Group,
I'm working up a wiring diagram and am a little confused on wiring ground pins in my panel.
What I'm finding is that my EFIS (advanced flight systems) uses 3 wires to a serial interface (RX, TX, and GND) which tells me that RX and TX are referenced to the GND pin, but some of the avionics that I'm connecting it to don't have a dedicated GND reference for the serial port.
For example, if I connect my GTX327 to serial 2 on the AFS then I run pin 13 on the AFS (Serial 2 TX) to pin 19 on the GTX-327 (RS-232 IN 1). That makes sense, but what does it reference to? The GTX doesn't have a dedicated GND pin for RS-232:1 so it must be referencing pin 19 to power or chassis ground.
Perhaps my understanding is limited, but doesn't this mean that the serial interface will be referenced against the aircraft ground path between the two boxes? Is that a good enough ground to make a serial interface work?
Let me break this down into specific questions:
1. If the serial interface is referenced against chassis ground then should I run a ground strap between each box?
2. If I run a ground strap between each box then wouldn't that cause a ground loop since I have both a chassis and power ground between each box?
3. Will the AFS box reference it's serial interfaces against chassis or power ground or do I need to run a wire from serial 2 GND on the AFS to aircraft GND on the GTX-327.
4. Any books or documentation that can help me understand how avionics grounding works when each box has a different way of doing this?
Thanks,
schu
I'm working up a wiring diagram and am a little confused on wiring ground pins in my panel.
What I'm finding is that my EFIS (advanced flight systems) uses 3 wires to a serial interface (RX, TX, and GND) which tells me that RX and TX are referenced to the GND pin, but some of the avionics that I'm connecting it to don't have a dedicated GND reference for the serial port.
For example, if I connect my GTX327 to serial 2 on the AFS then I run pin 13 on the AFS (Serial 2 TX) to pin 19 on the GTX-327 (RS-232 IN 1). That makes sense, but what does it reference to? The GTX doesn't have a dedicated GND pin for RS-232:1 so it must be referencing pin 19 to power or chassis ground.
Perhaps my understanding is limited, but doesn't this mean that the serial interface will be referenced against the aircraft ground path between the two boxes? Is that a good enough ground to make a serial interface work?
Let me break this down into specific questions:
1. If the serial interface is referenced against chassis ground then should I run a ground strap between each box?
2. If I run a ground strap between each box then wouldn't that cause a ground loop since I have both a chassis and power ground between each box?
3. Will the AFS box reference it's serial interfaces against chassis or power ground or do I need to run a wire from serial 2 GND on the AFS to aircraft GND on the GTX-327.
4. Any books or documentation that can help me understand how avionics grounding works when each box has a different way of doing this?
Thanks,
schu