Instead of using a counter-controlled, pushbutton-activated range switch, you can use an optical encoder. Inexpensive encoders are available, and they occupy minimal space on the front panel of an instrument. Moreover, an encoder gives you the opportunity to select the optimum operating speed. However, at positions near the transition points in counter position, mechanical shocks can provoke false switching. The circuit in figure above overcomes the false-switching problem. [...]

A programmable reference diode, such as the Motorola TL431A, can supply constant-current bias for a silicon pressure-sensor bridge. This circuit is simpler than using an op amp and separate reference diode or than using a current diode, which requires temperature compensation. [...]