Specifications

The unstrained reference measurement is made because of the

unbalanced bridge method of strain measurement. Instead of

balancing (nulling) the bridge before each measurement, an

unstrained reference ((Vout/Vs)unstrained) is measured for each

channel. The unbalanced bridge measurement technique is described

in the next section.

3. Add tension to the specimen.

4. Configure the multimeter and make the strain measurement(s).

MEASure:STRain:strain_function? (@channel_list)

CONFigure:STRain:strain_function,(@channel_list)

When MEASure is used, the multimeter is configured and the

measurement is immediately taken. Because of this, variations to the

multimeter configuration (range, aperture time) are limited to the

values set by the

MEASure command (see the table on page 77).

When

CONFigure is used, the multimeter is configured but the

measurement is not taken until

READ? or INIT is executed. Thus,

low-level multimeter commands (covered in the multimeter manual)

can be used to change the configuration (range, aperture time) before

the measurement is made.

Note The strain measurement commands identified in this procedure are HP

E1326B/E1411B Multimeter commands. Information on how these

commands relate to strain measurements and how the multimeter makes

strain measurements is contained in this manual. Information on the entire

multimeter command set and on general multimeter operation is contained

in the HP E1326B/E1411B User’s Manual.

Unbalanced Bridge

Measurement

Technique

The strain gage multiplexers measure strain using an unbalanced

Wheatstone Bridge (see “Understanding the Strain Gage Measurement

Circuits” on page 53). Unbalanced bridge measurement techniques do not

require the bridge to be balanced (manually or electronically) before strain

measurements are made.

50 Understanding the Strain Gage Multiplexers Chapter 4

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