Interfacing PIC Microcontrollers

Strain gauges are usually connected in this way; they might measure small

changes in the shape of a mechanical part under stress, such as a strut in a crane

jib. The sensor typically consists of four strain-sensitive resistors connected in a

bridge arrangement, such that a change in their resistance due to stretching is

output as a small differential voltage, typically in the range 0–10 mV.

A sensitive amplifier is needed, with a high gain and high input resistance,

which reduces the current drawn from the sensor and hence the errors. A sin-

gle-stage non-inverting amplifier has a high input resistance, but does not have

differential inputs. The difference ...