46 Function Description WAGO-I/O-SYSTEM 750
750-493 3-Phase Power Measurement Module
Manual
Version 1.2.0
5.4 Measuring Errors and Accuracy
The measuring errors of the I/O module are specified in the table below. The
values already take into account the errors caused by the connection method
(single-ended 0.1%) and the calibration tolerance (0.1%). They apply to the entire
temperature range of 0 to 55 °C and to frequencies of 45 to 65 Hz. Outside this
frequency range, the error is max. 2%.
750-493, 750-493/025-000, 750-
493/000-001 and 750-493/025-001
The measuring accuracy of the I/O module falls when an RMS voltage falls below
45 V. This state is called ZC limit and is displayed via the "D" LED (SAG LED).
The following conditions can also degrade the measuring accuracy of the I/O
module:
1. If only one or two phases of the three-phase supply network are connected,
higher measuring errors can occur in the voltage measurement (+0.1%).
2. In AC networks only:
If all phases fall below the ZC limit, accurate measurement of phase angle,
frequency and current are no longer possible. The measuring accuracy of all
current-depending variables (current, power, energy) falls off by 0.4%.
3. Near the ZC limit, the accuracy of the phase angle measurement decreases
to a value of ± 1.5 °.
4. If a current measuring input operates near no-load, higher measuring errors
can occur for this measuring path. Therefore, the measured current should
be min. 75 mA for 750-493 resp. 100 mA for 750-493/000-001.
For DC measurements, the error is <= 1% of the full-scale value for current,
voltage and power.
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