So the thermocouple temperature transmitter sensor is a digital board
I'm assuming this does not need to be replaced but the technician was talking about milliamps on the sensor - so I got curious! I think he was just trying to impress me. haha.
http://www.temflexcontrols.com/pdf/ttguid.pdf
The PIE 525Plus has all the functionalist of the PIE 422 Thermocouple Calibrator and the PIE 311 RTD Calibrator, plus a built-in Milliamp Calibrator, all in one tool. The 525Plus features advanced diagnostics including the ability to check the health of a thermocouple sensor by simultaneously displaying the resistance of the sensor and wiring as well as measuring the temperature, as sensed by the thermocouple element. This calibrator can power up a temperature transmitter while simulating the thermocouple or RTD sensor input.
This testing device of the milliamp ohms is apparently made in Minneapolis?
https://www.minco.com/
Wow -
Minco Global Headquarters
7300 Commerce Lane NE
Minneapolis, MN 55432
That's really wild.
the junction has come apart from the sheath of the probe and is no longer grounded and needs to be replaced....
Actually what happened to ours is probably just over-use!!
When this system malfunctions, it typically causes the pilot to go out and the gas will not flow.
do thermocouples go bad over time meaning produce less energy? Mine shows open circuit 325mV and pilot-only 264mV and main-valve-on 154mV, I'm seeing intermittent on/off issues and I suspect my thermocouple just isn't producing enough power any longer
Yes they do go bad. The difference on thermal bulb and thermopile is that the thermopile has several generators inside of it and thats how it produces the higher MV output compared to a single thermal bulb generator.
A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. The thermocouple is a device made up of two dissimilar metals. They are joined together at the tip (Hot Junction). When heat is applied to that hot junction, a small millivoltage is created. This develops because of temperature difference between the hot junction and what is called the cold junction. The flame has to envelop the upper 1/2" to 3/8" of the thermocouple and the tip should glow a "dull red". If the flame is adjusted to a sharp flame, it will glow "cherry red" this will cause the tip to be welded and eventually the thermocouple will fail.
So the tip got welded and failed ....
But they're going to replace the whole pilot assembly since it's not even igniting - and so the whole assembly is probably just over used.
Most thermocouples create a voltage signal of less than 50 mV, and a thermocouple has practically no ability to create a current flow. Therefore, any device that measures a thermocouple must have a very high input resistance, (usually 1 million Ω or more).
The combination of a low mV signal and no current flow makes thermocouples behave like an antenna. Electrical noise from 50/60 Hz power mains, burst noise from lightning, static electricity, radio frequency interference from portable radios, commutator noise from DC motors and many other sources of electrical noise can be “received” by a thermocouple – and the longer the wires are, the more opportunity there is to “receive” electrical noise.
some symptoms of noise-affected temperature signals are that temperature measurements:
immediately change when a nearby motor or heater starts.
- change when a part of a process is turned off or on.
- change when a mobile radio is transmitting.
- change based on time of day or weather patterns.
- change based on the location/orientation of sensor wiring.
Wow civilization really is sensitive! That's my personal joke that I like to say, "Civilization is sensitive."
So the technician would have had to take OUT the thermocouple to test it - since he didn't take it out then he didn't test it.
Instead he just tested the voltage at the circuits and inferred it was the thermocouple.
https://www.youtube.com/watch?v=RASBzK_XF2k
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