| ??? 11/02/11 14:48 Read: times |
#184519 - It depends... Responding to: ???'s previous message |
In order to achieve high reliability and redundance each load cell should have its own front end amplifier. The topology of this multi load cell arrangement should also withstand breaks and short circuits of cables of individual load cells, so that a reliable measurement can be guaranteed even if one of the load cells shows a catastrophic failure.
The front end amplifier need not to provide 24bit resolution and 18bit precision for an industrial weighing application, as I have pointed out earlier. Eventually even no instrumentation amplifier is needed. A careful error analysis has to be made, if costs is an issue here. The distance between a 4 wire load cell and its front end amplifier should be short. Longer distances can only be allowed, if 6 wire load cells are used. A careful error analysis has to be made, to find out, what's "short" and "long" here. If a galvanic isolation is needed between the individual load cells, one of these cheap and precise 14/16bit serial output ADCs could be used directly at the output of each front end amplifier. The signal could be transmitted to the summing and control board via optos then. Everything depends on the actual needs... Kai Klaas |
