×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Thermocouple Circuit

Thermocouple Circuit

Thermocouple Circuit

(OP)
I've decided to make my own digital thermometer as a side project. I want to use a type K thermocouple as the sensing element. I'm using a PIC16F777 micro with an LCD output. I've got code (using picbasic pro) that will display the ADC to the LCD. I'm looking for information that will help me linearize the Thermocouple. I'm assuming it will be a mix of ciruitry and code. If anyone has any app notes, or can point me in the right direction it would be greatly appreciated.

Thanks

RE: Thermocouple Circuit

More importantly have you measured your isothermal terminal block with a non-T/C sensor so you can negate that error voltage?

Look at the tech notes on Omega's website.

Go with a lookup table.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Thermocouple Circuit

(OP)
I think i'm going to use an NTC thermistor to measure the iso thermal block. Or probably an easier method would be to use a digital temperature sensor since it is linear and i can wire it directly to the uProcessor

RE: Thermocouple Circuit

The easiest are the linear temp sensors by National Semi.  10mV/degree.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Thermocouple Circuit

(OP)
I've been a controls engineer for about 6 years now using PLC's like Allen Bradley and Semens to control temperature within a specific environment. In my effort to understand the internal workings better (and to become more fluent with my electronics) I’ve decided to build a simple digital thermometer using various methods.

Thanks Madcow, I'll start with the app note you provided.

RE: Thermocouple Circuit

What range of temperature do you want to measure?  Solid state sensors are great, but operate over a range typical of semiconductors, something like -50 to 150 degrees C.  If that's sufficient, that's the way to go.

RE: Thermocouple Circuit

Welcome to the fora bioe007!

I agree that chip works well JKelly.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Thermocouple Circuit

Be aware of common mode voltage errors.  I think this chip likes to have a grounded T/C

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources