Campbell CR310 - Page 157

Power Usage:
l
Quiescent: 0.25 mA
l
Active: 66 mA
l
Measurement: 120 mA
Measurement time: 15 s
Timeout: 15 s
Probes 1, 2, 3, and 4 are connected to SDI-12 port C1.
The time line in the following table shows a 35-second power-usage profile example.
For most applications, total power usage of 318 mA for 15 seconds is not excessive, but if 16
probes were wired to the same SDI-12 port, the resulting power draw would be excessive.
Spreading sensors over several SDI-12 terminals helps reduce power consumption.
Table 19-2: Example power use for a network of SDI-12 probes
Time into
measurement
processes
Command
All
probes
awake
Time out
expires
Probe
1 (mA)
Probe
2 (mA)
Probe
3 (mA)
Probe
4 (mA)
Total
(mA)
Sleep    0.25 0.25 0.25 0.25 1
1
1M!
Yes  120 66 66 66 318
2–14    120 66 66 66 318
15   Yes 120 66 66 66 318
16
1D0!
Yes  66 66 66 66 264
17-29    66 66 66 66 264
30   Yes 66 66 66 66 264
Sleep    0.25 0.25 0.25 0.25 1
19. Communications protocols141