[Aidan, Kiwamu]
Kiwamu and I roughly calibrated the analogue output from the SR620 frequency counter yesterday. The input channel, intuitively named C1:PSL-126MOPA_126MON, now reads the measured frequency in MHz with an error of about 0.1MHz - this is, I think, due to the bit noise on the D/A conversion that Kiwamu discovered earlier. That is, the output range of the SR620 corresponds to around 100MHz and is digitized at 10-bit resolution, and ...
100MHz/(10^2) ~= 0.098MHz. [Sad Face]
Calibration:
We set the EPICS range to [-100, 100] (corresponding to [-5V, 5V]), connected a Marconi to the Freq Counter, input a variety of different frequencies and measured the counts on the EPICS channel.
The linear fit to the calibration data was F = 2.006*EPICScount - 0.2942. From this we worked out the maximum and the minimum for the range settings that give the channel in MHz: EGUF = -200.8942 and EGUL = 200.3058. The previous range was [-410, 410]
Calibration of SR620 analogue output
Input Frequency (MHz) |
Measured EPICS Value |
10 |
5.191 |
20 |
9.98 |
30 |
15.21 |
40 |
20.00 |
50 |
25.18 |
60 |
29.99 |
70 |
35.18 |
71 |
35.565 |
72 |
35.9894 |
73 |
36.3861 |
74 |
37.17 |
75 |
37.576 |
76 |
37.9669 |
77 |
38.3575 |
78 |
39.166 |
79 |
39.5691 |
80 |
39.978 |
|
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