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Installation of a UPS I/O dry contact card on the Ethernet-based monitoring device

Didactum's monitoring systems are equipped with inputs for dry contacts. A dry contact is also known as a potential-free contact or simply a dry contact. In simple terms, a potential-free contact is a relay with two possible switching states: Normally Open (NO) or Normally Closed (NC).

Dry contacts transmit status and fault messages to Didactum's Ethernet-based monitoring device. The Didactum monitoring device then sends notifications and alarms via email and/or SMS (via GPRS/GSM modem or email-to-SMS gateway). Additionally, messages can be sent as SNMP traps to building or network management solutions (e.g., Nagios or PRTG). The networked monitoring systems also support SNMPwalk functionality. This function queries the available potential-free contacts/dry contacts at timed intervals via a TCP/IP network.


Dry contacts are transmitted via a TCP/IP network. The Didactum monitoring device can also automatically execute actions such as switching 12V relay outputs via its actuator function. All events are recorded in the Didactum monitoring device's syslog database, including the time and date.

Fig.: This shows the underside of the UPS Dry Contact card. The description of the potential-free I/O contacts is shown at the very bottom.
Fig.: Below you see the I/O contacts of the UPS management card.

Connect two-wire cables to the dry contact terminals to be monitored.

The exact pin assignment can be found in the manual for your UPS dry contact management card.
Fig.: Here you see the Ethernet-based 500 II monitoring device including the expansion board.

The outputs of the UPS Dry Contact card are connected to the potential-free inputs (DRY CONTACTS (IN)).
Fig.: In the monitoring device's web interface, you can configure each individual dry contact input.

Set the name and define the normal state (normally open / normally closed) of the fault signaling contact.
Fig.: In the monitoring device's web interface, you can configure each individual dry contact input.

Set the name and define the normal state (normally open / normally closed) of the fault signaling contact.
Fig.: With the Dry Contact expansion unit (part no. 14028), the 500 II monitoring device can monitor up to 64 additional dry contacts via an Ethernet network.

Integrate existing emergency power systems, generators, sprinkler systems, air conditioning systems, video surveillance systems, CO2 extinguishing systems, alarm systems, etc., into the 24/7/365 network monitoring of the 500 II monitoring system.

Connections of the combined sensor

Here we will show you how to connect the AS-400 dry contact card for UPS systems to the Didactum Monitoring System 500 II. Using the potential-free relay contacts of the UPS dry contact board, the following information, among others, is transmitted to the Monitoring System 500 II:

  • UPS battery operation
  • UPS failure
  • UPS collective alarm (UPS running on battery / UPS battery charge level / internal UPS error)
  • UPS running in bypass mode
  • UPS running on battery

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