Omega RG-2500 User Manual
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RG-2500 Series
Tipping Bucket Rain
Gauge
03
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Unpacking Instructions
Remove the Packing List and verify that you have received all equipment, including the following
(quantities in parentheses):
RG-2500 Tipping Bucket Rain Gauge (1)
Operator’s Manual (1)
If you have any questions about the shipment, please call the OMEGA Customer Service
Department.
When you receive the shipment, inspect the container and equipment for signs of damage. Note
any evidence of rough handling in transit. Immediately report any damage to the shipping agent.
The carrier will not honor damage claims unless all shipping material is saved for
inspection. After examining and removing contents, save packing material and
carton in the event reshipment is necessary.
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TABLE OF CONTENTS
Chapter 1 Introduction
1.1 General Description
1.2 Specifications
Chapter 2 Installation
2.1 Site Requirements
2.2 Installation
Chapter 3 Operation
Chapter 4 Calibration
4.1 Factory Calibration
4.2 Calibration Procedure
4.3 Field Calibration
4.4 Adjustments
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Chapter 5 Maintenance
Chapter 6 Troubleshooting
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Chapter 1: Introduction
1.1 General Description
The RG-2500 Series consists of two high quality rain gauges, Models RG-2500 and
RG-
2500-12. Model RG-2500 features a standard eight-inch diameter orifice, while the Model
RG-2500-12 has a twelve-inch diameter orifice. Both gauges have been designed with high
grade materials and have been built to provide years of trouble-free operation.
Each of the two gauges consists of a main collection funnel, an outer cover, an internal
funnel, a tipping bucket and magnetic switch assembly, a base, and mounting feet with
leveling adjustments.
Electrically heated versions of both gauges can be provided for use in cold climates, for
measuring frozen precipitation such as snow and sleet. The electrically heated versions
include the features listed above plus a heater element, a thermostat, a fuse holder and fuse,
and associated wiring and terminal blocks. The model numbers for the heated rain gauges are
RG-2500E and
RG-2500E-12.
1.2 Specifications
Capacity:
Unlimited
Orifice:
RG-2500: 8” (20 cm)
RG-2500-12: 12” (30 cm)
Calibration:
Accuracy:
Switch:
0.01” per tip (0.25 mm), others on request
+
+
1% for 1 to 3 inches per hour,
3% for 0 to 6 inches per hour
Magnetic reed, SPST N.O., 10 Watts, 200 Vdc, 0.5 A max
Dimensions:
8”
RG-2500:
x 17”
RG-2500-12: 12” x 20”
Weight/Shipping:
RG-2500: 7
RG-2500-12: 14
lbs/12 lbs
lbs/18 lbs
Optional Accessories:
Wind Screen, Alter Type
Event Recorder, Drum Chart
Calibrator Bottle
Digital Event Counter
Model RG-952
Model RG-6113-A
Model RG-2595
Model RG-2596
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Chapter 2: Installation
2.1 Site Requirements
The location of the rain gauge is very important to the successful operation of the instrument.
The most accurate measurements are made in relatively sheltered areas protected from
gusting and turbulent winds. Openings in orchards or a grove of trees offer the best exposure
for the rain gauge. Fences and other structures can help serve as a wind break as long as
they are not too tall. In areas that are open with no nearby structures, a wind screen such is
recommended to protect against wind effects.
Generally, the heights of objects near a rain gauge should be proportional to the distance
away from the gauge. The distance of a nearby object should always be at least twice the
height of the object above the gauge.
Wind effects on catch losses are more pronounced during snow storms than during a rain
storm. A wind screen is generally not used at locations where snowfall constitutes less than
20% of the mean annual precipitation.
Good locations do not always remain free of obstructions. Vegetation can grow quickly,
changing an excellent exposure into a poor one. Sites should be inspected regularly in order
to properly maintain the exposure of the gauge.
In locations with heavy snowfall, the gauge should be mounted on a support or tower to
place the
tower were
gauge well above the average local snow level. The exposure would be best if the
to
be located among trees of the same height as the tower.
2.2 Installation
OMEGA@ rain gauges are shipped as a complete assembly with no additional assembly
required. ‘The gauge, however, should be installed onto a platform or foundation that is
fairly
close to being level to minimize the amount of adjustment required after the gauge is
mounted. Each gauge is equipped with three mounting brackets that also serve as feet. Each
foot has a mounting hole with a diameter of
3/8 inches. The holes in the feet should be
matched to anchor bolts located in the foundation or on the platforms. for severely tilted
foundations, use a set of three hex nuts on each bolt to provide leveling and locking of the
rain gauge onto the foundation. For slightly tilted foundations, use the adjustable leveling
knobs above each foot to level the gauge. An internally mounted spirit level may be used to
assist in the leveling process. A rough level can be taken by placing a carpenter ’s level
across the top of the gauge funnel. Flat washers may be used as shims to help correct large
leveling differences. Place the shims under the mounting feet. A lock washer and a hex nut
should be used to secure the gauge onto the anchor bolts. Some correction of the level may
be necessary after tightening the hex nuts.
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The leveling knobs located above the mounting feet are secured using
allen
head set screws.
These set screws must be loosened before the knobs can be moved. The set screws are
accessible from the sides of the base. Re-tighten the set screws after leveling the gauge to
help ensure that the level adjustment will not shift due to loose screws.
The gauge may be installed with the outer cover on or with it removed. Three screws hold
the outer cover in place. Take out these three screws to remove the cover. Carefully remove
the cover, avoiding hitting any of the internal rain gauge parts. Some of the moving parts are
tied down to prevent movement and possible damage during shipping. Remove any tape,
plastic ties, foam inserts, or other objects used to keep the tipping buckets from moving. The
bucket assembly should move easily with the packing materials removed.
Chapter 3: Operation
The rain gauge operation is relatively simple.
As rain is collected by the eight-inch diameter
orifice, the rain drops are directed down through the funnel and into the bucket assembly. As
soon as the bucket has collected enough rain to represent 0.01 inches (or 0.25 mm) of rain,
the bucket tips. The rain drains out through the drain collection tubes and the magnet is
moved past the reed switch. The reed switch closes momentarily, making an electrical
contact that is used in conjunction with electronic counting and recording instruments.
Chapter 4: Calibration
4.1 Factory Calibration
Each rain gauge is thoroughly tested before being shipped to the customer. A measured
amount of water is passed through the rain gauge to give an expected number of counts
according to the diameter of the orifice. The bucket calibration posts have screws that are
adjusted until the correct number of counts are achieved with repeated testing. The exact
number of counts or nearly the exact number are recorded for each gauge. As long as the
number of counts is within the specified accuracy of the gauge, the calibration will be
accepted. The calibration of the gauge should not change during shipping unless the gauge
becomes damaged. Checking of the gauge calibration may be made after the gauge has been
installed to ensure the accuracy of the data.
4.2 Calibration Procedure
The rain gauge calibration may be checked using a graduated burette or cylinder. Wet the
gauge thoroughly allowing water to flow through the gauge before beginning the test. The
wetting of the gauge helps compensate for water that may adhere to
portions.of the gauge
causing some error in the counts.
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