBRD function can be used to read the data Running this same sweep again only requires sending CLS and INIT over the bus Sending CLS again is necessary to reset the Sweep Done bit 14 Using Models 2015 2015 P and 2016 THD Multimeters Measuring AC volts and frequency In addition to measuring distortion the Model 2015 2015 P 2016 can also be used to make standard AC voltage and frequency measurements Be sure the correct voltage range is selected before making connections to INPUT HI and LO of the instrument 1 Selecting AC volts or frequency function Front panel Press the ACV or FREQ key Remote commands n SENS FUNC VOLT AC Selects AC Volts mode ENS FUNC FREQ Selects Frequency mode n 2 Setting the input voltage range Front panel Press the up or down RANGE key to select a manual range The display will briefly show the changed range Autorange can instead be used for ACV but not frequency Remote commands SENS VOLT AC RANG lt n gt
22. NAD occa ee iis ee cee teed 4 Distortion measurement operations 0 0 eee eee eeeeeeeeeeeeeeeees 4 Distortion measurement notes 0 eee eeeeeeeeeeeeeeeeeeee 10 Distortion measurement examples ees eeeeeeeeeeseeereeees ilu THD measurement example 0 0 0 eeeeeeseeeeeereeeeeeeees iu Distortion and RMS volts sweep example 12 Measuring AC volts and frequency eee eeeeseeseeeseeeeeeeeeeeeneees 14 Analyzing frequency spectrum Model 2015 P only 15 Frequency spettri c leccseceseeceeeessseaseceeneeeauseeeeeanesecnesesues 16 Frequency Dins sirrinin oeiia 16 Frequency boundaries sesssssseesseeeeesereresreresreserreereses 16 Basic peak analysis sscssssissiiciiiierieiisirsipiers 16 MAX and NEXT commands sssr 16 SFR lt freq gt and LOC commands eee eeeeeeeeeeees 18 LEFT and RIGHT commands n se 19 Peak analysis example 00 eeeeeeseeseeeeeeneeeaeeseeeaeee 20 Delta function ses 2iiecicieveds esses sides iartaee dusteeiabeceth ns 22 Acquiring reference frequency and amplitude 22 Move frequency pointer and calculate delta 22 Delta function example cecesceeceeeseeeseeeeeeeeseeeeeeeeee 23 Frequency list analysis cece eseeeesececeeseeeseeeeeseeeeeseeaes 24 Creating frequency list 0 eee eeeeeeeeeeeseeeeeeeeeeseeees 24 Returning amplitudes for listed frequencies 25 Frequency list example cee eeeeseeseeeeeeeeeneees 25 P
23. PULSE Tu Se lt N Se Se lt N rns output on or off ts frequency in Hz Rf gt 20 to 20000 ts output impedance of source ts amplitude Rf gt 0 to 4 O to 9 5 2016 HI Z O to 2 OHM50 or OHM600 ts the channel 2 mode in volts of source 2015 2015 P HI Z Using Models 2015 2015 P and 2016 THD Multimeters 9 Retrieving magnitudes of individual harmonics remote operation only The Model 2015 2015 P 2016 can return the levels of individual harmonics relative to the level of the fundamental in dB over GPIB or RS 232 The arguments for this command are given as the starting harmonic and ending harmonic Specifying 2 2 for the start and end har monics will return the level of the second harmonic twice the fundamental frequency The harmonic levels returned correspond to the last triggered reading and the unit has to be set for one shot readings INIT CONT off Remote command SENS DIST HARM MAGN lt start gt lt end gt Queries levels from starting harmonic to ending harmonic lt start gt 2 to 64 lt end gt 2 to 64 NOTE To query the level of one harmonic use the same harmonic number for both lt start gt and lt end gt 10 Retrieving RMS volts THD N or THD for an acquired reading remote operation only Once a single reading has been triggered the corresponding RMS volts value THD Noise value or THD value can be read for the same set of data regardless of
24. When MAX is sent as shown in Figure 3A the frequency pointer moves to the frequency that has the highest amplitude and reports the frequency and amplitude 1000Hz 12dBV When NEXT is sent Figure 3B the frequency pointer moves to the frequency that has the second highest amplitude and returns those values 1020Hz 13dBV When NEXT is sent again Figure 3C the frequency pointer moves to the frequency that has the third highest amplitude and returns those values 1040Hz 14dBV When NEXT is sent again Figure 3D the frequency pointer moves to the fre quency that has the third highest amplitude and returns those values 1040Hz 14dBV Figure 3 Peak analysis example using MAX and NEXT commands Amplitude dBV MAX returns 1000Hz 12dBV 12 1000 1020 1040 1060 Frequency Pointer A PEAK MAX sent Amplitude dBV 12 13 NEXT returns 1040Hz 14dBV 14 15 1000 1020 1040 1060 Frequency Pointer C PEAK NEXT sent Frequency Hz Frequency Hz Amplitude dBV 12 13 NEXT returns 1020Hz 13dBV 14 15 T000 1020 1040 1060 Freauency Hz Frequency Pointer B PEAK NEXT sent Amplitude dBV 12 13 14 NEXT 42 returns 1060Hz 15dBV Frequency Hz 1000 1020 1040 1060 Frequency Pointer D PEAK NEXT sent 18 Using Models 2015 2015 P and 2016 THD Multimeters SFR lt freq gt and LOC commands SENS DIST PEAK SFR lt
