Specifications

Section 11. Programming Resource Library
11-26
11.3.6 SDI-12 Power Considerations
When a command is sent by the datalogger to an SDI-12 probe, all probes on
the same SDI-12 port will wake up. Only the probe addressed by the
datalogger will respond, however, all other probes will remain active until the
timeout period expires.
Example
Probe: Water Content
Power Usage:
Quiescent: 0.25 mA
Measurement: 120 mA
Measurement Time: 15 s
Active: 66 mA
Timeout: 15 s
Probes 1, 2, 3, and 4 are connected to SDI-12 / Control Port 1.
The time line in TABLE 11.3-2 shows a 35 second power usage profile
exam
ple.
TABLE 11.3-2. Example Power Usage Profile
for a Network of SDI-12 Probes
All Time
Probes Out
milliAmps
Total
Sec Command Awake Expires 1 2 3 4 mA
1 1M! Yes 120 66 66 66 318
2 120 66 66 66 318
• • • • • •
• • • • • •
• • • • • •
14 120 66 66 66 318
15 Yes 120 66 66 66 318
16 1D0! Yes 66 66 66 66 264
17 66 66 66 66 264
• • • • • •
• • • • • •
• • • • • •
29 66 66 66 66 264
30 Yes 66 66 66 66 264
31 0.25 0.25 0.25 0.25 1
• • • • • •
• • • • • •
• • • • • •
35 0.25 0.25 0.25 0.25 1