Hi,
I have a gauge pressure transmitter STG73L of Honeywell Inc. Transmitter LRL is -100 and URL is 350 kPa and calibrated at -10~ 90 kPa that is fine. But in open atmosphere it shows -4.5kPa. please help me how can I do zero setting using hart communicator.
Rgds,
AhmadH

 

The Zero Correct function zeroes out the minor pressure offset due to the diaphragm being out of plumb (vertical).

Do the Zero Correct when the transmitter is installed in its service location.

When using the ST700's (optional) display and pushbuttons, there's a setting [after Pressure Units, before LRV Correct] called "Zero Correct" whose function is described in the ST700 user manual 34-ST-25-44 as "Executing this selection corrects the Zero based on the input pressure.

The ST700 HART/DE manual 34-ST-25-47 is written for Honeywell's handheld configurator. The same Zero Correct function, called "Corr. Input (zero)" is under 'Calibration > Input Calibration' group.

Honeywell doesn't publish the navigation menu its DD uses in the 475 communicator, nor the functions of its DTM in Pactware, so if you're using either, you'll have to poke around until you find the equivalent to "Zero Correct".

 

AhmadH,

FWIW, any pressure transmitter with that level of precision is going to vary when open to atmosphere just due to barometric pressure. You'd have to calibrate with an absolute pressure standard to get it zeroed.

 

The G in the part number STG indicates that it is a gauge pressure transmitter whose low side reference is atmospheric pressure, so changes in barometric pressure are automatically reflected in the gauge pressure measurement.

When it's 'open to atmosphere' the measurement is:
atmosphere minus atmosphere
which should equal zero.

But fill fluid behind the diaphragm will exert a pressure when the diaphragm is not plumb.

 

Aye... I wasn't taking the model into consideration, only expressing a generalization.

Nevertheless, he said the xmtr is being calibrated at -10 to 90kPa, so the span crosses atmospheric. If he is calibrating with a gauge pressure standard (or two), it (they) may not have atmospheric compensation. That will amount to compound errors with all error modes accounted for, including the one you mentioned.

 

See the smart transmitter calibration tutorial found here:
http://www.eddl.org/DeviceManagement/Pages/Calibration.aspx

Jonas