Data collection methods

The OPC-DA collector has 2 methods to collect measurement data, which are referred to as the collection type of a measurement.


Polled measurements are read every x milliseconds (minimum of 1000ms), which is the collection interval. This data collection method should be used for measurements for which the value changes regularly over time. Configure the interval depending on how frequent you want to collect data points for this measurement.


Monitored measurements collect data on every change of the measurements value. This data collection method polls the measurement at the minimum interval and notifies the collector whenever a change occurs. Typically, monitored measurements are configured for boolean or string data types that indicate an equipments state, f.e. for a valve that opens and/or closes only a few times per hour.

Collector health

OPC-DA Specific collector health messages. See here for all generic collector health messages.

You can find the collector health and the collector health history in the detail view on the right, when selecting a collector in the historian admin webpage.

Collector health history

Error initializing OPC-DA client

An error occurred while trying to initialize the OPC-DA client. This indicates that a collector setting hasn’t been configured correctly or that the OPC-DA server isn’t reachable during initialization.

OPC-DA server unavailable

The OPC-DA client lost connection with the OPC-DA server.