Keysight DAQ970A User Guide

Common mode noise can dramatically affect the internal DMM. A typical thermocouple output is a few mil-
livolts and a few millivolts of common mode noise can overload the input to the internal DMM.
Calculation Error
An error is inherent in the way a thermocouple voltage is converted to a temperature. These calculation
errors are typically very small compared to the errors of the thermocouple, wiring connections, and ref-
erence junction.
DC Voltage Measurements
To make a useful DC meter, a “front-end” is required to condition the input before the analog-to-digital
conversion. Signal conditioning increases the input resistance, amplifies small signals, and attenuates
large signals to produce a selection of measuring ranges.
Signal Conditioning for DC Measurements
Input signal conditioning for DC voltage measurements includes both amplification and attenuation. A sim-
plified input to the internal DMM is shown below:
Keysight DAQ970A User's Guide 193
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Keysight DAQ970A Specifications

General

Scan Rate	Up to 450 channels/sec
Connectivity	USB, LAN, GPIB (optional)
Display	4.3-inch color LCD
Operating Temperature	0 °C to 50 °C
Number of slots	3 slots
Measurement Types	DCV, ACV, DCI, ACI, 2-wire resistance, 4-wire resistance, frequency, temperature, capacitance
Voltmeter	6.5 digit
Resolution	22 bits
Memory	Non-volatile memory