CH2212
Vernier Lab Pro
Data Interface Tutorial (pH measurement)
1) Obtain the two pre-made pH buffer standards from the reagent shelf. pH 7.00 is
green. pH 4.00 is orange.
2) Place the LabPro interface on the lower shelf of the keyboard stand.
a) Connect the three cables/wires needed for operation. Try and avoid
unnecessary clutter.
b) Power supply. Plug in at lower left corner of LabPro. Run cable behind the
stand. Plug adapter and plug in AC adapter at nearest GFI outlet pH probe.
Plugs in at upper left corner (CH 1). Unwrap enough cable to allow probe to
be positioned and held in the buret clamp issued to you in your locker set.
Place the pH probe in the pH 7 buffer as shown by your TA.
c) USB cable. Plugs in at the middle right side of the Lab Pro. Runthe cable
behind the shelf and plug into a USB port on your computer.
3) If computer gives you a “You do not have permission…” message on sensing the
USB cable connection, see the instructor or try a different USB port.
4) Be sure the pH probe is plugged into the Lab Pro interface before you go to
the next step!!!
5) On your PC monitor screen, double-click on “Logger Pro”.
• You may get the pH vs. time window right from the start. This is where you
want to be.
• If you get the default window, click on File/Open/Probes and Sensors/pH
Sensor/pH vs. Time. You should get a multi-window display with a box for pH
readings in the upper right-hand corner.
If the “Sensor Configuration” window comes up, change the selection in the
“Sensor To Set Up” response field to Electrode Amplifier.
At this point, the Lab Pro should have a blinking green light visible, indicating that
it is on and ready for use.
6) Change the pH output format to read two decimal places. Go to Data/Column
Options/pH/Options. Under “Displayed Precision”, type in 2 and be sure the
Decimal Places radio button is pushed. Select “Done” You should see the pH
display immediately change to two decimal places.
7) If necessary, get rid of extraneous columns in the Table Window. Go to
Data/Delete Column.
8) Look at the x-axis of your displayed chart. If it doesn’t read in time units, you have
to change the experiment. Go to Experiment/Data Collection. From the “Mode”
tab, choose “Time Based”. Set the Experiment Length to 20 seconds and the
Sampling Rate to2 samples/second. “Over Sampling” should be turned off. Select
“Done”.
9) At this point, click on the “Collect” button in the top button bar. You should see
the pH display change randomly in the second decimal point, the data table in the
left frame filling with data, and a horizontal line of graphing symbols starting
across the graph grid from the left, indicating that the pH is being plotted vs. time.
10) To change the graphical output, make the Graph Window active by clicking in it.
Go to Options/Graph Options. Select the “Axes Options” tab and choose pH for
the y-axis. Set the pH units for Manual Scaling with a minimum of 2 and a
maximum of 10. Choose Time for the x-axis and set the time units for Manual
Scaling with a minimum of zero and a maximum of 20 seconds. You can always
change these parameters later. Select “Done”.
11) To change the graph visuals, go to Options/Graph Options and select the “Graph
Options” tab. Select “Connect Points” and de-select “Point Protector”. Change
the graph title in the text box at the top. Select “Done”.
12) Click on “Collect” again. You should see a flat line with minimal noise scrolling
across the screen from the left at a y-axis value corresponding to the pH indicated
in the Meter Window.
13) Now you are ready to calibrate your pH meter. Go to Experiment/Calibrate…” If
you get an error message, go to Experiment/Set Up Sensors and select LabPro as
the Default Interface. Select the “Calibrate Now” tab in the Sensor Setting
window. The display should indicate that pH is being read on CH 1. Click the
“Perform Now” button on the right-hand side. With the pH probe in pH 7 buffer,
type in “7.00” for Value 1. When the displayed voltage stabilizes, select “Keep”.
Lift up the pH probe with the buret clamp, rinse gently with a stream of distilled
water, and blot dry with a Kim-Wipe. Re-immerse the probe in pH 4 buffer and
type in “4.00” for Value 2. When the displayed voltage stabilizes, select “Keep”.
14) Your pH meter is now ready for use. If the display should seem unduly noisy, or if
there is a steady drift over time, alert your instructor. Use the pH probe in the same
way you have been shown for the pH standard buffers. Always rinse between
samples and blot the probe end dry to avoid contamination between samples.
15) When finished with the pH probe, rinse it clean and re-insert it into the storage
sleeve after putting a few drops of buffer standard in the sleeve. Store in the
cardboard box provided.