One of the bogie wheels on each side of a chain is replaced with a bogie mounted on a load cell.

For mini-tank harvesters with a scrub chain, the scrub chain is the preferred location. This allows for full use of the tank with no effect on yield mapping.
If it is not a mini-tank harvester, then the load cells are mounted in the truck loading conveyor.
A speed sensor is placed on a shaft collar of the conveyor on which the load cells are mounted.

This senses conveyor speed and allows the monitor to calculate a lbs/sec of sugar beet flow.
The leads from the load cells and the conveyor speed sensor come together into a junction box and one 1/4" wire is sent to the tractor cab for hooking to the display.