will be a series of articles for people who want to obtain the best possible results from their fluorometer. For example, you may have wondered what causes the variations in your fluorometer readings when you know your sample concentration has not changed.
The articles will cover: how to optimize your fluorometer installation; understanding how instrument specifications can affect readings; the impact of non-controllable variables such as environmental considerations; and other factors that can influence the accuracy and repeatability of your measurements.
This first article is for engineers monitoring chlorophyll a, in a continuous flow mode, using a fluorometer such as the Turner Designs AlgaeWatch.
Plumbing Kit Accessories Improve Measurement Repeatability
Two factors that can cause chlorophyll measurements to "drift" with time result from 1) build up of biofouling organisms (bacteria, algae, etc.) in the flow cell of the fluorometer and 2) air bubbles resulting from intermittent flow of sample water through the flow cell. To reduce these effects on measurement repeatability, Turner Designs offers two plumbing Kits for use with the AlgaeWatch: an Inlet Kit, see Photo 1, and an Outlet Kit shown in Photo 2. The Inlet Kit is designed to address the problems of debris in the water affecting the measurement of the amount of chlorophyll present. The basket strainer should be cleaned regularly depending on: the water conditions, and the efficiency of any earlier filtering that has been done before the pump in the system. (The basket strainer is conventional, and provides easy access to all parts for convenient cleaning).
The next component in the Inlet Kit is the Flow Switch with its electrical connection to the AlgaeWatch. For optimal measurements, the sample stream should be between 0.5 and 1.25 gpm. The purpose of the Flow Switch is to send a signal to the fluorometer if the sample stream flow falls below 0.5 gpm. (To prevent control valve chatter, or unnecessary relay action, the fluorometer needs to see the "no-flow" signal for more than 5 minutes before turning on the alarm flag on the display).
The third component is a Pressure Gauge calibrated to read up to 100 psi, the maximum specified pressure for the sample cell.
The Outlet Kit has a 3-Way Valve. Purpose of this valve is to make it easy to collect a sample of the water being measured for extraction purposes. (Extraction is a process for obtaining pure chlorophyll that can be measured very precisely, and then correlated to the fluorometer readings of chlorophyll in the water).