Measure water clarity. There are devices to measure turbidity but I am looking for something to measure water clarity similar to what a secchi disk does. Is there such a device or is it something that has to be built from scratch. In short a secchi disk is a alternating color disk (black and white) and it is lowered into the water and you record how many centimeters or inches when the disk is no longer visible. HELP !!!!
I want to add temperature, gps, ph and wifi, solar panel and battery but those are already available the clarity one has me stumped. All this will be floating on a buoy on a small lake.
There are plenty of turbidity sensors, so just work out (or look up) how the output units might relate to the water clarity system you are used to using.
Hi, yes currently this measurement is done by a human in a boat at close to the same spot (not ideal he is 78 yrs old) When lowering the slightly weighted disk into the water the cord is similar to a measuring tape. The depth at which you can no longer see the disk is the distance I am trying to measure. It does vary, based on the lake conditions. It is measured in centimetres.
Turbidity and Secchi readings are are similar in that they both measure water clarity but assess it differently.
Secchi measures based on depth of the disk being visible.
Turbidity measures how much light is scattered by suspended particles. Turbidity can and will change at different depths.
Seems like one easy way would be to use a turbidity meter that gives nephelometric turbidity units, and then use the equation in the upper right-hand corner to convert to Secchi:
That is the avenue I was thinking multiple sensors mounted in 1 cm increments and then when the Lumen is below a certain value it would be considered non visible at that point. Only sticking point is currently normal reading are 300-350 cm over 11 ft that’s a long pole/rod whatever to mount sensors on. It would be nice if a sensor could be lowered on a rope and the distance recorded when the light is no longer visible by the sensor. It would have to be a slow decent by the motor and then rolled back up for storage.
You don't need to trigger the distance light is no longer visible by the sensor. You can read the light level at certain distance and make your calculations...
True, I was suggesting a light for consistency of source on a cloudy day light may penetrate less than on a sunny day but I do understand what you are saying.
Get a flat sided transparent container and shine a light through it empty onto a photodetector on the other side and measure that analog. Fill the container and measure the light again.
How much less got through? How long is the path?
Alternate: build something similar to measure above the water and then down in the water. Perhaps a short metal pole with contained led at one end and contained detector at the other. That could have adjustable length and hang from one end.
Caveat: make sure you clean the 'windows' before use.
Your test will have to consider the light spectrum. On a bright sunny day, the blue of the sunlight will penetrate and be reflected much more than what happens on a cloudy day with little to no blue.
