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VIS (SR2)
fabian.arellano - 16:32 Wednesday 22 September 2021 (18334) Print this report
IM-V3 OSEM coil resistance check.

With Hirata-san.

See album SR2 Remedying work after O3.

According to report 18237, the coil in the IM-V3 OSEM had a higher resistance than expected (24.2 Ohm vs. 19.6 Ohm), so we investigated.

The OSEM is connected to the upper flange via three cable segments:

  • Segment 1: from the OSEM to the BF.
  • Segment 2: from the BF to the base of the preisolator.
  • Segment 3: from the base of the preisolator to the flange.

We found that the problem is in the male connector at the upper end of segment 2. When some of the pins are touched the resistance varies a lot, including becoming an open circuit sometimes.

We aim to fix the connector early next week.

Comments to this report:
fabian.arellano - 14:49 Thursday 20 January 2022 (19515) Print this report

With Hirata-san.

See album SR2 Remedying work after O3.

Summary: The connection is healthy, the resistance is slightly higher than expected because an extension cable was used.

The problem described in the commented entry was solved on the 29th of September 2021 according to notebook notes, but I forgot to write a klog report.  The instability of the resistance value was solved that day, but the value measured at the outside of the chamber remained higher than in other OSEMs, so we investigated this issue today. The measured value is 22.3 Ohm, whereas typical values are ~19.5 Ohm.

As reported before, this line has three segments. The last segment is an additional extension that is not used for connecting other devices. Therefore, we decided to measure the resistance introduced by this extension:

  • Resistance along the line connected to pin 2: 1.4 Ohm
  • Resistance along the line connected to pin 7: 1.3 Ohm

We checked two spare similar extension cables  and confirmed these values are typical.

At the top of the 2nd segment, the resistance of the coil is 19.7 Ohm, which is the value we were expecting. The addition of the three values is 22.4 Ohm, which is consistent with the value measured from the outside.

There is nothing wrong with the cables.

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