Direct Digital Readout: Instantaneous sensor output or 15-second averages can be shown on the LI-250A's display. Measurement units for any LI-COR sensor (µmol, lux, klux, or W m-2) are also displayed.

High Quality Circuitry: The high quality amplifier in the LI-250A provides excellent long-term stability and automatic zeroing. This high gain amplifier gives very low input impedance to sensors, resulting in excellent linearity. Typical accuracy is 0.4% of reading at 25 °C.

Automatic Range Selection: The LI-250A simplifies operation by automatically selecting the range with the best accuracy and resolution for a given sensor input signal. The wide dynamic range allows measurements in a wide variety of light environments.

Hold Key: Pressing the HOLD key lets you retain the current reading on the display. Pressing the HOLD key again returns the LI-250A to measurement mode where the display is continuously updated.

Average Key: 15-second averages can be collected and then held on the display by pressing the AVG key.

Hand-held, Battery Operated: The LI-250A's low power consumption gives you more than 150 hours of operation from a single 9-volt transistor battery. To conserve battery life, the meter auto-matically shuts off after 20 minutes of inactivity.

Weathertight: The LI-250A case is O-ring sealed to make it weathertight.

Sensor Calibration: Calibration multipliers for LI-COR sensors can be entered by simply pressing the CAL key, setting the display units (UNITS key), and then changing the sensor calibration multiplier with the up and down arrow keys. Two sensor multipliers can be held in memory to aid in switching between sensors.

Like all LI-COR instruments, the LI-250A is designed for applications demanding performance, reliability and ruggedness. The LI-250A provides direct digital readout of LI-COR radiation sensors.

Photosynthetically Active Radiation (PAR)
The LI-190 Quantum Sensor is used by plant scientists, horticulturists, and other environmental scientists to measure Photosynthetic Photon Flux Density (PPFD - the preferred measurement of PAR) in natural sunlight, under plant canopies, and in growth chambers and greenhouses.

The LI-190 is also used in oceanography, limnology and marine sciences as a reference sensor for comparison to underwater PPFD measured by the LI-192 Underwater Quantum Sensor. The LI-250A can hold calibration multipliers in memory for both a surface and underwater sensor.

Illuminance
For lighting studies or architectural modeling, the LI-250A and LI-210 Photometric Sensor provide a direct readout of illuminance in lux. The LI-210 measures visible radiation and has a spectral response curve equal to that for the average human eye. This curve is known as the CIE Standard Observer Curve and is matched by the LI-210 to within 5% under most light sources.

Solar Irradiance
Solar irradiance measurements for meteorological, hydrological and environmental research can be made using the LI-200 Pyranometer Sensor. The LI-200 measures global solar radiation (sun plus sky) and provides a typical accuracy of ±5% under unobstructed daylight conditions.

LI-250A Light Meter with LI-210 Photometric Sensor and 2003S Mounting and Leveling Fixture.

Sensor Compatibility
Designed for type "SA" sensors; type "SB" and "SL" sensors with BNC connectors are also compatible when calconnector or millivolt adapter are removed.

Other types of older LI-COR sensors can be made compatible by adding a BNC connector to the cable.

Accuracy:

• 25 °C: Typically ± 0.4% of reading ± 3 counts on the least significant digit displayed (all ranges).
• 0 - 55 °C: Typically ± 0.6% of reading ± 3 counts on the least significant digit displayed (all ranges).

Range Selection: Autoranging (3 ranges).

Linearity: ± 0.05%.

Sensors: Designed for type "SA" sensors; type "SB" and "SL" sensors with BNC connectors are also compatible when calconnector or millivolt adapter are removed.

Sensor Calibration: Each sensor is supplied with a calibration multiplier. Calibration multipliers for two sensors can be stored in memory. Calibration multipliers are entered from the keypad.

Signal Averaging: Sensor output can be collected and displayed as a 15-second average (approximately 60 readings). Averages are retained on the display in HOLD mode.

Display: 4 1/2 digit LCD display. Updated every 0.5 seconds in Instantaneous mode.

Keypad: Sealed, 5-key tactile response keypad.

Battery Life: 150 hours typical with continuous operation.

Power Requirement: One 9V Alkaline battery.

Low Battery Detection: Low battery indicator displayed with approximately 20 hours battery life remaining.

Operating Conditions: 0 to 55 °C, 0 to 95% RH (non-condensing).

Storage Conditions: -55 to 60 °C, 0 to 95% RH (non-condensing).

Size: 14 cm L x 7.7 cm W x 3.8 cm D (5.5" x 3" x1.5").

Weight: 0.26 kg (0.57 lbs).

Warranty: 1 year parts and labor.

The 250-01 Carrying Case has a tough nylon exterior and is padded to protect the LI-250A during transport. Internal compartments provide storage for the LI-250A and several sensors. For field use, the 250-01 Carrying Case also lets you hang the meter on your belt. Size: 20 cm L × 9.5 cm W × 9 cm D.