Specifications

Poisson Full Bridge
(FPOisson)
In applications where the specimen is stressed lengthwise, the measurement
sensitivity is increased and temperature compensation is achieved when the
gages are mounted to the specimen as indicated in Figure 4-16.
Measurements Using an External Voltmeter
This section describes how measurements are made using a strain gage
multiplexer switchbox and a voltmeter external to the HP 75000 Series B or
Series C mainframe.
Set Up When making strain measurements with an external voltmeter, the strain
gage multiplexer is configured for
1
⁄
4
,
1
⁄
2
, and full bridge measurements as
described in Chapters 1 and 2.
The external voltmeter is connected to the multiplexer through the HI, LO,
and G terminals on the multiplexer terminal module (Figures 2-7, 2-8).
Procedure Measuring strain with an external voltmeter involves measuring the
Wheatstone bridge output voltage (Vout) and the bridge excitation voltage
(Vs) under strained and unstrained conditions. These measurements allow
you to compute the value of Vr, which in equation form is defined as:
Vr = [(Vout/Vs)strained - (Vout/Vs)unstrained]
Vr is then substituted into the appropriate equation (Table 4-1 on page 52)
based on the bridge arrangement used.
Examples of strain measurements using the relay and FET multiplexers and
an external voltmeter are contained in Chapter 3.
Figure 4-16. Poisson Arrangement
Chapter 4 Understanding the Strain Gage Multiplexers 63
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