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???
10/31/11 02:34
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 		 #184467 - Keep the signal paths as simple as possible.
Responding to: ???'s previous message
Zeeshan Ashraf said:
The other way, perhaps could be to use a sort of NTC / PTC in the signal path of the Load-cell somehow to compensate for temperature changes.


This is not a good idea at all. Think about it for just a couple of seconds. Some sort of analogue temperature compensation circuits will add more areas of problems to the circuit that add to your error budget. I would not follow this path at all.

Follow what Kai suggested to add a separate channels that read the temperature of the load cells directly and bring them back into the digital realm of the controller firmware. This eliminates the multitude of additional error points that some type analogue temp comp will introduce. I suspect that for the temperature readings of the load cells for this digital compensation that a couple of degrees accuracy is quite good. This may let you try to actually use one of the common digital temperature sensors that have a digital serial type interface.

Michael Karas



List of 58 messages in thread
TopicAuthorDate
Load-cell conditioning / summing            01/01/70 00:00      
   what is that?            01/01/70 00:00      
      RE: #184430 - what is that?            01/01/70 00:00      
         then say what you mean            01/01/70 00:00      
            your description leaves something unclear            01/01/70 00:00      
               RE: #184435 - your description leaves something unclear            01/01/70 00:00      
                  where are the loadcells???            01/01/70 00:00      
                     RE:            01/01/70 00:00      
      RE: #184430 - what is that?            01/01/70 00:00      
         some Q/A            01/01/70 00:00      
            RE            01/01/70 00:00      
               Q/A 2            01/01/70 00:00      
                  RE            01/01/70 00:00      
                     re re            01/01/70 00:00      
                     get rid of that summing amp            01/01/70 00:00      
               you will be lucky to get 16 bits            01/01/70 00:00      
                  Precision again...            01/01/70 00:00      
                     Comparison            01/01/70 00:00      
                     RE            01/01/70 00:00      
                        why do you keep babbling about a summing amp            01/01/70 00:00      
                        Priorities...            01/01/70 00:00      
                           RE            01/01/70 00:00      
                              cirrus, ti            01/01/70 00:00      
                                 maxim, linear tech, Analog Devices            01/01/70 00:00      
                                 RE            01/01/70 00:00      
                              it takes the same time ...            01/01/70 00:00      
               500 running foot of cable            01/01/70 00:00      
                  RE            01/01/70 00:00      
                     Go for ADC with multiplexed inputs instead of multiple ADC            01/01/70 00:00      
                        Good Advice            01/01/70 00:00      
                           It depends...            01/01/70 00:00      
                              This is a MODULAR concept !            01/01/70 00:00      
                                 it depends            01/01/70 00:00      
                                 don't be ridiculous            01/01/70 00:00      
                                    Consider other parameters too.            01/01/70 00:00      
                                       calibration            01/01/70 00:00      
                                       if you do not buy bootleg parts ...            01/01/70 00:00      
                                          Voltage reference            01/01/70 00:00      
            Accuracy...            01/01/70 00:00      
               RE            01/01/70 00:00      
                  Keep the signal paths as simple as possible.            01/01/70 00:00      
                  sun umbrella            01/01/70 00:00      
   Separate Gain Paths - Not The Best            01/01/70 00:00      
      RE: #184439 - Separate Gain Paths - Not The Best            01/01/70 00:00      
         Error Budget Calculations?            01/01/70 00:00      
            Hysteresis            01/01/70 00:00      
         This should alarm you!            01/01/70 00:00      
            RE            01/01/70 00:00      
               No contradiction...            01/01/70 00:00      
                  RE            01/01/70 00:00      
                     Digital Summing            01/01/70 00:00      
               with DC exitacion ...            01/01/70 00:00      
            welcome on board            01/01/70 00:00      
      RE:            01/01/70 00:00      
   Look at ADuC845            01/01/70 00:00      
      ADuC845            01/01/70 00:00      
         Noise V good            01/01/70 00:00      
            Ok, then            01/01/70 00:00      

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