GND-Triggered Calibration (Blue Wire)
This is giving a calibration command by briefly touching the end of a wire to chassis, without using a separate button or display. On the GS740-3P this is done with the blue wire: when the end is touched to the black wire, that is to GND, the system detects the command and confirms it with the green light. There is a separate trigger wire per channel.
The logic of the method is that the controller pulls one of its inputs up through an internal resistor and counts a closure to GND as a command. This way no extra button, connector or panel hole is needed; the wiring is simplified. In dusty and damp environments such as drilling, every mechanical part removed means one less source of failure.
The points to watch in practice are these:
- The trigger wire is touched to GND only; it must not be brought into contact with the positive supply.
- The touch must be brief; the system reports that it has received the signal by the green light flashing.
- When not in use the wire end must be insulated and left free, and must not be left where it could contact the chassis continuously through vibration.
The same wire carries two separate functions: touched while running it teaches the upper limit; connected to GND before power is applied and then powered up, it erases the memory. What separates the two is the moment at which the trigger is given.
Context in which this term is used: Electronic speed and throttle control on a diesel engine