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For the whitening on the OSEM sensor input, FM1 is linked to the Contec binary I/O. FM1 is the inverse whitening filter. Turn it on, and the analog whitening is on (bit in the binary I/O screen turns red). Turn it off, and the analog whitening is bypassed (bit in the binary I/O screen turns gray). Good. Makes sense. Either way, the net transfer function is flat.
The dewhitening is not so simple. In FM9 of the Coil Output filter bank, we have "SimDW", and in FM10, we have "InvDW". Clicking SimDW on makes the bit in the binary I/O screen gray (off?), while clicking it off makes it red (on?). Clicking InvDW does nothing to the I/O bits. So. I think that for dewhitening, the InvDW is always supposed to be on, and you either have Simulated DW, or analog DW enabled, so that either way your transfer function is flat. Fine. I don't know why we don't just tie the analog to the InvDW filter module, and delete the SimDW, but I'm sure there's a reason.
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The input/whitening filters used to be in a similarly confused state as the output filters, but they have been corrected. There might have been a reason for this setup in the past, but it's not what we should be doing now. The output filters all need to be fixed. We just haven't gotten to it yet.
As with the inputs, all output filters should be set up so that the full output transfer function is always flat, no matter what state it's in. The digital anti-dewhitening ("InvDW") and analog dewhitening should always be engaged and disengaged simultaneously. The "SimDW" should just be removed.
This is on my list of things to do. |