LDM

This video shows the teardown and test of a distance miles indicator manufactured by Smiths. At the end a quick reverse engineering is performed for the input connections.
This instrument requires an external AC voltage reference voltage for the feedback potentiometer (out of phase regarding input signal). This permits to have a display which doesn't depend on the instrument itself.
00:00 - Intro
01:54 - In search for power supply pins
04:48 - In search for input pin
05:47 - In search for flag pins
06:11 - In search for ground pin
07:34 - Preliminary test (open loop)
08:33 - Final test (closed loop)
Pinout:
A-B : Power Supply input 26Vac 400Hz
C : input common
D(-) E(+) : flag (28Vdc)
F-G : feedback potentiometer (2k)
H : input

[@davidparrot4669]

toujours epater par la facilité avec laquel vous faite fonctionner ces petites merveilles , encore un grand merci pour le partage c'est a chaque fois un reel plaisir.

[@Cyrob-org]

Hello, funny, what is the need of such indicator with low range ?

[@ChipGuy]

This can count 10 nautical Miles in 1 second. That is roughly Mach 20 or so. I wonder whar aircraft this came out of....

[@lelabodemichel5162]

The actual display depends on the computer connected to the instrument and not the instrument itself. The servo control should be fast in order to have a fast response time, and the value displayed has the speed of the input signal speed.