Computer Interfacing

Data Logger Program

This is a must-have program. It's the workhorse that is used for >90% of the experiments we do. It drives most of the sensors and probes and is very capable at handling data analysis. Documentation comes with the program. I won't repeat the manual here -- rather, I'll try to share some tips, hints, and important aspects of the program. This page may change throughout the course of the exchange -- check back here once in a while!

Selecting and calibrating probes

1. Many of the probes do not have to be calibrated each day of use. You will find calibration files that students can load from disk for almost every probe.
2. Once you calibrate a set of probes (or load them from disk), you can save that calibration set to a disk. When you use two different probes in an experiment, this feature is very handy.
3. I've found that the calibration files supplied with the program only have calibration data in Port 1. If you have a probe in Port 2, you will need to load a pre-defined Port 1 calibration into Port 2.
4. Probes to calibrate every time they are used include:
   • Colorimeter Sensor
   • Dissolved Oxygen Probe (if you need more than 5% accuracy)
   • pH System (some disagree with me on this one)
5. Be careful about combining probes. The following probes should NOT be placed in the same solution if they are connected to the same computer interface or CBL:
   • Direct connect temperature system (the CBL's temperature probe is OK to use)
   • Dissolved Oxygen
   • pH System
   • Conductivity Probe
6. There are work-arounds, such as using two different interface boxes or isolating one of the probes by wrapping it in Saran Wrap or Parafilm. See the documentation accompanying these probes for details.

Setting up the program for an experiment

Experiment files

1. Unless students are designing their own experiment completely, always provide students with an experiment file. Compare what a student might have to do with and without an experiment file (click here). It's easy to make and will save endless frustration and lost time with students. When the program is adjusted to collect data the way you want, save the experiment, using the file menu. All of the options, calibrations, plot settings, et. al. will be saved to disk.

Setting plot axes

1. If only one plot is displayed (or you only want to change one plot), the fastest way to do it is to position the mouse cursor over the minimum or maximum tic value on the plot. Click the mouse button once. The value will suddenly appear highlighted in a text box. Just type in the value you want.
2. To adjust more than one plot at a time, choose Set All Min, Max from the Display menu.
3. Be aware that the experiment ends if time is on the x axis and the maximum displayed time on the plot is reached! I usually set it for a longer time period than I need -- just to be sure. If time is NOT on the x axis and the program is in event mode, time is irrelevant.

Event mode vs. continuous data collection

1. Event mode allows one to take data any time one desires. Measurements are not recorded at regular time intervals -- they are taken when you click on the Keep button.

Statistical analysis

You can fit a curve or perform other statistical analyses to any portion of your data. To select a range of data, just be sure to select Analyze Data A (or B) from the Analyze menu. Drag the mouse over the region to analyze -- and don't click anywhere else, or the highlight will disappear.

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