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fabian.arellano - 10:33 Friday 31 May 2019 (9025) Print this report
LVDT driver board settings (work carried on 27-05-2019).

With Yokozawa-san.

There is a similar entries for SRM, SR2 and BS.

  • Date 27-05-2019.
  • Input signal: 4.86 Vpk-pk at 10 kHz for BF, SF and IP LVDT #3 and 4.90 Vpk-pk at 10 kHz for F0, IP LVDT #1, #2.
  • Nominally, the external signal generator is set to 5 Vpk-pk at 10 kHz.
  • The input gain is the amplitude measured at the probe point (P0, P1, P2) divided by the amplitude of the reference signal (measured at probe point REF_SIG at the central board).
  • Phase measurements were recorded in photos which are uploaded to NAOJ's Google Photos on 31-05-2019.
  • A picture of the notebook can be found here.
  • This information should also be found in SR3 information page.
LVDT Input gain Output gain resistance (Ohm) Phase (µs) Board and probe point
BF 0.975 62.5 16, signal at probe point ahead. left board, P0
SF 0.983 60.6 10, signal at probe point ahead. left, P1
F0 0.967 60.8 17, signal at probe point ahead. left, P2
IP #1 0.975 50.6 10, signal at probe point ahead. right, P0
IP #2 0.967 50.4 8, signal at probe point ahead. right, P1
IP #3 0.975 50.2 10, signal at probe point ahead. right, P2
  • In the pictures of the oscilloscope screen, channel 1 is the reference signal and it's shown in yellow.
  • Channel 2 is the LVDT signal (e.g. BF, SF, etc.) shown in green.
  • The X2 cursor measures the position (in time) of the peak of the LVDT signal in channel 2.
  • The X1 cursor measures the position (in time) of the peak of the reference signal in channel 1.
Comments to this report:
fabian.arellano - 10:55 Friday 26 July 2019 (9658) Print this report

With Terrence

In case you don't see the picture attached to this report, please click this link: 9658.

After the LVDT driver broke down on the 24th of July (entry 9659) we replaced it by a new one. In order to keep the same LVDT calibration factors for each channel we adjusted the values of

  • One input gain resistor (see text below),
  • One output gain resisitor (see entry 9025) and
  • One phase determined by a resisitance value (see entry 9025).

According to Joris's and Enzo's documents (JGW-T1604798 and JGW-E1707287 respectively), the input gains (whose values were reported in entry 9025) are adjusted by changing the values of the variable resistors shown in the picture and the effect can be seen in the amplitude of the signal measured between ground and probe points P0, P1, P2 and P3 for each channel respectively. However, when we tried varying the amplitudes we didn't see any obvious change on the oscilloscope screen. Because the resistors are not labeled on the PCB board we even adjusted the four of them for one single signal but we didn't see any obvious change.

The alternative strategy was then to measure the values of the resistors in the broken LVDT driver cards and adjust the new driver accordingly. The resistors are labeled A, B, C and D as shown in the first picture. The values were measured between the resistors' accesible terminals and probe point P_resistor (see picture), which is terminal 2 of the OPA211 (see sheet 2 of the circuit diagram: JGW-D1301467-v1). The measured values are given according to the position of the board (as seen from the front) and the position of the resistor:

  • Left A: 5.811 kΩ
  • Left B: 3.750 kΩ,
  • Left C: 1.364 kΩ,
  • Left D: 5.187 kΩ,
  • Right A: 5.466 kΩ,
  • Right B: 5.408 kΩ,
  • Right C: 5.619 kΩ,
  • Right D: 5.498 kΩ.

Therefore, the settings of the boards are given by the table in entry 9025  with the resistance values given here replacing the input gain values in the table.

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