Young 50202 User Manual

METEOROLOGICAL INSTRUMENTS

INSTRUCTIONS

PRECIPITATION GAUGE

MODEL 50202 / 50203

R.M. YOUNG COMPANY 2801 AERO PARK DRIVE, TRAVERSE CITY, MICHIGAN 49686, USA

TEL: [phone] FAX: [phone] WEB: www.youngusa.com

50202-90(D)

REV: D062309

MODEL 50202

PRECIPITATION GAUGE

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

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 cm2. Captured precipitation drains from this
funnel into a measuring tube which has a cross sectional area of 20cm2.
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.

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 cm2 (60.8 in2)

Mounting: U-bolts t vertical pipe 25-50 mm

(1-2 in) diameter.

Weight: 2.5 Kg (5.5 lb)

Shipping Weight: 4 Kg (9 lb)

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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 lling 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...

50202-90(D)

INSTALLATION

CALIBRATION

The Model 50202 / 50203 is fully calibrated at the factory before
shipment, but does require care in the installation and initial priming of
the gauge. The following procedure should be followed.

1. The gauge is designed to installed on a vertical pipe mounting.
The mounting U-bolts are intended for use with ¾ inch to 1½ inch
Standard Iron Pipe Size (1.05 in to 1.90 in / 26.7 mm to 48.3 mm)

2. The base of the mounting pipe should be rmly anchored on a
level surface so that the sides of the gauge are vertical and the
top of the catchment is horizontal.

3. Slide both Mounting Bracket Assemblies (Part No. 50220) over
the mounting pipe.

4. Secure the U-bolt of the upper bracket near the top of the
mounting pipe. The mounting pipe should not extend above the
top of the gauge.

5. Mount the gauge itself on the upper bracket.

6. Slide the lower bracket up so that it engages the lower support of
the gauge.

7. Tighten the lower bracket.

8. Tighten the bolts that secure the brackets to the side of the gauge.

9. Verify the top of the catchment is horizontal. If not loosen the
mounting U-bolts and adjust accordingly.

10. Loosen the 3 thumb nuts on the side of the gauge to gain access
to the terminal strip for wiring the power, signal, and heater (Model
50202 only) wires.

11. Carefully slide the upper Catchment Assembly (Part No. 50230)
up to expose the terminal strip.

12. Connect wires according to enclosed wiring diagram.

13. Before operation the gauge must be primed to provide the
necessary reservoir in the bottom of the gauge.

14. Over a 1 minute period slowly pour approximately 500 ml of water
into the catchment.

15. When the measuring tube is full, the siphoning action will begin
and water will be discharged out the bottom of the gauge. Stop
pouring water into the catchment at this time.

16. The gauge is now ready for operation

17. Connect the power source and signal wires on the other end of
the cable to the data logger or display.

MAINTENANCE

The gauge should be inspected periodically. Accumulated dirt and
debris should be cleaned from the catchment area and screen (Part
No. 50238). The Measuring Tube Assembly (Part No. 50240) may be
removed for cleaning, but this would only be required on a much longer
interval.

1. VOLUME CALIBRATION CHECK

1.1 EQUIPMENT NEEDED
Water
500 ml graduated cylinder
25 ml syringe

1.2 PROCEDURE

1.2.1 PRIME GAUGE
a) Pour water slowly into catchment funnel until unit self

siphons.

1.2.2 MEASURE VOLUME
a) Pour 490 ml of water into catchment funnel.
b) Use syringe to add 5 ml of water very slowly. Measuring

tube should be nearly full.

c) Use syringe to add more water very slowly. Siphoning

should begin before 10 ml is added: tolerance is 495

- 505 ml, (±1%). Catchment funnel is 100 cm2 and
measuring tube is 20 cm2 (5:1 ratio). 1 mm of collected
precipitation equals 5 mm of masuring tube depth.

2 ELECTRONIC CALIBRATION

2.1 EQUIPMENT NEEDED
Water
500 ml graduated cylinder
Fixed DC power source (12 to 24 VDC)
Voltmeter
25ml syringe

2.2 PROCEDURE

2.2.1 MAKE ELECTRICAL CONNECTIONS
a) Refer to wiring diagram for proper connections.
b) Connect 12 to 24 VDC to power input.
c) Connect a voltmeter to circuit output.

2.2.2 PRIME GAUGE
a) Pour water slowly into the catchment funnel until the unit

self siphons.

2.2.3 CALIBRATE VOLTAGE OUTPUT FOR ZERO
a) Turn ZERO trimpot (R4) on circuit board until a positive

change is observed in the voltage output.

b) Then turn trimpot until voltage output just reaches 00.0

volts. Do not turn it any further.

2.2.4 CALIBRATE VOLTAGE OUTPUT FOR FULL SCALE
a) Pour 450 ml into catchment funnel.
b) Adjust GAIN trimpot (R13) for 4.50 VDC on the output.

Output voltage is now scaled for 20 mV per millimeter of
water depth in the measuring tube which equals 100 mV
per millimeter of precipitation.

50202-90(D)

2.2.5 CHECK OUTPUT LINEARITY
a) Pour water slowly into catchment funnel until unit self

siphons.
b) Add 50 ml of water and observe output voltage.
c) The output voltage is calculated using the ratio of 500

mV per 50 ml. Gauge accuracy is specied as ± 1 mm of

collected precipitation. Measured output voltage should

be within ± 100 mV of the calculated value.
d) Continue adding water in 50 ml increments and observing

voltage output until measuring tube is full at 500 ml total

volume. Measured output voltage should be within ± 100

mV of the calculated value at each 50 ml increment.

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