Evaporation Gauges / 255-100
255-100 Analog Output Evaporation Gauge
Reliable in Harsh Environments
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications


The 255-100, manufactured by Novalynx, determines evaporation rate by measuring the changing water level in your evaporation pan. The evaporation gauge produces a resistance output that Campbell Scientific dataloggers can monitor. The 255-200 or another standard National Weather Service Class A evaporation pan must be purchased separately.

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Benefits and Features

  • Compatible with most Campbell Scientific dataloggers
  • Low-power device for reading the water level of an evaporation pan such as the 255-200


255-100 Evaporation Gage attached to the 255-200 Evaporation Pan

Detailed Description

The 255-100 consists of a float, pulley, and counterweight attached to a precision 1000-ohm potentiometer mounted through a gear assembly in a weatherproof housing. It has a triangular base plate equipped with three leveling screws and a bubble level. The potentiometer produces a resistance output proportional to the position of the float, which can be monitored on site using a datalogger or monitored remotely by telemetry equipment.

The 255-100 can be placed directly in the pan, or connected to the pan using the 255-100P/F stainless-steel pipe and fittings. Instead of using the 255-100P/F, a 1/2-in. polybraid (fiber reinforced) flexible tubing, nylon fittings (1/2-in. NPT x Hose Bar), and small stainless-steel hose clamps can be used; this equipment is available from a local hardware store.


Water Input Port 1/2-in. NPT coupling, female
Counter Weight 114 g (4 oz) stainless steel
Total Resolution 0.76 mm (0.03 in.)
Potentiometer Accuracy 0.25%
Rotation 360° continuous
Electrical Angle 340°, ±1° (20° gap)
Resistance 1,000 ohm, ±10%
Operating Temperature Range -40° to +60°C
Linearity 0.25%
Mechanical Range 0 to 254 mm (0 to 10 in.)
Electrical Range 0 to 240 mm (0 to 9.44 in.)
Float 10.2 cm (4 in.) diameter, plastic
Cable Description 3-conductor, 24 AWG, shielded
Cable Length 15 m (50 ft)
Diameter 203 mm (8 in.)
Height 700 mm (27.5 in.)
Base Dimensions 40.6 cm (16 in.) triangle with leveling screws
Weight 3.4 kg (7.5 lb)
Shipping Weight 6.8 kg (15 lb)


Datalogger Considerations

Compatible Contemporary Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR6 CR9000X

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

Frequently Asked Questions

Number of FAQs related to 255-100: 2

  1. The 255-100 Evaporation Gauge is a potentiometer-type sensor. The 255-100 only draws a few milliamps of power momentarily. If the 255-100 is the only sensor in the system, the datalogger has an average power draw of approximately 1 mA.

  2. The 255-100 Evaporation Gauge is a 1000 ohm potentiometer sensor that can be measured using the Half Bridge instruction listed in the Generic Measurements folder in Short Cut.

Listed Under

Common Accessory for the following products: