Instruments Calibration
About calibrating instruments
An instrument only conforms to stated
static and dynamic patterns of behavior after it has been calibrated.
It can normally be assumed that a new instrument will have been
calibrated when it is obtained from an instrument manufacturer, and
will therefore initially behave according to the characteristics
stated in the specifications. During use, however, its behavior will
gradually diverge from the stated specification for a variety of
reasons. Such reasons include mechanical wear and the effects of dirt,
dust, fumes and chemicals in the operating environment. The rate of
divergence from standard specifications varies according to the type
of instrument, the frequency of usage and the severity of the
operating conditions. However, there will come a time, determined by
practical knowledge, when the characteristics of the instrument will
have drifted from the standard specification by an unacceptable
amount. When this situation is reached, it is necessary to recalibrate
the instrument back to the standard specifications. Such recalibration
is performed by adjusting the instrument at each point in its output
range until its output readings are the same as those of a second
standard instrument to which the same inputs are applied. This second
instrument is one kept solely for calibration purposes and whose
specifications are accurately known.

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