Well we’re two days late, but the data on our new turbidimeter setup were worth the wait. WASH For All members Alex Krolick and Chris Kelley tested the current build (single-beam IR LED with TSL230R sensor) against a handheld MicroTPI turbidimeter freshly calibrated at the factory. The two driving questions were: (1) does this perform to expectation for the intended use range (0-100 NTU) and how turbid can a water sample be before the setup stops accurately reporting. To explore these questions eight readings were taken with the experimental setup and the MicroTPI at each of 60 turbidity intervals from 0-1,000 NTU (there went Saturday afternoon). The chart below compares the average NTU measurements from the MicroTPI turbidimeter with the average arbitrary units (AU) readings of our prototype.
The curve shows two highly linear regions with an inflection point at roughly 300 NTU. Needless to say we are pleased, and pleasantly surprised that the prototype faithfully measured up to 1,000 NTU. This setup achieved the following accuracy measures:
± 0.5 NTU in the range of 0-20 NTU
± 2.0 NTU in the range of 20-200 NTU
± 2% in the range of 200-1000 NTU
These achievements surpass most of our design goals for this summer’s public release, and fall just short of goal for the range 20-50 NTU. We are busy at work refining this prototype and will have more to report soon, including photos of the sleek new 3D-printed casing!