Rejecting Power Line Noise Voltages | HP WaterSkis E1412A specification

Rejecting Power

Line Noise

Voltages

Adesirable characteristic of integrating analog-to-digital (A/D) converters is their ability to reject spurious signals. The integrating techniques reject power-line related noise present with a dc signal on the input. This is called normal mode rejection or NMR. Normal mode noise rejection is achieved when the multimeter measures the average of the input by “integrating” it over a fixed period. If you set the integration time to a whole number of power line cycles (PLCs) these errors (and their harmonics) will average out to approximately zero.

The HP E1312A and HP E1412A provide three A/D integration times (1, 10 and 100PLCs) to reject power line frequency noise (and power-line frequency harmonics). Power line frequency defaults to 60Hz unless you specifically set it to 50Hz with the CAL:LFR command. The multimeter determines the proper integration time based on which power line frequency is set. Table 2-2 shows the noise rejection achieved with various configurations. Select a longer integration time for better resolution and increased noise rejection.

Table 2-2. Noise Rejection

		Integration Time
	Power Line	60Hz		(50Hz)
	Power Line
	Cycles (PLCs)				NMR
	Cycles (PLCs)				NMR


	0.02	400μs		(400μs)	NONE

	0.2	3ms		(3ms)	NONE

	1	16.7ms		(20ms)	60dB

	10	167ms		(200ms)	60dB

	100	1.67sec		(2sec)	60dB

Common Mode Rejection (CMR)

Ideally, a multimeter is completely isolated from earth-referenced circuits. However, there is finite resistance between the multimeter's input LO terminal and earth ground as shown below. This can cause errors when measuring small voltages which are floating relative to earth ground.

Chapter 2

HP E1312A/E1412A Multimeter Application Information 27

Image 27

HP WaterSkis E1412A, WaterSkis E1312A manual Rejecting Power Line Noise Voltages, Common Mode Rejection CMR