25. a calculation Move frequency pointer and calculate delta SENS DIST PEAK SFR lt freq gt Move frequency pointer lt freq gt 20 to 20480 Hz SENS DIST PEAK DELTA Perform delta calculation In Figure 6B the SFR 1040 command moves the frequency pointer to 1040Hz The DELTA command then uses the frequency amplitude values at this location 600Hz 20dBV to calculate delta as follows delta frequency reference frequency frequency at present location 1000Hz 600Hz 400Hz delta amplitude reference amplitude amplitude at present location 12dBV 20dBV 8dBV Using Models 2015 2015 P and 2016 THD Multimeters 23 Figure 6 DELTA peak analysis example Amplitude Amplitude dBV dBV MAX SREF 12 12 14 14 SFR 1040 DELTA 20 20 Frequency Frequency 600 1000 3000 Hz 600 1000 3000 Hz Frequency Frequency Pointer Pointer A Establish pointer and acquire B Move pointer and calculate delta reference values Delta function example The following example calculates delta at two frequencies 600Hz and 3000Hz The fre quency amplitude values at both these frequencies are referenced to 1000Hz This example assumes that the internal sine source is connected to the input as shown in Figure 1 1 Acquire distortion reading Perform steps 1 through 6 of the Peak analysis example to acquire a distortion reading 2 Establish frequency pointer position
26. curacy or The user may preset the incoming ssens dist freqg acg frequency or program the instrument to measure the frequency once and hold that value sens dist rang auto on Sets the input voltage range to auto or The user can also set a manual input ssens dist rang 1 voltage range th xample command pro grams the instrument to the 100mV range sens dist type THD Sets the type of harmonic distortion mea surement The user can select THD THDN or SINAD depending upon desired distortion measurement THD amp THDN are measured in dB or using the unit dist db or sunit dist per command SINAD is measured in dB refer to 2015 2015 P User s Man ual Section 5 sens dist harm 12 Defines number of harmonics included in the measurement The default is 2 with the maximum at 64 read This queries the distortion measurement from the instrument 28 Using Models 2015 2015 P and 2016 THD Multimeters RMS voltage measurement This is an AC voltage measurement but it is calculated from data collected in the frequency domain using the DSP not the time domain that uses the DMM RMS converter to measure a value If the fundamental frequency is not known the instrument can be set to auto or to 20Hz for maximum spectrum resolution rst Will reset the instrument to default set tings Should be done here unless don above while setting up unit to output sine wave Sets the measurement funct
27. e measured UNIT DIST PERC Selects THD measurement units SENS DIST SFIL NONE Selects no shaping filter SENS DIST RANG AUTO ON Selects auto range for THD voltage input OUTP FREQ 1000 Sets the frequency of the source OUTP IMP HIZ Selects output impedance of source OUTP AMPL 1 Sets amplitude of source OUTP CHAN2 ISINE Selects inverted sine for second source OUTP O Turns output on READ Triggers one THD measurement and requests reading SENS DIST RMS Requests RMS volts reading for the TDH measurement Distortion and RMS volts sweep example The following remote command sequence configures and runs a 10 point sweep to measure distortion and RMS volts This example includes the use of the high and low cutoff filters This command sequence also demonstrates how to program the Model 2015 2015 P 2016 to use SRQ When SRQ is asserted to indicate that the sweep is completed the sweep data points distortion and AC volts readings are read from the instrument Make sure the internal source of the instrument is connected to the input as shown in Figure 1 Using Models 2015 2015 P and 2016 THD Multimeters Restores default conditions Clears status registers Causes the Operation Summary Bit to set 13 when the sweep is done Allows sweep end to be detected Enables Operation Summary Bit mask Causes SRQ line to be asserted when th sweep is completed Se
28. e concept erst Will reset the instrument to default settings soutp freq 1000 Sets the output frequency to 1000Hz can be set from 20Hz to 20000Hz soutp imp hiz Sets the sine wave s output impedance It may be set to 50 ohm or 600 ohm to match the load impedance The output impedance also can be set to assume the load is high impedance hiz soutp ampl 1 Sets the amplitude of the output sine wave Ranges are from OV to 4V RMS with hiz impedance and OV to 2V RMS with the other two impedances for 2015 models For 2016 models the value can be set from OV to 9 5V RMS with high impedance hiz outp on This turns the output sine wave on Figure 7 Connections to double generator amplitude SOURCE INV PULSE OUTPUT SOURCE OUTPUT New Double Amplitude Output Using Models 2015 2015 P and 2016 THD Multimeters 27 Measuring THD THD noise or SINAD The user can define one of three distortion measurements an input voltage range and a method of mea suring the input signal frequency This code measures the distortion of a 2kHz input signal ESE Will reset the instrument to default set tings Should be done here unless don above while setting up unit to output sine wave sens func dist Sets the measurement function to distortion ssens dist freg auto on By default the instrument is set to or measure the input signal frequency ssens dist freq 2000 continuously for maximum ac
