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How to measure resistance with an SCXI-1520?
dj143
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09-10-2004 11:36 AM
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In addition to measuring the mV/V output from full bridges, I also need to record the bridge resistance (between the two excitation terminals). Does anyone have any tips or suggestions on how this can be done using the SCXI-1520? For example, is it feasible to place a reference resistor in series with the bridge and then measure the voltage drop across the bridge. (The voltage source would be the excitation available from the SCXI-1520 channel.) The bridge voltage drop would then be compared to the reference resistor's voltage drop and ultimately the bridge reistance calculated. Maybe there's a better way?
sergesl
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09-14-2004 06:31 PM
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The formula used to obtain strain in a full bridge configuration can be found at the following link: http://zone.ni.com/devzone/conceptd.nsf/webmain/C83E9B93DE714DB08625686600704DB1?OpenDocument&node= . It uses the exitation voltage, the output voltage and the gauge factor. All the above but the ouput voltage are set by the user. So the strain, the measured voltage, the gauge factor and the gauge base resistance values could be used in a formula node to convert from strain to resistance.
Serges
Serges
09-15-2004 08:44 AM
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This is a good introductory article on how strain gauges are used in conjunction with signal conditioning. However, it's not clear how this relates to measuring bridge resistance. We make full bridge force measuring sensors that use strain gauges. (i.e. tension or compression load cells) The calibration report that I need to generate using LV must also indicates the bridge resistance for both input and output. (Previously I mentioned only the input.) Currently, we take a common ohmmeter and manually measure the resistance and then record the values on the calibration certificate. The sensor is not under any load while measuring the resistance. Even if it was under load, you probably would not see any change in the bridge resistance. (The mV/V output
is very low for typical load cells.) At this point I�m trying to figure out the best way to automatically do this using an SCXI-1520. In other words, I need to use one of the channels of the 1520 to operate as a common ohmmeter and I'm looking for ideas on how to do this.
is very low for typical load cells.) At this point I�m trying to figure out the best way to automatically do this using an SCXI-1520. In other words, I need to use one of the channels of the 1520 to operate as a common ohmmeter and I'm looking for ideas on how to do this.
