The multi-beam difference and how it works
People often ask how our multi-beam technology works, and why it’s so much better than single-beam sensors. The short answer is that it’s all in the maths.
When an LED fires a single beam of light through a liquid to a detector, we can measure turbidity – at least in theory.
Turbidity
Some of the beam hits the solids that are suspended in the liquid, and scatters. This light scatter is called turbidity.
The rest of the beam makes it through to the detector, which measures how much light intensity is lost, giving us a turbidity reading.
In reality it’s a little more complicated with three other variables that can affect the measurement, and they all need to be controlled for:
Distance
Distance
Can be controlled
First, as light travels, it naturally gets less intense, which could be misread as turbidity. All sensors control for this by fixing the distance between the LED and the detector.
Dirt
Dirt
Introduces measurement error
Second, dirt build-up on sensors blocks light and causes false readings until it’s cleaned off. Single-beam sensors try to control for this with mechanical wipers, but that only gives you partial accuracy which undermines the reliability of the whole measurement.
Ageing
Ageing
Introduces measurement error
Third, electronics age, so they might not send or receive as much light as they once did. Single-beam sensors don’t have any controls for this.
The solution is a multi-beam sensor that self-compensates by using a ratio-metric algorithm.
Dirt
Quadbeam's multi-beam sensors have two LEDs and two detectors. When the first LED switches on, it fires a beam to both detectors - one closer, and one further away.
Both detectors take a reading, and the readings are turned into a ratio: Ra = Ix1/Ix2.
Ageing
Then the second LED switches on, and again both detectors take a reading.
Both detectors take a reading, and the readings are turned into a ratio: Ra = Ix1/Ix2.
Combining these ratios gives Quadbeam sensors their precision and their unique advantage
Quadbeam sensors bring both of these ratios together to eliminate the effects of dirt and ageing: Rc = Ra/Rb.
The result of all this maths is that we’re left with just one factor that can influence the light readings – the turbidity itself.
Quadbeam sensors will give accurate readings unless they’re completely clogged. If that happens, just use the simple cleaning process. By calibrating the sensor, we can use turbidity to tell us the exact concentration of the suspended solids that cause it – giving you more insight and more control than ever.