Thermocouples have several advantages over other methods of measuring temperature. They are very small in size; have a low time response (from 10 to 20 ms, compared to several seconds for some elements); are reliable; have good accuracy; operate over a wide temperature range; and can convert temperature directly into electrical units. The disadvantages are the need for a reference and the low signal amplitude. Thermocouples are compensated, as shown in Figure 10.6. The amount of conditioning required by a thermocouple will depend on its temperature-measuring range. An accuracy of ±1% over a limited temperature range without compensation can be obtained, as shown in Table 10.6, but conditioning (linearizing) is needed if used over its full operating range. Nonlinear amplifiers can be used to obtain an accuracy of ±0.5% of FSD. The set zero conditioning is a part of the reference temperature correction. Thermocouple voltages also can be sensed directly by the controller using an internal amplifier, and then conditioned internally. This is discussed in Section 10.3.4.