29. e done her above while setting up unit to output sine wave unless don Sets the measurement function to distortion By default the instrument is set to measure the input signal frequency continuously for maximum accuracy The user may preset the incoming frequency or program the instrument to the frequency once and hold that measur value Sets the input voltage range to auto The user can also set a manual input voltage range th xample command pro grams the instrument to the 100mV range Sets the High frequency cutoff can be set from 20Hz to 50000Hz Turns High frequency cutoff off and on Sets the Low frequency cutoff ranges from 20Hz to 50kHz Turns Low frequency cutoff off and on Triggers a reading Makes sure trigger is complete Measures RMS voltage 30 Using Models 2015 2015 P and 2016 THD Multimeters Background noise measurement Noise can be measured in the presence of a signal with the Background noise command Background noise is the residual voltage after the input signal s fundamental and harmonics are removed The input signal must have a frequency of at least 61Hz If the frequency is smaller than 61Hz the instrument will not have enough resolution for a background noise measure ment The measurement is returned in VRMS rst Will reset the instrument to default set tings Should be done here unless don above while setting up unit to output sine
30. e harmonic distortion measurements standard AC volts and frequency measurements and frequency spectrum analysis Model 2015 P only This guide covers front panel operation and remote operation over the GPIB or RS 232 The SCPI commands provided are generic actual syntax depends on the test programming lan guage being used Information in this guide is organized as follows Measurements overview Summarizes the measurements used to analyze an AC input signal Measuring harmonic distortion Harmonic distortion calculations Shows how harmonic distortion is calculated for the three measurement types THD THD noise and SINAD Distortion measurement operations Covers the various operations front panel and remote commands used to configure and measure distortion Distortion measurement examples Includes an example to measure total harmonic distortion THD and an example that uses a source sweep to measure distortion and RMS volts Measuring AC volts and frequency Provides the basic procedure to measure AC volts or frequency Analyzing frequency spectrum Model 2015 P only Basic peak analysis Covers the commands used to measure the peak amplitudes of the frequencies in the spectrum Includes a remote command sequence example to find and measure the frequencies that have the three highest amplitudes Delta function Covers the commands to measure the difference in frequency and amplitude between two frequenc
31. ects the sweep list source mode OUTP LIST lt ampll gt lt freql gt lt ampl2 gt lt freq2 gt Creates sweep list see Note 1 OUTP LIST ELEM lt item list gt Specify data returned by DATA see Note 2 lt item list gt DIST AMPL OUTP LIST DEL lt NRf gt Sets source delay see Note 3 lt NRf gt 0 to 999999 999 sec TRIG COUN lt n gt Specifies number of measurements see Note 4 lt n gt 1 to 9999 OUTP ON Turns output on It must be on before starting the sweep INIT Starts the sweep OUTP LIST DATA Returns sweep data see Note 5 OUTP LIST APP lt ampl gt lt freq gt Adds sweep points to sweep list see Note 6 NOTES 1 The sweep list can have up to 50 sweep points Each sweep point is made up of an amplitude and a frequency For example assume a 3 point sweep list with the following points Point 1 0 5V 1 0kHz lt ampll gt 0 5 lt freql gt le3 Point 2 0 5V 1 2kHz lt ampl2 gt 0 5 lt freq2 gt 1 2e3 Point 3 0 5V 1 4kHz lt ampl3 gt 0 5 lt freq3 gt 1 4e3 The following command will create the above sweep list SOUTP LIST 0 5 1e3 0 5 1 2e3 0 5 1 4e3 2 You can specify distortion DIST readings andlor RMS volts amplitude AMPL read ings to be returned by the OUTP LIST DATA command When specifying both ele ments separate
32. ent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 ITALY Viale San Gimignano 38 e 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 JAPAN New Pier Takeshiba North Tower 13F 11 1 Kaigan 1 chome Minato ku Tokyo 105 0022 81 3 5733 7555 Fax 81 3 5733 7556 KOREA FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 130 82 2 574 7778 Fax 82 2 574 7838 NETHERLANDS Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 SWEDEN c o Regus Business Centre Frosundaviks All 15 4tr e 169 70 Solna 08 509 04 679 Fax 08 655 26 10 SWITZERLAND _ Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 TAIWAN 1FL 85 Po Ai Street Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 2 02 AC Signal Analysis Using Models 2015 2015 P and 2016 THD Multimeters Quick Reference Guide 2001 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A First Printing December 2001 Document Number 2015 903 01 Rev A Manual Print History The print history shown below lists the printing dates of all Revisions and Addenda created for this manual The Revision Level letter increases alphabetically as the manual undergoes sub sequent updates Addenda which are released between Revisions contain important change in formation that the user should incorporate immediately into the manual Addenda are numbered sequentially When a new Revision is created all
