Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Thermocouple Type J circuit design using a AD594

Status
Not open for further replies.
P

PHILTHOM

Newbie level 3
Joined
Jul 21, 2013
Messages
4
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
29
Hi,

I am looking for information to help get an output of 0-10V for a corresponding temperature range of 35-100 deg C from utilising a Analog Devices AD594 in conjunction with a Type J thermocouple.

(For info - I had previously looked at the use of an instrumentation amplifier but was steered away from this)

I have searched the forums here and cannot find information on:-

i) Offseting - @ 35 degC the output is equal to 0V?
ii) Increase in gain - Rated output of AD594 is 10mV/degC output, to 153.846mV/degC required (100-35/10-0)?

I have also tried application notes for this device and cannot seem to find the answer.

Any advice you can provide would be greatly appreciated
 

Mention max current at AD594 o/p if temperature is 100 deg C. A non-inverting Op-Amp has to be used to amplify AD594 voltage and make it 5V i.e., if temperature is 100 deg C adc input should be 5V.
 
Jayanth,

Thanks for the reply - I think I am understanding this now.

At 35 deg C the output from the AD594 will be 0.35V (10mv/degC) - hence this is the offset voltage required against the output of the AD594 in the Non-Inv Op-Amp with an amplification of 15.3846V/V.

Does this sound correct?

Thanks,

Phil
 

If you do like that you will get wrong values for temperatures below 35 deg C. If temp is 27 deg C you will get wrong value.

If AD594 voltage for 0 deg C is 0V (say) and for 35 deg C = 50mV (say) and for 100 deg C = 250 mV (say) then Op Amp should amplify 250 mV to 5V. Your adc will then measure temp between 0 deg C to 100 deg C. Zip and post your project files and proteus file.

Just mention what voltage you get at AD594 o/p if temp is 100 deg C. Just measure temp when thermocouple is immeresed in boiling water.
 

Thanks for that but the temperature range to be measured is 35 - 100 deg C (For this range i have to provide a t35=0V to t100=10V), temperatures outside this range are not required to be measured.

This is theoretical design only - I do not have components available.

Thanks for your pointers.

Regards,

Phil
 

jayanth.devarayanadurga said:
t100 = 10V is beyond adc i/p range.

why do you worry about adc i/p vaoltage for out of range values. You can use a condition in code to just find and display temp for range 35 to 100 deg C.
Click to expand...

Can you clarify this point please?
 

Using a if((temp >=35) && (temp <= 100)){ //display temp} will do the work.

94090d1374932692-jtherm.png
 

Attachments

  • JTherm.png
    JTherm.png
    38.4 KB · Views: 272
  • Like
Reactions: PHILTHOM

    P

    PHILTHOM

    Points: 2
    Helpful Answer Positive Rating
    V

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top