Hello,
I've been trying to measure turbidity using sensor SEN0189 from Gravity. I've seen the producer site (Turbidity_sensor_SKU__SEN0189-DFRobot) but the diagram showing relationship between NTU and voltage is not working for me (I get values that are around 2000 NTU in crystal water so it is outrageous). I've also seen many posts here about this sensor, but the formulas are obtained from 3 measurement points, so it is a useless formula (see Getting NTU from Turbidity Sensor on 3.3v - #8 by Fredx)
Has anyone came up with an accurate formula for measuring turbidity using this sensor with 3.3V power supply? I could make my own formula using distilled water and 4000 NTU solution but I am running out of time in my project and prefere to base my work on already derivated formulas. Below I am adding the diagram from producer page.
That formula is, of course, utter nonsense. A straight line is a reasonable fit to the data.
Most people calibrate sensors by collecting data under known conditions, and fitting an appropriate curve. In your case I would dilute the 4000 NTU standard a couple of times to get 1000 and 2000 NTU (for example, with clear water as 0 NTU), then make some measurements and see.
Here is a DIY "Citizen Science" example to consider: Sensors: OpenOBS | Coastal & Fluvial Sediment Dynamics
Thank you for the additional information, but is it possible that my calibration will differ if I am using 3.3 V power supply rather than suggested or used by the producer, 5 V power supply?
Absolutely. Post the results you obtained for clear water and 4000 NTU.
This thread may be helpful: https://publiclab.org/questions/wmacfarl/10-28-2019/how-can-i-calibrate-a-turbidity-sensor
The problem with the 4000 NTU method is that it pretty expensive (as well making it on my own or buying ready product) as it is only my uni project. So I am thinking about making a solution that would "simulate" around 3000 - 4000 NTU, but there aren't many good explanations how to prepare one not using strictly chemical ingredients used for making 4000 NTU.
If you are at a university, ask around to borrow a professional turbidity meter, to use for calibrating your own. Then it doesn't matter what solution you use, as long as the turbidity is in the measurement range.
Using lower than the recommended supply voltage will significantly reduce the amount of light from the sensor emitter, and increase the apparent turbidity.
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