Last Update: January 3, 2007
First, set up the spectrometer and allow it to warm up (click here if your spectrometer is a one-piece unit or here if it consists of multiple parts to read instructions on how to set up the spectrometer). Start LoggerPro from the desktop shortcut, or from the Start menu on the lower left-hand side of the screen. If you can't find LoggerPro by either of these methods, please consult your instructor.
LoggerPro will start and the screen shown in Fig. 1 will be displayed. If status line displays the message "No device connected," as it does in Fig. 1, you will need to connect the spectrometer. Do this by selecting Experiment from the menu bar and then select Connect Interface, Spectrometer and Scan for Spectrometer.
Figure 1. Starting screen for LoggerPro.
If program finds spectrometer, the “No device connected” message will be replaced by the spectrometer icon and the message “Absorbance = x.xxx” where “x.xxx” is some number, as shown in Fig. 2. You will also hear a click, if you are using one of the one-piece spectrometers.
Figure 2. LoggerPro screen that is displayed once the Ocean Optics spectrometer has been found by the software.
Once the computer has located the spectrometer, the
software must configured to acquire the data. Click on the spectrometer icon
(or
select from menu bar Experiment, Set Up Sensors and select Spectrometer:1). The
Set Up Sensors pop-up shown in Fig. 3 will appear. You probably won’t have to change anything
there. However, if you do change something and want to return the spectrometer to
its factory-default settings, simply click on the Restore Defaults button. Note
that if you change something in this box after you have taken a background (vide
infra), you will need to reacquire the background. Click
here to read more about each
parameter.
Figure 3. Set Up Sensors pop-up box for the Ocean Optics spectrometers.
Before continuing prepare a cuvette containing your blank. If you are using a spectrometer that has the detector and light source separated, you must place a thick piece of paper in the sample holder to block the light beam before proceeding.
In the Set Up Sensors pop-up click on the spectrometer
icon 
and a new pop-up will appear. Your options here are Calibrate,
Configure Collection and Current Units (under Current Units,
Absorbance should be
selected; do not change). Select Calibrate. If you have a one-piece
spectrometer, it will click and the pop-up shown in Fig. 4 will be displayed.
If you have a spectrometer where the detector and source are separate, you will
not hear a click (make sure the light beam is still blocked).
Figure 4. Calibrate Spectrometer pop-up immediately after it has been activated.
After 1 minute the warm-up is complete and the Calibrate Spectrometer pop-up will look like that shown in Fig. 5. If you are using a one-piece unit, simply insert the blank into the spectrometer's sample holder. The light travels across the spectrometer in the long direction, so make sure the cuvette is arranged so that the light travels through the unfrosted sides of the cuvette. If you have a spectrometer with separated detector and light source, first remove the piece of paper that you used to block the beam and then insert the blank into the sample holder. IMPORTANT! If you don't have a one-piece spectrometer and did not block the beam, click Cancel and start the calibration again. Be sure that the unfrosted sides of the cuvette are pointed toward the fiber optic cables. Once the cuvette is in place click Finish Calibration to complete the spectrometer calibration. Close the pop-up by clicking OK when finished.
Figure 5. Calibrate Spectrometer pop-up after warm up is complete.
Simple Absorbance Measurements
If you have successfully complete all of the steps above,
the Collect button
should now be active and you are ready to acquire absorbance data as a function
of wavelength (the default for the spectrometer). Just click on the Collect button
to acquire the spectrum and
Stop button
when you are
done. If wavelength is not on the x-axis, please check that the
spectrometer is not in the Absorbance vs Wavelength mode, as described below.
Click here to review the
function of the other buttons on the LoggerPro tool bar.
Before configuring the spectrometer for a kinetics experiment, you must first calibrate the spectrometer, as described above.