33. example if 1019Hz is a listed frequency the amplitude for 1000Hz will be returned by LIST DATA Frequency list example This example creates a 3 point frequency list and returns their amplitudes This example assumes that the internal sine source is connected to the input as shown in Figure 1 1 Acquire distortion reading Perform steps 1 through 6 of the Peak analysis example to acquire a distortion reading 2 Create frequency list Use the following command to create a frequency for 1000Hz 1100Hz and 1200Hz values 35 ENS DIST PEAK LIST 1000 1100 1200 3 Request frequency list amplitudes Creates frequency list Use the following command to request the amplitudes for the three frequencies in the list S ENS DIST PEAK LIST DATA Requests amplitudes After the above command is sent the amplitude values will be sent to the computer when the Model 2015 P is addressed to talk 26 Using Models 2015 2015 P and 2016 THD Multimeters Programming examples Programming sine wave source Defining frequency magnitude and expected load impedance sets up the output signal The example below outputs a 1000Hz 1V RMS sine wave to a high impedance load To achieve twice the output amplitude or a differential output the user can take the high from the source output and the high from the inverted output to create a differential output Figure 7 below is a diagram illustrating th
34. f telephone lines The default filter setting is NONE Front panel a Press THD MEAS Press ENTER until the display shows SFIL Select NONE C CCITT CCIRARM A or CCIR using the left right arrow and up down range keys d Press ENTER Remote command SENS DIST SFIL NONE C CCITT CCIRARM A CCIR Selects shaping filter for THD 7 Setting the THD voltage input range The Model 2015 2015 P 2016 defaults to autoranging for the voltage input range If using manual ranging it is important to use the lowest range possible for the signal level Not using the appropriate range will cause inaccurate readings or the display may show underflow or overflow Front panel With the instrument in the THD mode press the up range or down range key The display will show the chosen range Otherwise press AUTO for autoranging Remote commands SENS DIST RANG lt n gt Specify expected voltage to set range turns off autoranging lt n gt 0 to 757 5 SENS DIST RANG AUTO ON OFE Turns autoranging on or off Using Models 2015 2015 P and 2016 THD Multimeters 8 Configuring the internal sine source The Model 2015 2015 P provides a 10Hz 20kHz 0 4V or 0 2V into a 50 or 600 load sine source The Model 2016 provides a 10Hz 20kHz 0 9 5V or 0 2V into a 50Q or 600Q load sine source This source can be used to evaluate amplifiers filters etc or can be con nected direc
35. frequency spectrum into 20Hz bins SENS DIST FREQ 20 Set distortion frequency to 20Hz Figure 2 Frequency spectrum example Frequency Spectrum 1kHz to 2kHz Bin Bin Bin Bin Bin Bin 1 2 3 4 5 51 e 1000 1020 1040 1060 1080 2000 Lower Boundary Upper Boundary Frequency boundaries Upper and lower boundaries can be set for the frequency search Frequencies outside the boundaries are excluded from the search The example in Figure 2 shows boundaries of 1kHz and 2kHz The following commands set the lower and upper boundaries SENS DIST PEAK LOWER lt freq gt Specifies lower frequency boundary lt freq gt 20 to 20480 Hz SENS DIST PEAK UPPER lt freq gt Specify upper frequency boundary lt freq gt 20 to 20480 Hz NOTE The default boundaries are 20Hz lower and 20480Hz upper Basic peak analysis Basic peak analysis consists of moving the frequency pointer to the appropriate frequency bin and reporting the frequency and amplitude values The commands to do this are explained as follows MAX and NEXT commands SENS DIST PEAK MAX Finds frequency having max amplitude Returns frequency and amplitude SENS DIST PEAK NEXT Finds frequency having next highest amplitude Returns frequency and amplitude Using Models 2015 2015 P and 2016 THD Multimeters 17 An example using these commands is provided in Figure 3
36. ings to stabi 15 When the display shows RDGS select the number of readings to average 1 to 100 When the display shows TYPE select MOVING AV or REPEAT and then press ENTER The FILT annunciator turns on to indicate that the filter is on lize Front Panel a Press FILTER b and then press ENTER c d Press FILTER again to disable the filter Remote commands wS ENS VOLT AC AVI SENS VOLT AC A ER TCON MOV REP Selects moving or repeating filter ER COUN lt n gt Sets number of averaged readings lt n gt 1 to 100 SENS VOLT AC A ER STAT ON OFF Turns filter on or off Analyzing frequency spectrum Model 2015 P only The Model 2015 P can analyze the frequency spectrum of a signal and return the frequency and amplitude values over the bus Peak commands are used to search the frequency spectrum and return the frequency and amplitude values NOTE Frequency spectrum analysis cannot be performed from the front panel remote com mand programming only 16 Using Models 2015 2015 P and 2016 THD Multimeters Frequency spectrum Frequency bins In order to get maximum frequency resolution from the FFT calculation the frequency spec trum must be separated into 20Hz bins The example frequency spectrum in Figure 2 shows the 51 frequencies that can be analyzed for a spectrum from 1kHz to 2kHz The following command separates the
