Hi,I am using a K type thermocouple with MAX6775IC to read temperature from a metallic dye which is in the form of a box. The temperature probe is being inserted into the cavity of metallic dye to measure its temperature but the problem is as soon as my probe is placed my temperature readings become zero.This is due to the metal part of probe being shorted with the metallic dye. Can you suggest some other contact based temperature sensor with high temperature range (upto 200C) which can detect temperature of dye without shorting it,.Like some sort of insulated probe

 

Hi 1026,
Welcome to AAC.
Are any probes in this link suitable?
E
https://www.google.com/search?client=firefox-b-d&q=insulated+probe+K+type+thermocouple+

 

the above probes do not have insulated sensing probe rather the probe is still metallic at the tip which will again short with the metallic box.I need those probes whose end sensing tips are insulated/coated with some insulators

 

hi 1026,
OK.
Is using a glass insulated thermistor probe suitable, the glass types that are used for liquid temperature measurement?

E
https://atcsemitec.co.uk/product-category/glass-ntc-thermistors/

 

hi,eric the glass insulated thermistor may work but my need is that sensor needs to be in direct contact with metallic box,and the temperature needs to be raised to 150C.These thermistors may break at this high temperature

 

Hi,
There are glass types rated for up to 350C.

You could consider encapsulating the end of your K type in a thin high temperature epoxy coating, for electrical insulation.

E

 

Hi,Yes The epoxy coating may work for thermocouple i will try and let you know the results

 

What are you using to measure the thermocouple voltage? Can you isolate it from ground or make a differential measurement about ground potential?

 

[QUOTE="KeithWalker
hi, I am using MAX6675IC to convert thermocouple voltage into digitized form and receiving it on controller through SPI

 

What is the output from the controller? Can you isolate the power supplies from ground? Here is an app note that will tell you how to do it:
an_123.pdf (qsl.net)

 

I have used insulated stainless steel tube thermo-couples a lot. They work quite well, but of course the response time is not quite as fast. The simple solution was to order thinner tube and a TC made with thinner wire, possibly #24 or #26, wire. And with the silicon dioxide insulation also having silicone oil to improve conductivity. Some companies do sell much faster insulated thermocouples.