The example project includes a Scanners group.
The Scanners group contains the Totalflow Scanner items that connect the Point items to the Channel items.
A Totalflow Scanner can only have one sampling interval and one offset. The example database includes multiple scanners, each with their own polling rate. They are set up as follows:
- Daily history points, which can be polled at a slow rate, are attached to the ScannerDaily scanner. This scanner also polls for new events and alarms and reads and sets the clock, since none of those tasks require a fast poll rate.
- Hourly history points are connected to the ScannerHourly scanner. In the example configuration, this scanner is configured to poll twice per hour. However, because the driver will back fill data, you could configure the scanner to poll as slowly as once or twice per day.
- Trend points and current data points are connected to the ScannerCurrentData scanner. In the example configuration, this scanner is configured to poll every 30 seconds. However, because the driver will back fill data, you could configure the scanner to poll as slowly as once or twice per hour.
- Configuration points are connected to the ScannerConfig scanner. This scanner is configured to poll once per day. However, you could configure the scanner with a polling rate of 0, so that it would not poll automatically; instead, you could poll the points manually, so that they are updated on demand only. This should be sufficient, as there is no point in continuously reading the gas composition, or firmware version, when those values might not change for months at a time.
Using a single scanner on a Totalflow device would be acceptable, providing that only one sampling interval and offset were required.
Further Information