Commissioning
EL3692
122
Version: 2.1
For analog I/O devices from Beckhoff the rule is that the limit with the largest value is chosen as the full scale
value of the respective product (also called the reference value) and is given a positive sign. This applies to
both symmetrical and asymmetrical measuring spans.
Fig. 144: Full scale value, measuring span
For the above
examples
this means:
• Measuring range 0..10 V: asymmetric unipolar, full scale value = 10 V, measuring span = 10 V
• Measuring range 4..20 mA: asymmetric unipolar, full scale value = 20 mA, measuring span = 16 mA
• Measuring range -200..1370 °C: asymmetric bipolar, full scale value = 1370 °C, measuring span =
1570 °C
• Measuring range -10..+10 V: symmetric bipolar, full scale value = 10 V, measuring span = 20 V
This applies to analog output terminals
± measuring error [% of full-scale value] (also referred to as measurement deviation)
The relative measuring error is referenced to the full scale value and is calculated as the quotient of the
largest numerical deviation from the true value (‘measuring error’) referenced to the full scale value.
The measuring error is generally valid for the entire permitted operating temperature range, also called the
‘usage error limit’ and contains random and systematic portions of the referred device (i.e. ‘all’ influences
such as temperature, inherent noise, aging, etc.).
It always to be regarded as a positive/negative span with ±, even if it is specified without ± in some cases.
The maximum deviation can also be specified directly.
Example
: Measuring range 0..10 V and measuring error < ± 0.3 % full scale value → maximum deviation ±
30 mV in the permissible operating temperature range.
Note: 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.
This applies to analog output devices.
