On Sept 21st, 2018

1. Repaired the electric wire of LVDT#4 being cut at Mitaka.
2. Applied vac-seal to an actuator coil (forgot the serial number) as the wire was about to loose.
3. Meausured resistances of the coils for LVDTs and actuators as much as possible for their sanity check. No bad coils.

Reparing an LVDT and an actuator coil

As reported here, the outer coil of LVDT#4's wire was cut at Mitaka for some reasons (Fig 1). By using the backside of a cutter knfie according to the N. Satou-san's suggestion, a certain length of the kapton jacket of each side of the cut wires were peeled off (Fig 2 and 3). Then I connected those wires by swaging a copper pipe to both of the edges in the same manner I did for the WAB's electric connection (Fig 4 and 5). Then I covered the copper pipe by two small pieces of kapton sheet with vac-seal (Fig 6) for electric isolation.

Before the reparing, I measured the resistance between the pins for the damaged outer coil, which was a dual coil but one was cut as described, and the measured value was just one coil's resistance:  184.7 ohm; then after the reparing, it recoeverd to dual (parallel) coil's value: 92.3 ohm, which is not so different from the other coils ones shown below.

Next, I applied vac-seal to the body of an actuator coil, which had a loosen electric wire (and kapton sheet) (Fig 7 and 8).

Sanity check of the coils

The measured values as tabulated below. The #3 LVDT was inaccessible due to the safety wall, and I did not remove the wall to measure them. LVDT#4 was the one I repaired this day. Comparing the value described above, it is different but I believe this is in the error bars. By the way, the manufacture's measurements were uploaded here and here.

To complete the sanity check it would be nicer to measure the inductances as well...