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Simultaneous use of DO and AI on SCB-68

Hello! My name is Alexandra. I am trying to make my first device using labview. I'm using NI PCI-6221 and SCB-68 board. I need to measure an unknown resistance. I've made a voltage divider which must substitute several resistors of different values to the circuit, choose the closest value to the unknown one, and then show voltages over these two resistors on the graph. Supplied voltage for the divider comes from "5volts-fused" channel. To change load resistors I use digital out channels.

 

The problem is that it is not working properly((( Analog input channels show something wrong...  Measured supplied voltage using voltmeter and what labview measures through these channels are diffferent values((( How can it be? What am I doing wrong?( When I use only analog channels without using digital channels everything works perfectly...

 

Hope, someone can help me and understand my english) please!

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Could you supply some code?  There could be a configuration issue there.  Also, where is AI_GND connected?


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Oh, here is my program! Upper part of the code is a process where the program selects a proper load resistor. And the lower part must calculate an unknown resistor value.

 

AIGND is connected to channel #67. I tried to connect it to DGND, because I guess analog and digital grounds are physically connected inside the board... but with same result(

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Could anyone help me? Please...

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