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 Fri Jul 17 18:04:54 2009, Clara, Update, PEM, Guralp Box Fail 
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 Sat Jul 18 19:49:48 2009, rana, Update, PEM, Guralp Box Fail
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Mon Jul 20 17:06:29 2009, Jenne, Update, PEM, Guralp Box Fail
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Message ID: 1761
Entry time: Sat Jul 18 19:49:48 2009
In reply to: 1760
Reply to this: 1765
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| Author: |
rana |
| Type: |
Update |
| Category: |
PEM |
| Subject: |
Guralp Box Fail |
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That's terrible: R5 & R8 should definitely be 100 Ohm and not 100kOhm. 100k would make it a noise disaster. They should also be metal film (from the expensive box, not from the standard box). This is the same for all channels so might as well stuff them.
The circuit diagram between TP3 and TP4 appears to be designed to make the whitening not work. That's why R6 & R7 should be 100k. And R2 should be metal film too.
Basically, every time we want good low frequency performance we have to use the metal film or metal foil or wirewound resistors. Everything else produces a lot of crackling noise under the influence of DC current.
I'm also attaching the voltage and current noise spectra for the AD620 from the datasheet. These should allow us to compare our measurements to a reasonable baseline. |
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