- Location
- Connecticut
I tried my hand at extending the low range of the Salifert nitrate test kit with a photometer built with an Arduino Uno, a blue LED and a photoresistor. One hard and fast design criterion was for the device to measure the color of the 1 mL test solution the Salifert test generates. The electronics were trivial but building a DIY sample cell to measure small volumes of liquid consistently was a challenge for me. In the end I reached a level of consistency that convinced me that the test color for 0.2 ppm nitrate was not much different from tank water in color as far as my photometer was concerned.
The final sample cell design was made from a piece of 3/16 inch rigid plastic tubing with a tiny acrylic window glued on at the sensor side and the blue LED plugging the other end. The plastic bottle with the white tubing (bell wire insulation) was how I was able to fill the sample tube with a half mL of test solution while excluding air bubbles.
The final sample cell design was made from a piece of 3/16 inch rigid plastic tubing with a tiny acrylic window glued on at the sensor side and the blue LED plugging the other end. The plastic bottle with the white tubing (bell wire insulation) was how I was able to fill the sample tube with a half mL of test solution while excluding air bubbles.
