Part 2

598 Example 3497A ConfigurationsEXAMPLE 11STRAIN GAUGE MEASUREMENTSDESCRIPTIONThe 1201350 Ohm Strain GaugelBridge Completion assemblies (Options 0701071)can be used to measure the strain from 120 ohm or 350 ohms strain gauges. Thisexample shows how to measure the strain from up to ten 120 ohm strain gaugesby using an Option 070 assembly configured for ?h bridge completion on each ofthe 10 channels.PROCEDURETo make strain gauge measurements using the Option 070 (or 071 ), a four-step procedureis used:1. Measure the excitation voltage, Vs.2. Measure bridge output voltage (Voutu) with gauge unstrained.3. Measure bridge output voltage (Vouts) with gauge strained.4. Compute strain from E = -4VrlGF(1 + 2Vr) where GF = Gauge Factor of thestrain gauge and Vr = [(Vout/Vs)strained - (Vout1Vs)unstrainedl.CONFIGURATIONFigure 198 shows a connection diagram and equivalent circuit for '/4 bridge configurationof a strain gauge connected to channel A0 of a terminal card. To connect upto 10 strain gauges, connect a gauge to Al, A2, .. A9 and cut jumpers JO-J9 forchannels used. Note that only one excitation voltage supply (Vs) is required, whether1, 2, ..., or 10 gauges are connected to the assembly.Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com