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String Pot. Hook Up and Scaling

Can anyone point me in the correct direction?

I am trying to hook up a Celesco SP2-12 String Potentiometer and am having the following issue: I am using SignalExpress to look at the input signal from the device hooked up to a NI cDAQ-9172 with an NI 9201 voltage analog input card. I can acquire data, and the signal varies with displacement of the string on the sensor (assume it is hooked up correctly). The stroke/max displacement on this sensor is 12.5 inches, however the signal levels off after extending the string maybe 3/4 of the way and there is no change in signal from that point to the max reach. I have the device powered by a 24V power supply and the potentiometer is 10k Ohm. Is it possible that I am hitting the maximum allowed current of the DAQ at that point in the potentiometers extension? (What is the limit on the chassis/input module?)

 

Could this problem simply be solved by using like a 10V power supply instead... 1mA vs 2.4mA? 

 

I'm only trying to measure short displacements which would always occur within the region of the string which generates signal, but I feel as though I will not be able to appropriately scale the signal from voltage to displacement (inches). Ultimately my goal is to use multiple modules to hook up to 20 of these potentiometers for a test.

 

Thanks for your help 🙂

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The input range on the 9201 is +/-10V. Does the signal level out at 10V?

 

I do not think it is a current issue, but use of the 24V supply at the terminal ends of the pot. Try using a 10V supply instead.

 

-AK2DM

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"It’s the questions that drive us.”
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I will look into getting a 10V AC->DC transformer or power supply and let you know how it goes. Thanks for your help!
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