Campbell CS230, Руководство по эксплуатации продукта

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CS230/CS231 Temperature Profiler
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8.1.2 Metadata
Every temperature point in a probe includes the following metadata, which can
be retrieved using the aR1! SDI-12 command. This information can be used to
identify details of the temperature probe and its individual temperature points.
TABLE 8-3. Metadata Details
Name Value Range Description
Serial
Number
0 to 65534
The serial number that is unique to each probe
unit.
Location
Number
1 to 255
Each temperature sensor within a probe is
assigned its own unique location number
which by default is in relation to the SDI-12
address (see TABLE 8-2 ).
Depth
Value
0 to 65535 cm
The distance values in centimet
re
s (cm).
These are intended to reflect the profile
distances. Typically, the top most temperature
point would be designated as 0 cm and if the
next temperature point below was 10 cm
away, then its distance value would be 10 cm.
Users may designate other starting values.
These can be configured at the time of
ordering.
8.2 Long Cables
As the measurement data is transferred between the temperature profiler and
data logger digitally, there are no offset errors incurred with increasing cable
length as seen with analog ue sensors. However, with long enough cable lengths,
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 61 m (200 ft), but we are
able to exceed this limit by:
•
Using low capacitance, low resistance, screened cable
•
Ensuring that the power ground cable has low resistance and is
connected to the same ground reference as the data logger control or
U terminals
8.3 Power Conservation
The CS230/CS231 draws less than 1 mA of current per sensor between polling
sessions from its 12 V supply. In many applications, this is minimal compared
to overall system power use, so the sensor can be permanently powered to
avoid the warm-up period.
In low power applications, you can switch the power on a minimum of
10 s (allowing for the warm-up period) before polling the CS230/CS231. This
switching can be achieved in different ways depending on the type and model
of your data logger. If available, the switched 12 V output of the data logger
can be used.