The Caliper
A Publication for Users of Vernier Products

Tips & Tricks

Computers Too Expensive? Look Again!

We often talk to teachers who tell us that they cannot afford to spend $2000 for a computer to use for data collection. Looking at recent back-to-school computer advertisements, we notice that $2000 can now get you as many as four or five desktop computers! Here are a few of the special deals we noticed:

• Circuit City, Inc. is selling an eMachines PC desktop with an AMD 2.3 GHz processor, 128 MB RAM, 40 GB HD, a 16-inch CRT monitor and color printer for $370 (after $260 in rebates).
• Dell, Inc. has a Dell Dimension with a Celeron 2.2 GHz processor, 256 MB RAM, 40 GB HD, CD-ROM drive, and 15" flat panel monitor for $499.
• Gateway sells a desktop computer with a Pentium 4, 2.2 GHz processor, 256 MB RAM, 30 GB HD, CD-ROM drive, and a 17" CRT Monitor for $618.
• Apple, Inc. has a Power PC G4, with an 800 MHz G4 processor, 128 MB RAM, 40 GB HD, CD-ROM drive, and a 17" CRT monitor, for $799.
• Amazon has a Toshiba 1805-S203 laptop with a 800 MHz processor, 128 MB RAM, 15 GB HD, and CD-ROM drive, for $699 (after $100 in rebates).
• Dell, Inc. has a Dell Inspiron 1100 laptop with a 2 GHz processor, 128 MB RAM, 20 GB HD, and CD-ROM drive, for $745 (after $50 in rebates).

FAQs about Computer Data Collection

Should I purchase a desktop or laptop computer for data collection?
Desktop computers are priced lower, but also require more counter space. Laptops have dropped significantly in price, and take up less counter space, but are a security issue for schools. We have talked to many teachers who use desktop computers, yet save counter space by placing CPU towers under counters. Flat-panel monitors have decreased significantly in price, and require less counter space than CRT monitors. Purchasing a keyboard with a trackpad eliminates the need for a mouse at each lab station.

Do I need to worry about using chemicals and solutions near my computers?
We have never heard of any "bad-spill accidents" from chemistry teachers who use our equipment in their classes. Some teachers elevate monitors and keyboards (or laptops) on small platforms on the lab-counter surface, and CPU towers can easily be stored below a counter. Keyboards are replaceable in most cases.

How much RAM, processing speed, and hard disk space do I need for data collection?
"Not much," is the short answer. Any of the computers listed above have far more capability and capacity than you will need to collect data using Vernier equipment.

What computer operating system (OS) should I have?
Our Logger Pro 3 data-collection software runs on the latest operating systems, including Mac OS X and Windows XP. We also have software and hardware to support older operating systems.

Care and Maintenance of pH Electrodes

Maintain accuracy and performance, and extend the lifetime of the electrode through proper maintenance and storage. With proper care, you may get as many as 6-8 years of use from an electrode; poor care and storage may shorten the life to 1-2 years.

pH Electrode storage
To ensure a quick response and free-flowing liquid junction, the sensing bulb and reference junction must not be allowed to dry out. Always keep the tip in contact with a solution. The soaking bottle we include with our pH Sensors makes this very easy to do.

Long-term storage
Fill the soaking bottle half full of pH Storage Solution. You can prepare this solution yourself: add 10 g of solid potassium chloride, KCl, per 100 mL buffer pH 4. Preferably add some buffer mold inhibitor. (Flinn Scientific sells Buffer Preservative.) Or, Vernier sells pH Storage Solution with the same recipe (500 mL bottle, order code PH-SS, $12). Helpful tip: If you find that you or your students are occasionally spilling storage solution when the soaking bottle is not on the electrode, simply place a nickel coin into the lid, and tighten the lid for a good seal.

Reviving dried out or slow-responding electrodes
If you have accidentally left your pH Sensor out of storage solution for a considerable period of time, you will likely be able to revive the electrode. Soak it in 0.1 M HCl solution for 2-4 hours, followed by a rinse with distilled or dionized water. Place the electrode back in soaking solution. Test its response by placing it into 2 or more buffer solutions and see if good pH readings and faster response time result. Note: Do not test response time in water with few ions (soft water, rainwater, or deionized water); pH electrodes always respond very slowly in low-ion situations!

Can I use third-party pH Electrodes with the Vernier LabPro interface? Yes! Our Electrode Amplifier is designed with this in mind (Electrode Amplifier, order code EA-BTA, $40). This amplifier allows you to use a third-party pH Electrode with a BNC connector and typical Nernst equation output with our LabPro interface. The Electrode Amplifier now has auto-ID capability (for either pH or mV readings). We also have a reliable, low-cost pH Electrode that can be used with this amplifier (pH Electrode, order code 7120B, $32).