37. ion to sens func dist distortion ssens dist freg auto on By default the instrument is set to or measure the input signal frequency ssens dist freq 2000 continuously for maximum accuracy or The user may preset the incoming ssens dist freqg acg frequency or program the instrument to measure the frequency once and hold that value sens dist rang auto on Sets the input voltage range to auto or The user can also set a manual input ssens dist rang 1 voltage range th xample command pro grams the instrument to the 100mV range sinit Triggers a reading opc Makes sure trigger is complete sens dist rms Measures RMS Voltage value Using Models 2015 2015 P and 2016 THD Multimeters 29 Bandwidth limited RMS voltage measurement The user defined high frequency cutoff filter and low frequency cutoff filter will determine the bandwidth of the measurement For this example the lower cutoff is set to 50Hz and the high cutoff is set to 5000Hz rst Ssens SENS or SENS or SENS Sens or SENS Sens Sens Sens Sens init opc Sens func dist dist dist dist dist dist dist dist dist dist dist freg auto on freq 2000 lt freq acq rang auto on rang 1 HCO 5000 HCO stat on LCO 50 LCO stat on rms Will reset the instrument to default set tings Should b
38. lects distortion mode Turns off the AUTO frequency mode Selects THD tnoise mode Configures low cutoff to filter out noise below 500Hz Turns on the low cutoff filter Configures high cutoff to filter out noise above 10kHz Turns on the high cutoff filter Sets the manual range for the sweep since autoranging is not allowed Change the range value as necessary Sets impedance of the output before creating the sweep list so that the output has the correct amplitude Change impedance as necessary 1 1000 1 1100 1 1200 1 1300 1 1400 1 1500 1 1600 Creates 10 point sweep list 1kHz to 1 9kHz in 100Hz steps one volt amplitude for all points Selects sweep mode Sets a source delay of 0 1 seconds Selects distortion and amplitude as the data elements to be returned Sets instrument to take 10 triggered measurements Turns the output on Starts the sweep asserted s NOTE at end of command sequence RST CLS d STAT OPER ENAB 8 SRE 128 r SENS FUNC DIST SENS DIST FREQ AUTO OFF SENS DIST TYPE THDN i SENS DIST LCO 500 d ENS DIST LCO STAT ON A SENS DIST HCO 10000 SENS DIST HCO STAT ON y SENS DIST RANG 1 i OUTP IMP HIZ OUTP LIST 1 1700 1 1800 1 1900 OUTP MODE LIST OUTP LIST DEL 1 OUTP LIST ELEM DIST AMPL g TRIG COU
39. o the main power cord is restricted such as rack mounting a separate main input pow er disconnect device must be provided in close proximity to the equipment and within easy reach of the operator For maximum safety do not touch the product test cables or any other instruments while power is applied to the circuit under test ALWAYS remove power from the entire test system and discharge any capacitors before connecting or disconnecting ca bles or jumpers installing or removing switching cards or making internal changes such as installing or removing jumpers Do not touch any object that could provide a current path to the common side of the circuit under test or power line earth ground Al ways make measurements with dry hands while standing on a dry insulated surface capable of withstanding the voltage being measured The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equipment may be impaired Do not exceed the maximum signal levels of the instruments and accessories as defined in the specifications and operating in formation and as shown on the instrument or test fixture panels or switching card When fuses are used in a product replace with same type and rating for continued protection against fire hazard Chassis connections must only be used as shield connections for measuring circuits NOT as safety earth ground connections If you are using a te
40. plitudes of frequencies in a spectrum The lower bound for the frequency spectrum can be set as low as 20Hz while the upper bound can be set as high as 20480Hz The 20Hz and 20480Hz bound aries are the default settings The Model 2015 P can perform the following operations e Determine the amplitude for any individual frequency in the spectrum Values are returned for the frequency in Hz and the amplitude in dBV e Calculate the difference in frequency and amplitude between two different frequencies The results of the calculation are returned in Hz and dBV e Determine the amplitudes of a specified list of frequencies Frequency amplitude pairs are returned for every frequency in the list Using Models 2015 2015 P and 2016 THD Multimeters 3 Measuring harmonic distortion Harmonic distortion calculations THD Total harmonic distortion THD is the default type for the THD measurement and is defined as follows Jv22 y3 yi THD 100 Vi Where V2 through Vi represent the RMS levels of the harmonics of the signal and V1 is the RMS level of the fundamental frequency THD can also be expressed in dB as follows Jv22 v3 t y THD dB 20 log V1 THD N Total harmonic distortion plus noise THD N is what conventional analog THD meters display A conventional THD meter has a notch filter that removes the fundamental frequency from the signal and measures THD based on what is left This
