All about diaphragm seal Transmitter 2

[Michael2009]

Helo. I have a project using a lot of diaphragm seal DP tx to measure level. But i have a lot of query regarding this. Because i nvr do it before. Any experience guy please help to advise me. Thanks

1. Anyone know why usually diaphragm seal transmitter did not have small range like -100 mbar to 100 mbar???

2. Any mounting concern about diaphragm seal transmitter???

3. how we gonna handle those extra long capilary???

4. Any one hear before the distance transmitter mount below H side cannot be more than distance H side tapping point and L side tapping point.

Thanks for your advise.

 

[Mass44]

Hi there,

Yes you are correct that the needle valve acts like the equilising valve similar to when you use a 3 or 5 way manifold.

About the moving vessel setup,

What you will find is that the level readings is never stable since the ship list and tilt and move all the time and therefore the liquid in the vessels slosh around as well giving you then a high reading and then a low reading again.

During initial setup what I normally do to compensate for this I would get the transmitter in a process zero position and stand there for about 15 minutes looking at the process zero as it moves up and down. I would then start writing down the highest readings and also writing down the lowest reading the indication goes to. Once I am sure that it continuously moves to this high and low readings I split the error and use the halfway mark as the process zero. For example if the reading goes down to say -1530mmH2O and up to -1430mmH2O I would use -1480mmH2O as my process zero.
If you do the calibration from this point and you draw a error graph of the full calibration later on you will find that although the reading still fluctuate but will now move then over the under the true calibration line, making it much more accurate than using the lowest or highest zero
point.
This method can also work to compensate for drifting problems, providing that the drift is a constant up and down drift and not continuous into one direction only.