Measurement error/measurement deviation/measurement inaccuracy

The relative measurement error as a specification value of a Beckhoff analog device is specified in % of the nominal full scale value and calculated as a quotient of the numerically largest possible deviation from the true measurement value with reference to the full scale value:

It should be noted here that the "true measured value" cannot be determined with infinite accuracy either, but can only be determined via reference instruments with a higher expenditure of technology and measuring time and thus a significantly lower measurement uncertainty.

The value thus describes the result window in which the measured value determined by the device under consideration (Beckhoff analog device) lies with a very high probability in relation to the "true value". In colloquial terms, this is therefore a "typical" value (typ.); this expresses the fact that the large statistical majority of values will lie within the specification window, but that in rare cases there can/will also be deviations outside the window.

For this reason, the term "measurement inaccuracy" has become established for this window, since "error" is now used to refer to known disturbance effects that can generally be systematically eliminated.

The measurement inaccuracy must always be seen in relation to potential environmental influences:

• unchangeable electrical channel properties like temperature sensitivity,
• variable settings of the channel (noise via filters, sampling rate, ...).

Measuring inaccuracy specifications without further operational limitation (also called "service error limit") can be assumed as a value "over everything": entire permissible operating temperature range, default setting, etc.

The window is always to be understood as a positive/negative span with "±", even if occasionally specified as a "half" window without "±".

The maximum deviation can also be specified directly.

Example: Measuring range 0...10 V and measuring error < ± 0.3 % _{full scale value} → expected maximum usual deviation ± 30 mV in the permissible operating temperature range.

Lower measuring error Since this specification also includes the temperature drift, a significantly lower measuring error can usually be assumed in case of a constant ambient temperature of the device and thermal stabilization after a user calibration.

The above also applies to the output end value of analog output devices in a technically equivalent manner.