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05/17/05 22:03
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#93556 - making a pt100 thermometer using a 8051
hi guys i was hoping someone might be able to help me. I am currently trying to design a digital thermometer using a pt100 sensor and a 8051. The pt100 is a (A class) and has an accuracy of +/- 0.15 degrees at 0 degrees. At 0 degrees its resistance is exactly 100.00 ohms.I am trying to keep to that accuracy with my thermometer. But in oder to calibrate it i need to be able to measure the resistance to eg. to 100.00. To keep that accurcy but my multimeter will only show eg. 100.0. Which could cause a error of +/- 0.25 degrees. So my idea is to calculate the resistance using ohms law. And puting a voltage across it and measure the current. But the problem with that is my multimeter accuracy. Which for voltage is 0.3% of the reading + 2 digits. The accuracy the current is 1% of the reading + 2 digits.I was planning on using the 400 microamps range and the 400 mv range. Can anyone suggest how i might be able to calculate what the true readings would be on my multimeter. with those ranges and the accuracy specs i have given as i haven't done much of this stuff before.

List of 23 messages in thread
TopicAuthorDate
making a pt100 thermometer using a 8051            01/01/70 00:00      
   you are usually better off            01/01/70 00:00      
   current sources            01/01/70 00:00      
      TI (Burr-Brown) App Note SBAA050            01/01/70 00:00      
         That's great            01/01/70 00:00      
         ads574            01/01/70 00:00      
         Indeed a very good link!            01/01/70 00:00      
      calculating resistance            01/01/70 00:00      
         Where are the problems, concretely?            01/01/70 00:00      
            measuring resistance            01/01/70 00:00      
               Use better mulitmeter...            01/01/70 00:00      
                  2 multimeters            01/01/70 00:00      
   max1410            01/01/70 00:00      
   Theoretical curve            01/01/70 00:00      
      PT100            01/01/70 00:00      
   pt100s            01/01/70 00:00      
   Look at LT1001data sheet            01/01/70 00:00      
   wheatstone bridge            01/01/70 00:00      
      Look at it this way.....            01/01/70 00:00      
         anyone knows            01/01/70 00:00      
            Keep it simple...            01/01/70 00:00      
               So does Maxim            01/01/70 00:00      
               Already done...            01/01/70 00:00      

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