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FIGURE 4-12. CSAT3BH power cable compensation plug
The primary indicator of low voltage is in the diagnostic flags returned by the CSAT3BH to the
data logger. Flag number 32 (0x0020) indicates detection of a low-voltage condition. If the
instrument returns flag 32, first measure the power source voltage and ensure that its DC value
meets specifications. If that value is appropriate, the voltage at the far end of the cable should be
checked. This must be tested under load so a splitter at the end of the cable will be required to
measure the terminal voltage. These two tests will eliminate the DC voltage as the source of the
problem. Any DC voltage below 12 V at the sensor would be suspect for susceptibility to droop.
In larger systems, even DC voltages of 13 to 15 V can still experience enough droop to trigger the
detection under the right conditions. Power systems of 24 V are very unlikely to experience
enough droop to observe this problem. If the DC case checks out but the flag is still observed,
then the system would probably benefit from the addition of a power compensation plug
(
(p. 15)).
4.2.4.3 HUB-SDM8
The HUB-SDM8 (shown in
(p. 16)) allows up to six SDM devices (typically, one data
logger and multiple SDM sensors) to be connected in parallel. In the case of the CSAT3BH, up to
five CSAT3BHs, or CSAT3BH daisy chains using CSAT3BCBL1 cables, may be connected to the
HUB-SDM8. In cases where multiple CSAT3BHs are installed some distance from the data logger,
the HUB-SDM8 can be placed near the CSAT3BHs with a single SDM cable extended from the
hub to the data logger. This decreases the total network cable length, which limits signal
attenuation.
The HUB-SDM8 has eight terminal strips and features spring-loaded guillotine terminals for easy
wiring. It comes in a watertight enclosure and includes a U-bolt for mounting to a vertical pipe or
mast. An SDM cable (CABLE5CBL-L; see
(p. 16)) should be ordered to
connect the HUB-SDM8 to a data logger and a power supply.
CSAT3BH Three-Dimensional Heated Sonic Anemometer
15