Open the Set Up Sensors
pop-up box again, click on spectrometer icon
and select
Configure Collection or click on the Configure Spectrometer Data
Collection
icon on the tool bar. The window shown in Fig. 6 will open. Set the data collection mode
to Absorbance vs Time (for kinetics experiments) or Absorbance vs
Wavelength (used to obtain a spectrum). When Absorbance vs
Time is selected, the check boxes under Full Spectrum are activated
and you can choose which wavelength, or wavelengths, to follow as a function of
time. Note that the software automatically selects the first
point in the list when you check the Absorbance vs Time box; unselect it before
selecting your wavelength. Click OK when finished to close this window.
Figure 6. Configure Spectrometer Data Collection window.
Upon closing the Configure Spectrometer Data Collection window, the main LoggerPro page should now have absorbance on the y axis and time on the x axis, as shown in Fig. 7. The current absorbance at the wavelength(s) that you specified will be displayed in the lower left-hand portion of the screen.
Figure 7. LoggerPro screen after the data collection mode has been set to absorbance as a function of time.
Now set the data acquisition parameters by clicking the
Data Collection button
on
the tool bar (or from the menu bar by selecting Experiment, Data
Collection). If you have successfully switched the spectrometer to
time-based measurement mode, then the window shown in Fig. 8 will open. If
not, then the data collection window for an absorbance as a function of
wavelength measurement will appear (Fig. 9) and you will need to reset the
collection mode. Note that if you try to change between a time-based
measurement and a wavelength-based measurement without changing the data
collection mode as described above, then you will see an error message and
things will not work properly.
Figure 8. Data Collection window for time-based measurements.
Figure 9. Data Collection window for wavelength-based measurements.
In the Data Collection window for a time-based measurement, you need to set four parameters. First, select the Length of the experiment (enter the number in the first box and the units in the second). Check the Sample at Time Zero check box if you want the computer to measure the absorbance immediately at the start of the experiment (a good idea in most cases). Select Sampling Rate either using slide bar or by typing a number into one of the boxes below the slide bar. Some important things to know about the sampling rate: 1) the units on the sampling rate are the same as those you selected in the Length of the experiment, 2) when you type a value in one the sampling rate boxes, the computer automatically calculates the other and 3) if you select a sampling rate that is faster than the spectrometer can actually do, a message will be displayed and you will not be allowed to proceed.
To have the spectrometer wait before it begins to record data (i. e., set a delay), select the Triggering tab and the window should now look like that shown in Fig. 10. Click on the Triggering check box to activate triggering and select either the On Keyboard or On Sensor Value options. On Keyboard means that the computer will wait until you press a key on the keyboard before it starts taking data, while On Sensor Value means that the computer will wait until the reading from the sensor is a particular value before beginning. Of the two On Keyboard is usually more useful.
Figure 10. Triggering control window.
You can add a delay to the start of data acquisition by typing a number in the Collect Samples before Trigger box. What will happen is that once you hit a key on the keyboard, the spectrometer will start acquiring data at the frequency that you told it to under Select Sampling Rate until it has collected the required number of samples. For example, let’s say you want a 90 sec delay at the start of your experiment and you are sampling every 30 sec. You would then enter "2" in the Collect Samples box so that the instrument will, after waiting the length of the sampling time, collect two data points before starting collection at time zero.
When you finish setting up the collection and triggering
parameters for your experiment, click Done. You should now be ready to
make a run. To initiate the run, push the Collect button
.
If you selected the On Keyboard trigger then the message "Waiting for Keyboard Trigger" will be
displayed in the center of the graph. Hit any key to start data acquisition, or
to start the countdown to data acquisition, if you selected a delay. The
"Waiting for Keyboard Trigger" message will go away, but there will be no other
obvious sign that the computer is counting down until the first sample collected
before "0" is collected. For example, if you have set the instrument for a
90 second delay with a 30 second sampling rate, you will first see a data point
at "-60 sec" approximately 30 seconds after you have triggered the system.
To
stop data acquisition simply click the Stop button
.