Le labo de Michel | LDM #344: Intertechnique Fuel Quantity Indicator - Teardown, reverse engineering and test @lelabodemichel5162 | Uploaded 1 year ago | Updated 2 hours ago
This video shows the teardown, the reverse engineering and the test of a digital fuel quantity indicator manufactured by Intertechnique.
fr.wikipedia.org/wiki/Intertechnique

00:00 - Intro
00:55 - teardown
03:36 - Reverse engineering part 1: power supply
04:49 - Reverse engineering part 2: dimmer circuits
06:13 - Reverse engineering part 3: analog board
07:04 - Test

Connector pinout:

A: ground
B: negative power supply -20V
C: positive power supply +20V
D: input voltage (1 to 5V with 5V reference voltage)
E: reference voltage input
F: ground
H: 82 ohms to E
J: digital ground (connected to analog ground through two diodes back to back)
T-U: lighting (0 to 5Vrms 400Hz)

Technical description:

- The input voltage is fed to a 10-bits ADC made with a 4040 counter, one 10-bits DAC, two comparators and one JK flip-flop.
- The 5V power is an SMPS which uses a classic SG1524 configured as a step-down DC-DC converter.
- Display value is 0 for 1V input voltage and 5V reference voltage
- Display value is 9900 for an input voltage equals to the voltage reference
- The rightmost digit is always 0, fuel quantity displayed is XXX0 pounds
- This instrument requires two power supply voltages: +20V and -20V.
- There is a dimmer circuit which permits to attenuate the display luminosity according to the level of the lighting voltage.
- The refresh rate is approximately 2 seconds.
- The display is blank if the reference voltage is below 2V
- The display is blinking if the lighting voltage is not present