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ADuCM360 - excitation current source tolerance

Question asked by tkotwaltx on Jan 18, 2018
Latest reply on Mar 6, 2018 by barryzhang

The ADuCM360 Datasheet (Rev D, page 7) says that the initial tolerance of the excitation current source is +/- 5% (25 degC, currents above 50 uA). Are there any conditions that might help to improve the tolerance? For example, as current increase above 50 uA, would you expect the tolerance to improve?

 

For some background, I'm using the current source to drive an RTD and would like to improve the repeatability from unit to unit. I've got some flexibility in the way I use the excitation source and I'm wondering if there's anything I can do to help. I've currently got it set to drive 150 uA and I turn it on shortly before I start the ADC conversion to read the RTD voltage, and then I turn it off after the conversion has completed. From looking at the RTD voltage on an oscilloscope, I can see that it takes less than 15 usec for the voltage to come up to it's full value after the current source is turned on. The conversion takes just over 3 ms.

 

Would the current source tolerance improve if I were to either increase the current or leave the current on all the time?

 

Thank you.

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