A pushpull bridge can double the system output comparing to

A \"push-pull\'\' bridge can double the system output comparing to a simple bridge. Assume that two strain gauges (resistance-type) with the same characteristics but exact opposite directions in output, are connected in two adjacent arms the bridge. Both initial resistances are 750 omega, plusminus 20% resistance changes correspond to the maximum measured pressure delta P = 100 kPa on R_i and R_2. R_3 and R4 in the bridge are also 750 omega. A d.c. power supply E = 5V is used. Calculate: Maximum output V _out Sensitivity of the system if output is analog (voltage) Resolution of the system if output is 10-bit (binary)

Solution

Vout = E/( 1/r1 + 1/r2 +1/r3 + 1/r4)R

= 2.5 V

WHERE R = R1 +R2 +R3 +R4

SENSITIVITY = 1/I

= 1/2.5

RESOLUTION = 0.36