Chapter 3 System Overview

Measurement Input

d”x

k” Wg :AFD7O x z” x

Sdd /”” ””0

z” x

Sdd ” z”“ ”” zx” ” x x

5 S x zx ” ”

z”

 

x x”” zx”

 

 

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.

u

A transducer or sensor converts a physical quantity being measured into an electrical signal which can be measured by the internal Sdd. To make these measurements, the internal Sdd incorporates the following functions:

Temperature (thermocouple, ikS, 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 Sdd provides a universal input front-end for measuring a variety of transducer types without the need for additional external signal conditioning. The internal Sdd includes signal conditioning, amplification (or attenuation), and a high resolution (up to 22 bits) analog-to-digital converter. A simplified diagram of the internal Sdd is shown below.

Analog

 

 

Analog to

 

To / From

Signal

Amp

Main

Earth

Input

Digital

Referenced

Conditioning

Processor

Signal

 

Converter

Section

 

 

 

 

 

 

 

 

= Optical Isolators

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Image 60
HP 34970A manual Measurement Input