Position probes measure the position of a target’s surface, usually with a high degree of accuracy. Suppliers divide products into several categories. Sensor elements or chips are simple devices such as thermocouples or bare dies that do not include packaging. Sensors or transducers are more complete products that include packaging and/or signal conditioning. They are powered by an external source and provide outputs in volts, direct current (DC) or current loops. Meters and instruments are self-contained units that provide an output at or near the position probe. They usually include signal processing and conditioning. Gauges and indicators feature an analog display, but do not provide electronic outputs. Recorders and totalizers record values, accumulate totals, and may include statistical functions. Measurement range and accuracy are the most important specifications to consider when selecting position probes. Operating temperature, shock rating, and vibration rating are additional considerations.