Author Topic: RTD PT1000 circuits  (Read 7999 times)

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Offline dissidence

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RTD PT1000 circuits
« on: December 26, 2013, 09:48:53 pm »
i have been looking for a circuit for some RTD Pt1000 temp sensors, but i have not been able to find any circuits that i have the hardware to build with at the moment.

so i was wondering if anyone out there has seen a circuit for them that i can use just 1 lm358, i keep finding ones that use the lm354 i think it was.

if i can get it to work with 2 probes all the better.

i am just looking to make a small temp logger. on a attiny85 or some attiny84 if i can figure out how to program them.
 

Offline Vgkid

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Re: RTD PT1000 circuits
« Reply #1 on: December 27, 2013, 07:19:10 am »
Are you stuck using pt1000 probes, or will pt100 work as well. Look up AN-11, slyt442,AN-687. I have a few more on my computer.
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Offline miceuz

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Re: RTD PT1000 circuits
« Reply #2 on: December 27, 2013, 08:11:49 am »
You'll need an opamp with a low Vos to get any kind of accuracy, forget LM358

Offline branadic

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Re: RTD PT1000 circuits
« Reply #3 on: December 27, 2013, 02:15:50 pm »
I'm currently working on a PT1000 circuit, but instead of using an opamp and an adc I use TDC-parts, like GP22 or similar.

Please refer to the application note of the previous version GP2:

http://www.etracker.de/lnkcnt.php?et=UKbtw3&url=http://www.acam.de/fileadmin/Download/pdf/TDC/English/AN024_en.pdf&lnkname=AN024_en
« Last Edit: January 15, 2014, 09:04:22 pm by branadic »
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Offline blackdog

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Re: RTD PT1000 circuits
« Reply #4 on: December 27, 2013, 06:00:01 pm »
Hi,

Just look @ this link, several RTD amplifiers...

http://www.linear.com/search/search.php?q=rtd%20amplifier

Kind regarts,
Blackdog
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Offline nctnico

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Re: RTD PT1000 circuits
« Reply #5 on: December 27, 2013, 06:08:43 pm »
I just power a PT1000 sensor with a series resistor (2k is nice when powered from 3.3V) and feed that into an ADC. Adding an amplifier introduces a lot of offset. 16 bit ADCs with low conversions rates are not extremely expensive.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline dannyf

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Re: RTD PT1000 circuits
« Reply #6 on: December 27, 2013, 09:23:04 pm »
Quote
i have been looking for a circuit for some RTD Pt1000 temp sensors,

Google is quite helpful.

Quote
but i have not been able to find any circuits that i have the hardware to build with at the moment.

It is easy to find a circuit for your temp sensor;

It is impossible to find a circuit for your temp sensor using parts you have, when you haven't told us what you have.
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Offline dannyf

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Re: RTD PT1000 circuits
« Reply #7 on: December 27, 2013, 09:24:30 pm »
Quote
I just power a PT1000 sensor with a series resistor (2k is nice when powered from 3.3V)

The power source + the serial resistor form a (crude) CCS.
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Offline nctnico

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Re: RTD PT1000 circuits
« Reply #8 on: December 27, 2013, 10:55:44 pm »
Yes but this solution is surprisingly linear around room temperature as well. Multiplying the ADC result and substracting an offset is enough to get a reasonable temperature reading.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline NANDBlog

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Re: RTD PT1000 circuits
« Reply #9 on: December 27, 2013, 11:48:59 pm »
Yes but this solution is surprisingly linear around room temperature as well. Multiplying the ADC result and substracting an offset is enough to get a reasonable temperature reading.
Yes, but PT1000 used on room temperature for "reasonable" readings are total overkill. You might just use an NTC as well, which probably costs thousand times less. PT1000 is  made for hundreds of celsius range and 0.1 accuracy.
 

Offline dannyf

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Re: RTD PT1000 circuits
« Reply #10 on: December 28, 2013, 12:11:47 am »
Quote
this solution is surprisingly linear around room temperature as well.

Depends on your definition of "reasonable".

If this is a case of mcu-based adc, you can easily correct it to obtain a much better temperature reading.
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Offline dissidence

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Re: RTD PT1000 circuits
« Reply #11 on: December 28, 2013, 01:46:08 am »
lol i ended up with 20 of them when my friend though he just ordered 4, so i got my half of the orders, so i would like to do something useful with them..lol :-DD

i am almost interested in trying to see if i could make a circuit so that i could use them just like a drop in replacement for my repraps thermistors.

i have been trying google, but i have not been finding much i could build with what i got at home at the moment.

has for what i have for parts on hand are resistor (a good assortment of 1%), 1 lm358, and a small assortment of your other small parts. not much for ic's besides my attiny chips.
« Last Edit: December 28, 2013, 01:51:06 am by dissidence »
 


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