Two-wire bridge-to-frequency converter
Johan H. Huijsing, G.A. van Rossum, M. Van der Lee · IEEE Journal of Solid-State Circuits · 1987
An integrated two-wire bridge-to-frequency converter is presented for use as a remote-signal conditioner for sensor bridges such as strain-gauge bridges of platinum-wire temperature-sensing bridges. The converter has a sensitivity on the order of 1 Hz per 1-/spl mu/V/V relative bridge output. A center frequency of 10 kHz allows the application of an untrimmed bridge with an imbalance up to /spl plusmn/10000 /spl mu/V/V. The instability is less than 10/SUP -4/ per Kelvin and per 1-V supply-voltage variation. The untrimmed transfer inaccuracy is lower than 1%. The linearity error is lower than 0.01%. Different bridge readout functions can be chosen by different circuit configurations. The converter can be connected to a single supply voltage. The frequency output is modulated on the supply current. The supply voltage is 12-24 V.