CSAT3B Three-Dimensional Sonic Anemometer
15
(p. 20)
) for each communication type and data rate should be
followed.
Because CPI communications can support longer network cable lengths, it is
generally recommended as the communication method for sensor networks.
For more detailed information on network topologies and limits on cable
lengths for CPI networks, see the white paper titled
Designing Physical
Network Layouts for the CPI Bus
5.2.4.1 Power/SDM Splitter
The Power/SDM splitter (pn 30293) has three 6-pin M16 connectors. The
splitter, shown in FIGURE
, allows connection at the
Power/SDM
port on
the back of the CSAT3B block to two CSAT3BCBL1 or CSAT3BCBL2
cables. The splitter is IP68 rated, meaning it is dust and watertight. It is used
for daisy-chaining multiple CSAT3Bs in series. A Power/SDM Splitter is
required for each CSAT3B in the daisy-chain (regardless of communication
method used) except for the terminal one.
FIGURE 5-9. CSAT3B Power/SDM splitter
5.2.4.2 CPI/RS-485 Splitter
The CPI/RS-485 splitter (pn 30294) has three 8-pin M16 connectors. The
splitter allows connection at the
CPI/RS-485
port on the back of the CSAT3B
block to two CSAT3BCBL3 cables. The splitter is IP68 rated. It is used for
daisy-chaining multiple CSAT3Bs in series that use CPI or RS-485
communications. A splitter is required for each CSAT3B in the daisy-chain,
except for the terminal one. For a daisy-chain of CSAT3Bs using SDM
communications, the CPI/RS-485 splitter is not needed. Only the Power/SDM
(p. 15)
) is needed.
Transient voltage drop is commonly caused by the large series inductance
introduced by either long power cables, multiple CSAT3Bs connected by
splitters, or a combination of both. Because the measurements are
synchronized, multiple CSAT3Bs connected to the same power cable each
draw a pulse of current at the same moment. This has a cumulative effect on
the voltage drop. If the voltage drop is sufficiently large, then the low-voltage
detection circuit inside the CSAT3B sensor can be tripped which forces the
device to reset. A power cable compensation plug for the CSAT3B (FIGURE
) is needed if voltage drop creates problems. The plug is compatible with
all CSAT3Bs. The plug should be placed on the final Power/SDM splitter in
the CSAT3B daisy-chain, farthest from the power supply.