3051TG1A2B Transmitter LSL and LRV on HART


Thread Starter

Esoteric Stone

LSL = Lower Sensor Limit
LRV = Lower Range Value

LSL of 3051TG on HART = 0 Kg/Cm2
LRV is configured at -1 Kg/Cm2

On data sheet of 3051 TG range is given from -1 Kg/Cm2 to 2 Kg/Cm2. Why HART is reading LSL 0 Kg/cm2? It is not possible to configure transmitter outside range of LSL and USL, then how this transmitter is calibrated below LSL. Also on datasheet of 3051TG it is mentioned that lower range varies with atmospheric pressure. what does this exactly mean? I know that value of maximum vacuum can not be less than atmospheric pressure.

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Thanks for attention
I wonder if you have a TG or a TA model.

The US Rosemount spec sheet for the 3051Tx in-line transmitters is here:
or http://preview.tinyurl.com/789h3zm

The range specs are on page 10 in two columns, one column for the gauge pressure TG model, a 2nd column for the absolute pressure TA model.

The specs show a TG range with a Lower Range Limit (LRL) of -14.7psi to some URL positive value, depending on TG gauge pressure model. So a zero LRL for a TG transmitter is not consistent with the specs. I assume the SI version spec sheet is consistent with the one I found.

However, all the absolute pressure TA model transmitters have a zero value LRL, as one would expect.

It raises the question as to whether the transmitter in question is a TG or a TA model transmitter.

Is the original stainless ID tag still on the transmitter?

Does it act like a barometer, giving a barometric reading when it's open to atmosphere? Is the output elevated well above 4mA at atmospheric?

I suppose it could be mislabeled by the factory, but that's pretty unusual in this class of instruments.

What does note mean?
Next to the 3051TG column header is note (1).
Note (1) is on page 13: (1) 3051TG lower range limit (LRL) varies with atmospheric pressure.

The note means that the range of the LRL changes depending on the barometric pressure.

Since -14.7psi represents absolute zero, a low barometric pressure is closer to absolute zero than a high barometric pressure. So the span between absolute zero and atmospheric pressure varies depending on the barometric pressure.

The LRL for the absolute TA model can't go lower than zero, zero being absolute zero, established by the vacuum on the reference side of the cell internally.

Esoteric Stone

Thanks for your reply David.

The transmitter in question is TG model.

The Stainless ID tag is still present on the Transmitter.

Yes the transmitter is acting like a barometer and its output is elevated well above 4mA (12mA in my case).

And in my opinion it is not mislabeled by company. We are able to configure it via HART and it is giving correct reading.

This transmitter is working fine and actually I am worried because I have read and experienced that HART does not calibrate a transmitter below its lower range limit. but in my case HART is showing lower limit as zero and still it is not giving any error while calibrating lower range value to -1. I tried to configure other transmitters below their lower range value but HART didn't allow me to do so.

I do agree with you that lower range limit of 3051TG is -14.7PSI. But this transmitter is showing lower range limit 0 on HART.

Now my actual question is that when HART is reading its lower range limit 0 then why it is not giving any warning (error) while calibrating it to -1 (I am using kg/cm2 when I am using -1 or 1).
If you've decoded the model number correctly and the transmitter is truly a model TA gauge pressure transmitter, then ranging the URL to -14.7 psi (or -1.0kg/cm^2) will show an elevated mA output when the port is open to atmosphere.

The HART indication of zero for LRL is just wrong for a gauge pressure transmitter. Maybe the DD (or DOF or EDD or whatever file is used for your HART device) has a bug. Maybe there's version release issue with the DD and this model.