A load-cell weighing-scale chain: the load cell's small differential voltage is…
PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Feedback, operational amplifiers and analogue signal processing · Digital electronics, embedded systems and data acquisition
Electronics for Measurement, Ch Sampling, quantisation and the acquisition chain
Problem
A load-cell weighing-scale chain: the load cell's small differential voltage is raised by an instrumentation amplifier (gain 1000, input-referred noise density 50.0nV/Hz), which feeds an anti-alias filter of noise-equivalent bandwidth 15.0Hz, then a 12-bit converter on a 1.00V reference; a full-scale load gives 1.00V at the converter.
((a)) Find the quantisation noise and the amplifier noise at the converter input, their quadrature sum, the signal-to-noise ratio for a full-scale sine and the effective number of bits.
((b)) A pin-compatible 16-bit converter with the same 1.00V reference is offered as a drop-in replacement, with nothing else in the chain changed. Recompute the total rms error, the signal-to-noise ratio and the effective number of bits with this converter, and decide whether the extra four bits are worth specifying. Name one change to the chain that would help more.