Florida Solar Energy Center (FSEC) maintains meteorological instrumentation to support its research activities. The instruments are located at two sites: the FSEC Field Test Site and the FSEC office building (28.4N, 80.8W). These sites, about 1 mile apart, are located in Cocoa, FL. Eighteen years of data are available from FSEC's previous location in Cape Canaveral, FL, located 10 miles east of the current site. Currently, the following measurements are made:

• Wind speed average (10 meter tower)
• Maximum wind gust
• Wind direction (10 meter tower)
• Dry-bulb temperature
• Dew point temperature
• Barometric pressure
• Precipitation
• Total horizontal solar radiation
• Total solar radiation on a tilted plane
• Direct normal solar radiation
• Total normal solar radiation
• Total horizontal infrared sky radiation

The meteorological measurements are made at the Field Test Site and the radiation measurements are made on the roof of the office building.

Dry-bulb, dew point, and barometric pressure are recorded once every six minutes. Precipitation is summed continuously and the total in every six minute period is recorded. The other measurements are made once every second and a six minute average is recorded. The recorded maximum wind gust is the highest of these one second readings.

The meteorological measurements, excluding radiation, are made with sensors and translators made by Weather Measure Corp. The sensor types and accuracies are listed below:

Parameter	Sensor	Accuracy
Wind speed	3 cup anemometer  photon coupled chopper  0.5 mph threshold	+ 0.15 mph or 1%
Wind direction	light-weight vane  low torque potentiometer  0.5 mph threshold	0.5% linearity
Dry-bulb temperature	platinum resistance thermometer	+ 0.1 degree C
Dew point temperature	chilled mirror system with  platinum resistance thermometer	+ 0.3 degree C
Barometric pressure	piesoresistive element	0.08% of  reading
Precipitation	tipping bucket  0.01 inch resolution	0.5% at 0.5 in/hr

The dry-bulb temperature sensor is mounted in a motor aspirated radiation shield. The barometric pressure sensor is located 17 feet above mean sea level. The precipitation gage is protected by an alter type wind screen. All sensors and translators are calibrated at least annually.

The radiation sensors are class 1 instruments manufactured by Eppley Laboratories. The Precision Spectral Pyranometer (PSP) is used for total radiation, the Normal Incident Pyrheliometer (NIP) for direct normal, and the Precision Infrared Radiometer (PIR) for infrared sky radiation. All solar radiation sensors (PSP and NIP) are calibrated annually by comparison with FSEC's model H-F absolute cavity radiometer. The absolute cavity itself has participated in the New River Intercomparison of Absolute Cavity Solar Pyrheliometers (NRIP VII) and the First Regional Pyrheliometric Intercomparison, providing traceability of the NOAA primary reference standard and the World Meteorological Organization working standard group.

In addition to this set of standard radiation measurements, individual experiments and research projects make other radiation measurements as needed. FSEC has a complement of over 40 solar radiation instruments.

WIND Wind speed and direction are measured at a height of 10 meters above the ground. This is the standard height for meteorological wind measurements. A special "photo-chopper" design is used in the anemometer (wind speed) to enable it to measure wind as slow as 0.2 meters per second (one half of a mile per hour).

SOLAR RADIATION  The instrument used to measure solar radiation is called a pyranometer. It consists of a blackened disk containing temperature measuring sensors. The disk is protected from the environment by two domes of glass. When exposed to the sun, the disk heats up. The glass domes prevent cooling by the wind. The temperature of the disk is a function of the amount of solar radiation hitting it. Calibration against more sophisticated radiation measuring devices gives a repeatable multiplier to convert the pyranometer's output to units of solar radiation.

DIRECT SOLAR RADIATION

Direct normal solar radiation is that part of the radiation coming directly from the sun without bouncing off clouds or the atmosphere. This measurement gives an indication of the clearness of the sky. It is also measured for researching concentrating solar collectors which can utilize only this portion of the solar radiation. The instrument used to measure Direct Normal solar radiation is called a normal incidence pyrheliometer (NIP). A NIP consists of a long tube placed over the sensing element of a pyranometer. The tube blocks out all solar radiation except that coming directly from the sun. This instrument must track the sun such that the sun is always shining directly down the tube. A tracker called an equatorial mount is used to keep the NIP pointed at the sun. To measure the total amount of available solar radiation, a pyranometer is also mounted on the tracker. The difference between the pyranometer and the NIP is called the diffuse solar radiation.

PRECIPITATION  Rainfall is measured by a tipping bucket rain gauge. Rain is collected in a funnel and alternately fills two small cups (buckets). These two cups are attached together and placed on a pivot such that when one fills up, the assembly tips to the side. At each tip, the full cup is emptied and the empty cup is placed under the funnel.

AIR TEMPERATURE