Colorimeter specs and other FAQs !
First of all, a really big thank you to all of our wonderful backers ! You have all made this process very exciting and worthwhile. With just over 2 weeks left we still have 30% left to go. We think we can do it ... we are harnessing all of our nervous energy into development and we will be posting more updates to hopefully garner 30% more support :) To get the updates rolling, we decided to post our responses to three of your FAQs.
Q1. Is an Arduino necessary to use the colorimeter?
A1. Yes, the Arduino is necessary. Many people already own Arduinos, which is why we have the two different levels. if you prefer to buy and program yourself, you can buy an Arduino Uno (for example) from many different distributors for $29.95 plus shipping. We would recommend purchasing your Arduino from Sparkfun (cat # DEV-11021) http://www.sparkfun.com/products/11021 or Adafruit (# 50) http://www.adafruit.com/products/50.
Q2. Does the colorimeter require separate reagents?
A. Yes, in most cases additional reagents are required*. For example, many water parameters that you would like to test (pH, chlorine, phosphate, water hardness etc.) are colourless, so we have to use a colorimetric assay*. There are many colorimetric test kits available. Each one needs to be calibrated with this particular colorimeter against a standard solution of known concentration. We can't do all of the tests right away, so we have started with ones that are readily available, affordable and useful. For measuring ammonia, nitrite and nitrate we currently use the API aquarium test kits which you can buy from any pet store. In addition to measuring water quality in an aquarium, they can be used in hands-on environmental science and biology activities such as nitrogen cycle labs. Depending on the interest from the Kickstarter community, we will be expanding the list of solutions that we have tested to include more water quality tests (e.g. phosphate, chlorine and water hardness). These will be posted on our website along with instructions and sample results sometime after the Kickstarter funding period is finished.
* Of course some solutions are already colored (such as food dyes or other colored chemical solutions) so no additional colorimetric tests are required.
Q3. What are the specs of the colorimeter ?
A3. We have been working on getting the specs out as soon as possible, and apologize for not having them up earlier !
Resolution: The colorimeter has a resolution of 0.01 Absorbance Units (AU).
Accuracy: The colorimeter has an accuracy of 0.02 AU. With ammonia, this is an accuracy of +/- 0.06 ppm. We expect to have the accuracy results for nitrate and nitrite shortly, although preliminary data suggests they should be within the same range (+/- 0.02 absorbance units).
Precision within the cuvette. Absorbance of the solution in the same cuvette was measured at least 3 independent times. Standard deviation was calculated for all of the measurements. In all tests so far, this value is no more than 0.01 AU;
- Precision between cuvettes. This takes into account variations between cuvettes. The same sample was pipetted into at least 3 different cuvettes and absorbance was measured. Standard deviation was calculated for all of the measurements. In all tests so far, this value is no more than 0.03 AU;
For more information on the specs for the colorimeter (with the ammonia assay) we have published some sample data on the website here: http://iorodeo.com/blog/colorimeter.