22 Chapter 2 Assumed relationship Decreasing Actual relationship Non-linearity error True value (a) (b) Sensor output Measured value Increasing Hysteresis error Value being measured Figure 2.1: Some sources of error: (a) nonlinearity; (b) hysteresis. (Figure 2.1b) is used for the difference in outputs given from the same value of quantity being measured according to whether that value has been reached by a continuously increasing change or a continuously decreasing change. Thus, you might obtain a different value from a thermometer used to measure the same temperature of a liquid if it is reached by the liquid warming up to the measured temperature or it is reached by the liquid cooling down to the measured temperature. · The range of variable of a system is the limits between which the inputs can vary. For example, a resistance temperature sensor might be quoted as having a range of À200 to þ800 C.