Go Direct^® PAR (Photosynthetically Active Radiation) (GDX-PAR)

Specifications and User Guide

Troubleshooting

General: Press the power button on the sensor to turn it on. Connect your sensor as described in the Getting Started instructions for your device.

• Primary Test: Make sure that the sensor detects sunlight. Values for a bright sunny summer day should approach 2500 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 Go Direct PAR uses a sensor head that is a SQ-100x series quantum sensor from Apogee Instruments. The head of the Go Direct 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 sensor head and cable are waterproof. Please do not remove the sensor head from the main cable.

The 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, use the PAR Corrected channel and enter the correction factor for your light source / condition. See Can I use Vernier PAR sensors with electric lights? When do I need to use a Correction Factor?

Additional Troubleshooting

• Which Apogee sensor head does my PAR Sensor 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?
• How do I apply a Correction Factor to Vernier PAR sensors?
• Can I use a Vernier light sensors to measure PAR?
• Are Vernier PAR sensors waterproof?
• How are Vernier PAR sensors calibrated?

Specifications

• Sensing Element: SQ-100x series quantum sensor (calibrated for sunlight and electric light sources)
• PAR Range: 0 to 2500 μmol m‾²s‾¹ (PPFD) in full sun
• Absolute Accuracy: ±5% (full scale)
• Repeatability: ±1%
• Long-Term Drift: Less than 2% per year
• Cosine Response:
  ⚬ 45° zenith angle: ±2%
  ⚬ 75° zenith angle: ±5%
• Wavelength range: 370 nm to 650 nm
• Typical Resolution: 1 µmol m‾²s‾¹ (PPFD)
• Sensor dimensions
  ⚬ Diameter: 2.4 cm
  ⚬ Height: 3.3 cm
  ⚬ Cable length: 5 m
• Sensing Head Materials: Anodized aluminum with case acrylic lens
• Operating Environment
  ⚬ Sensor Head and Cable
   ▸ –10 to 60 °C
   ▸0 to 100% relative humidity
   ▸Sensor head and cable can be submerged in water to the level of the sensor box.
  ⚬ Sensor Box
   ▸0 to 40 °C
   ▸Sensor box is not waterproof or weatherproof.
• Connections:
  ⚬ Wireless: Bluetooth^® v4.2 (wireless range 30 m unobstructed)
  ⚬ Wired: USB 2.0 full speed
• Battery: 300 mAh Li-Poly
  ⚬ Battery Life (single, full charge): ~24 hours continuous data collection
  ⚬ Battery Life (lifetime): 2 – 5 years (typical)

Calibration

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.
   1. Access the Clear Sky website where you can enter data into the web application to have the photosynthetic photon flux (PPF) calculated.
   2. Input values for the calculation including latitude, longitude, altitude, time of day, day of year, air temperature, and relative humidity.
   3. You can compare the calculated value with the reading on the PAR Sensor.
   4. This procedure should be done at several different times. If the readings are consistently off, contact Vernier.

Note: Debris build-up on the lens of the PAR Sensor is a common cause of inaccurate readings.

Battery Troubleshooting

1. If the sensor won’t turn when on its own, but does when connected to a USB power source, try charging the sensor for at least 2 hours using a known-to-work USB cable.
2. If you continue to have trouble, try swapping the battery with a working sensor to see if the problem follows the battery or stays with the sensor.
   ⚬ If the problem stays with the sensor, the battery is probably not the issue.
   ⚬ If the problem follows the battery, the battery has likely reached its end of life.
3. If the battery is indeed at the end of its life, the battery should be replaced.
   Go Direct® 300 mAh Replacement Battery (GDX-BAT-300)
4. See How do I remove or replace a Go Direct battery? for more information (including a video).

Rechargeable batteries are covered by a one-year warranty.
Batteries should last two to five years in typical use.

Additional Products

Here are some additional products appropriate for experiments involving photosynthesis of plants, algae, and other photoautotrophs under terrestrial and aquatic conditions.