National Weather Service Class A Evaporation Pan

Stainless Steel Stilling Well For Precise Evaporation Measurement

English Hook Gauge is used to measure water level changes inside an evaporation pan.

Water Evaporation Meausrement with National Weather Service Class A Evaporaton Pan

255-211 Replacement Graduate for Evaporation Pan

Totalizing Anemometers display Module Measures Wind Velocity

National Weather Service Class A Evaporation Pan

from $282.00

Ships in 3 - 5 d days, contact us for more details.

Model 255-200

Specifications

Material: Low carbon stainless steel, type 304, 18 gauge

Construction: Heliarc welded, 1/2" drain plug, NPT female coupling
Size: Cylindrical, inside dimensions 10" deep x 47-1/2" dia (254 mm x 1206 mm), wall thickness 0.047"
Volume: Approx 77 gallons (adding 7.7 gallons will raise water level in pan by 1")
Weight/shipping: 50 lbs/68 lbs (23 kg/31 kg)
Shipping box: 50" x 49" x 11" (Oversize item must ship via LTL Freight)

Product Options:

255-200 Class A Evaporation Pan (Pan Only) 255-205 Stillingwell - Accessory 255-210 Stillwell with Fixed Point 255-214 Hook Gauge (English) 255-215 Hook Gauge (Metric) 200-2510-B & 200-2511-B Totalizing Anemometers Call for pricing & Info on other accessories

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Datasheet

Learn more bout evaporation stations

The 255-200 Evaporation Pan is a standard National Weather Service Class A type for measurement of water evaporation. It is normally installed on a wooden platform set on the ground in a grassy location. The pan is filled with water and exposed to represent an open body of water. The pan is filled to within 2.5 inches of the top of the pan. The evaporation rate can be measured by manual readings or with an analog output evaporation gauge.

About Evaporation Pan

Pan evaporation is a measurement that combines or integrates the effects of several climate elements: Temperature, humidity, rain fall, drought dispersion, solar radiation, and wind. Evaporation is greatest on hot, windy, dry, sunny days; and is greatly reduced when clouds block the sun and when air is cool, calm, and humid Pan evaporation measurements enable farmers and ranchers to understand how much water their crops will need.

An evaporation pan is used to hold water during observations for the determination of the quantity of evaporation at a given location. Such pans are of varying sizes and shapes, the most commonly used being circular or square.

The best known of the pans are the "Class A" evaporation pan and often the evaporation pans are automated with water level sensors and a small weather station is located within a close proximity.

We can supply your evaporation pan along with other essential instruments, such as water level transmitter, data logger, weather station and more.

Optional Accessories

HOOK GAUGE 255-214 and 255-215

The **255-214 (English) & 255-215 (Metric) Hook Gauge** is used to measure water level changes inside an evaporation pan. NovaLynx produces a micrometer-style hook gauge that conforms to the classical US Weather Bureau style hook gauge. It features a sharply pointed "U" shaped hook attached to a calibrated stem and a micrometer dial. Measurements are made by placing the hook gauge into an evaporation pan and on top of a stilling well. The micrometer dial is rotated until the point at the end of the hook pierces the water's surface from below. As the water evaporates, the hook point is moved to the new surface position. Adjustments to the hook's point are made daily and the new dial reading is recorded to determine the amount of water loss.

255-205 Stilling Well

The **255-205 Stillwell** is a stainless steel tube with a triangular base for stability. It is placed in the evaporation pan to support a fixed point or hook gauge. The stillwell (or stilling well) makes readings more precise by eliminating wind-caused surges and ripples in the water level. It has two small openings located opposite each other near the base to permit the flow of water in and out of the stillwell.
This item is normally used with submersible water level transmitters or water level loggers.

255-210 Stilwell W/ Fixed Point

**255-210 Stillwell with Fixed Point** consists of a pointed rod called the fixed point mounted in a tube called the stilling well. It is placed inside the evaporation pan, one foot from the north edge. The fixed point is attached to the center of the base inside the stillwell. The point is 7.5 inches above the bottom of the evaporation pan when in position.
The stillwell makes readings more precise by eliminating wind-caused surges and ripples in the water level
This item is normally used with HOOK GAUGE 255-214 and 255-215

Replacement Graduate

The 255-211 Replacement Graduate is used to replace evaporated water in an evaporation pan. It is a transparent tube with an inside diameter of 4-3/4 inches, which is one-hundredth of the surface area of the evaporation pan. The tube is graduated at one-inch intervals, with the zero mark at the top. One inch of water in the measuring tube is equivalent to .01 inch in the evaporation pan.

255-620A Automatic Refill System For Class A Evaporation Pan — 255-620-A Automatic Refill System

The 255-620-A Automatic Refill System provides a simple method to automatically refill an evaporation pan at specified times. It consists of an electronic water timer and an automatic float valve. The water timer switches on at a user-specified time, allowing water from an external water source to flow into the pan. Works with low (gravity flow) or high (city) water pressure. The float valve will stop the water flow at approximately 8-1/2" to 9-1/2" depending upon the water pressure. The timer then shuts off until the next programmed time.

200-2510-B and 200-2511-B Totalizing Anemometer

**The 200-2510-B & 200-2511-B Totalizing Anemometers** are simple to install and operate. The easy-to-read display is housed in a NEMA-4X enclosure and is powered by an internal lithium battery with a 5+ year life.
The display module measures wind run by counting pulses generated by the cup-style wind sensor. The number of pulses is multiplied by a scaling factor and displayed in units of statute miles or kilometers. Average wind speed can be calculated from the difference between successive counter readings divided by the time interval between readings.
In an evaporation station, the anemometer is typically mounted on the platform supporting the evaporation pan. The unit is supplied with a pre-drilled mounting flange for this purpose.

Contact AWM Instruments for questions or other accessories or how to build your evaporation monitoring station. AWM Instruments offers battery operated water level loggers designed to measure and record small changes in water level.