General Information On Measuring Accuracy/Measurement Uncertainty - Beckhoff EPP3504-0023 Short Manual

3.4 General Information on Measuring Accuracy/
Measurement Uncertainty
For basic information regarding the explanatory notes below, please refer to chapter "Notes on analog data
values" under Continuative documentation for I/O components with analog in and outputs [} 245],
particularly for full scale value.
This guidance should be read and followed in order to save extra work, time and, presumably, money.
In-depth familiarization with these instructions will make it easy to master this technology and thus facilitate
your work.
Basic information on measurement technology:
Measuring devices are used to try to determine the true value of a measured variable, e.g. ambient
temperature, with the amount of effort put into this varying. For various practical reasons this cannot be
performed conclusively. Depending on the work involved, the measurement/measured value is subject to a
random measuring error that cannot be eliminated. With its practically determined specification data,
Beckhoff provides an approach that can be used to calculate the residual measurement uncertainty in the
individual case. The following paragraphs elucidate this.
General notes
No special maintenance required, although an annual inspection is recommended for the box module.
If a factory calibration certificate is available for the device, a one-year recalibration interval is recommended,
unless otherwise specified.
Notes regarding the specification data:
• Measurement specifications are usually specified as "% of nominal full scale value" = "% full scale
value (% )", unless otherwise specified.
FSV
• With regard to an individual value, "typical" means that on average, this parameter has the specified
value. For individual Box modules, the parameter may deviate from the typical value. Current
consumption is an example of this.
• In the context of a limit (parameter is typically max./min. X) or with two limits (parameter is typically
between X and Y), "typical" means that this parameter predominantly between the limits for the
individual Box modules. However, deviations may occur: see confidence level. Noise is an example of
this. Usually, no measurements are taken, in order to be able to make statements about standard
deviations or result frequencies. A typical value is usually indicated with the abbreviation "typ." after the
unit.
• The confidence level is 95%, unless otherwise specified.
• When operating in EMC-disturbed environments, twisted and shielded signal cables which are
grounded at one end, at minimum, must be used in order to comply with the specification. The use of
Beckhoff shielding accessories ZB8511 or ZS9100-0002 is recommended:
EPP3504-0023 Version: 1.2
Product overview
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