Contents

Contents Frequency and Period Measurement Errors Zeroauto ZEROAUTO? IMMediate Chapter Multimeter Command Reference Appendix a Appendix B Contents HEWLETT-PACKARD Warranty Statement Documentation History Manufacturer’s Name July 31 Jim White, QA Manager Business Reply Mail Page Using This Chapter HP E1312A and HP E1412A Multimeter Module Setup Setting the Module Address Switch Setting the Line Frequency Reference Interrupt PriorityChecking the Line Frequency Reference Page Multimeter Functional Connections Switch Module Analog Bus Connections Voltage Measurement Connections Wire Ohms Measurement Connections Initial Operation HP E1312A and HP E1412A Multimeter Module Setup Chapter Function Prototype HP E1312A and HP E1412A Multimeter Module Setup Chapter Thermal EMF Errors Measurement TutorialDC Voltage Measurements Thermoelectric Voltages Loading Errors dc volts Leakage Current Errors Common Mode Rejection CMR Rejecting Power Line Noise Voltages Noise Caused by Ground Loops Noise Caused by Magnetic Loops Resistance Measurements Wire Ohms Measurements Set to 2-wire ohms function Power Dissipation Effects Errors in High Resistance MeasurementsMaking High-Speed DC and Resistance Measurements True RMS AC Measurements DC Current Measurement Errors Common Crest Factors Example Crest Factor Errors non-sinusoidal inputs Function and Range Change Internal Offset Correction Loading Errors ac voltsTemperature Coefficient Errors AC Measurements Below Full Scale Voltage Measured = Vin2+ Noise2 Low-Level Measurement Errors AC Current Measurement Errors Frequency and Period Measurement ErrorsMaking High-Speed AC Voltage or Current Measurements AC Signal Filter DC Input Resistance Measurement Configuration Number of Power Line Cycles Nplc Resolution Chapter HP E1312A/E1412A Multimeter Application Information SENSeZEROAUTO Offonceon Null Relative Function Math Operations CALCulate Subsystem CONFfunction DB Measurements DBm Measurements Storing the dB Reference ValueStoring the dBm Reference Resistance Value HP E1312A/E1412A Multimeter Application Information Chapter Triggering the Multimeter TRIGgerSOURce EXTernal Checking the Trigger Source Wait-for-Trigger State Bus Triggering Checking the Trigger Count Inserting a Trigger Delay Example Setting the Trigger CountExample Inserting a Trigger Delay Default Trigger Delays Querying Delay Time Sample Count Example Setting the Sample CountChecking the Sample Count HP VTL Software Visa HP E1312A and HP E1412A Multimeter Application Examples Making Multimeter Measurements MEASure Command MEASURE2 Source Code File MEASURE1 Source Code File Init MEASURE3 Source Code File MEASURE4 Source Code File HP E1412A Multimeter and Switch Module Synchronization Synchronizing Multimeter With a Switch Module See -5 for the HP E1312A/E1412A Multimeter status system Retrieve the readings from the multimeter Set up the MultimeterNow set up the switch module Check the multimeter for system errors Multimeter Status System Examples RST CLS *ESE Init OPC Synchopc Source Code File RST Init FETC? Synchmav Source Code File End Loop Check the multimeter for system errors Limittst Source Code FileLoop Programming Example Device ConfigurationPage HP E1312A/E1412A Multimeter Application Information Chapter Command Types Common Command FormatCommand Format Command Abbreviated Commands Implied CommandsSeparator Parameters Linking Commands PLC Multimeter Range and Resolution Tables Scpi Command Reference AC Voltage Range versus ResolutionAC Current Range versus Resolution Related Commands INITiate, TRIGger ABORtAborting a Measurement CALCulate Subsystem SyntaxValid Math/Measurement Function Combinations AVERageMINimum? AVERageAVERage?AVERageCOUNt? AVERageMAXimum? DBMREFerence? DBREFerenceDBREFerence? DBMREFerence Example Query the Calculate Math Function FUNCtionFUNCtion? Parameter Summary Example LIMitUPPer? LIMitLOWerLIMitLOWer? LIMitUPPer STATe? NULLOFFSetNULLOFFSet? STATe Comments CALibrationCOUNt? LFRequency Example Enter a New Calibration Security Code Example Query the Line Frequency SettingLFRequency? SECureCODE Example Set the Calibration State to Unsecured SECureSTATeSECureSTATe? STRing Example Query the Calibration Message STRing?VALue VALue? Zeroauto CAL? CALibration? Command Setting CONFigure Function Range Resolution Default Settings for CONFigure Command by Function Example Making AC Current Measurements CURRentAC Example Making DC Current Measurements CURRentDC ResolutionMINMAXDEF selects the frequency function FRESistance Example Making 4-Wire Ohms Measurements PERiod Example Making 2-Wire Ohms Measurements Resolution Minmaxdef Example Making AC Voltage Measurements VOLTageAC Example Making DC Voltage Measurements VOLTageDC Sense HI and LO input VOLTageDCRATio String Returned CONFigure? POINts? Data Example Transferring Stored Readings to Output Buffer FETCh? INITiate IMMediateExample Placing Multimeter in Wait-For-Trigger State IMPedanceAUTO? Example Query the Input Impedance ModeINPut IMPedanceAUTO MEASure MEASCURRAC? 1,MAX CURRentAC? MEASCURRDC? .1,MAX CURRentDC? FREQuency? MEASFRES? 