Jennie W, Sheila D, Jenne D

Summary: JAC TRANS A LF calibration gives correct ratio now but PD is too noisy to give us sensible values when the light pipe is closed.

On Tuesday I changed the scaling filter in JAC-TRANS_A_LF to give us an output calibrated in W out of HAM1. The previous calculation (alog #89805) gave us too large a value.

When we checked the power on the JAC-TRANS PD in chamber (alog #89251) we did not monitor the JAC input power between successive measurements and since we had purge air on I think the input power drifted.

To avoid confusion  I just took a time when the output power was measured in chamber and used the JAC TRANS LF OUTPUT power at that time to give the calibration into HAM2 W.

When we measured 96mW out of HAM1, the JAC-TRANS_A_LF filter bank was roughly calibrated into mW (using standard values for V/count, A/V, mW/A) but had not been calibrated using in-chamber measurements.

For 96mW we got 0.00120mW on JAC_TRANS_A_LF_OUTPUT on 2026/02/24 at 20:30:10 UTC, see image.

We want the output in W so the calibration factor is 80000/1000. This value is now in FM10 in the filter bank. Unfortunately the signal still is too nosiy to give a sensible looking value and so changes from -20 to 20 W.

Jenne and I put a 0.01Hz pole to low pass the noise in the FM7 filter, and also tuned the offset on the filter bank.

This channel still seems too noisy though (image) and changes between -0.5 W and 0.5.

So maybe we need a filter that goes down to lower frequency, or its just too noisy a PD to use as a JAC input power monitor.

I'm going to revisit this after the BSC2 work when we next have an opportunity to open the light pipe.