GHM Delta OHM HD52.3D Series, Руководство по эксплуатации

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HD52.3D…
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V2.2
9 NMEA MODE
NMEA protocol, mainly used in the nautical field and in satellite-based navigation systems,
specifies that only one of the devices connected can send data, while the others can only act
as recipients.
In NMEA mode, the instrument sends automatically the acquired measurements at regular in-
tervals. The interval is factory-set to 1 second and can be configured within 1 and 255 sec-
onds. To change the interval you should access the configuration mode and send CU4Rnnn
command, where nnn indicates the interval value in seconds (see chapter 6 “CONFIGURATION”
for details regarding the setting of operation parameters).
This mode is available with RS232, RS485 and RS422 serial connections. Communication pa-
rameters should be set in the PC or data logger as follows:
 Baud rate: same as the setting in the instrument (default = 4800)
 Data bits: 8
 Parity: same as the setting in the instrument (default = None)
 Stop bits: same as the setting in the instrument (default = 1)
The instrument is compatible with NMEA 0183 V4.00 protocol.
The protocol establishes that data are sent in the following format:
$<Prefix>,<Data>*<hh><CR><LF>
with <Prefix> = field consisting in 5 alphanumeric characters: the first two indicate the type
of transmitting device, the other three indicate the type of transmitted data
<Data> = values measured by the instrument, separated by commas
<hh> = checksum, consisting in two hexadecimal characters
<CR> = character ASCII Carriage Return
<LF> = character ASCII Line Feed
The checksum is calculated by performing the exclusive OR of all characters ranging within $
and * symbols. The 4 most significant bits and the 4 less significant bits of the result are con-
verted in hexadecimal. The hexadecimal value corresponding to the most significant bits is
transmitted as the first.
The instrument regularly sends a string in the following general format requested by the proto-
col:
$IIMDA,x.x,I,x.x,B,x.x,C,x.x,C,x.x,x.x,x.x,C,x.x,T,x.x,M,x.x,N,x.x,M*hh<CR><LF>
Barometric pressure, inHg (mercury inches)
Barometric pressure, bar
Air temperature, °C
Water temperature  not measured, empty field
Relative humidity, %RH
Absolute humidity, g/m 3
Dew Point, °C
Wind direction with respect to geographic North, degrees
 not available, empty field
Wind direction with respect to magnetic North, degrees
Wind speed, knot
Wind speed, m/s