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AdV-COM (AdV commissioning (1st part) )

ruggi, boschi - 19:37 Monday 12 November 2018 (43542)

unplugging WE coils

The test of unplugging WE coils has been repeated (with P4 coil driver installed), having a reference curve taken just before. The result is that the noise decreased a bit at 20-40 Hz (fig 1).

In order to understand if the excess noise is 'common' or 'differential', a measurement in LN1 has been taken. This measurement, rescaled by the ratio between LN2 ans LN1 series resistors, explains well the noise (fig 2), so we conclude that the noise is differential, and an eventual common component cannot be appreciated.

Fig 3 shows an attempt to project back the LN1 measurement in terms of board differential noise. The result is slightly higher than expected, and has to be confirmed.

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Comments to this report:

ruggi - 10:47 Wednesday 14 November 2018 (43572)

I made a mistake in the evaluation of P4 differential noise, because I was assuming the impedance in LN1 to be 228 ohm as for P6, but in fact it is 128 ohm. In fig 1 the new evaluation of the differential noise (in agreement with the lab measurement).

The conclusion about the limiting noise before unplugging the coils does not change: differential noise can explain the excess noise. This is shown in fig 2: adding in quadrature the differential noise to the residual (unplugged) noise, we obtain the'plugged' noise.

The increased series resistor should put the differential noise at a negligible level.

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ruggi - 10:55 Thursday 15 November 2018 (43585)

Yesterday the unplugging test at WE has been repeated, in the new configuration with 13kohm series resistor instead of 4.5 kohm. No visible reduction wrt clean data (fig 1). Unfortunately yesterday the ITF was noisier than the day before (fig 2), so the accuracy in detecting some common noise from the board was again poor. Let's say that we have no new diagnostics about WE P4 board.

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