transmitter calibration

N

Thread Starter

NVQ

Dear All,

I have one question about the sensor trim of transmitter.--General procedure as bellow.

1. Apply standard input LRV to transmitter
2. Execute the low trim sensor function and wait for it stable.
3. Apply standard input URV to trans.
4. Execute the high trim sensor function and wait for it stable.

question is: LRV; URV here is the same of the range LRV/URV setting of transmitter? because this value we can re-range anytime. So should we apply the LRL; URL to trim the sensor (LRL- low range limit; URL-upper range limit)???

Please explain.
 
The sensor trim is an internal function in the transmitter that makes the CPU read the input value accurately. The LRV/URV are settings that tells the transmitter what input value range corresponds to the 4 -20 mA output. You only need to do the sensor trim if the PV you read with the HART communicator is wrong. To maximize total accuracy, you may want to do the sensor trim at input values near the actual LRV/URV, especially if you use the transmitter near the range limits.

Geir
 
As per your reply, I understand that for trimming the sensor input by apply LRV, URV to sensor. this LRV, URV is exactly the range we setting in transmitter that correspond to output 4/20mA.

As per your reply, it will be more accuracy if LRV, URV near LRL, URL.

So i will rearrange the LRV, URV to LRL, URL after that I perform the sensor trim with LRL, URL.

After finish trimming sensor, i rearrange again to LRV, URV required by process.

Is my thinking is correct????
 
Not exactly, you may gain some accuracy if you do the sensor trim close to the values of LRV/URV your process requires, especially if you are close to the lower end of the span limit. Say, if you have a transmitter with an URL of 138bar and you want to use it with an URV of 1,38bar, you can optimize the performance by doing the sensor trim at 0 and 1,5 bar. See for example page 4 -5 onward for the Rosemount 3051S trim procedure.

http://www2.emersonprocess.com/siteadmincenter/PM Rosemount Documents/00809-0100-4801.pdf

Geir
 
Top