255-100 Novalynx
Analogue Output Evaporation Gauge
11
provides the recommended solenoids for the different water types
TABLE 7-1. Recommended Solenoids
Water Type
Part Number
Description
Clean water only
ASCO pn
#
8210G94
0.5 inch, 12 Vdc
Acidic water
ASCO pn
#
SC827012E
0.5 inch, 12 Vdc solenoid with
a plastic valve that can handle
up to 40% sulfuric acid.
Acidic water also requires
plastic pipes.
Use NPT fittings with a 0.5 inch inside diameter. Mount the solenoid next to
the tank (0 psi) or next to the pan (1 psi). Use a solenoid that requires 0 psi
differential pressure.
Do not use the datalogger switched 12 V terminal to power
the solenoid. Campbell Scientific offers an SPST single-
channel solid-state relay for this purpose. Mount the relay in
the enclosure and run the control voltages and lines (+12 V
and ground) to the solenoid.
Refer to
Campbell Scientific recommends that the solenoid valves
have a power supply independent of the weather station. If
the fill tank runs dry, the solenoid could remain open for an
extended period, draining the battery.
7.3 Storage Tank Size
If a storage tank is used, you need to determine the best size of tank for your
application. You determine this by estimating the amount of water you’ll use
and deciding the number of trips to refill the tank you’re willing to make. You
can estimate the amount of water you’ll use by multiplying the pan’s surface
area by the evaporation rate of the worst case condition (hot dry summer day).
Example
If you’re using a 48 inch diameter evaporation pan, the surface area is:
π
R
2
=
π
(24 in)
2
= 1,809.56 in
2
or 11,674.56 cm
2
Assuming you refill the pan once a day and the evaporation rate is 10 mm
(1 cm) per day, the amount of water you’ll use is:
(1 cm/day)(11,674.56 cm
2
) = 11,674.56 cm
3
/day or
11.675 lit
re
s/day or 3.1 gallons/day
If you use a 125 gallon tank, you will need to refill the tank in approximately:
(125 gallons)/(3.1 gallons/day) » 40 days
CAUTION
CAUTION
