Overview
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 data loggers 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 data loggers
- Low-power device for reading the water level of an evaporation pan such as the 255-200
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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 data logger 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.
Specifications
| 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 Evaporation is normally not measured at temperatures below freezing. |
| 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) |
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Frequently Asked Questions
Number of FAQs related to 255-100: 2
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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 data logger has an average power draw of approximately 1 mA.
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The Half Bridge instruction should be selected (not the 3 Wire or 4 Wire options) in Short Cut. The following parameters are data logger specific, but the following can be used on the CR1000 datalogger with the sensor wired to SE1, and Vx1:
How many HalfBr Sensors? 1 Total Bridge Resistance 1000 ohm Excitation Voltage 2500 mV Sensors per excitation channel 1 Range of sensor voltage 2500 mV Reverse Excitation Yes Measurement Integration 50 or 60Hz
Settling Time 20000 µs Multiplier Determined during installation (see manual) Offset Determined during installation (see manual)
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