Conversion: Input signal AIO has to be manipulated

[shankaryr]

Hi,

I have a Voltage Divider circuit with a 1K resistor and a Force Sensing Resistance. I receive a voltage value at AI0. I can manually compute the Resistance value of the FSR(Variable resistance) using the formula :

R2 = (Vin of 5V * 1K) / Vout at AIO - 1K. The inverse also gives me the conductance.

I understand that we can do this in the DAQFactory using conversions. I have been trying to do so but the steps given to in the manual are a little confusing.

How do I do this? and how do I create a graph or an LED display for the convertred value of the Resistance and Conductance.

Thanks and all help is appreciated.

[AzeoTech]

Can you provide the exact formula's that give you resistance and conductance based on AI0?

[shankaryr]

The formula is:

Resistance of FSR = (5000/ Local.AI0) - 1000

Conductance = 1 / Resistance of FSR

[AzeoTech]

OK, so the conversion would be:

(5000 / Value) - 1000

Apply this to your analog input channel and the channel will only read resistance (instead of voltage). You have three choices for conductance:

1) Put 1 / resistance wherever you want to display or graph the conductance. This, however, won't let you log it using a logging set (though you could use an export set or file. functions)

2) Create a V channel with 1/resistance in it and reference the V.Channel everywhere. This really just saves you a little typing, and allows you to change the formula from one place

3) Create a test channel called "Conductance", Device type "Test", I/O type "A to D", Timing = "0". Then, in the Event for your resistance channel put:

Conductance.AddValue(1/Resistance[0])

This will cause the conductance channel to update with 1/resistance every time a resistance measurement is read. Make sure your conductance channel has a Timing of 0.