| Similar to the unity gain buffer, these interfaces isolate the output from the high source impedance of the Bend Sensor® device. These alternatives allow adjustment of the output offset and gain. In Figure 1.1, the ratio of resistors R2 and R1 sets the gain of the output. Offsets resulting from the non-infinite Bend Sensor® resistance at zero deflection (or bias currents) can be trimmed out with the potentiometer, R3. For best results, R3 should be about one-twentieth of R1 or R2. Adding an additional pot at R2 makes the gain easily adjustable. Broad range gain adjustment can be made by replacing R2 and R1 with a single pot. The circuit in Figure 1.2 yields similar results to the previous one, but the offset trim is isolated from the adjustable gain. With this separation, there is no constraint on values for R6. Typical values for R5 and R6 are around 10 kQ. |