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••••
Appendices
Document code: SS1-UM-1.05
Appendices
A. Logging the probe as a Linear Quantum Sensor
This application of the SunScan probe turns it into a simple Line Quantum sensor
that can be attached to a data logger. No Data Collection Terminal is used, but you
do require a data logger that can supply power to the probe when taking readings.
The Delta-T DL2e and DL3000 loggers are suitable for this purpose.
If you want to mount the probe on a tripod, a camera mount is provided in the base
of the probe handle. The probe's coiled RS232 cable is not used, and it must be
protected from moisture by enclosing it in a bag with desiccant, for example.
Note: no batteries are required in the probe for this mode, but it does not hurt to
leave them in situ.
Wiring connections
You must use the (optional) special logging cable which plugs into the socket on the
probe handle normally occupied by the Beam Fraction sensor. The cable is 10 metres
long. If you need more length, simply join on extra screened multicore cable of a
similar type. Make sure the joint is weatherproof.
The cores of the probe logging cable have the following functionality:
Core
Function
Logger Connection
orange
V+ Power supply positive
Sensor power positive (switched for warm-up)
green
0V Power supply negative
Sensor power negative (0V)
brown
HI Signal output positive
Input c
grey
LO Signal output negative
Input channel -
blue
not used
braid
Screen
Not connected (see below)
Note: the grey, green and braid are connected internally in the probe handle.
Connecting the braid to an earthing point on the logger could create earth loops, and
is not recommended.
Output
•
The output signal is the transmitted PAR irradiance, averaged along the length of
the probe. (Individual photodiode readings are not accessible in the Linear
Quantum Sensor mode.)
•
The millivolt output is linear, with a sensitivity of
1 mV = 1
µµµµ
mol.m
-2
.s
-1
.
Maximum output is 2500 mV.
Logger requirements
•
The probe requires a voltage supply of 7-15 V dc (unregulated), at about 30 mA
current. The analogue output is enabled when the external voltage is greater than
the battery voltage.
•
Configure one channel of the logger for voltage input, with the above sensitivity.
•
Use a "warm-up" time of 1 second (the logger must apply the power 1 second
before taking its reading).
•
The output voltage will be stable 120 ms after applying external power, and is
updated every 60 ms while external power remains connected.
