Thermocouple Extension Wire for Temperature Measurement in an Oven

[WEAVER]

I need to get the temperature of the chip while being cured inside an oven for about 2 hrs 175 deg. celsius. the condition should be that the sensor is also covered with the paste onto the chip and we need six points. the paste would then be hardened after being exposed to this condition and i fear that the thermocouple sensors would be useless after this test.

Is there a way that we can use thermocouple extension wire instead of thermocouple in obtaining temperature measurements(for cost reasons)?i can then cut its end after one test and again join its ends so that i can reuse it. what are the limitations or the problems that would arise from this and how can we maintain the quality of the data that we would get?

 

[BradM]

Re: thermocouple extension wire for measurement

The short answer is yes. It will deliver a millivolt signal.

However, you need to check the temperature rating of the insulation.

The extension wire has quite a bit more error than thermocouple grade.

I would suggest you consider how much good data is worth, versus the extra cost of certified thermocouple wire.

 

[Jerry Eldred]

There is always some amount of offset in theory when you add an extension. You need to re-verify each new piece. Depending on what accuracies are needed and/or what traceability/certification requirements you have, you could do a a zero offset check. For some requirements, that may be sufficient.

 

[WEAVER]

Sir- how can i do that without taking so much time ...verification involving temperature always involves too much time-fact that the bosses find hard to understand...

 

[Hershal]

Sir- how can i do that without taking so much time ...verification involving temperature always involves too much time-fact that the bosses find hard to understand...

The question given that becomes, does management want measurements that are valid?

 

[WEAVER]

They want valid and quick results.

 

[BradM]

Sir- how can i do that without taking so much time ...verification involving temperature always involves too much time-fact that the bosses find hard to understand...

They want valid and quick results.

Weaver, I think just about every member of the Cove can empathize with your situation. It's frustrating being asked to produce a quality product but not providing the suitable resources.

I know you know this... but they are going to get what they pay for.

In general....

1. You will need certified thermocouple wire that provides you the roll error. You will need that to know the proper offset yielded by the temperature recorder. The recorder needs to be calibrated also.
2. They will have to allow the oven to be down from production. Even a single temperature uniformity survey (I don't recommend) will take three hours for set up/ take down.
3. You need to test the oven across its range of use. The higher the temperature, the less uniform an oven becomes.
4. Management (like most people) will trust better what they see rather than what they read. If there is an issue, don't wait until the final report prints. Show them the values while the survey is running.

If you haven't written a uniformity survey procedure, you need to do that next. AMS 2750 (an aerospace procedure) is a pretty good one to start with.

 

[Mikishots]

The question given that becomes, does management want measurements that are valid?

Exactly. Do they want it fast, or do they want it right?

 

[WEAVER]

ok, got it sir

 

[WEAVER]

Exactly. Do they want it fast, or do they want it right?

they want it fast, AND right (to a certain extent). If i could only quantify the uncertainties that are involved (and explain it in simple terms) to management maybe things would be much easier