Part 2

Plug-In Assembly Configuration 45 7b. The second method uses a reversible excitation supply. For each unstrained andstrained measurement, reverse the supply polarity and take a second measurement.Average each pair of measurements and use these values in equation (3). In thismethod, offsets are cancelled and there is no waiting for the gauges to cool.Lead Wire ResistanceThe equations previously used do not include compensation terms for lead wireresistance (see Figure 123 at the end of this section for bridge equations which includelead resistance). Although the bridges can be connected with two wire configurations,we highly recommend a three-wire arrangement (with shielding) to reducethe effects of lead wire resistance.If lead wire resistance is a critical factor for your application, choose a 350 ohmgauge and use the 44427B assembly, since this gauge is less susceptible to leadwire resistance effects. If you are using ?4 bridge configuration, you can measurethe lead wire resistance on channels A7, A8 and A9, as follows.As shown in Figure 120, the lead wire resistance (Rd can be computed from thefollowing equation. Since R3 is specified to + 0.12%, this is the overall accuracyof the measurement.[(voltage A-B)Ra 1 (R3) [& .I2961- VexFigure 120. Options 0701071 - Lead Wire ResistanceArtisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com