Load cells are sold with raw mV/V, amplified analogue, or digital outputs. The choice is usually made by habit, but it determines how the system behaves over distance and how it is calibrated.
mV/V
Raw bridge output is the most transparent and the cheapest, but it must travel to an amplifier without picking up noise. Good for short runs inside a machine, and for any application where a junction box sums several cells.
4-20 mA
Current loop transmission is immune to voltage drop and works over hundreds of metres. It suits single-cell process weighing feeding a PLC analogue card. The cost is that the transmitter must be mounted at the cell, and the loop adds its own temperature drift and zero offset.
Digital
A digital cell or a digital junction box converts at the cell and transmits counts or weight over RS-485 or Ethernet. Each cell is individually addressable, which makes corner calibration and diagnostics far easier and removes the summing errors of analogue junction boxes. For multi-cell silos and platforms, digital is now the default choice.
Kevin Huang