What is Hach LDO and how does it work?

FAQ - Hach LDO™

1. Are first and second generation LDO sensors interchangeable?
2. What is the difference between the first and second generation Hach LDO sensor for Hydrolab sondes?
3. What is the recommended calibration procedure for Hach LDO?
4. Q: What is Hach LDO and how does it work? A: The Hach LDO sensor cap is coated with a luminescent material. Blue light from an LED strikes the luminescent chemical on the sensor. The luminescent chemical instantly becomes excited. As the excited chemical relaxes, it releases red light. The higher the oxygen concentration, the less red light given off by the sensor cap. The red light is detected by a photodiode. The time it takes for the chemical to return to a relaxed state is measured. The oxygen concentration is inversely proportional to the time it takes for the luminescent material on the sensor cap to return to a relaxed state. Between flashes from the blue LED, a red LED of known intensity is flashed. The red LED acts as an internal standard for reference comparison to the red light given off by the luminescent sensor cap. This comparison allows the sensor readings to remain stable for long periods of time.
   
   
5. Is a circulator required with the Hach LDO sensor?
6. Will fouling affect the DO readings from a Hach LDO sensor?
7. How long will the sensor cap last?
8. What is the warranty on the Hach LDO sensor?