DAQ which can measure high resistance value...

[gauravmohta]

Hello,

I am working on a project wherein I am using tactile (pressure) sensor. I need to measure pressure in real time(continuously). 

I am currently using NI-DAQ 6221. Using DAQ assistant VI, I wanted to see pressure values at different instances. But unfortunately, when I click on acquiring force or pressure it shows "NO SUPPORTED DEVICES FOUND". Hence I decided to measure resistance values to set required threshold levels. But I faced another problem here.

The maximum resistance which 6221 can measure is limited to 10K. But the amount of pressure applied on the sensor will give resistance values more than 10K. So please help me with DAQ models which can:-

1) Either measure pressure or force directly  and/or,

2) A DAQ model which has higher resistance measuring capability....(upper range should at least be 100K) 

Regards,

Gaurav

PS:- i am using LabVIEW 2010.

[crossrulz]

How are you measuring resistance?  That DAQ can only read voltage.

[gauravmohta]

Go to block diagram --> Measurement & I/O --> NI-DAQ --> DAQ assistant --> double click on VI --> Acquire signal --> Analog signal--> Resistance. 

[johnsold]

Regardless of how you have set the DAQ Assistant, if the hardware you are using does not support resistance measurements, you will not get a resistance measurement.

To measure resistance you need to generate a source of voltage or current to apply to the unknown resistance and you need to measure both the voltage and current through the resistance.  The 6221 has no direct means of measuring current.

You might be able to make a voltage divider with a known fixed resistor and your sensor.  Apply a voltage from the Analog Output of the DAQ device.  Measure the voltages across both the fixed resistor and the sensor.  Do the Ohm's Law calculations to determine the unknown resistance.

The range of resistance values you can measure will depend on the value of the external resistor, the available ranges of AO voltage outputs, AI input ranges, and device resolution.  The accuracy will be less than the accuracy with which you know the value of the fixed resistor.

Lynn