The success of the luminescent technology for dissolved oxygen has raised several questions by the supporters of the conventional galvanic and polarographic cell methodology for measuring D.O. PREI Instrumentation offers the following answers to give users of this new technology peace of mind.
How does a polystyrene coating compare with a silicon rubber coating on other luminescent dissolved oxygen probes?
The polystyrene coating allows the dissolved oxygen to quickly penetrate the coating and reach the sensor. Experience has shown that silicone rubber does not absorb the dissolved oxygen as quickly as polystyrene. Polystyrene coated sensors respond faster to changes in dissolved oxygen levels than silicon rubber coated sensors.
Can the Hach LDO sensor cap be damaged or destroyed by sunlight?
The black polystyrene coating on the Hach LDO sensor protects the sensor from sunlight. Research has shown that with the polystyrene layer, the sensor could withstand a simulated year of direct exposure to sun. As long as the cap is on the Hach LDO probe, there are no issues with degradation. There also are no issues with degradation of the inside of the sensor cap during maintenance or cap changes (the interior of the cap would need to be exposed for over two hours for degradation to occur). The only reason to remove the cap is when replacing it with a new cap, in which case the sun exposure time for the inside of the cap is minimal.
What type of material is the Hach LDO sensor, and how does it compare to other sensor technologies on the market?
The Hach LDO uses a platinum-based luminophore. This sensor material is superior to other materials such as ruthenium because it allows for a greater dynamic range in measurement allowing for higher accuracy and precision.
How long is the warranty on the Hach LDO probe and the sensor cap?
The Hach LDO probe is warranted for three years from the date of shipment. The Hach LDO sensor cap is warranted for one year from the date of installation or 18 months from the date of shipment, whichever comes first.
What kind of calibration does the Hach LDO probe require?
The Hach LDO is self-zeroing and calibration is stable over the year life of the sensor cap. For this reason, Hach does not recommend that a customer calibrate the Hach LDO.
What warm up time is required?
Once the analyser is on, it responds quickly, giving readings in less than 60 seconds.
Is the sensor self-cleaning?
Cleaning the sensor during normal operations is a matter of wiping the sensor with a cloth. For extreme conditions where build-up on the sensor is a concern, Hach Company offers an airblast unit.
Does the air-blast system damage the sensor?
The airblast unit will not damage the sensor coating on the Hach LDO. In fact, the Hach LDO sensor is capable of surviving harsh environments (with or without an airblast) where other sensors will fail (eg, pure oxygen aeration basin, floating media, etc).
For more information contact Steve Herbst, Hach representative, PREI Instrumentation, 011 448 2172, [email protected]
| Tel: | +27 11 867 5001 |
| Fax: | +27 11 867 7631 |
| Email: | [email protected] |
| www: | www.prei.co.za |
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