| ??? 07/12/09 14:10 Read: times |
#167125 - Surprise! Responding to: ???'s previous message |
Saman said:
Well, I hope to solve this problem with 0.1% resistors not expensive 0.01% ones. Surprise, these special divider resistors are way less expensive compared to other 0.01% resistors, because they are widely used! Saman said:
the main point that was in Per Westermark suggestion, was to remove temporary erroneous parallel shunt, but I said to him considering bounce time of switches is it do any good? Yes, if the regulation time the current source needs lasts longer than the swicthing, then the "bump" is dominating the error. But what Per wanted to know is, whether the discontinuity of the both ramps could be an effect of your make before break scheme. Saman said:
about thermocouples, what if temperature of one end differs from the other?
The question is,can it solve(or alleviate) my problem? This depends on your full range voltage. What is the maximum voltage drop across your shunts? Then you can estimate the effect of thermovoltage. Yes, temperature differences are an issue in such precise measurement applications, they should be kept as small as possible. Not only because of the thermovoltages themselves, but also because the drift increases with the surface temperature of presision resistors! Kai |
