What has to be considered when connecting an energy meter with pulse output to a PLC?

The pulse output of energy meters is standardized in EN 62053-31 or DIN 43864 and has the following timing:

• In order to detect the pulses by simple means the ON state should be as long as possible, the limitation is given by the set pulse rate. At high pulse rates and full load, the ON state must be short enough so that the minimum time for the OFF state can still be observed.

• If the shortest permissible ON state of 30ms is selected and this signal is sent to a digital input card of a controller, this can lead to problems with pulse detection in some controllers with long cycle times and high program volumes. A remedy is often to select an ON state of 100 ms or longer.

• With oversized converters or networks, it may now be necessary to work with high pulse rates in favor of better resolution. Due to the lower load, the pulse train will be low enough that the ON state can also be longer than restricted by full load. In these applications, however, it must be ensured that the load on the network generally remains below the upper limit specified by the timing.