Agilent Technologies 34972A User's Guide

The Agilent Technologies 34970A combines precision measurementcapability with flexible signal connections for your production anddevelopment test syst

Shielding TechniquesShielding against noise must address both capacitive (electrical) andinductive (magnetic) coupling. The addition of a grounded shi

Sources of System Cabling ErrorsRadio Frequency Interference Most voltage-measuring instrumentscan generate false readings in the presence of large,

Thermal EMF Errors Thermoelectric voltages are the most commonsource of error in low-level dc voltage measurements. Thermoelectricvoltages are genera

Measurement FundamentalsThis section explains how the 34970A makes measurements anddiscusses the most common sources of error related to these measure

Rejecting Power-Line Noise Voltages A desirable characteristic ofan integrating analog-to-digital (A/D) converter is its ability to rejectspurious si

Temperature MeasurementsA temperature transducer measurement is typically either a resistanceor voltage measurement converted to an equivalent tempera

RTD Measurements An RTD is constructed of a metal (typicallyplatinum) that changes resistance with a change in temperature in aprecisely known way. Th

Thermocouple Measurements A thermocouple converts temperatureto voltage. When two wires composed of dissimilar metals are joined,a voltage is generat

An ice bath is used to create a known reference temperature (0 °C).Once the reference temperature and thermocouple type are known,the temperature of t

To make a more accurate measurement, you should extend the coppertest leads of the internal DMM closer to the measurement and hold theconnections to t

The Front Panel at a Glance 1 State Storage / Remote Interface Menus2 Scan Start / Stop Key3 Measurement Configuration Menu4 Scaling Configurati

In some measurement situations, however, it would be nice to removethe need for an ice bath (or any other fixed external reference). To dothis, an iso

Loading Errors Due to Input Resistance Measurement loadingerrors occur when the resistance of the device-under-test (DUT) is anappreciable percentage

Loading Errors Due to Input Bias Current The semiconductordevices used in the input circuits of the internal DMM have slightleakage currents called bi

Resistance MeasurementsAn ohmmeter measures the dc resistance of a device or circuit connectedto its input. Resistance measurements are performed by s

The 4-wire ohms method is used in systems where lead resistances canbecome quite large and variable and in automated test applicationswhere cable leng

Low-Level Signal Multiplexing and SwitchingLow-level multiplexers are available in the following types: one-wire,2-wire, and 4-wire. The following se

One-Wire (Single-Ended) Multiplexers On the 34908A multiplexer, all of the 40 channels switch the HI inputonly, with a common LO for the module. The m

Four-Wire Multiplexers You can make 4-wire ohms measurements using the 34901A and34902A multiplexers. For a 4-wire ohms measurement, the channels ared

Signal Routing and Multiplexing When used stand-alone for signal routing (not scanning or connected tothe internal DMM), multiple channels on the 3490

DC, Resistance, and Temperature Accuracy Specifications± ( % of reading + % of range ) [1]Includes measurement error, switching error, and transducer

The Rear Panel at a Glance WARNINGFor protection from electrical shock, the power cord ground must not bedefeated. If only a two-contact electrical ou

To Calculate Total Measurement ErrorEach specification includes correction factors which account for errorspresent due to operational limitations of t

Understanding the “ % of range ” Error The range error compensatesfor inaccuracies that result from the function and range you select.The range error

Interpreting Internal DMM SpecificationsThis section is provided to give you a better understanding of theterminology used and will help you interpret

Resolution Resolution is the numeric ratio of the maximum displayed value dividedby the minimum displayed value on a selected range. Resolution isofte

24-Hour Accuracy The 24-hour accuracy specification indicates the internal DMM’s relativeaccuracy over its full measurement range for short time inter

The Plug-In Modules at a GlanceFor complete specifications on each plug-in module, refer to the modulesections in chapter 9. 34901A 20-Channel Arm

To Connect Wiring to a Module 6 mm 20 AWG Typical Channel Number:Slot Channel 5 Install the module into mainframe.Wiring Hints...• For detailed

DC Voltage / AC Voltage / Frequency ThermocoupleThermocouple Types: B, E, J, K, N, R, S, TSee page 351 for thermocouple color codes.Ranges

System OverviewThis chapter provides an overview of a computer-based system anddescribes the parts of a data acquisition system. This chapter is divid

The system configuration shown on the previous page offers thefollowing advantages:• You can use the 34970A to perform data storage, data reduction,ma

Multiplexer Switching Multiplexers allow you to connect one ofmultiple channels to a common channel, one at a time. A simple 4-to-1multiplexer is sho