Output Reversing of transmitter

Can you be more specific? Reverse polarity? 4-20 mA transmitter?

Can you provide an example?

Hi Sanjay,

The only case that comes to mind is on a wet leg level measurement using DP cell...

The Wet leg is the reference leg and when fully filled onto the H side of the DP Cell, with no pressure onto the L Side, the DP is at it's greatest. This represents 0% level.

Conversely, when the pressure on the L side of the DP Cell equals the pressure on the H side of the DP Cell (i.e. the DP=0). This represents 100%


Curt Wuollet

Why, it can change your whole outlook on life! Instead of the glass being half full, it's now half empty. Seriously sometimes the data varies in the opposite direction you want. The advantage of reversing is then apparent.



I assumne you are asking why transmitter output could be 4-20mA and /or 20-4ma (???) never worked with one like that.

I guess the answer lies in what device the signal is going to.

If you are using the signal to directly control an element via a controller then being able to reverse the transmitter signal gives you flexibility in the Control action (Direct action or reverse action).

Overall loop control action also depends upon the action of the final control element AND also your PID action.