PV Sensor: The meter uses a polycrystalline silicon PV cell as the sensor. The cell is mounted on the top end of the meter, perpendicular to the display. The sensor responds to a spectum bandwidth of approximately 0.3-1.1 microns. The meter is intended for outdoor measurements of natural sunlight. The PV sensor is located behind a plastic diffuser.

Meter Calibration: Meters are calibrated on clear days in natural sunlight and adjusted to a reference cell periodically calibrated with pyranometers at Sandia National Laboratories. Meters are pointed directly at the sun for calibration with the plastic protection cover in place. Off-angle calibration is not done. However, empirical data indicate meter-to-meter performance remains consistent up to 40 degrees off-angle from the direct normal. Beyond 40 degrees the readings start to diverge and may reach 10 - 15% when pointed 70-80 degrees away from the sun. The meters are calibrated in groups and records for individual meters are not maintained.

Care of your Meter: The meters are designed for use in the field but you should treat them as you would your voltmeter; avoid dropping them, do not leave them out in the rain. They are not sealed for continuous exposure to weather. The LCD display may darken if exposed to direct sunlight for a prolonged period.