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Tipping Bucket Rain Gauge Models 6011-A 6011-B 1165 National Drive Sacramento, CA 95834 800.824.5873 User’s Manua l

Tipping Bucket Rain Gauge Models 6011-A 6011-B · Tipping Bucket Rain Gauge Models 6011-A 6011-B 1165 National Drive • Sacramento, CA 95834 • 800.824.5873 User’s Manual iii

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Tipping BucketRain GaugeModels 6011-A

6011-B

1165 National Drive • Sacramento, CA 95834 • 800.824.5873

User’sManual

iii

Table of ContentsGeneral Information ........................................................................................... 1

Introduction .............................................................................................................. 1

InstallationGeneral ...................................................................................................................... 2Siting ......................................................................................................................... 2Standard Installation ................................................................................................. 2AWOS Installation .................................................................................................... 2 AWOS Pad Installation ........................................................................................... 2 AWOS Tower Installation ....................................................................................... 2Connection ................................................................................................................ 3

Theory of Operation ............................................................................................ 4Operation ................................................................................................................... 4

Calibration .......................................................................................................... 5Calibration Requirements .......................................................................................... 5Calibration ................................................................................................................. 5Adjustment ................................................................................................................ 5Field Checks .............................................................................................................. 6

Maintenance ...................................................................................................... 8General ...................................................................................................................... 8AWOS Periodic Maintenance ................................................................................... 8 Tools and Equipment Required ............................................................................... 8 Monthly Maintenance ............................................................................................. 8 Quarterly Maintenance ............................................................................................ 8 Annual Maintenance ............................................................................................... 8

Warranty .............................................................................................................. 9

Specifications .................................................................................................... 10

Drawings ............................................................................................................ 11

1

1 General Information1.1Introduction

The Tipping Bucket Rain Gaugeis a precision sensor used to mea-

sure rainfall volume and/or rate. Rainenters the gauge through a machinedorifice and fills one of two buckets lo-cated inside the gauge. Each tip of thebucket represents 0.01 inches (0.25 mm)of rainfall with the Model 6011-A, whileModel 6011-B accommodates 0.1 mm

of rainfall per tip. As the bucket tips, areed switch makes a momentary closure,registering the tip.

Corrosion-resistant materials are used inconstruction of this instrument, and allexternal openings are protected frominsects and foreign material by meshscreens.

2

2 Installation2.1General

This instrument is thoroughly tested and fully calibrated at the factory and is ready forinstallation.

2.2Siting

2.3Standard Installation

2.4.1AWOS PadInstallation

Two prime considerations must be evalu-ated when locating an installation site forthis rain gauge. The gauge must bemounted level and the gauge must beadequately protected from high winds.Errors of more than 5% can occur if notprotected from the wind, due to rainfallblowing over the lip of the orifice.

Consider the height of surrounding ob-stacles. Install the rain gauge at a dis-tance away from the obstacles two tofour times the obstacle’s height. Al-though the obstacle makes an ideal windshield, it may block the normal rainfallpath into the gauge or rainfall may blowoff the obstacle and into the gauge.

The rain gauge is normally mounted to apoured concrete pad with embeddedmounting bolts. To mount the rain gaugeto a pad:

Pour a 2 ft. x 2 ft. level concretefoundation about 4 inches deep.

Embed three 1/4" or 3/8" diameterbolts so that they protrude outwardfrom the foundation, spaced to fitthe three feet on the gauge.

If strong winds are common at the site,the model 6410 Wind Screen isrecommended. Mount the wind screenas described in its accompanying manual.

Remove the collection funnel and checkthe bubble level on the base assemblybefore bolting the gauge to the foundationor tower mount. If the bubble is notcentered, add washers between the baseand the base assembly’s feet in such away that the bubble is centered exactlywhen the bolts are tightened. This is ofcritical importance to the accuracyof the gauge.

Connect the input of the recording de-vice to the two binding posts that termi-nate the reed switch.

Replace the collection funnel and securethe two side screws.

To mount the sensor to a pad, constructthe pad using a Ready-Form tube, rebar,and foundation bolts as shown in Figure2-1, then proceed as follows:

Remove the collection funnel and checkthe bubble level on the base assemblybefore bolting the gauge to the foundationor tower mount. If the bubble is notcentered, add washers between the baseand the base assembly’s feet in such a

way that the bubble is centered exactlywhen the bolts are tightened. This is ofcritical importance to the accuracyof the gauge.

Connect the input of the recording de-vice to the two binding posts that termi-nate the reed switch.

Replace the collection funnel and securethe two side screws.

2.4AWOS Installation

Rain gauges used at AWOS installations can be mounted to a pad or to the sensortower.

3

MODEL 6011 TIPPING BUCKET RAIN GAUGE

2.5Connection

Connect a two-conductor cable betweenthe two terminal posts on the gauge andthe event accumulating device.

Be sure to remove any packing materialand the bucket retaining clips from theinstrument.

Verify correct calibration before rein-stalling the outer housing.

(Figure 2-1) AWOS rain gauge pad construction.