41. r than the fundamental frequency of the signal The low cut off is used to limit noise frequencies below the fundamental for THD noise and SINAD measurements no effect in THD mode Similarly the high cutoff limits noise frequencies above the specified frequency for THD noise and SINAD In THD mode the limiting fre quency is determined by the high cutoff or the harmonic number whichever is lower Remote commands SENS DIST LCO lt NRf gt Sets the low cutoff frequency lt NRf gt 20 to 50000 Hz SENS DIST LCO STATe ON OFF Turns the low cutoff on or off SENS DIST HCO lt NRf gt Sets the high cutoff frequency lt NRf gt 20 to 50000 Hz SENS DIST HCO STATe ON OFF Turns the high cutoff on or off Distortion measurement notes 1 The digital averaging filter moving or repeat and the REL feature can be used for THD The RATE key has no effect on THD since there is no NPLC setting 2 The Auto or Acquire frequency mode is recommended instead of the Set mode as the programmed frequency of an external source may not be accurate 3 Querying the RMS volts value in the distortion mode sens dist rms may yield a reading slightly different from a reading in the AC Volts mode This is because of the differences in how the two modes make the measurement 4 The output impedance needs to be set prior to setting the amplitude or starting the sweep The impedance of the second output reflec
42. requency in Hz disables AUTO n frequency if enabled lt NRf gt 20 to 20000 4 Setting number of harmonics to use in the THD measurement 2 to 64 The Model 2015 2015 P 2016 can use up to the 64 harmonic of a signal 64 times the fun damental frequency in the THD measurement but only recognizes frequencies below 50kHz Harmonics with frequencies above 50kHz are ignored therefore acting as an adjustable low pass filter Front panel a b d Press THD MEAS Press ENTER until the display shows HARMONICS Set the number of the highest harmonic to use in the measurement using the left right arrow and up down range keys Press ENTER and then press EXIT Remote command zS ENS DIST HARM lt NRf gt Sets the number of harmonics to include in the THD measurement lt NRf gt 2 to 64 6 Using Models 2015 2015 P and 2016 THD Multimeters 5 Selecting THD measurement units percent or dB Front panel Press THD MEAS Press ENTER until the display shows UNITS Select PERCENT or dB using the left right arrow and up down range keys Press ENTER and then EXIT Bo Pf Remote command UNIT DIST PERC DB Selects percent or dB units for THD 6 Selecting the THD shaping filter None C weighting CCITT CCIRARM A weighting or CCIR The Model 2015 2015 P 2016 includes digital shaping filters to simulate having the sample signal pass through various types o
43. ress ENTER Press the THD SOURCE key When the display shows SINE OUT select ON and press ENTER When the display shows FREQ select 1 0000 kHz and press ENTER When the display shows IMPEDANCE select HI Z and press ENTER setting does not matter in this example When the display shows AMPL select 1 000 volts and press ENTER When the display shows CHAN2 select ISINE and press ENTER The display should be reading approximately 0 02 THD 12 Using Models 2015 2015 P and 2016 THD Multimeters To illustrate the reason why the instrument needs to know the source frequency exactly per form the following steps 1 Press THD MEAS and then press ENTER once 2 Change the frequency mode to SET and press ENTER 3 For the frequency enter 1 002 kHz and press ENTER four times 4 The display should be reading approximately 0 2 THD and will be unstable Note that the settings for the source did not change Go back into the THD MEAS menu and select ACQUIRE for the frequency mode The THD reading will return to approximately 0 02 THD Remote command sequence Use the following command sequence to measure THD RST Restore default settings SENS FUNC DIST Selects distortion function SENS DIST TYPE THD Selects THD distortion measurement type SENS DIST HARM 2 Sets the highest harmonic number to b
44. ribed in the Manual Exercise extreme caution when a shock hazard is present Lethal voltage may be present on cable connector jacks or test fixtures The American National Standards Institute ANSI states that a shock hazard exists when voltage levels greater than 30V RMS 42 4V peak or 60VDC are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Operators of this product must be protected from electric shock at all times The responsible body must ensure that operators are prevented access and or insulated from every connection point In some cases connections must be exposed to potential human contact Product operators in these circumstances must be trained to protect themselves from the risk of electric shock If the circuit is capable of operating at or above 1000 volts no conductive part of the circuit may be exposed Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sourc es NEVER connect switching cards directly to AC mains When connecting sources to switching cards install protective de vices to limit fault current and voltage to the card Before operating an instrument make sure the line cord is connected to a properly grounded power receptacle Inspect the con necting cables test leads and jumpers for possible wear cracks or breaks before each use When installing equipment where access t
