Calibrating the WX200 Rain Gauge

by Lee Staudacher

I have notice many folks including myself, commenting that some rain gages REGISTER lower than they should - that is when compared to a Commercial Collection Vessel - where one measures with a scale the depth of water in the collection vessel! ( When you live in a DRY climate such as southern Idaho, an accurate gage is a must!!)

My rain gage is reading about 25% less than it should when compared to the above! These units are molded BLACK plastic - subject to warpage! One reason they are subject to warpage is the POOR design of using BLACK plastic for the molded collection tank! (This is also true of ALL of the EXTERNAL sensors - it is very bad to have a Temp Sensor BLACK in color, as if ANY sunlight strikes it, will be quickly absorb heat) I have wrapped my sensors - rain gage included in TIN FOIL to reflect any HEAT away from the unit!

Calibrating your Rain Gage- (Example for a gage reading 25% too low!)

(1) Remove the top collector cover - (TWO screws in base.)

(2) Make sure BOTH collection cups on the teeter totter are empty.

(3) Temporarily place the collection cover back on. ( MAKE SURE IT IS LEVEL IN A (X) PATTERN!

(3) Use a SMALL measuring vessel - such as a GLASS cylindrical rain gage. (NOT THE TAPERED KIND!)

(4) Fill the GLASS rain gage up to the top mark - note the level using the gradient marks on the gage.

(5) Carefully pour water into the collection tank until you hear/see water pouring out the bottom of the gage. (Once you see water pouring out of the bottom - STOP pouring any more! RECORD the amount water used!) NOTE: When you see water coming out, the teeter totter has tripped to the other side!

(6) Re-fill the GLASS gage back up to the PREVIOUS amount. (Record the AMOUNT used!)

(7) Remove the BLACK collection tank from the Rain Gage Sensor.

(8) On the UNDER side of the teeter totter - temporally glue a small WEIGHT ( a beeby) under each collection cup. This will ADD weight to each collection bucket - thus LESS water/weight will be needed next time to teeter the totter! <G>

(I did NOT want to place anything inside these buckets as that may impede the flow of water - splashes!)

(9) Place the cover back on - once again pour water into Rain Gage Sensor tank - it should take less water this time because of the weight we added under the collection teeter totter buckets. If you get lucky and the amount of water used is 75% of what was used to trip it the first time, we have corrected the 25% error! If not you will have to move the weights on each side either closer to
the end of the arm, or further from end of arm! If you need less weight - move it closer to the FULCRUM of the teeter totter - further from the FULCRUM for more weight!

(10) Securely attach the weights once you have your gage calibrated. Replace the cover and attach the TWO screws - re-level if necessary! This gage MUST be level in ALL planes!

NOTE: Check the BALANCE of your teeter totter after you have the weights in place! The teeter totter MUST be balanced in order to work properly! This is CRITICAL - some minor adjustments may be necessary! BOTH weights should be in the EXACT place on the UNDER side of each collection bucket - make sure they DO NOT hit anything when in the DOWN position! NOTE: As time permits I hope to have pictures of the process!

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