LDM

Errata: the range of this accelerometer is +/-30g not +/-20g as I said in the test section at 11:05. Therefore an acceleration of +/-1g corresponds to an output voltage of +/-0.167V.

00:00 - Intro
01:11 - Teardown
02:13 - First analysis
04:17 - Electronic boards
05:29 - Reverse engineering
07:40 - Test coils
08:46 - Faulty detector
11:05 - Bypassing the faulty detector
11:23 - Test

This videos shows technical details about a Russian servo accelerometer ДЛУММ-30 (DLUMM-30). This accelerometer was installed inside a 9E420 radar seeker.

How it works:
A mass translates the acceleration into a torque which is balanced by a second torque generated by two coils. A sensitive zero detector detects any deviation of the moving mass from the zero position. The resulting voltage is amplified and fed to the torque generator, keeping the mass at the same zero position.
The zero detector uses two variable transformers. The primaries are supplied with an ac voltage at 830 kHz. A small piece of copper mechanically linked to the moving assembly penetrates between the primary and the secondary, which modifies the differential induced voltage.

Schematic diagram: