1. Forum
  2. Usenet
  3. SCI.ELECTRONICS.REPAIR

  • Mechanical damping of panel meters

    From Andrew Smallshaw@21:1/5 to All on Mon Sep 11 11:27:28 2023
    Hi all

    I've recently picked up an old Weir bench PSU and recalibrated it
    to within quite sharp tolerances. However, the front panel meter
    (switchable between voltage and current, although the schematic
    shows it is working as voltmeter in both modes) reads accurately,
    but the settling time must be a good 10-15 seconds before it stops
    oscillating back and forth.

    I haven't got as far as pulling the meter out yet but I expect
    obtaining a compatible replacement will be difficult. Looking at
    online it seems most practical sources sources address electrical
    damping for brief transients in the signal, this is rather the
    mechanical side of things. Basic research suggests pneumatic
    damping is the usual order of the day but I haven't found anything
    relating to actual maintenance and adjustment.

    Does anyone have practical experience or is a replacement meter
    the usual approach?

    --
    Andrew Smallshaw
    andrews@sdf.org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to andrews@sdf.org on Mon Sep 11 09:13:45 2023
    On Mon, 11 Sep 2023 11:27:28 -0000 (UTC), Andrew Smallshaw
    <andrews@sdf.org> wrote:

    Hi all

    I've recently picked up an old Weir bench PSU and recalibrated it
    to within quite sharp tolerances. However, the front panel meter
    (switchable between voltage and current, although the schematic
    shows it is working as voltmeter in both modes) reads accurately,
    but the settling time must be a good 10-15 seconds before it stops >oscillating back and forth.

    I haven't got as far as pulling the meter out yet but I expect
    obtaining a compatible replacement will be difficult. Looking at
    online it seems most practical sources sources address electrical
    damping for brief transients in the signal, this is rather the
    mechanical side of things. Basic research suggests pneumatic
    damping is the usual order of the day but I haven't found anything
    relating to actual maintenance and adjustment.

    Does anyone have practical experience or is a replacement meter
    the usual approach?

    . . . . unless the meter is reading a real disturbance . . .

    There's probably a failed capacitor inside that needs replacing.
    Could even be an electrolytic across the meter terminals.
    Most sensitive moving coil meters (<1mA) are pretty much self-
    damping and won't require much filtering to average a measurement.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)