Campbell Scientific 255-100 Novalynx Analog Output Evaporation Gauge - Manual (Page 13)

255-100 Novalynx Analog Output Evaporation Gauge
between 8 1/2” and 9 1/2” (depending on water pressure). The Electronic
Water Timer will enable tank filling at a user set time and interval.
If more precise fill control is wanted, program the datalogger to control a
solenoid valve in a fill line that’s connected to a water supply. A second
solenoid may be used for draining the pan in areas of high rainfall. Power
requirements need to be taken into consideration when using a solenoid valve.
8. Recommended Solenoids
Solenoid for clean water only — ASCO p.n. 8210G94
A 1/2”, 12 VDC solenoid.
Solenoid for acidic water — ASCO p.n. SC827012E
A 1/2” 12 VDC solenoid with a plastic valve that can handle up to 40%
sulfuric acid. Acidic water also requires plastic pipes.
Use 1/2 inch inside diameter NPT fittings. 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.
The solenoid cannot be powered by the switched 12 volts of the
datalogger. CSI part number 7321 Crydom Relay is
recommended for this purpose. Mount this in the enclosure and
run the control voltages and lines (+12 V and ground) out to the
solenoid. NOTE
It is highly recommended that the solenoids 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. NOTE
9. 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 (i.e., a hot dry summer
day).
Example
If you’re using a 48 inch diameter evaporation pan, the surface area is:
π R² = π (24”)²
= 1,809.56 in² or 11,674.56 cm²
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