3 System Overview
90 Keysight 34970A/34972A User’s Guide
Measurement Input
The 34970A/34972A allows you to combine a DMM (either internal or external)
with multiplexer channels to create a scan. During a scan, the instrument
connects the DMM to the configured multiplexer channels one at a time and
makes a measurement on each channel.
Any channel that can be “read” by the instrument can also be included in a scan.
This includes any combination of temperature, voltage, resistance, current,
frequency, or period measurements on multiplexer channels. A scan can also
include a read of a digital port or a read of the totalizer count on the multifunction
module.
The internal DMM
A transducer or sensor converts a physical quantity being measured into an
electrical signal which can be measured by the internal DMM. To make these
measurements, the internal DMM incorporates the following functions:
– Temperature (thermocouple, RTD, and thermistor)
– Voltage (dc and ac up to 300V)
– Resistance (2-wire and 4-wire up to 100 MΩ)
– Current (DC and AC up to 1A)
– Frequency and Period (up to 300 kHz)
The internal DMM provides a universal input front-end for measuring a variety of
transducer types without the need for additional external signal conditioning. The
internal DMM includes signal conditioning, amplification (or attenuation), and a
high resolution (up to 22 bits) analog-to-digital converter. A simplified diagram of
the internal DMM is shown below.
To/From
Earth
Referenced
Section
= Optical Isolators
Amp
Signal
Conditioning
Analog to
Digital
Converter
Main
Processor
Analog
Input
Signal
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