- Rain Gauge - The rain gauge is mounted atop the
CFHT/Gemini weather tower.
- Operational concept:
- The Rain Gauge receives precipitation and funnels
the liquid into a small "vessel". Each time it fills this vessel,
the unit "tips" and triggers a momentary closure of a
switch. This switch triggers the input pin of a 24 volt input
module. Each of these pulses are equal to 0.01" of
rainfall. The PLC at the tower counts these values and adds them
for a total, daily rain fall.
- The Weather PLC in the control room reads the data
from the Weather Tower PLC. At 23:59.59 of each day, the PLC
copies the data into its corresponding day and then clears the register
so the PLC can start "counting" rain fall for the next day.
- Wiring:
- There are two connections for the rain
gauge. These are the "heater" and "signal" cables.
- AC Power provides power to a heater. The
AC power is brought up from the junction box at the base of the tower
through a conduit. The heater is plugged into this AC power at
the top of the tower in the junction box.
- Signal:
- Signal Path:
- The PLC provides 24 volts from the PLC
cabinet, through a conduit down to the junction box at the base of the
tower. The 24 volts goes from this cabinet up through another
conduit to the top of the tower. The 24 volts sits on one side of
the switch. Each time the switch closes, it sends 24 volts down
the other wire and eventually into the PLC module to be read.
- A3 - +24Volts - From PLC cabinet
- Red Wire.
- A4 - Signal pulse - Black
Wire (cable) - Black Wire (at terminal strip A4) - White Wire (cable to
PLC).
- Novalynx Tipping Bucket Rain Gauge Model
260-2500E-12 - User's
Manual
- Data (Inches of rain):
- F30:0 - Today's accumulated rain value.
- F30:1 - Sunday's accumulated rain value.
- F30:2 - Monday's accumulated rain value.
- F30:3 - Tuesday's accumulated rain value.
- F30:4 - Wednesday's accumulated rain value.
- F30:5 - Thursday's accumulated rain value.
- F30:6 - Friday's accumulated rain value.
- F30:7 - Saturday's accumulated rain value.
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Rain Gauge