For information on correction factor values, see Can I use Vernier PAR sensors with electric lights? When do I need to use a Correction Factor?

You may need to apply a PAR sensor correction factor if you are measuring PAR underwater, in certain filed conditions, or when using LED-based light sources. A correction factor is a multiplication factor applied to a PAR sensor’s Photosynthetic Photon Flux Density (PPFD) readings that adjusts for spectral errors from the sensor or the conditions. Simply multiply the sensor reading by the correction factor to get a more accurate measurement of PAR. This can be done in the data collection software.

For Go Direct PAR (GDX-PAR)

GRAPHICAL ANALYSIS or LABQUEST APP

1. Launch the data collection app (Graphical Analysis or LabQuest App) and connect your Go Direct Par sensor.
2. Activate the PPFD-CF sensor channel. For specific instructions on how to do that, see How do I turn on other sensor channels for Go Direct Sensors?.
3. Click or tap the meter for this channel, choose calibrate, and enter the correction factor for your condition.
4. Click or tap Keep to apply the correction factor, then click or tap Done.
5. This channel will now report the corrected PAR value using the applied correction factor.

For PAR Sensor (PAR-BTA)

GRAPHICAL ANALYSIS APP

1. Launch Graphical Analysis app, select Sensor Data Collection, then connect the sensor to your device.
2. If running the progressive web app, connect the sensor to Graphical Analysis (see How do I connect USB sensors to the Progressive Web App version of Graphical Analysis (and other Vernier apps)?).
3. Click or tap View Options, , and select to show the Data Table.
4. Click or tap Column Options, , next to the PPFD column heading, then choose Add Calculated Column.
5. Name the Column PPFD-CF and use the same units used for the PPFD column (μmol∙m⁻²∙s⁻¹).
6. Select Insert Expression and choose A*X+B.
7. Enter the correction factor for your condition as Parameter A.
8. Verify that Column X is the PPFD column, and set Parameter B to zero.
9. Select Apply. This will create a calculated column that displays the corrected PPFD.
10. Click or tap the Y-axis label to display the PPFD and/or the PPFD-CF readings.
11. Optional: Show a meter for the PPFD-CF column. (Graphical Analysis Pro only)
    1. Click or tap on View Options, , and select Meters.
    2. Click or tap Meter All Columns, , in the top right corner of the PPFD meter.
    3. Select Add / Remove Meter and select to show the PPFD-CF. This meter will display the corrected PPFD readings.

LABQUEST APP

1. Connect the PAR sensor to your LabQuest.
2. Tap the Table tab to display the data table.
3. Choose New Calculated Column from the Table menu.
4. Enter the Name PPFD-CF and enter the proper units for PPFD (μmol∙m⁻²∙s⁻¹).
5. Select AX from the Equation Type drop down menu.
6. Select PPFD as the Column for X, and enter your correction factor as the value for A.
7. Select OK. A graph of PPFD-CF vs. time will be displayed. A live read out of the corrected PPFD will be displayed next to the graph.
8. Optional: Show a graph of both PPFD and PPFD-CF columns.
   1. Tap on the Graph drop down menu.
   2. Select Show Graph and then select All Graphs. Two graphs, the corrected PPFD reading (PPFD-CF) and PPFD reading without a correction, are displayed.

LOGGER PRO

1. Choose New Calculated Column from the Data menu.
2. Enter PPFD-CF as the Name and and enter the proper units for PPFD (μmol∙m⁻²∙s⁻¹).
3. Enter the correction factor for your condition under Expression followed by an asterisk (*) and then select PPFD under the Variables (Columns) drop down menu. (e.g., 1.15*”PPFD”)
4. Click Done.
5. Click or tap the Y-axis label and select to display the PPFD and/or the PPFD-CF columns.
6. Optional: Add a digital meter for the PPFD-CF column.
   1. Select Meter from the Insert menu.
   2. Select Digital Meter. A meter displaying the corrected PPFD values should be displayed.
   3. Select Auto Arrange from the Page Menu. This will place the PPFD-CF meter directly below the original PPFD meter.