Repeatability is self-defining; it is the ability of an instrument or process to faithfully repeat itself, given identical conditions. For instrumentation, this is synonymous with precision, and the mark of better grade instruments. Regarding instrumentation, a general statement is that accuracy can be adjusted, but repeatability is a function of the instrument quality and cannot be changed. Repeatability is determined, in large part, by the stability of the output in the face of environmental changes, such as ambient temperature effect, voltage fluctuation, pressure fluctuation, etc. Instruments whose readings are susceptible to changes in ambient temperature can be very problematic if located in areas where the temperature is expected to change, however this specification (and the cost to mitigate it with higher quality instruments) is of much less concern if located in areas of constant temperature. Commercial grade pneumatic instruments are usually susceptible to problems from ambient temperature changes, since thermal expansion changes the volume of tubing, size of orifices, etc. Some lower grade electronic components are also affected by ambient temperature changes.

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