Vaisala Hydromet Data Collection Platform - Manual (Page 112)

User's Guide ______________________________________________________________________
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Data Acquisition Methods
In general, there are two alternate methods to connect a serial sensor to
the QML logger:
1. Automatic transmission
- Device transmits the measurement results automatically
- Only one device per serial port
- Physical connection can be RS-232 or RS-485
- Higher data throughput
2. Polled transmission
- QML logger polls periodically for measurement data
- Allows multiple sensors per serial port providing that all
devices have the RS-485 interface and support multi-device
operation
- Can also be used for a point-to-point connection with RS-232
or RS-485
- Lower data throughput
Typically, sensors with high data output rate, such as wind sensors,
should use automatic transmission with only a single connected device
per serial line.
Sensors that produce new measurement data only a few times per
minute can use polled transmission, and multiple devices can be
connected to the same RS-485 line.
Configuring Serial Line Parameters
NOTE The QML logger does not perform any automatic configuration of the
connected sensors. You have to perform the configuration and store it
manually by using the sensor's own service interface.
For sensors without a human-readable command interface, extra QML
logger shell commands are provided. For further information, refer to
detailed sensor interface descriptions or separate Technical
References.