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Temperature probe - how to wire it up?

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I have a platinum wire wound temperature probe that is 8mm long and also the wires are about 15mm long. As it is designed to go up to 800C then how does one connect it to wiring to go to the circuit.

I have never used one of these before so it is all new to me, if any one has a simple conditioning circuit it would be much appreciated.

The project is to measure the exhaust temperature from a 6 cyl 6 litre engine for monitoring purposes.

Thanks

Q
 

Reloadron

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First I would start here for a good overview and determine exactly what you have and what you want from it. If you want to measure EGT (Exhaust Gast Temperature) will you be using a compression fitting to embed your element directly into the hot gas flow at the exhaust manifiold?

The diameter of your probe should give an indication of the wire gauge used within. That is important to avoid self heating from the current passed through the probe. You need to read and understand the link. Especially things like a 3 or 4 wire measurment plane?

Guessing pt100 probe? The resistance at 32 F or 0 C should be 100.00Ω assuming a pt100 probe using platinum.

Ron
 

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Thanks Ron - I had a read up from your link and then found some others.

You are right it is a PT100 and is 1.5mm dia but I still cant find any recommendations on how to mechanically connect it to the leads, cant solder it, cant weld it, cant use a chocolate block in that heat? puzzling. It is not going inside to read EGT but on the outside of the exhaust and under a hear shield.

It seems there will always be an offset on the voltage so I have included a circuit that hopefully removes the offset so it can be easily displayed on a meter (an SP300 to be precise) as it is part of the same project as the pressure sensor, it will be switch selectable which sensor is monitored.

Do you think the circuit will be OK
 

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Reloadron

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As to signal conditioning of the pt100 I like designs like this one and if we get fancy and accurate I like this design also.

Actually I frequently use small temperature transmitters made by INOR to scale pt100 units.

Mounting is always a problem. For getting surface temperatures of pipes and like I have had various degrees of success using assorted hose clamps. There are spring loaded devices made to do it.

Overall if I were looking to measure EGT accurately I would drill and tap the manifold and use a compression fitting on a Type K thermocouple. That places my sensor directly in the hot gas temperatures. This allows seeing pretty quick changes as the burn of fuel changes. Monitoring the manifold surface is OK but can be sluggish as the cast iron reacts to port temperature changes.

I guess it really gets into how accurate you need to be and how quick the measurment plane needs to change (respond). :)

Ron
 

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I looked at the circuits and the first one seems fine if a little complex and the second one is way beyond the project.

Really just interested in a rough estimate of temperature and a hose clip with fibreglass covering the PT100 would deem a good idea. We like to monitor the temp from the cockpit and see if it changes from known temp if it does then something has also changed so if it reads 485C instead of the real value of 500C it is OK.

It is a new engine and has more power (than before) so if we start to run it hard then the exhaust will get very hot and maybe too hot so we want to see from the cockpit what it is and reduce power if starts to cook up a bit. It has 1" of special thermal insulation that is wired on with SS mono wire.

Q
 
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