Threshold is the amount of measurement change required before a measuring instrument reacts to a change in measurement output or produces a specified result.
For example an analogue pressure transducer with a wheatstone bridge strain gauge output has no signal conditioning components to limit the measurement resolution, and the threshold in this case is a factor of the amount of pressure change required before the sensing diaphragm produces a change in output signal. In this case the non-responsiveness of the transducer is mostly attributed to the mechanical properties of the sensing diaphragm due to the lack of signal conditioning components.
Some types of sensors include additional electronics to condition the output from the transducer. Typically a digital amplifier would be incorporated to condition the transducer signal, which has a defined analogue to digital resolution which is normally specified as a number of bits. For example a 14 bit resolution output would be 16384 counts which is equal to a 0.006104% resolution. In this case the threshold of the electronics would further restrict the response of the output to a change in measurement input. The overall threshold required to produce a change in measurement reading is dependent on the combined lag due to the transducer and resolution of the signal conditioning electronics.
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