2.4.2AWOS TowerInstallation

Using the M488169-01 tower mountingkit, the sensor mounts to a horizontalboom attached to the tower approximately7' above the ground. To mount the raingauge to a tower, refer to Drawing No.M488169-01-007 at the back of thismanual, then proceed as follows:

Remove the collection funnel and checkthe bubble level on the base assemblybefore bolting the gauge to the foundationor tower mount. If the bubble is not

centered, add washers between the baseand the base assembly’s feet in such away that the bubble is centered exactlywhen the bolts are tightened. This is ofcritical importance to the accuracyof the gauge.

Connect the input of the recording de-vice to the two binding posts that termi-nate the reed switch.

Replace the collection funnel and securethe two side screws.

4

3 Theory of OperationThe rain gauge’s eight inch diameterorifice was chosen as a compromisebetween two conflicting elements — theincreased accuracy of a large samplingarea, and the practical benefits of a smalltipping bucket mechanism.

Precipitation is collected by the largefunnel at the gauge orifice, which helpsprevent evaporation inside the instru-ment. The collected precipitation is thenchanneled to the small funnel inside theinstrument and directed to one of twotipping buckets. When one bucket fills,its weight tips the next bucket into positionand the first empties. At the same time,a 100 millisecond momentary contactclosure increments an event accumulat-ing device. The measured water is

drained out the bottom of the instrument.A tank can be designed, if needed, tocatch the water draining out of the in-strument for further evaluation.

In AWOS systems, the rain gauge isused to correct visibility measurementswhen precipitation is present. Whenprecipitation is falling, visibilitymeasurements register a value less thanthe actual visibility. The degree to whichthe visibility value is affected dependson the intensity of the precipitation. Tocorrect for this, the AWOS interpretsthe rain gauge data and corrects thevisibility value with one of severalcorrection factors corresponding to theintensity of the precipitation.

3.1Operation

5

4 Calibration4.1CalibrationRequirements

This instrument was calibrated beforeleaving the factory and should not re-quire any further calibration unless main-tenance is performed on the instrument.

For Model 6011-A, 8.683 milliliters ofwater is equivalent to 0.01" of rainfalland 8.493 milliliters of water is equiva-lent to 0.25 mm of rainfall. For Model6011-B, 3.418 milliliters of water equals0.1 mm of rainfall.

4.2Calibration

To calibrate the tipping bucket rain gauge,follow the steps below:

Remove the two screws at the baseof the gauge and remove the outercover. Be sure the gauge remainslevel. Use the built-in bull’s eyelevel as an indicator.

Devise a water source with a uni-form flow rate of approximately 400milliliters per hour. Direct this flowonto the wall of the small funnel.

Set up a counting device, such asan event recorder or solenoidcounter, to count the number of tipsof the bucket assembly, or countthe tips yourself.

After the gauge has tipped severaltimes and the buckets are wet, col-lect the water in two containers(one beneath each drain tube).Carefully insert the collection con-tainers between tips and allow atleast 10 tips of each bucket (20counts on the recorder).

Remove the containers between tipsafter an even number of tips.

Measure the amount of water ineach container by weight or vol-ume.

Divide each quantity by the num-ber of tips of each bucket. Thevalue should be within 0.5% of thevalue listed in Figure 4.1.

4.3Adjustment

Adjustments may be made to the stopslocated under the buckets. Raising thestop of the bucket will reduce the catchfor that bucket; conversely, lowering thestop will increase the catch.

NOTE: The stop for a bucket is locatedunder the opposite bucket. Make adjust-ments in small steps (1/4 turn per test).Repeat the calibration procedure untilthe gauge is within specifications.

The above procedure is for a rate of0.5" per hour. The gauge may be cali-brated at any selected rate.

After calibration, note the date and placeof calibration and reinstall the outer coverand three screws. Be sure the cover islined up correctly.

If the gauge has been removed from afield location for calibration, be sure tolevel it properly following installation.

6

MODEL 6011 TIPPING BUCKET RAIN GAUGE

To check for calibration in the field, makesure the buckets are empty and add theamount of water specified in Figure4.1. If the buckets tip too soon or do nottip at all, the instrument requires alaboratory calibration as previouslydescribed. A standard 10 milliliterspipette or a Model 60103 Calibrator canbe used as a field test device.

For maximum sensitivity, remove boththe outer cover and the small funnel.Direct the water toward the center ofthe bucket partition when the bucketsare at midpoint. The errors introducedby surface wetting and droplet forma-tion at the funnel tip are eliminated usingthis method of calibration.

4.4Field Checks

For Model 6011-A:.01 in. of rain = 8.683 cc per tip.25 mm of rain = 8.493 cc per tip

For Models 6011-B:.1 mm of rain = 3.418 cc per tip

Use the following equation to calculate cc per tip:cc per tip = pr2 x depth of rain per tip

Example:For .01 in. of rain per tip–

cc per tip = pr2 x 0.01 in.where r = 4.107 in.cc per tip = 52.98 in.2 x .01 in.cc per tip = 0.5298 in.3

.5298 in.3 = 8.682 cc(1 in. = 2.54 cm)

(Figure 4-1) Calculating water volume per bucket tip.

