I am looking to find some temperature transmitters for a concrete sump having water at up to 90 degC.

My client insists on using filled system type measurements with capillary length approximately 5 meters, connected to an indicating transmitter.

The measuring bulb needs to be fully submersible.

Anyone got any ideas about where I can buy such instruments? I need 21 of them.

 

Why don't you ask the customer? If he wants them that bad, he must have seen them, and in all likelihood has a specific make and probably model in mind. He probably has others and likes them or wants to maintain commonality of spares and maintenance.

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Steve Myres
Automation Solutions

 

Thanks for the suggestion Steve.

Situation is he has had bad experience of other ideas, and wants to try this as a solution. My problem is I can't find anything suitable in the marketplace! Guess I'll need to ask him to think on something else.

 

a liquid filled system will not work in that application since you are at the limits of correcting for bulb elevation error, that forces you consider a vapor pressure or gas-filled system, if the supplier will make it.

there are sealed t/c or rtd elements that can be suspended in the sump or the more traditional sealed and properly restrained protection tube designs.

 

Fake it with a proportional only capillary bulb controller. I think Honeywell still makes one, T77x maybe?

The output of a proportional only controller will mimic a transmitter's output when the controller is setup for
- direct action (rising output for rising process variable)
- gain = 1
- reset/integral totally disabled (if PI)
- rate totally disabled (if PID/PD)
- control setpoint at the lowest range value.

Any PV above the lowest range value will call for a proportional only output at a gain of 1 (or PB = 100% span) and sit there, without modification by reset or rate action.

Hence, PV = output, proportional to the input span of the controller.

The trick is getting a capillary bulb controller with a suitable range, direct action (cooling) and no reset/rate.

Good Luck.