4.21History recorder

The History Recorder stores the readings of KNX, Modbus and Zigbee values on the gateway over time. The Graph object draws them. This page lists every field of the recorder and its dialog.

#What it does

You define recorded values. Each one is tied to a KNX group address or to a Modbus or Zigbee value, and has its own rules for when to store a sample and how long to keep old samples. The gateway writes the samples to its own storage and serves them to the apps when a Graph is opened. The recorder publishes no live System Object: a Graph series picks a recorded value by name.

#Before you enable it

• The service is Disabled by default. A recorder that is not enabled stores nothing. Turn Enabled on and deploy the project (see Deploying to a gateway).
• A KNX value is recorded only while the gateway sees telegrams for its group address. Check the address in the KNX engine first.
• For Modbus values, add the device and datapoints first (see Modbus devices and datapoints). Zigbee values come from the devices on the Zigbee gateway.
• History starts when you deploy. It cannot be filled in for earlier dates.

#Settings

#History Recorder Values dialog

The list has Add, Clone, Remove, Up and Down. Import and Export in the header save and load the list as history-recorder-values.json. Importing replaces the whole list, and a file the Configurator cannot read is ignored without a message. Cancel and Save Changes only close the dialog.

#Retention

Five rows control what happens to samples as they get older. Each row has an Action and an Interval in minutes (the interval is only used by the two average actions).

The actions are Keep all values, Discard values (the day is deleted), Simple average per interval and Weighted average per interval (one sample per interval, averaged over time).

#How it works on the gateway

• Once a second the gateway looks at the latest value of every recorded value. It uses the latest value it has seen for the group address, or the latest published Modbus or Zigbee value.
• The first reading is always stored. After that the trigger decides. On every value update stores when the value differs from the last stored one. The threshold triggers compare against the last stored value in percent. If that value was 0, any next reading counts as a change, so a value sitting at 0 is stored every second until it moves.
• Value to store decides what the sample contains. Rate of change is the change per second since the last sample. Accumulated value is the reading multiplied by seconds, added up since the gateway started. The two averages use all readings since the last sample.
• Samples go to one file per recorded value per day and are written to storage every few seconds. A day holds at most about 86,400 samples per value.
• Retention runs once a day. A day older than 1 day, 7 days, 30 days, 182 days or 365 days gets the action of the matching row, and a day passes through every row it has reached.
• The apps ask the gateway for a recorded value by range: Day, Week (7 days) or Month (31 days) ending on a chosen date.

#Example

Record the living room temperature for a Graph:

1. Enable the recorder. Add a recorded value: Name Living room temperature, Unit of measure °C, Multiplying factor 1, Source KNX, Type DPT 9.001, KNX group 2/1/5.
2. Set Store trigger After a fixed interval, Interval (seconds) 300, Value to store Last received value. Leave the retention rows at their defaults.
3. Deploy. Add a Graph object and press Add Series, then choose Living room temperature. See Graph.

#Tips and common problems

• The Graph says there is no recorded data: the recorder is not enabled, the project has not been deployed, or no telegram has reached the group address since the gateway started.
• A value is 10 times too big or small: set Multiplying factor. The Graph has no factor of its own.
• Choosing a very short interval: it multiplies the data stored. Use the longest interval that shows what the customer needs.
• Zigbee and Modbus lists are empty: configure the devices first. Other System Objects, such as Network I/O values, cannot be recorded here.

#See also

• Graph
• Modbus devices and datapoints
• Zigbee
• KNX engine