rosemount transmitter

i have rosemount transmitter 3051 cd with remote cell to measure level after intalling it there is no reading i check everything related to plc and when i connected it by hart the reading constant at 3.90 mA i change the URV and there is no change what i can do...

No reading means what? Do you have 4mA at the PLC? Do you see a value in the software? Do you have the correct analog input card / configured correctly? Simulate a value of 12mA from the transmitter, either using a signal generator or the onboard output simulator, do you get anything at the PLC? Have you checked the wiring? Has this worked previously?

Need a few more details....

everything is ok

What is the transmitter ranged? What is its LRV and URV?

The weight of the fill fluid in remote diaphragm seals means that the LRV and URV for a level transmitter are negative values, as shown in the graphic below.


rough conversions:
197 inches = 5.0m
217 inches = 5.5m

- 40.5 inches = - 1029mm (water column)
- 204 inches = - 5152mm (water column)

If the transmitter is 'seeing' negative values but it is configured for positive values, like 0-5.00 m, the pressure the transmitter 'sees' at empty is nowhere near 0, it's some very negative value, so effectively it is offscale, downscale so the output is 3.9mA.

To determine the LRV and URV you either need data on the fill fluid, its specific gravity, the specific gravity of the medium in the tank, the mounting elevation dimensions, and the level above the lower datum that is considered 'full'; ie, those boxes shown on the graphic.

Or, with a HART communicator, you can empty the tank and tell it, 'this is the LRV', then fill the tank to the full level and tell it, 'this is the URV'. It would be prudent to record the values for LRV and URV.

thanks alot but i need the program that you calculate with,

shkoko2000 said:

everything is ok

Click to expand...

Clearly not, or your system would work.

Nobody can help you if you don't provide accurate information on the symptoms of your problem, what you are trying to accomplish, and what diagnostic tests you have run.

Dan had good info in his post. If you don't understand what he is telling you I suggest you get the local supplier in to help you on site.

Rosemount's 1199 remote seal system installation guide provides the formula for calculating the LRV/URV range.

http://www2.emersonprocess.com/siteadmincenter/PM Rosemount Documents/00809-0100-4002.pdf

If you have a closed tank and two capillary seals, then you have what Rosemount calls a "balanced system", which starts on page 44 (pdf).

Note that their example uses a specific gravity (SG) of 0.934 specifically for silicone 200 fill fluid.

You'll have to use whatever the SG is for your transmitter's fill fluid.

Sounds like you have your transmitter setup to fail low (and it is failing).

No, this is not a 'transmitter' failure mode. Failure mode (low) would be the 3.75mA output. It is a configuration issue, the range is wrong.

His 3.9ma signal shows the transmitter is functional, but at low saturation because the pressure(s) the DP is/are seeing are lower than the configured range for the 4-20mA output.

People don't realize that closed tank, dual remote seal ranges are negative values because of the weight of the capillary fill fluid on the sensing diaphragms.

So either the transmitter is delivered at its default 0-100 inches w.c. or the actual tank's level span, but as positive values.

When the LRV is zero and the transmitter 'sees' -122.2 inches w.c. (that's negative), then the current output saturates low at 3.9mA. The transmitter's only doing what it is configured to do.

how can i sure that the remote seal diaphram is not working

Do you have a hart programmer? It would give you an fault reading as soon ans you link up to it. Are both seal remote or is the hi side a direct mount? I tried to get rosemont to set me up a 3051L with the 1199 on the hi side and the direct mount on the low to combat the negative readings. They tried to sell me the electronic remote seal. No dice