Ultraviolet Sensor

This sensor measures the ultraviolet radiation between 250 and
400 namometers in μmol m-2 s-1 (micromoles of photons per sqare
meter second).
Although the relative wavelengths of UV radiation differ among
sunlight and electric lights, our measurements, shown in the graph
below, indicate that this sensor provides a close estimate of the UV
radiation coming from electric lamps. This sensor is particularly useful
for determining the UV filtering capacity of the transparent plastic and
glass barriers that are commonly used below electric lamps.

Attach the sensor to a meter or datalogger
capable of displaying or recording a mV output.
The model, serial number, production date, and
conversion factor are located on the sensor cable.

Mount the sensor as level as possible. Small
changes in level can cause measurement errors. We
recommend using our leveling plate (model LEV) for
the most accurate measurements.
The sensor should be mounted with the cable pointing
toward the nearest magnetic pole to minimize azimuth
error.

Why this sensor cannot selectively
measure UV-B Radiation (280-320 nm)
Our measurements confirm those of others and indicate that less than
0.4 % of the photon flux from sunlight falls below 320 nm; 2.3 % falls
between 320 and 350 nm, and 6 % falls between 350 and 400 nm. Although
the UV radiation between 250 and 320 nm is critically important
in photochemical and photobiological reactions, only about 5 % of the UV
photons are in this range. Because only a small fraction of the photons
are in the UV-B range, this meter cannot be used to selectively measure
UV-B radiation. The sensor is sensitive to UV-B radiation, but it is included
with the UV-A radiation to provide a total measurement of UV radiation.

Effects on Output
Level
The sensor must be exactly horizontal for the most
accurate measurement. The largest error is often
caused by small changes in the position of the sensor.
The sensor should be mounted with the cable pointing
toward the nearest magnetic pole.
Cosine response
Some of the radiation coming into a sensor at low
angles is reflected, which causes the reading to be less
than it should be. The cosine-corrected head helps to
capture radiation at low angles. The cosine error for
typical applications is less than 10 %.
Temperature response
The temperature response is about 0.1 % per degree
celsius. This temperature error is insignificant for most
applications.
Long-term stability
The output of all radiation sensors tends to decrease
over time as the detector ages. Our measurements
indicate that the average decrease of the sensor is
about 1 % per year. We recommend returning the
sensor for recalibration every 3 years.

Specifications
435-792-4700
www.apogeeinstruments.com
techsupport@apogee-inst.com
Absolute accuracy ± 10 %
Uniformity ± 5 %
Repeatability ± 1 %
Output Responsivity Approximately 0.15 mV per μmol m-2 s-1
In full sunlight Approximately 26 mV (170 μmol m-2 s-1)
Linear range 0 to 400 μmol m-2 s-1
Sensitivity Calibrated to approximately 6.5 μmol m-2 s-1 per mV
Input power None, self-powered
Operating environment Can be submerged underwater (with or without
mounting bolt).
Materials PVC head, potted solid
Cable 3 meters of shielded, twisted-pair wire with
Santoprene casing, ending in pigtail leads.
Additional cable $1.95/meter.
Dimensions 2.4 cm diameter, 2.75 cm high
Mass 70 g (with 3 m lead wire)
Warranty 1 year parts and labor

Handheld Readings
1. Turn the dial clockwise to the “on” position.
2. Handheld UV meters should be held level as shown
below. Separate sensors should be mounted on a
horizontal surface.
3. The number displayed is the μmol m-2 s-1
4. Turn the meter off after use to conserve battery
power.

Calibration
Although the relative wavelengths of UV radiation differ
among sunlight and electric lights, our measurements, shown
in the graph below, indicate that this sensor provides a close
estimate of the UV radiation coming from electric lamps. This
sensor is particularly useful for determining the UV filtering
capacity of the transparent plastic and glass barriers that are
commonly used below electric lamps.

Why this Meter cannot selectively
measure UV-B Radiation (280-320 nm)

Our measurements confirm those of others and indicate that less than
0.4 % of the photon flux from sunlight falls below 320 nm; 2.3 % falls
between 320 and 350 nm, and 6 % falls between 350 and 400 nm. Although
the UV radiation between 250 and 320 nm is critically important
in photochemical and photobiological reactions, only about 5 % of the UV
photons are in this range. Because only a small fraction of the photons
are in the UV-B range, this meter cannot be used to selectively measure
UV-B radiation. The sensor is sensitive to UV-B radiation, but it is included
with the UV-A radiation to provide a total measurement of UV radiation