User manual

User Guide
For other applications the CS215 can be installed in any orientation. Install it
away from obvious sources of heat, including solar radiation.
NOTE: It is best to protect the filter at the top of the sensor from
direct exposure to liquid water as whilst the hydrophobic nature of
the filter will repel light rain, driving rain can force itself into the
pore structure of the filter and then take some time to dry out.
4. Wiring
The CS215 can be used with all Campbell Scientific and most other dataloggers
that support the SDI-12 protocol. Wiring colours and connections between the
sensor and a datalogger are shown in Table 1.
Table 1 Cable Connections
Cable Description Connection to
Datalogger
Red 12V supply 12V
White & Black Power ground G
Green SDI-12 signal Control port or dedicated
SDI-12 port (CR5000)
Screen Power ground G
To use more than one probe per datalogger, you can either connect the different
probes to different SDI-12 compatible ports on the datalogger or change the
SDI-12 addresses of the probes and let them share the same connection. Using the
SDI-12 address minimizes the use of ports on the datalogger and also allows
probes to be connected in a “daisy-chain” fashion which can minimize cable runs
in some applications. (However, see below for limits on the total cable length.)
There are two ways to set the SDI-12 address of the CS215:
• By sending the required commands to the sensors via an SDI-12
recorder/datalogger that allows talk through to the sensor.
• By loading a program into the recorder that sends the required commands –
see section 6 below.
4.1 Long Cables
As the measurement data is transferred between the probe and datalogger digitally
there are no offset errors incurred with increasing cable length as seen with
analogue sensors. However, with increasing cable length there is still a point
when the digital communications will break down, resulting in either no response
from the sensor or corrupted readings. The original SDI-12 standard specifies the
maximum total cable length for the cable as being 200 feet (61 metres). In practice
even longer cables than this can be used, but to ensure proper operation with long
cables follow these guidelines:
• Use low capacitance, low resistance, screened cable (as fitted by Campbell
Scientific). With such cable, distances of several hundred metres to the
sensor are possible.
• Ensure that the power ground cable has low resistance and is connected to
the same ground reference as the datalogger control ports.
• Be aware that “daisy chaining” sensors reduces the maximum cable length
roughly in proportion to the number of sensors connected in parallel.
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