PAR Sensor, PAR Sensor (PAR-BTA)
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 PAR sensor uses a sensor head that is a SQ-100x series quantum sensor from Apogee Instruments. Older models used an SQ-110 sensor calibrated for sunlight. The sensor model number can be found on a white label wrapped around the cable that is located a few centimeters from the sensor head (SQ-100X-SS or SQ-110).

Notes: In May of 2023 the SQ-100X sensor head was introduced for this sensor. The head of the new Vernier PAR Sensor is attached to the main cable using a P68-rated stainless-steel marine grade (M8) connector. This connector is located 25 cm from the sensor head. The new sensor has a default calibration for solar radiation (outside light) and electric light sources.

To accurately measure light from an artificial source that uses LEDs, a correction factor must be used.


Which PAR Sensor (PAR-BTA) do I have?
Does Vernier make PAR or Quantum Light Sensors?
How do Vernier PAR sensors work?
How is Photosynthetically Active Radiation (PAR) Measured?
Do I need to calibrate Vernier PAR sensors?
How are Vernier PAR sensors calibrated?
Can I calibrate my PAR Sensor using the clear sky calculator
Can I use Vernier PAR sensors with electric lights? When do I need to use a Correction Factor?
How do I clean a PAR Sensor?
Can I use a Vernier light sensors to measure PAR?
Are Vernier PAR sensors waterproof?
How are Vernier PAR sensors calibrated?

-PAR Range: 0 to 2500 µmol m‾²s‾¹ in full sun
-Absolute Accuracy: ±5% (full scale)
-Repeatability: ±1%
-Long-Term Drift: Less than 2% per year
-Spectral Range: 370 – 650 nm
-Resolution: 1 µmol m‾²s‾¹
-Interface Compatibility: LabPro, LabQuest- any model, Go! Link, SBI, ULI II, CBL 2
-Sensor Dimensions:

  • Diameter: 24 mm OD
  • Height: 33 mm
  • Cable Length: 5 m

-Sensing Head Materials: Anodized aluminum with cast acrylic lens
-Operating Environment: -10 °C to 60 °C, 0 to 100% relative humidity, sensor head and cable can be submerged in water to the level of the sensor 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

Vernier Optical DO Probe (ODO-BTA)
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O2 Gas Sensor (O2-BTA)
Extra Long Temperature Probe (TPL-BTA)
pH Sensor (PH-BTA)
Tris-Compatible Flat pH Sensor (FPH-BTA)
Conductivity Probe (CON-BTA)
Salinity Sensor (SAL-BTA)
Water Quality Bottles (8 bottles) (WQ-BOT)

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