Jeppesen Nobeltec Solid State Heading Sensor, Руководство пользователя

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Solid State Heading Sensor (SSHS) Owner’s Manual
26
B
: Always reads “01”
C
: Message identifier (see
Table 3
)
D
: Text string (see
Table 3
)
SSHS NMEA 0183 Received Sentences
Note on NMEA 0183 Checksums
For ease of manual configuration of the SSHS via the NMEA 0183 Interface, NMEA 0183
checksums are optional. If no checksum is present in a received sentence, then the sentence
is treated as if a valid checksum were present. If a checksum is present in a received
sentence, then it is used to check the integrity of the sentence, which is accepted only if the
calculated checksum agrees with the checksum at the end of the received sentence.
To ensure the best possible data integrity, Jeppesen Marine recommends using NMEA 0183
checksums whenever possible.
RMC – Recommended Minimum Specific GNSS Data
The SSHS is capable of receiving the RMC sentence and extracting the magnetic variation
data for subsequent insertion into the appropriate fields for transmission of the HDG and HDT
sentences.
The SSHS uses an aging technique (referred to as “Variation Lifetime”) where variation data is
output in the HDG and HDT sentences for a period of 5 seconds after the RMC sentence is
received. The Variation Lifetime can be re-programmed to a shorter or longer period (see
PMARSETP on
Page 29
).
VTG – Course Over Ground and Ground Speed
The SSHS is capable of receiving the VTG sentence and computing the magnetic variation
data for subsequent insertion into the appropriate fields for transmission of the HDG and HDT
sentences. The variation is computed by observing the difference between the true course
over ground and the magnetic course over ground.
The SSHS uses an aging technique (referred to as “Variation Lifetime”) where variation data is
output in the HDG and HDT sentences for a period of 5 seconds after the VTG sentence is
received. The Variation Lifetime can be re-programmed to a shorter or longer time period (see
PMARSETP on
Page 29
).
PMAREXE – Manufacturer’s proprietary Execute Sentence
The SSHS can be commanded via this proprietary sentence to execute one of several
commands.