Tuesday, December 30, 2014

Meters That Use Light Versus Meters That Use Electrodes

I'm just beginning to understand the differences between meters that measure pH, turbidity, dissolved oxygen, and other components of water. The traditional meter measures light or color. For instance in the Secchi scale, one drops a disk in the water until it just fades from view. What is measured is the length of line played out. The Secchi disk is easy to use by volunteers to monitor inland lakes  (e.g., Indiana Clean Lakes Program, and Citizen Lake Monitoring Program in Minnesota). A modification of that principle is used in the World Water Monitoring Challenge Test Kit in which the distance is controlled by the depth of the container and the clarity of the water is compared to a standard chart. Charts are also used in the Kit for color comparisons when color-activating chemicals are added.
Modified Secchi Scale controls the depth and compares the clarity of the disc on the right to a standard shown on the card to the left. 

Color spectrometry is used to calculate the pH value. The chart on the left is compared to the chemical-filled water sample on the right. 
Although the naked eye can do a good job of comparing standards to samples, there is error introduced from the light source and the human eye. Spectrometers are more accurate. Chemicals are available to colorize for many molecules contained in water (or soil). For instance, Phosphate and Nitrate amounts can be detected using appropriate chemicals and a spectrometer. An example of a spectrometer used to measure swimming pool water is the eXact iDip.

An alternative to measuring color through spectrometry is to measure electrical conductivity with a galvanometer and electrodes. Doing so requires specific electrodes and calculations, but not added chemicals. A simple device is the total dissolved solids meter (e.g., Dr. Meter TDS conductivity meter). To learn more, read about ion selective electrodes on Wikipedia. One advantage of using electrodes is the elimination of chemicals and color analysis. Another advantage is automation. For instance, an electrode-based probe can be connected to a smartphone to read, geolocate, calculated, store, and transmit automatically. For instance, Sensorex makes a general smartphone interface for its probes and pH interface for iPhone (approximately $300). YSI has an interesting multi-electrode product that is portable [Meter ($1500), assembly ($1700), and sensors ($450-$1000].
Sensorex iPhone adaptor and probe.

Tuesday, December 23, 2014

A Lake Michigan Cruiser Takes to the Land

Beth and I have been cruising on Lake Michigan for 8 seasons and have put about 8,000 miles on Speakeasy, mostly going from Chicago to Beaver Island, Michigan. In October, we got the chance to try a small motorhome for a weekend and since then have been to Bay Field on Lake Superior, Lake Winnebago, both in Wisconsin, Traverse Bay in Michigan, and Lake Eloise, where Cypress Gardens used to be in Florida. In a few months, we've traveled 4,000 miles. Our next land-cruising trip will be to Los Angeles via the great Southwest United States—another 4,000 miles. We'll have put as many miles on VERA in 6 months as we have on Speakeasy in 8 years.
Beth, Mark, and Java before VERA in Winter Haven, FL

We're so lucky that I have a generous brother who is willing to travel vicariously while he waits for more time off. It's his family's motorhome. The van is a Dodge Sprinter conversion by Winnebago. At 24-feet long, it is a perfect size for a couple with a dog. Like Speakeasy, it has a large berth for sleeping, comfortable salon seats, a salon table, galley, head, and fresh water. In addition, VERA has both heating and air conditioning. We're still learning about the land cruising world, but will share more along the way. 

Lakewood RV Resort in Hendersonville, NC is near Flat Rock where Carl Sandburg lived the last 2 decades of his life. 

Fort Clinch State Park on Amelia Island, FL is a wonderful beach park. 

At the old train station with old friend on Amelia Island, FL