STAN system
The system on the Merchantman worked by measuring the hydraulic pressure in each undercarriage strut using a transducer mounted at the top of the leg. The main inaccuracy came if the strut wasn't charged correctly or was leaking. The system was tested by the crew and gave a fixed weight and C of G value determined from set resistors in each transducer - this ensured the continuity of all the system wiring. It was still in use at AirBridge in the late 80's.