A surgical drill for drilling a hole in a workpiece includes a housing, a probe moveably mounted to the housing, and a transducer assembly. The transducer assembly includes a gear coupled to the probe and at least two rotational sensor devices coupled to the gear to determine an amount of movement of a probe relative to a housing to determine a bore depth of the hole. The gear has a reference point having an angular path of rotation about a gear axis subdivided into separate first and second arcuate regions. A first sensor device is configured to detect a rotational position of the reference point in the first arcuate region, and a second sensor device is configured to detect a rotational position of the reference point in at least the second arcuate region, with the first sensor device incapable of detecting the reference point in the second arcuate region.