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Originally Posted by unregistered
you take the RTD to your cal lab and tell them the temp range over which you wish to use it, and the increment at which you wish the indicated vs. actual temps recorded
$80 to 120 or so
and it helps if the indicator is calibrated at the same time and/or with the same probe, as then there is another correlation resolved
a single point 'calibration' is pointless
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Bill,
Your word is one of the few I will take without question. With that being said, is this worth persuing any further? But, before you are quick to pass judgement let me share my thoughts.
- PSRT's have a good approximation of linearity (link). Keep in mind they are talking about 100 Ohm PSRT's. A 1000 Ohm'er would be a magnitude of order better.
- I have the nescessary multimeter. It was calibrated two months ago IAW ISO 9001 controls. It's accurate to .0001 Ohm (picked it up brand new in the box at a probate auction for $50, with the cal sheet).
- With a single point calibration, it would be close enough for an apples to apples comparison in my own little world. I'm OK with .04C accuracy @50C (based on single point callibration with TP of water). What I really care about is the potential for outstanding resolution.
What I am planning to do:
- Build two of these. I don't need the temperature range the one in the article is built for, therefore I can cut out the spot-welded nickel wires and the Pyrex tubing. That is the bulk of the cost.
- Calibrate one (#1) against the triple-point of water as a starting point.
- Put them both in a water bath and slowly heat them, while continously monitoring #1 PSRT
- At a TBD interaval, measure both PSRT's. By doing this I can build a correction table for #2 PSRT and have two PSRT's callibrated against each other offering mediocre accuracy (to the rest of the world), but very accurate between themselfs and with kick ass resolution.
Can it get any better for $100?
Fire away.