Temperature Transmitter Span Setting and Calculations

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Thread Starter

Rizal28

I want to know for Span Setting of Temp Transmitter connect to RTD.

Let's say we have 3 Temp Transmitter with different span:

1) 0-160 degC
2) 0-250 degC
3) 0-400 degC

As I know, setting zero-span for 4-20mA analog transmitter will effect operating temperature shall working within that range.

But, let's say I received current 8mA from above transmitters installed on the same process line. For 3 different span will give different temperature (degC) in the DCS.

Which one is correct? And how to understand the calculation?
 
> 1) 0-160 degC
> 2) 0-250 degC
> 3) 0-400 degC

Assuming the transmitters are properly calibrated spanned, and that all linearization is done in the transmitter.

For X ma loop current

T = Lower Limit +
(Upper Limit-Lower Limit)x(X ma-4ma)/(20ma-4ma)
 
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