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???
08/24/05 14:45
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 		 #100003 - Acceptable limits
Responding to: ???'s previous message
+/- 0.5C is acceptable, but due to interference from local 3 phase inverter speed controllers (without any EMC compliance)
the actual noise induced on the probe cables causes a shift of about +/- 2.0C depending upon inverter speed settings, local earthing (seems to depend on weather) etc.etc. I have tried filtering/averaging etc without success. For various reasons, I cant filter the inverters and I cant change the probe system easily, so the only way is to to change the amount of current through the Pt100 whilst the ADC measures.
The only good thing is that I dont have to read the probes very often, once a minute would be fine.
Chris

List of 37 messages in thread
TopicAuthorDate
Analog mux for Pt100            01/01/70 00:00      
   Precision            01/01/70 00:00      
      Precision is the same?            01/01/70 00:00      
         Err            01/01/70 00:00      
            Inertia!            01/01/70 00:00      
               Precision.            01/01/70 00:00      
                  Precision            01/01/70 00:00      
                     PT100 sensors            01/01/70 00:00      
   try another way, have a look at Linear T            01/01/70 00:00      
      No choice            01/01/70 00:00      
         it is still valid            01/01/70 00:00      
         The usual solution is...            01/01/70 00:00      
            As I said before            01/01/70 00:00      
               Whats the problem ?            01/01/70 00:00      
                  Acceptable limits            01/01/70 00:00      
                     hooking the PT100s up to differential in            01/01/70 00:00      
                        Thanks            01/01/70 00:00      
                           4 wire ?            01/01/70 00:00      
                     Filtering MUST help. So, there's a mista            01/01/70 00:00      
                        Ditto, filtering must work            01/01/70 00:00      
                           Exactly!            01/01/70 00:00      
                     Errm.            01/01/70 00:00      
   Look at existing products for ideas            01/01/70 00:00      
      that will give you more problems than it            01/01/70 00:00      
         It's not what I suggested            01/01/70 00:00      
            No chance            01/01/70 00:00      
               Again, not what I meant            01/01/70 00:00      
                  Sorry            01/01/70 00:00      
   Switched Higher Current does help            01/01/70 00:00      
      I am interested, it took some search, fo            01/01/70 00:00      
      I heavily doubt this            01/01/70 00:00      
         not as to noise, but it does have the ef            01/01/70 00:00      
         higher current does help            01/01/70 00:00      
            You can use pulsing and filtering            01/01/70 00:00      
               It's the same as DC measurement            01/01/70 00:00      
                  How pulsing improves performance            01/01/70 00:00      
   Averaging(filtering) has the same effect            01/01/70 00:00      

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