1102C Excitation Voltage Correction

[zecha]

I am setting up a new SCXI system for our test lab.  I will be using an SCXI-1102C module with a 1303 terminal block and LV 8.5 to acquire signals from a lot of pressure transducers.  With the old system (IOTech PDaq's and DASYLab) we read the excitation voltage from an external power supply into a separate channel.  Then we divided all the millivoltage signals from the transducers by the excitation voltage to correct for any fluctuations.    How do I accomplish the same thing using DAQ Assistant?  It appears to me that I am only able to type in a value for excitation.  Thanks for your time!

Ryan

[Vanessa L]

Hi Ryan,

The SCXI-1102C is normally used to do thermocouple measurements.  However, when you are setting up your task in the DAQ Assistant and you choose the measurement type,  you can choose custom voltage with excitation.  Usually you use this option with SCXI modules that include an excitation source and configure a custom scale to convert the voltage that you are measuring to the units that you need.  In the custom voltage section, you can choose to have a external excitation source (like the power supply that you were using before).  There is also an option to check "use Ex for scaling".  This will allow DAQmx to divide the measurement by the excitation that you provide.  This information is provided on the right hand side of the DAQmx dialog box when you set up the measurement type.  Hopefully this information has been helpful!

[zecha]

Thank you very much for your answer.  It was very helpful.  I have one last question on this subject.  What channel should I use for excitation?  All 32 channels are selectable for inputs, and there does not seem to be special pins on the 1303 terminal block for excitation.  

Ryan

[Ana P]

Hi Ryan,

The 1102C module does not have an external excitation input. In Vanessa’s suggestion you are telling the software to account for a specific excitation that you provided externally to the transducers. So in the "Ex Value" box you’ll have to enter the excitation voltage provided to the transducers. When you select the "Use Ex for Scaling" box you are telling the software to divide the measurements by that excitation value you specified. I hope this is helpful for your application,