Delta SS1-UM-1.05 User Manual download pdf (Page 75)

SunScan User Manual v 1.05 Appendices •

••

• 75

B. Logging the Beam Fraction sensor

You can log the Beam Fraction sensor in a similar manner, using the (optional)

special logging cable for it. Two outputs are available, corresponding to the Total

incident PAR and Diffuse PAR photodiode readings.

Be aware that the shade ring elevation may need readjustment after an hour or two.

Also, that separately logged incident PAR readings cannot at present be merged

with probe readings of transmitted PAR to give LAI estimates using the SunScan

mathematical model.

Wiring connections

The Beam Fraction sensor logging cable plugs into the BFS cable connector, giving

up to 12 metres distance from the logger. 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 BFS 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 Total PAR signal output

positive

Input channel +, for Total PAR

grey LO Common signal output

negative

Input channels - common negative

blue HI Diffuse PAR signal output

positive

Input channel +, for Diffuse PAR

braid Screen Frame earth, or 0V

Note: the grey and green are connected internally in the BFS case. The braid is not

connected to any other core.

Output

• The output signals are the Total and the Diffuse PAR irradiance.

• The millivolt outputs are linear, with a sensitivity of 1 mV = 1 µ

µµ

µmol.m

-2

-1

Maximum output is dependent on the supply voltage, and can exceed 2500 mV.

Logger requirements

• The BFS requires a voltage supply of 5-15 V dc (unregulated), at about 1 mA

current.

Warning! Pre-Release Beam Fraction sensors require a regulated voltage supply of

5 V dc (

±±

0.25 V). Refer to Delta-T if you are uncertain about this.

• Configure two logger channels 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). Outputs will be stable after 10 ms.

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Delta SS1-UM-1.05 User Manual Page 75

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