How do I manually calibrate my sensor in Logger Pro?

In most cases it is not necessary to calibrate sensors, however for optimum accuracy you may choose to calibrate manually.

To perform any calibration you will need one or more external references for your sensor. For example, to do a two-point calibration for a pH sensor you will need two pH buffer solutions. Your calibration is only as good as your knowledge of the reference values. Note: For best results the two calibration points should be widely separated and be on either side of the intended readings you anticipate in your experiment.

A two-point calibration is always better than a one-point calibration, but sometimes it is more convenient to adjust the sensor reading to a single reference. A one-point calibration assumes that the slope for a sensor's calibration is good and that only the intercept needs to be adjusted (these are all linear calibrations: y = mx + b). Some sensors (e.g. Go! Temp) will default to single point calibration. Others will have single point calibration available as a check box in the calibration dialog, but it won't be the default.

Performing a Two-Point Calibration (pH Example)
1. Choose Calibrate from the Experiment menu and select the sensor you want to calibrate.
2. Click Calibrate Now to begin the calibration process.
3. Place the sensor in the first calibration environment (e.g., the pH buffer solution).
4. Enter the known calibration value in the Reading 1 box (e.g., the known pH).
5. Once the readings in the input field(s) stop changing significantly, click Keep to record the input value(s).
6. Place the sensor in the second calibration environment (e.g., the second pH buffer solution).
7. Enter the known calibration value in the Reading 2 box (e.g., the known pH).
8. Once the readings in the input field(s) stop changing significantly, click Keep to record the input value(s). After Keep is selected for the last time, a new calibration is created. The calibration is added to the list of available calibrations and it is marked as Not Saved. This new calibration becomes the current calibration for the sensor.
9. If you want to use the calibration for the current session only, click Done to complete the calibration process. There are several ways to store a custom calibration. See: TIL 2342: How do I store the calibration for my sensor using Logger Pro?

Performing a One-Point Calibration (Go! Temp Example)
1. Choose Calibrate from the Experiment menu and select the sensor you want to calibrate.
2. Click Calibrate Now to begin the calibration process.
3. Place the sensor in the calibration environment (e.g. a water bath of known temperature).
4. Enter the known calibration value in the Reading 1 box (e.g., the known temperature).
5. Once the readings in the input field(s) stop changing significantly, click Keep to record the input value(s). After Keep is selected, a new calibration is created. The calibration is added to the list of available calibrations and it is marked as Not Saved. This new calibration becomes the current calibration for the sensor.
6. If you want to use the calibration for the current session only, click Done to complete the calibration process. There are several ways to store a custom calibration. See: TIL 2342: How do I store the calibration for my sensor using Logger Pro?

Note: Specific manual calibration instructions are provided in the booklets that come with the sensor. They can also be viewed on the web at:
http://www.vernier.com/probes