1500,MAX FRESistance? PERiod? RESistance? VOLTageAC? VOLTageDC? Example Making DC Voltage Ratio Measurements VOLTageDCRATio? OUTPut TTLTrgSTATeRST Condition OUTPTTLTn OFF TTLTrgSTATe? Example Route Voltmeter Complete to Trigger LineExample Query Voltmeter Complete Destination Example Transfer Readings Directly to Output Buffer READ? SAMPle COUNtRST Condition Sampcoun Example Set the Sample Count SAMPCOUN? Example Query the Sample Count SENSe Zero Auto Offonceon AUTO? Function Example Query the Measurement Function CURRentACRANGe CURRentACRANGe?Example Query the AC Current Measurement Range CURRentACRANGeAUTO? Example Disable AC Current AutorangingExample Query the AC Current Autorange Mode CURRentACRANGeAUTO CURRentACRESolution? CURRentACRESolution Example Query the Aperture Time CURRentDCAPERtureCURRentDCAPERture? Example Set an Aperture Time of 16.7ms CURRentDCNPLC CURRentDCNPLC?Example Query the DC Current Integration Time Example Query the DC Current Measurement Range CURRentDCRANGeCURRentDCRANGe? Example Set the DC Current Range to 3A CURRentDCRANGeAUTO? Example Disable DC Current AutorangingExample Query the DC Current Autorange Mode CURRentDCRANGeAUTO CURRentDCRESolution? CURRentDCRESolution DETectorBANDwidth Example Query the Detector Bandwidth DETectorBANDwidth?FREQuencyAPERture FREQuencyAPERture? Example Query the Measurement Range FREQuencyVOLTageRANGeFREQuencyVOLTageRANGe? Example Set the Voltage Range for Frequency Measurements to FREQuencyVOLTageRANGeAUTO? Example Disable AutorangingExample Query the Autorange Mode FREQuencyVOLTageRANGeAUTO FRESistanceAPERture? FRESistanceAPERture FRESistanceNPLC FRESistanceNPLC?Example Query the Integration Time FRESistanceRANGe? FRESistanceRANGe FRESistanceRANGeAUTO? FRESistanceRANGeAUTO RST Condition Fresres 1mΩ 1E-03 FRESistanceRESolutionFRESistanceRESolution? Example Query the Resolution PERiodAPERture PERiodAPERture?RST Condition 0.1 100ms Example Set the Aperture Time Example Query the Period Voltage Range PERiodVOLTageRANGePERiodVOLTageRANGe? Example Set the Voltage Range for Period Measurements to PERiodVOLTageRANGeAUTO? PERiodVOLTageRANGeAUTO RESistanceAPERture? RESistanceAPERture RESistanceNPLC? RESistanceNPLC RESistanceRANGe RESistanceRANGe?RST Condition Resrang 1kΩ Example Change the Range RESistanceRANGeAUTO? RESistanceRANGeAUTO RESistanceRESolution RESistanceRESolution?Example Change the Resolution VOLTageACRANGe? VOLTageACRANGe Example Disable AC Voltage Autoranging VOLTageACRANGeAUTOVOLTageACRANGeAUTO? VOLTageACRESolution VOLTageACRESolution?RST Condition 1E-04 Example Change the Resolution VOLTageDCAPERture? VOLTageDCAPERture VOLTageDCNPLC? VOLTageDCNPLC VOLTageDCRANGe? VOLTageDCRANGe VOLTageDCRANGeAUTO? VOLTageDCRANGeAUTO VOLTageDCRESolution? VOLTageDCRESolution Example Query the Autozero Mode Example Disable Autozero QUEStionableCONDition? PRESetQUEStionableENABle STATus QUEStionableEVENt? QUEStionableENABle? VERSion? ERRor?Example Reading the Error Queue SYSTem RST Condition Trigcoun Example Set the Trigger Count TRIGger DELay Example Set the Trigger DelayExample Query the Trigger Count Example Disable Automatic Trigger Delay DELay?DELayAUTO Example Query the Trigger Delay Example Query the Trigger Delay Mode DELayAUTO? Related Commands INITiate, READ?, MEAS? SOURceExample Set the Sample Source Example Query the Trigger Source SOURce? Category Command Title Description Ieee 488.2 Common Command Quick Reference ESE and *ESE? Example Enable All Error Events ESR? RST does not affect SRE and *SRE? STB? HP E1412A C-size 6½-Digit Multimeters Scpi Command Quick Reference Data 67sMINMAX Zeroauto Offonceon DC Characteristics HP E1312A and HP E1412A Multimeter Specifications 60 Hz 50 Hz Measuring Characteristics Operating Characteristics True RMS AC AC Characteristics True RMS AC Voltage System Speeds 10 Accuracy Specifications ±% of reading 1 Frequency and Period Characteristics Configuration Rates 14/sec Autorange Time General Specifications Understanding the % of reading Error To Calculate Total Measurement Error Total Measurement Error Number of Digits and Overrange Interpreting Multimeter Specifications Accuracy DC Voltage, DC Current, and Resistance Measurements Configuring for High Accuracy Measurements Execution Errors 123Numeric overflow 112Program mnemonic too long113Undefined header 121Invalid character in number 211Trigger ignored To -168Block data errorsTo -178Expression errors 221Settings conflict 350Too many errors 330Self-test failed440Query Unterminated after indefinite response Cannot use overload as math reference Cannot achieve requested resolution Invalid secure code Cal signal measurement out of rangeCal signal frequency out of range Cal secured No cal for this function or range HP E1312A and HP E1412A Multimeter Error Messages Appendix B Measurement Speed and Accuracy Trade-offs Measurement Speed and Accuracy Trade-offs Appendix C HP E1312A/E1412 Special Function Minimize Number Command Response Sessions General Guidelines for Increasing Measurement SpeedAvoid Function Changes Avoid Aperture Changes Decrease Aperture Time or NPLCs Set Autozero to Once or OFF Turn Autorange INITFETCH? Setting the Resolution Index 197 Index 124 Index Index Error, 180 See online help Cycles, 27, 38, 123, 132, 140 Errors 130 Setting resolution, 15, 38 160 Index