To produce a full-scale output of +4 V, a gain ´40 is used, adjustableby ±5% to absorb the tolerance in the sense resistor. There issufficient headroom to allow at least a 10% overrange (to +4.4 V).The roughly triangular voltage across the sense resistor is averagedby a single-pole low-pass filter, here set with a corner frequencyof fC = 3.6 Hz, which provides about 30 dB of attenuationat 100 Hz. A higher rate of attenuation can be obtained by atwo-pole filter having fC = 20 Hz, as shown in Figure 11. Althoughthis circuit uses two separate capacitors, the total capacitanceis less than half that needed for the single-pole filter.