Re: shift in RTD Reading

If possible and not doing, use differential input.

Are you using twisted shielded pair wiring, all shields grounded to one
point. Is signal wiring and power wiring ran in parallel and unshielded?

Look for ground currents or some sort of RC filter or rectifier being formed
by the hook up and charging up some capacitance.


"Dan Wright" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hey all,
> Using an RTD to measure temperature in a fluid flow line.  When a VFD
> gets turned on to start a fan (600V) the temperature reading drops by
> ~4°C.  Using National Instruments Fieldpoint RTD module to read
> temperature. It is my understanding that noise that causes an offset
> like this has a DC component.  Is this true?  If so, Why (or how)would a
> variable frequency drive cause DC level noise?  Any ideas on how to
> remedy this?
>
> Dan W
>