45. rogramming examples 000 0 cee eeeeseceeeeseceeeeseeseeeseeeeeeaeeseeeaeees 26 Programming sine wave Source 0 ees eeeeeseeeeeseeeseeeeeeseeeee 26 Measuring THD THD noise or SINAD 0 eee 27 RMS voltage measurement 00 0 eee eeeeeseeeeereeeeeeeeeeseeees 28 Bandwidth limited RMS voltage measurement 29 Background noise measurement 0 0 eee eeeeseeeeeeseeeeeeees 30 Fast frequency sweep RMS voltage measurements 31 Frequency domain components 000 eeeeseeeeeeeeeeeeeeeseeees 32 Measurement of individual harmonics sssssseeseseereseeeereeee 33 Peak measurements ee eee eeeeeeseeeeeeseeseeeseeseeeaeeeeeeseeeseaes 34 List of Illustrations Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Source CONNECTIONS to input 0 eee eeeeeeeteeeteeeeeeeteeeteeeteeeeaeeee 11 Frequency spectrum example 0 ce eeeeeeeseceeeeseeseeeseeeseeseees 16 Peak analysis example using MAX and NEXT commands 17 Peak analysis example using SFR and LOC commands 18 Peak analysis example using RIGHT command 19 DELTA peak analysis example 0 0 0 0 ee eeeeeeeeeseeeeeseeeseeeeees 23 Connections to double generator amplitude 0 0 eee 26 AC Signal Analysis Using Models 2015 2015 P and 2016 THD Multimeters About this guide This guide is designed to familiarize users with basic Model 2015 2015 P 2016 operations to analyze an AC input signal Operations includ
46. s are adequately trained Operators use the product for its intended function They must be trained in electrical safety procedures and proper use of the instrument They must be protected from electric shock and contact with hazardous live circuits Maintenance personnel perform routine procedures on the product to keep it operating properly for example setting the line voltage or replacing consumable materials Maintenance procedures are described in the manual The procedures explicitly state if the operator may perform them Otherwise they should be performed only by service personnel Service personnel are trained to work on live circuits and perform safe installations and repairs of products Only properly trained service personnel may perform installation and service procedures Keithley products are designed for use with electrical signals that are rated Installation Category I and Installation Category II as described in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data T O signals are Installation Category I and must not be directly connected to mains voltage or to voltage sources with high tran sient over voltages Installation Category II connections require protection for high transient over voltages often associated with local AC mains connections Assume all measurement control and data I O connections are for connection to Category I sourc es unless otherwise marked or desc
47. st fixture keep the lid closed while power is applied to the device under test Safe operation requires the use of a lid interlock Ifa screw is present connect it to safety earth ground using the wire recommended in the user documentation The J symbol on an instrument indicates that the user should refer to the operating instructions located in the manual The A symbol on an instrument shows that it can source or measure 1000 volts or more including the combined effect of normal and common mode voltages Use standard safety precautions to avoid personal contact with these voltages The WARNING heading in a manual explains dangers that might result in personal injury or death Always read the associated information very carefully before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the war ranty Instrumentation and accessories shall not be connected to humans Before performing any maintenance disconnect the line cord and all test cables To maintain protection from electric shock and fire replacement components in mains circuits including the power transformer test leads and input jacks must be purchased from Keithley Instruments Standard fuses with applicable national safety ap provals may be used if the rating and type are the same Other components that are not safety related may be purchased from other suppliers as long as they
48. t freg auto on By default the instrument is set to or measure the input signal frequency ssens dist freg 2000 continuously for maximum accuracy or The user may preset the incoming ssens dist freg acg frequency or program the instrument to measure the frequency once and hold that value sens dist rang auto on Sets the input voltage range to auto or The user can also set a manual input ssens dist rang 1 voltage range th xample command pro grams the instrument to the 100mV range sens dist harm 21 Sets up instrument to measure 21 harmon ics Can be set from 2 to 64 init Triggers readings opc Makes sure trigger is complete sens dist harm magn 2 21 Will return values for harmonics in dB 34 Using Models 2015 2015 P and 2016 THD Multimeters Peak measurements The commands below for the Model 2015 P allow the user to find a peak amplitude The Left and Right commands will go to the next highest spectral component to the right or left of the current peak The user must set the measurement frequency to 20Hz otherwise the instru ment will not perform the peak search Setting the instrument to 20Hz gives maximum fre quency resolution for the frequency spectrum The readings are returned in dBV rst vinit trig Sens Sens sinit opc sens Sens Sens Sens dist dist dist cont coun func dist dist off dist freq 20
