Young Precipitation Gauge No Moving Parts Model 50202 - Manual (Page 2)

Page 1
50202-90(D)
MODEL 50202
PRECIPITATION GAUGE
INTRODUCTION
The Model 50202 Precipitation Gauge accurately measures rain or
snow precipitation without moving parts.
Durable thermoplastic construction with no moving parts offers
excellent corrosion resistance and long term reliability. Insulated
housings and thermostatically controlled heaters permit operation at
temperatures below freezing. Unique design with centrally located
capacitive sensor is unaffected by unsteady conditions: making
the instrument ideal for use on moving platforms such as buoys
and ships. For extra security in extreme conditions, Model 50222,
Heavy Duty Mounting Bracket is recommended.
Rain or snow collected in the catchment funnel is directed into the
measuring chamber; 1mm of precipitation produces a 5mm rise in
the chamber. Column level is sensed by a capacitive probe and
converted to a linear voltage signal that can be read by external
electronics. When the column level reaches a maximum of 250mm
(50mm of precipitation), the chamber automatically empties and the
process repeats. Total precipitation can be tracked by a datalogger
or recorder.
Model 50203 is unheated.
THEORY OF OPERATION
Model 50202 Precipitation Gauge collects and measures precipitation.
Unlike conventional tipping-bucket and weighing gauges the 50202 has
no moving parts. Precipitation measurement is made with a capacitive
transducer and electronic circuit that produces a calibrated voltage
output. Standard output is 0 to 5.00 VDC for 0 to 50mm precipitation
with an accuracy of ±1mm. The low power signal conditioning circuit
requires 8 to 30 VDC at 3mA. Self contained thermostatically controlled
heaters allow operation at temperatures as low as -20°C (-4°F).
Collected snow is melted and measured as rainfall equivalent. The
heaters operate from 28 volts AC at approximately 48 watts.
Precipitation is collected in a catchment funnel which has a cross
sectional area of 100 cm 2 . Captured precipitation drains from this
funnel into a measuring tube which has a cross sectional area of 20cm 2 .
Since the area of the catchment funnel is 5 times that of the measuring
tube, 1mm of captured precipitation produces a 5mm column of water
in the measuring tube. A capacitive transducer in the center of the
measuring tube senses the water column height. A self contained
electronic circuit converts the capacitance value to a calibrated
voltage output that is proportional to collected precipitation. Periodic
interrogation by a data logging system allows computation of total
precipitation and rate.
The full column height of the measuring tube is 250mm representing
50mm of collected precipitation. Additional precipitation starts a self
siphon process which empties the measuring tube in approximately 30
seconds. The water column in the tube returns to a level representing
0mm of precipitation and the voltage output goes to 0 VDC. Additional
precipitation begins filling the measuring tube again and the cycle is
repeated. Evaporation of water remaining in the measuring tube is
negligible between siphoning events.
LOCATION OF RAIN GAUGE
Precipitation measurement is greatly affected by location of the rain
gauge. Select a location that is naturally protected from gusts and
crosswinds. Avoid a site prone to contamination from debris such as
falling leaves, dirt, etc...
PRECIPITATION GAUGE SPECIFICATION SUMMARY
Threshold: 1 mm (.04 in)
Accuracy: ± 1 mm (±.04 in)
Signal: 0 to 5.00 VDC = 0 to 50 mm
precipitation
Chamber Drain Time: 30 seconds approx.
Power Requirement:
Measuring Circuit: 8 to 30 VDC unregulated
Heater: 48 Watts @ 28 VAC
Operating Temperature:
-20°C to +50°C (-4°F to 122°F)
Dimensions:
Height: 65 cm (25.6 in)
Diameter: 14 cm (5.5 in)
Catchment Dia: 133 mm (4.4 in)
Catchment Area: 100 cm 2 (60.8 in 2 )
Mounting: U-bolts fit vertical pipe 25-50 mm
(1-2 in) diameter.
Weight: 2.5 Kg (5.5 lb)
Shipping Weight: 4 Kg (9 lb)