Influence Of Operational Limits And Basic Error Limits - Siemens SIMATIC S7-300 Manual

Representation of the analog values of analog modules
5.4 Reactions of the analog modules
5.4.3

Influence of operational limits and basic error limits

Operational limit
The operational limit represents the total measuring/output error of an analog module within
the permissible temperature range, based on the module's rating.
Basic error limit
The basic error limit represents the total measuring/output error at 25 °C, based on the
module's rating.
Note
The percentile values of operational and basic error limits in the module's technical data
always refer to the highest possible input and output value within the nominal range of the
module.
Example of the determination of the output error of a module
An analog output module SM 332; AO 4 x 12 Bit is being used for voltage output. An output
range of "0 to 10 V" is set. The module is operating at an ambient temperature of 30 °C, i.e.
the operational limit applies. The technical data of the module state:
● Operational limit for voltage output: ±0,5 %
Hence, an output error of ±0.05 V (±0.5 % of 10 V) across the nominal range of the module
must be expected.
At an actual voltage of 1 V, for example, the module will then output a value in the range
from 0.95 V to 1.05 V. The relative error is ±5 % in this case.
For the example, the figure below shows how the relative error decreases as the output
value approaches the end of the 10-V range.
Figure 5-3
5-26
Example of the relative error of an analog output module
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04