Manually Calibrate a Sensor
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 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. Others will
have single point available as a check box in the calibration dialog
but it won't be the default.
Performing a Two-Point Calibration (pH Example)
- Choose Calibrate from the Experiment
menu and select the sensor you want to calibrate.
- Click Calibrate Now to begin the
calibration process.
- Place the sensor in the first calibration environment
(e.g., the pH buffer solution).
- Enter the known calibration value in the Reading 1 box
(e.g., the known pH).
- Once the readings in the input field(s) stop changing
significantly, click Keep to record the input
value(s).
- Place the sensor in the second calibration environment
(e.g., the second pH buffer solution).
- Enter the known calibration value in the Reading 2 box
(e.g., the known pH).
- 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.
- 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 Calibration Storage
for the options.
Performing a One-Point Calibration (Go! Temp Example)
- Choose Calibrate from the Experiment
menu and select the sensor you want to calibrate.
- Click Calibrate Now to begin the
calibration process.
- Place the sensor in the calibration environment (e.g. a
water bath of known temperature).
- Enter the known calibration value in the Reading 1 box
(e.g., the known temperature).
- 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.
- 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 Calibration Storage
for the options.
Note: Specific manual calibration
instructions are provided in the booklets that come with the sensor.
They can also be viewed on the Vernier
web site.
See Also: