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# +/- 0.1 Deg. C. temperature controller.

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#### rauol

##### Full Member level 6
i have to design a temperature controller with +/- 0.1 deg C. accuracy.
Input is PT100 and temperature range is from 30 t0 45 Deg C.
Any referances?
Thanx

#### nicleo

Improving the accuracy of temperature measurements
http://www.picotech.com/applications/temperature.html

Usually 4-wire is used to measure, but if you think it's not accurate enough, you can try 6-wire method as follows:

Very accurate low resistance measurement problem

mitultaillor

### mitultaillor

Points: 2

#### IanP

Do you prefer Amplifier/AD conversion/Microcontroller approach or would you like to stay with op amps and comparators?

#### usernam

##### Full Member level 5
Perhaps this book will be helpful.
Electrical Temperature Measurement
with thermocouples and resistance thermometers
Matthias Nau
10th expanded. edition, August 2002; 163 pages
ISBN 3-935742-07-X

Code:
http://www2.jumo.de/service/literatur/pdf/FAS146gb_ElektrischeTemperaturmessung.pdf

#### mgajo

##### Full Member level 2
Hi
Do you have new link for book

h**p://www2.jumo.de/service/literatur/pdf/FAS146gb_ElektrischeTemperaturmessung.pdf

thanks

#### sinatra

##### Full Member level 4
ElektrischeTemperaturmessung mit thermoelementen und widerst

Hello Mgajo and the others.
The book from M. Nau can be found in the following link:

ElektrischeTemperaturmessung mit thermoelementen und widerstandsthermometern - M. Nau

This is a very nice book. But you should be able to read german.

S.

rosenvik

### rosenvik

Points: 2

#### lambtron

##### Full Member level 5
rauol said:
i have to design a temperature controller with +/- 0.1 deg C. accuracy.
Input is PT100 and temperature range is from 30 t0 45 Deg C.
Any referances?
Thanx

There are lots of references out there, but what to do, what to do?

Here are some guidelines for issues to focus on:

1. Use a constant-current source to excite the rtd. Set the current high enough to produce an rtd voltage well above the noise, but not so much as to cause rtd self-heating. Constant current will enable you to run long cables to the rtd without suffering lead-loss degradation.

2. Rather than try to control the current exactly, simply measure it with the adc.

3. Sense the rtd voltage out at the rtd (i.e., "4-wire" circuit) so as to eliminate the cable losses in the current loop. If throughput is not an issue, consider an integrating type adc, which will further help to reduce noise.

4. Convert the measured rtd voltage to temperature units. This can be done to your specified accuracy with a simple lookup table. You don't need a huge table; simply interpolate between table values. You can easily determine the number of table values by simulating on a spreadsheet.

#### pridepk

##### Member level 1
Hi, can any one share the circuit with PIC microcontroller in which PT 100 sensor is used. Have very accurate in reading to .01 accuracy.

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