The 255-100 Analog Output Evaporation Gauge is used to determine the evaporation rate by measuring the changing water level in an evaporation pan. The sensor consists of a float, pulley, and counterweight attached to a precision 1000-ohm potentiometer mounted in a weatherproof housing. The potentiometer produces a resistance output proportional to the position of the float which can be monitored on site using a data logger or remotely by telemetry equipment.
A standard National Weather Service Class A Evaporation Pan is recommended for use with the gauge. The NovaLynx 255-200 Class A Evaporation Pan is designed to be coupled to the gauge by means of stainless steel connecting pipes and fittings.
Addition of the 255-620-A Automatic Refill System maintains water level in the pan on a scheduled basis, reducing visits to the site.
The 195-704-B Evaporation Logger is one method of collecting data on-site from the evaporation gauge. This 4-channel logger can also monitor temperature sensors (sold separately) to read air temperature and the temperature of the water in the evaporation pan.
Users who have their own monitoring equipment can interface with the evaporation gauge in two ways:
1. If a voltage output is desired, the logger or PLC must supply a regulated voltage to the gauge (typically 5.00 volts). When 5 volts is used, the output of the gauge is 0 to 5 volts, changing linearly as the water level in the pan decreases.
2. If a current output is desired, the 255-100C-4 Signal Conditioning circuit board generates the regulated voltage and its current loop output provides a proportional 4-20 mA signal. The 255-100C-4 can be purchased as a bare board or mounted in a NEMA enclosure (PN 255-100C-4N).