Counting inputs

The M700 (older version, not supplied anymore – 2 counting inputs) and M710 (four counting inputs) modules have fast pulse counting inputs for potential-free contacts with maximum input frequency 50 Hz. Minimum ON time is 10 ms. The module provides 12 V DC at the CNTx terminals, which should be brought back through the counting contact to the COM terminal.

The module has an  internal battery which backups the counter, so that the counted values are retained even when the power is off.

Some of the meters (pulse modules of gas meters, electrical meters etc.) do not have reed relays, and use open collector transistors together with protecting resistors. For correct functionality they need slightly higher operating voltage, typically 24 V DC. The  M710 may be supplied with a 24 V DC/DC converter. Please note it in the project and when ordering, e.g. „M710 (24V contact)“.

0213_counting_input
Connection of a counting input 

M700 and M710 contain auxiliary variables for peak shaving function (E-Max). It is possible to read cumulated value for the last 15 minutes, cumulated value for the current 15 minutes, and running time of the measuring interval (typically 0…900 s). These variables are used in the SoftPLC E-Max function block. CNT1 must be connected to the energy meter pulse output, CNT2 to the 15 min. synchronisation output.

If there are M-Bus communicative emters in the system, it is advisable to use pulse to M-Bus converters (Relay PadPuls, Siemens AEW…) rather than M710. The converters are then integrated together with the regular M-Bus meters over a M-Bus converter M095 or M096. For the E-Max functionality, M710 is necessary because of its short response time and internal variables.

If the I/O modules have been assigned to the buses, the next step is to specify the system topology.