Accubar SDI-12 Barometric Pressure Sensor Operations & Maintenance Manual Rev-B 30 Nov 2017
pg. 14
In most cases, you will not set up the recorder to store this units identifier. It is provided in response to
the standard measure command to eliminate confusion as to the computation used to come up with the
final value.
Making a Non-Concurrent Measurement with CRC-16 (MC command)
The command to tell the ACCUBAR
®
to make a non-concurrent measurement with a CRC-16 check on
the data is:
aMC!
where a is the address character, and MC is the command to
make a non-concurrent measurement with a CRC-16
The non-concurrent measurement with CRC-16 command was first defined in version 1.3 of the SDI-12
specification. Therefore the data recorder will have to be SDI-12 version 1.3 or higher compliant before
it can be expected to issue this command and automatically handle the reply to collect data. You can
also issue the command yourself. In reply, the ACCUBAR
®
will respond with
attt2
acknowledging it is address a and indicating that after ttt
seconds are allowed for the measurement, 2 values can be
collected.
When the measurement is complete, the sensor responds with a service request
a
where a is the address character
Note that you still do not have any data from the ACCUBAR
®
. To request the data after a measurement,
aD0!
where a is the address character and D0 is the command to
retrieve measured data. Note: the number zero follows D, not
the letter O.
In this case, the sensor will reply with two values in the format:
avuC
where a is the address, v is the data value, u indicates the units,
and C is the CRC-16 encoded into 3 ASCII characters. Both v and u
have the format of a polarity sign (
or
) followed by up to seven
digits, including a decimal point. The CRC-16 is always the last
three characters which are never a numeric digit.
