Troubleshooting Temperature Gauge: How to Measure and Replace Wires

[mikex24]

Hello folks. I have a sangamo weston temperature gauge. Back of this gauge there is 2 screws and a small wire(5cm) connecting the 2 wires. I want to taking measurement in 1m distance from the gauge so I tried to replace this wire with a copper one but the gauge doesn't work with copper wire. I tried it with the wire which i bought it(this wire it has silver colour but as it is a second hand gauge i don't know what wire is this one and the seller doesn't know anything of this gauge. he just sell it to me) and in steam water the gauge shows 98 Celsius which means that the gauge is working. But why is not working with the copper wire? Is there a way to check why is this happening? How these gauges works? Cheers

 

[dlgoff]

Back of this gauge there is 2 screws and a small wire(5cm) connecting the 2 wires.

Maybe this is a http://en.wikipedia.org/wiki/Thermocouples"

 

[Integral]

I did some googling on your gauge, it looks like it may be WWII era airplane engine temperature gauge. I could not find any information on how it works. I doubt if it is a thermocouple, I would guess that it is a resistive bridge. If that is the case then the resistance of the sensor wire is critical.

What kind of power does it need?

Have you measured the resistance of the wire connecting the terminals?

 

[mikex24]

No i don't measure the resistance but the gauge is not need any voltage supply.. I don't have a device to measure the resistance.. :(

 

[nucleus]

That is a cylinder head temperature gauge (CHT), and a thermocouple type. It should use either iron constantine or copper constantine leads. Getting the right resistance in the leads is important for it to work. It may say on the back of gauge what lead resistance needs to be.

 

[mikex24]

Yes it says inside the gauge 8Ω. I also ajdust the screw which is front of the gauge and the point moves. How can i readjust it properly and how to make it work? Cheers

 

[dlgoff]

How can i readjust it properly and how to make it work? Cheers

Does it have a 100 C° point on the dial? If so, you could use boiling water to calibrate at that point.

 

[Integral]

Ah! someone knows about it great! You should be able to move the junction but you need to use appropriate connectors. Check out http://www.omega.com/"

Could you post a pic, front and back?

 

[mikex24]

Ok mate i did in the freezer with zero degrees. I also remove the two screws and i observed that the one of the two threats its material is Brass or copper. The other one it seems to be steel. Now what type of thermocouple will work on this gauge? Cheers

 

[nucleus]

8 ohm is Iron-Constantan. The following site sell the leads but you may be able to get a better price elsewhere.
http://www.aircraftspruce.com/menus/in/thermocouples.html

If you use the lead do not cut the wire. If it is too long just roll the excess into a loop and tie out of the way.

You also need to get a sender or probe for the other end.

The adjustment screw on the front is for setting ambient temperature. When gauge and sender is set up you can adjust the room temperature with that screw.

 

[mikex24]

Hope work the links
http://img26.yfrog.com/img26/1796/videocallsnapshot1ki.png
http://yfrog.com/bfvideocallsnapshot4op

 

[mikex24]

According to this site (http://www.aircraftspruce.com/menus/...mocouples.html) as NUCLEUS advice the type of thermocouple i will have to use is Type K or Type J. So you think this one will be ok... ??

http://cgi.ebay.co.uk/Thermocouple-Extension-Cable-Type-K-Brand-New_W0QQitemZ220590273582QQcmdZViewItemQQptZUK_BOI_Electrical_Test_Measurement_Equipment_ET?hash=item335c34742e#ht_725wt_1165

Also this thermocouple is not needed to be with a probe as i will use it on a cylinder head to taking the temperature. I will need just a ring on the end of the wire and it have to fit on the spark. Is all these true?


Any Help?

 

[dlgoff]

If the thermocouple is made with iron and constantan wire as nucleus says, then you need a type J not a type K.

The wire you are considering is an extension wire for a type K.

 

[mikex24]

The thermocouple you are speaking for you mean the one which is attached on the gauge at the moment? how can i find what material is my thermocouple?

 

[mikex24]

Any help?? What thermocouple i have to use to measuring temperature?