A useful way to verify the whole loop, which reduces the risk of multiple instruments contributing to total loop error. However, I don't believe this process can be called calibration. It is for me, verification against a transfer standard. In a calibration process I prefer to see the steps to remove errors using the adjustment available within the instrument (either the transmitter or the dcs). Just imagine if the two instruments in the loop (TX &DCS) had opposing and equal errors. This method would result in a "Pass"?. So what I hear you cry!, ; Well is easier to injecting pressure (even with a nice portable piece of test equipment) in a comfortable calibration room, rather than 80ft up a distillation column. Verification with the DCS is much easier with a radio. The skill of a good instrument tech is being able to improve the performance of an instrument, through adjustments in the calibration process.
Thanks for comments. Many customers seems to calibrate the whole loop and only if it is out of tolerances, they calibrate each individual instrument in the loop to see where the issue is. The terminology question is another one... The international standards specify calibration being a "documented comparison against traceable reference standard". The required adjustment or trimming is normally not included in the term calibration. I know that in everyday language the trimming/adjustment is often also included in the calibration, or sometimes that is what is called calibration. And of course if there is error found in the as found calibration, it calls for corrective actions. Thanks, Heikki Laurila Beamex
A useful way to verify the whole loop, which reduces the risk of multiple instruments contributing to total loop error.
However, I don't believe this process can be called calibration. It is for me, verification against a transfer standard. In a calibration process I prefer to see the steps to remove errors using the adjustment available within the instrument (either the transmitter or the dcs). Just imagine if the two instruments in the loop (TX &DCS) had opposing and equal errors. This method would result in a "Pass"?.
So what I hear you cry!, ; Well is easier to injecting pressure (even with a nice portable piece of test equipment) in a comfortable calibration room, rather than 80ft up a distillation column. Verification with the DCS is much easier with a radio.
The skill of a good instrument tech is being able to improve the performance of an instrument, through adjustments in the calibration process.
Thanks for comments.
Many customers seems to calibrate the whole loop and only if it is out of tolerances, they calibrate each individual instrument in the loop to see where the issue is.
The terminology question is another one... The international standards specify calibration being a "documented comparison against traceable reference standard". The required adjustment or trimming is normally not included in the term calibration.
I know that in everyday language the trimming/adjustment is often also included in the calibration, or sometimes that is what is called calibration.
And of course if there is error found in the as found calibration, it calls for corrective actions.
Thanks,
Heikki Laurila
Beamex
On mc6 did you set with an external power supply or with internal power supply to see the reading also in control room?