Matrix user forums

Hi all!

Martin medelec35 gave a nice reply here: http://www.matrixtsl.com/mmforums/viewt ... tor#p97159

Maybe you can/will help again Martin or another expert. Will it be possible to use a PT100 with this component in FC8?
If it should be possible, I suppose it must be connected as a voltage divider and the scaling/linearity from the datasheet for PT100 must be set in the thermistor value in properties.

Thank´s in advance

Br Jorgen

Hi Jorgen,
The PT100 has a very small resistance change with temperature compared to the 10K thermistor.
For example for every degree C change, the resistance will change by 0.4 ohms
Therefore you will need an amplifier to convert the small voltage change into a much
larger one.
So the answer is no, your PT100 won't work in place of a much higher thermistor value without amplification.

Hi Martin!

I see and understand,. Thank you very much Martin.

Br Jorgen

Hi Jorgen,

PT100's also tend to have a constant current source to supply them.
The voltage is then measured across the device.

Microchip have a application note on using RTD's

http://ww1.microchip.com/downloads/en/A ... 00687c.pdf

Have a look at Fig 4.

A Tl341 is a good little reference

Steve

Hi Steve!

Thank you very much, I´ll have a lokk at it.

Br Jorgen

Hi Jorgen

Some of the resistor values are a bit obscure. I did have difficulty finding some of them and some that where available where "reel" qtys of 5000

This web page turned out to be a godsend.

http://mustcalculate.com/electronics/resistorfinder.php

so for the 2K5 resistors used - see attached screen shot as an example

Steve

Thank´s again Steve.

Talig promised to come bag with an "clean" example from here http://www.matrixtsl.com/mmforums/viewt ... 6&t=21640t with the MAX31865 amplifier this weekend. I think this would be easier to use If not, I will build an analog amplifier. Meanwhile I will look at your data. Thank´s.

Br jorgen