measurement command and others require that multiple measurement commands
be given.
In the case of the devices that return more than one reading to a single measure
command, the “SDI-12 Param” specifies which of the sensor readings returned by
the SDI-12 device to use. Setting the parameter to 1 tells MONITOR to use the
first value returned from the device; setting parameter to 3 tells MONITOR to use
the third value returned from the device. If more than one parameter needs to be
measured, a different measurement needs to be set up for each parameter. These
measurements should have identical setups, except for the “SDI-12 Param”. Be
sure to keep the measurement time and interval the same for these measurements.
If you vary the time and interval, MONITOR will end up taking multiple sensor
measurements even though one would have sufficed (thus slowing down the
system and using more power). Also see how to read
multiple parameters from
the same sensor
.
In the case of devices which require multiple commands to be issued (e.g. 0M1!
Retrieves pressure, 0M2! Retrieves temperature) multiple measurements need to
be set up. It does not matter if these measurements are scheduled for the same
time, as MONITOR will have to issue multiple commands to the sensors.
When multiple measurements of type SDI-12 are scheduled to go at the same
time, MONITOR orders the measurement commands so that concurrent
measurements are commanded first. Non-concurrent measurements occur while
waiting for concurrent results. Also, MONITOR is able to recognize when two
different measurement schedules rely on data from a single measurement
command (e.g., measurement 1 commands “0M!” and expects parameter 1 while
measurement 2 commands the same and expects parameter 2, both scheduled at
the same time). In such cases, MONITOR outputs the measurement command
only once.
Analog
Analog measurements involve reading a voltage or current provided by a sensor.
Analog sensors come with instructions that provide information on how to
translate the output voltage into desired units. Translating the analog sensor
output into environmental units can be done via slope and offset for simple
sensors, and via equations for non-linear sensors.
Analog Type
This setting directs the input channel to which the sensor should be connected and
the type of analog measurement to make. These options are available
•
0-5V A
•
0-5V B
•
Diff C
•
Diff D
•
4-20 mA
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