49. tly to the Model 2015 2015 P 2016 input This source has a selectable 6009 50 or HI Z output impedance and is unbalanced coaxial A second output provides a selectable inverted sine opposite in phase to the main output or a 0 5V logic level pulse in phase with the main output having the same frequency Front panel a Press SRC THD b When the display shows SINE OUT use the left right arrow and up down range keys to select ON then press ENTER c When the display shows FREQ use the left right arrow and up down range keys to select the frequency 01 to 20 k then press ENTER d When the display shows IMPEDANCE use the left right arrow and up down range keys to select 50 600 or HI Z then press ENTER e When the display shows AMPL use the left right arrow and up down range keys to set the amplitude 0 to 2V for 50 and 600 ohms 0 to 4V for 2015 2015 P HI Z 0 to 9 5V for 2016 HI Z then press ENTER Note for 600 and 509 impedances the actual no load voltage at the output will be twice the selected value f When the display shows CHAN2 use the left right arrow and up down range keys to select the mode for the second source output Select either an inverted sine ISINE or square wave PULSE and press ENTER Remote commands OUTP ON OFF OUTP FREQ lt NRf gt OUTP IMP OHM50 OHM60 OUTP AMPL lt NRf gt O HIZ OUTP CHAN2 SHAP ISIN E
50. ts the impedance of the main output 5 The output sweep can only be performed in distortion mode When performing a sweep use the SET frequency acquisition mode to achieve maxi mum speed The remote command is sens dist freq auto off Using Models 2015 2015 P and 2016 THD Multimeters Distortion measurement examples The following examples to measure distortion use the internal sine source of the Model 11 2015 2015 P 2016 Figure 1 shows how to connect sine SOURCE OUTPUT to INPUT HI and LO Figure 1 Source connections to input THD measurement example BNC to Banana Plug Cable 6 OR SENSE INPUT Q 4W SOURCE INV PULSE OUTPUT SOURCE OUTPUT Model 2015 2015 P 2016 Rear Panel The following example for both front panel and remote operation measures the THD of the internal sine source Make sure the internal source of the instrument is connected to the input as shown in Figure 1 Front panel operation Perform the following steps to measure THD 12 13 Ree Fee eT OO OY Se Press SHIFT then ACV to put the instrument into the THD mode Press the THD MEAS key When the display shows TYPE select THD and press ENTER When the display shows FREQ select AUTO and press ENTER When the display shows UPPR HARM select 2 and press ENTER When the display shows UNITS select PERC and press ENTER When the display shows SFIL select NONE and p
51. what distortion mode the unit is set for SINAD can be calculated from the THD noise reading Remote commands NOTE These commands only work if the unit is set to trigger one reading at a time INIT CONT OFF Errors will occur if the unit is continuously updating SENS DIST RMS Returns the calculated RMS volts value for the last triggered reading SENS DIST THDN Returns the THD tnoise reading for the last triggered reading SENS DIST THD Returns the THD reading number of harmonics to use was set in Step 4 11 Configuring and running internal sweep remote operation only The internal source of the Model 2015 2015 P 2016 can be set to sweep through up to 200 frequencies and then return distortion and or RMS volts for each frequency The results of the sweep can be returned using the SREAL data format fastest or in ASCII default The sweep uses the current distortion measurement settings The sweep must be allowed to complete before requesting the data otherwise the data will be incomplete The sweep end can be detected by reading bit 3 of the operation event register stat oper which will set to 1 at the end of a sweep Likewise this bit can be used with the SRQ function of the instrument to trigger a service request when the sweep is completed Using Models 2015 2015 P and 2016 THD Multimeters 9 Remote command sequence OUTP MODE FIXED LIST LIST sel
52. y pointer positions Includes a command sequence example Frequency list analysis Covers the commands to create a frequency list and return the amplitudes of the listed frequencies Includes a command sequence example 2 Using Models 2015 2015 P and 2016 THD Multimeters Measurements overview Harmonic distortion measurement The Model 2015 2015 P 2016 uses a DSP Digital Signal Processor to perform a Fast Fou rier Transform FFT on a voltage signal applied to the front or rear voltage inputs It then ana lyzes the levels of the harmonics present in the signal to calculate THD THD noise SINAD or RMS volts The instrument can measure harmonic distortion from 20Hz to 50kHz A DDS Direct Digital Synthesis module is included in the THD circuitry to provide a pro grammable sine source The source has a second output which can be set to provide the inverse of the sine output shifted 180 degrees or to put out a 0 5V logic level pulse in phase with the main output A sweep feature enables the user to program a list of up to 200 sweep frequencies and amplitudes then have the unit return distortion and or RMS volts for each frequency AC volts and frequency measurements The Model 2015 2015 P 2016 can measure true RMS AC voltage from 0 1uV to 750V 1000V peak It can also measure frequency from 3Hz to 500kHz Frequency spectrum analysis Model 2015 P only Using remote command programming the Model 2015 P can measure the am
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