daq question

[wv]

I would like labview to read the temperature of a omron digital panel meter
with a 3 wire pt100 sensor. I don't want to diconnect the sensor from the
existing meter. How can I read the resistance of the sensor without reading
the input res. from the meter?

thanks,
w

[Process_Systems]

First off, you must ensure that the daq channel you wish to use is a high impedance input. This is not normally a problem, as any daq board I have used is in the hi-K's to Meg ohms input.
The Omron will normally supply a constant current drive to the RTD, and then measure the voltage across it, internally in the meter. You could hook your daq input across the RTD resistance terminals ( not the lead compensation terminal), and measure the voltage. You would then have to do a conversion to engineering units (temperature) in Labview. You will need a table of resistance vs. temperature, and ohm's law to do this.

[wv]

Thanks,

w.


"Process Systems" wrote in message
news:506500000005000000147B0100-1079395200000@exchange.ni.com...
> First off, you must ensure that the daq channel you wish to use is a
> high impedance input. This is not normally a problem, as any daq board
> I have used is in the hi-K's to Meg ohms input.
> The Omron will normally supply a constant current drive to the RTD,
> and then measure the voltage across it, internally in the meter. You
> could hook your daq input across the RTD resistance terminals ( not
> the lead compensation terminal), and measure the voltage. You would
> then have to do a conversion to engineering units (temperature) in
> Labview. You will need a table of resistance vs. temperature, and
> ohm's law to do this.