7

MODEL 6011 TIPPING BUCKET RAIN GAUGE

(Figure 4-2) Model 60103 Rain Gauge Calibrator

The Model 60103 Precipitation Gauge Calibrator simplifies field checks of tipping bucket rain gauges byregulating the flow of water into the gauge during calibration. The calibrator consists of a plastic water bottle, astand for holding the bottle and directing the flow into the funnel, and an orifice.

During calibration, a measured amount of water equal to 100 tips of the bucket assembly is directed intothe gauge at a constant rate of 2 inches per hour. A laboratory balance should be used to measure the water. Ifthe counter attached to the gauge records more or less than 100 tips, recalibration of the gauge should beconsidered.

This calibration method provides the greatest accuracy and repeatability since measurement is based onan average over 100 tips. The rugged nature of the calibrator also makes it more practical than fragile pipettesor graduated cylinders for field use.

8

5 MaintenanceNormal maintenance is limited to cleaningdebris out of the orifice. When the sensoris installed as part of an AWOS system,

5.1General

5.2AWOS PeriodicMaintenance

special maintenance procedures arerequired. Refer to the following sectionfor details.

Periodic maintenance of AWOS sensorsis divided into three categories: monthlymaintenance, quarterly maintenance, and

annual maintenance. The listedmaintenance routines are performedaccording to that schedule.

The following tools and equipment arerequired for performing periodic AWOSmaintenance:

• 1/4" wrench

Remove the screen from the funnel ofthe rain gauge and gently tap the screento free any dirt or debris. Replace thescreen.

5.2.1Tools and EquipmentRequired

5.2.2MonthlyMaintenance

Quarterly maintenance of the Model 6011is identical to the monthly maintenanceprocedure: Remove the screen from the

5.2.3QuarterlyMaintenance

funnel of the rain gauge and gently tapthe screen to free any dirt or debris.Replace the screen.

5.2.4AnnualMaintenance

During annual maintenance, perform thefollowing procedures in addition to thoseoutlined for monthly and quarterlymaintenance.

1 The output of the rain gauge is aswitch closure, each closure beingequivalent to a known volume ofcollected rainfall (0.01"). The fun-nel, screen, and buckets shall becleared of debris before this proce-dure as described in the monthlytasks.

2 Remove the outer cover by remov-ing two 1/4" bolts. Check for sen-sor level using the bubble level pro-vided on the base. Adjust if neces-sary.

3 Inspect the interior of the gage forphysical lightning damage.

4 Note the precipitation quantity onthe DCP's LCD display. Toggle thebucket assembly one cycle (2 tips).Again read the precipitation quan-tity on the LCD display. It must be2 counts greater than before.

5 Replace the outer cover, bolts, andscreen.

9

6 WarrantyUnless specified otherwise, All Weather Inc. (the Company) warrants its products tobe free from defects in material and workmanship under normal use and service forone year from date of shipment, subject to the following conditions:

a. The obligation of the Company under this warranty is limited to repairing orreplacing items or parts which have been returned to the Company and which uponexamination are disclosed, to the Company’s satisfaction, to have been defective inmaterial or workmanship at time of manufacture.

b. The claimant shall pay the cost of shipping any part or instrument to theCompany. If the Company determines the part to be defective in material orworkmanship, the Company shall prepay the cost of shipping the repaired instrumentto the claimant. Under no circumstances will the Company reimburse claimant forcost incurred in removing and/or reinstalling replacement parts.

c. This warranty shall not apply to any Company products which have beensubjected to misuse, negligence, or accident.

d. This warranty and the Company's obligation thereunder is in lieu of all otherwarranties, express or implied, including warranties of merchantability and fitness fora particular purpose, consequential damages, and all other obligations or liabilities.

No other person or organization is authorized to give any other warranty or to assumeany additional obligation on the Company's behalf, unless made in writing and signedby an authorized officer of the Company.

This equipment has been manufactured and will perform in accordance withrequirements of FAA Advisory Circular 150/5220-16B. Any defect in design,materials, or workmanship which may occur during proper and normal use during aperiod of 1 year from date of installation or a maximum of 2 years from shipment willbe corrected by repair or replacement by All Weather Inc.

6.1Standard Warranty

6.2AWOS Warranty

10

7 Specifications

Type Tipping BucketSensitivity

6011-A 0.01" (0.25 mm)6011-B .1 mm

Resolution6011-A 0.01" (0.25 mm)6011-B .1 mm

Orifice opening 8" dia. (20 cm)Calibrated accuracy ±0.5% at 0.5"/hr.Repeatability ±3%Insect protection Mesh screensCapacity UnlimitedOutput 100 ms switch closureSwitch type Form A reedSize 8" dia. x 18" H (203 mm dia. x 457 mm H)Weight/Shipping 8 1bs./15 lbs. (3.6 kg/6.8 kg)

11

The following pages include reference drawings to aid in maintenance and use of thisinstrument.

8 Drawings8.1Contents

All Weather Inc.1165 National DriveSacramento, CA 95818Fax: 916.928.1165Phone: 916.928.1000Toll Free: 800.824.5873www.allweatherinc.com

6011-A-001Rev. L

ECO 1454March, 2008