PT100 circuit with limited temperature range
PT100 circuit with limited temperature range
(OP)
Hi all,
I'm trying to design a PT100 circuit to range 10degrees to 50degrees into a 0-5V signal. The resistance at 10degrees is 103.9Ohms and at 50degrees is 119.4Ohms, so I need to get a signal out of my board of around 0V when resistance is 103.9Ohms and around 5V when resistance is 119.4Ohms.
I've tried simple circuits like voltage dividers, and op-amp circuits, but I'm running into trouble due to the small difference in the range of resistance I require. Would anyone be able to advise, or direct me to someone who can?
Many thanks,
Ross
I'm trying to design a PT100 circuit to range 10degrees to 50degrees into a 0-5V signal. The resistance at 10degrees is 103.9Ohms and at 50degrees is 119.4Ohms, so I need to get a signal out of my board of around 0V when resistance is 103.9Ohms and around 5V when resistance is 119.4Ohms.
I've tried simple circuits like voltage dividers, and op-amp circuits, but I'm running into trouble due to the small difference in the range of resistance I require. Would anyone be able to advise, or direct me to someone who can?
Many thanks,
Ross





RE: PT100 circuit with limited temperature range
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Dan - Owner

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RE: PT100 circuit with limited temperature range
Use any of these instead.
LM35
LM34
LM61
LM60
LM335
LM19
They're linear. They cost a fraction of what an RTD costs. They put out high level signals, unlike RTDs. You can get versions that are C or F if you care. They need NO highly complex calculations nor even lookup tables.
Keith Cress
kcress - http://www.flaminsystems.com
RE: PT100 circuit with limited temperature range
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RE: PT100 circuit with limited temperature range
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RE: PT100 circuit with limited temperature range
Keith Cress
kcress - http://www.flaminsystems.com
RE: PT100 circuit with limited temperature range
Thank you very much for all the replies. I think the best way forward is to do as itsmoked said and ditch the resistance device and use IC type sensors. Having looked at some of the datasheets, the 10mV/degC can be easily amplified into the range I want.
Thanks all!
RE: PT100 circuit with limited temperature range
Unless there is some special specific reason you pretty must always want to grab for those devices in the temperature realm they're good for.
Keith Cress
kcress - http://www.flaminsystems.com