Campbell CR6 Series, Operator'S Manual

Page: 323 / 690

Section 7. Installation
323
SDI-12 Sensor Configuration CRBasic Example — Results
Measurement
Command from
SDI-12 Recorder
Source Variables
Accessed from the
CR6 acting as a
SDI-12 Sensor
Contents of
Source Variables
0M!
Source(1) , Source(2)
Temperature °C, battery
voltage
0M0!
Same as 0M!
0M1!
Source(3) , Source(4)
Temperature °F, battery
voltage
0M2! Source(5) , Source(6)
Temperature °C, battery
mV
0M3! Source(7)
,
Source(8)
Temperature °F, battery
mV
0M4!
Source(9) , Source(10)
Serial number, lithium
battery voltage
7.7.15.4 SDI-12 Power Considerations
When a command is sent by the CR6 to an SDI-12 probe, all probes on the same
SDI-12 port will wake up. However, only the probe addressed by the datalogger
will respond. 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 C1 .
The time line in table Example Power Usage Profile for a Network of SDI-12
Probes
(p. 324)
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
will help reduce power consumption.