Specifications

Strain Gage Wiring Diagrams
This section contains the wiring diagrams for the strain measurement
configurations available with the multiplexers. The section also shows how
to connect an external voltmeter to a switchbox in order to make strain
measurements. The example programs in Chapter 3 also refer to these
diagrams.
Wiring
Considerations
Before connecting strain gages to the bridge completion channels, consider
the following.
Using a
Twisted-Shielded Cable
To ensure the most accurate measurements possible, a twisted-shielded
cable should be used when connecting the strain gages to the bridge
completion channels (see Figure 2-3).
Connecting the shield to the specimen and to the G (guard) terminal of the
channel will help keep noise induced currents out of the conductor (H, L)
leads. The guard connection also takes advantage of the multiplexer’s
Wagner Ground (see “ The Wagner Ground” on page 57). The Wagner
Ground drives the midpoint of the bridge to the same potential as the
specimen, thus preventing stray leakage currents from affecting
measurement accuracy. Note that the shield must be connected to the
specimen and not the gage.
Twisting the conductor leads reduces the loop area formed by the
Wheatstone Bridge arms which may be exposed to magnetic fields which
can degrade measurement accuracy.
Wire Gage Another factor to consider is wire gage since leadwire resistance can affect
measurement accuracy when long cable runs are involved. The effects of
leadwire resistance can be predicted and corrected for by using the wire
resistance table in Appendix B and the Leadwire Resistance Diagnostic on
page 108.
Figure 2-3. Using a Twisted-Shielded Cable
Chapter 2 Connecting Strain Gages to the Multiplexers 27
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com