4-wire RTD PT100 ohm to three wire device?
- Thread starter Adam303
- Start date
danw
Lifetime Supporting Member
Use 3 of the 4 wires.
It doesn't matter which one you don't use, just make sure that the resistance element gets wired between the two 'resistance element' terminals and the remaining compensating wire goes to compensating terminal.
It doesn't matter which one you don't use, just make sure that the resistance element gets wired between the two 'resistance element' terminals and the remaining compensating wire goes to compensating terminal.
jdbrandt
Lifetime Supporting Member
The Pt100 RTD is a standard, and the standard range is way beyond 100 C. (850C, I think).
If its a Pt100 probe, it should be good to beyond 100C, unless, of course, the probe is made of wax or plastic.
If its a Pt100 probe, it should be good to beyond 100C, unless, of course, the probe is made of wax or plastic.
Gil47
Member
Because they made the assumption that you were only wanting to measure water temperatures and not ice or steam.
The schematic may have been part of an article talking about water temperatures
The RTD to mA or Volts is the part that normally has the range scale supplied.
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sthompson
Lifetime Supporting Member + Moderator
Hi Adam:
As Gil47 said, the PT100 is good over a wide range of -200°C to 850°C. See attached Chart link.
http://www.michshur.com/image/users/190375/ftp/my_files/Files/TD_TV_PT1A.pdf?id=8609087
The Converter converts the PT100 Resistance to a 4-20 mA Signal. In other words, it is scaling it for you. I have Converters that I can Program to any Valid Range. In this case, your Converter is set up to give you 4 mA for 0°C and 20 mA for 100°C. This is a pretty standard measurment range, and takes you from ice to boiling water. If you need a different measurement range, you will need to order a different Converter, or a Programmable one.
Stu....
Timbert
Member
As said earlier, there should be no problem using an RTD with a greater range.
The only caveat is there RTD's with two different coefficients, usually called alpha. The standard DIN RTD has an alpha of 0.00385 ohm/ohm/degC and nominally 100 ohms (hence PT 100). There are some RTDs with an alpha of 0.00392. So both the RTD and convertor should be designed for the same curve. Over 0 to 100 the difference is probably negligible, but you should know there is a difference.
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