Delta-T Devices SunScan SS1 User Manual page 45

Beam Fraction Sensor Handling in the Field
The Beam Fraction sensor is definitely recommended for taking most
types of readings, however the extra cable connection to the standard
SunScan probe does add an unwelcome practical complication!
Use of the BF5 radio link may be preferable
See also SunScan System Radio Link User Manual
Using the tripod
The BF5 has a tripod mount, which will probably be the most convenient
mounting method to use above low field canopies (up to about 1.8 m
high). If you are working with canopies higher than this, you will need to
devise an alternative mounting method.
Levelling the BF5
The BF5 is equipped with a miniature bubble level. The tripod supplied
has 3-axis adjustment to facilitate levelling.
It is more important to level the BF5 accurately than the probe.
Extension cables, and the location of the BF5
Extension cables of 5, 10 and 25 m can be fitted between the BF5 and
SunScan, to extend your range of operation from the BF5. There is a
trade-off between range and convenience: the greater your range, the
fewer times you need to re-site the BF5, but the more time you are likely
to spend handling the cable.
Extension cables can be joined together. A combination of two shorter
cables may be preferable to one long one.
If connected by cable SunScan will read the BF5 and probe
simultaneously.
If the different locations are widely spaced apart, the light levels could
momentarily be different - cloud shadows can easily travel at 20 m.s-1.
If connected by radio the BF5 signal is read up to 3 seconds before the
probe reading is made.
The solution is to be aware of this in fast changing conditions and avoid
taking readings at critical moments.
Very long cable lengths may introduce a small systematic error in BF5
readings.
Up to 100 metres, this should not be significant (< 10 μmol.m-2.s-1).
At 200 metres it could add about 20 μmol.m-2.s-1 to the readings, which
may need subsequent adjustment.
What to Measure and How  45
SS1 User Manual v3.3