PAR Sensor, PAR Sensor (PAR-BTA), $189
Specifications and User Guide Specifications and User Guide

-Primary Test: Make sure that the sensor detects sunlight. Values for a bright sunny summer day should approach 2000 µmol m‾²s‾¹ of photosynthetic photon flux.
-Secondary Test: If indoors, you can use an electric lamp that should produce a PAR reading greater than 10 µmol m‾²s‾¹. Place the sensor head approximately 10 cm away from a lit lamp source where values should be greater than the residual background value. When the PAR Sensor is used with some artificial lighting, the lamp flicker may cause a fluctuating signal.
-The default setting for this sensor is for solar radiation (outside light). To accurately measure light from an artificial source, the calibration equation must be modified in accordance with the directions presented in the PAR Sensor User Manual. A video is available at

Does Vernier have a PAR or Quantum Light Sensor?
How does the PAR Sensor Work?
How is Photosynthetically Active Radiation (PAR) Measured?
Do I need to calibrate my PAR Sensor?
Can I calibrate my PAR Sensor using a standalone PAR Meter?
How is the PAR Sensor calibrated?
Can I measure Yield Photon Flux with the PAR Sensor?
How do I measure PAR from artificial lighting using the Vernier PAR Sensor?
How do I clean the PAR Sensor?
Can I use a Vernier Light Sensor to measure PAR?
Is the PAR Sensor waterproof?
How is the PAR Sensor calibrated?

-PAR Range: 0 to 2000 µmol m‾²s‾¹ in full sun
-Absolute Accuracy: ±5% (full scale)
-Repeatability: ±1%
-Long-Term Drift: Less than 2% per year
-Spectral Range: 410 – 655 nm
-Resolution: 1 µmol m‾²s‾¹
-Interface Compatibility: LabPro, LabQuest- any model, Go! Link, SBI, ULI II, CBL 2
-Diameter: Approximately 24 mm OD
-Cable Length: 5 m
-Sensing Head Materials: Anodized aluminum with cast acrylic lens
-Operating Environment: -40 °C to 70 °C, 0 to 100% relative humidity, sensor head and cable can be submerged in water to the level of the in-line circuit box.
-Stored Calibration Values: slope = 500 µmol m‾²s‾¹/ Volt, intercept = 0

-Calibrate? No. The sensor is set to the stored calibration before shipping.
-If you are suspicious about the calibration, there are two ways to check.
1. Compare the PAR value with another Quantum sensor.
2. Use the Clear Sky Calibration method. You will need a sunny day with no clouds or pollution effects. Access the Clear Sky website and by entering data into the web application, photosynthetic photon flux (PPF) will be calculated. Input values for the calculation including latitude, longitude, altitude, time of day, day of year, air temperature, and relative humidity. You can compare the calculated value with the reading on the PAR Sensor. This procedure should be done at several different times. If the readings are consistently off, contact Vernier S&T.
-Debris build-up on the lens of the PAR Sensor is a common cause of inaccurate readings.
-Solar Calibration information for PAR Sensor (PAR-BTA):
-Equation: Linear
-Reported Reading = Slope * voltage + intercept
-Slope: 500 µmol m‾²s‾¹/V
-Intercept: 0

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For experiments involving photosynthesis of plants, algae, and other photoautotrophs under terrestrial and aquatic conditions.