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16
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.
The u indicates the units of the measurement. When u is 0, the value has units of mB(hPa). When u is 1,
the units are inches of mercury ("Hg). When u is 9, the units depend on a user entered slope and offset. u
can also take on additional values if a station elevation offset has been entered The following table
summarizes all the values of u.
0
units are mB (hPa)
1
units are "Hg
2
units are kPa
3
units are mmHg
4
units are Atm
5
units are psia
9
units depend on user-entered scale and offset.
If the station elevation offset is non-zero, then one of the
following values of u will be returned:
10
units are mB + station elevation offset
11
units are "Hg + station elevation offset
12
units are kPa + station elevation offset
13
units are mmHg + station elevation offset
14
units are Atm + station elevation offset
15
units are psia + station elevation offset
19
user units with non-zero station elevation offset
(mB + elevation offset)
user scale + user offset
set by XE or XS
Set by XUU
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 Concurrent Measurement with CRC-16 (CC command)
The command to tell the ACCUBAR
®
to make a concurrent measurement with CRC-16 check on the data
is:
aCC!
where a is the address character, and CC is the command to
make a concurrent measurement with a CRC-16 check on the
returned data
The 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
