Sea-Bird Electronics SBE 45 MicroTSG, User Manual, Page: 20 / 143

Section 2: Description of MicroTSG SBE 45
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Baud Rate, Cable Length, Power, and Data Transmission Rate
Baud Rate, Cable Length, and Data Transmission Rate
The rate that data can be transmitted from the MicroTSG is dependent on the
amount of data to be transmitted per scan and the serial data baud rate:
Time to transmit data =
(number of characters * 10 bits/character) / baud rate
where
Number of characters is dependent on the included data and output
format (see
Data Output Format in Section 4: Setting Up MicroTSG ).
Add 2 to the number of characters shown in the output format, to
account for the carriage return and line feed at the end of each scan.
Include decimal points, commas, and spaces when counting the
number of characters.
Note that the MicroTSG transmits data
after it has completed the previous
sample and before it starts the next sample. See Sample Timing above for
information on sampling time.
The length of cable that the MicroTSG can drive to transmit real-time data is
also dependent on the baud rate. The allowable combinations are:
Maximum Cable Length (meters) Maximum Baud
800 1200
400 2400
200
4800 (factory set default)
100 9600
50 19200
25 38400
Notes:
•
Baud rate is set with Baud= .
•
Real-time output rate is set
with Interval= .
•
Output format is set with
OutputCond= , OutputSal= , and
OutputSV= .
See Command Descriptions in
Section 4: Setting Up MicroTSG for
command details.
Example –
What is the minimum transmission time over 100 m of cable with
OutputCond=Y , OutputSal=Y , OutputSV=Y , and
OutputFormat=0 ?
With 100 meters of cable, the MicroTSG requires a baud rate of 9600 or less.
Number of characters (from
Data Output Format in Section 4: Setting Up MicroTSG ) =
8 (T) + 2 (comma & space) + 8 (C) + 2 (comma & space) + 8 (salinity) + 2 (comma & space) + 8 (sound velocity)
+ 2 (carriage return & line feed) = 40
Time required to transmit data = (40 characters * 10 bits/character) / 9600 = 0.042 seconds = 42 msec
What is the minimum
total time required per sample ( Interval= ), if averaging 4 measurements/sample ( NCycles=4 )
and operating in Autonomous Sampling Mode?
In Autonomous mode, time to acquire T and C (from
Sample Timing above)
= ( NCycles * 0.1336) + 0.287 = (4 * 0.1336) + 0.287 = 0.82 seconds
Total sampling time
= time to acquire T and C + time to compute parameters (from
Sample Timing above) + time to transmit data
= 0.82 + (.0088 + .0154 + .083 + .035) + .042 = 1.00 second
Therefore, set
Interval=1 , transmitting 1 sample every second.
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