Apogee released their newest PAR light meter, the MQ-500 earlier this year with a brand new and improved light sensor. The improvements to the sensor of the Apogee MQ-500 increased the accuracy of this PAR meter across across the visible wavelengths of light, especially its sensitivity in the blue end of the spectrum.
With our reef tanks being dominated by blue-LED lighting we expected the new Apogee MQ-500 PAR meter to registermuchhigher light levels than the previous MQ-200 meter. Contrary to our expectation, our real world experiencecomparing the new and old PAR meters from Apogee对于几乎所有的光波长,MQ-200显示了MQ-200的总体读数较高。
我们与Apogee的工程师讨论了这种差异,他们起初无法确定可能导致这些意外读数的原因。除了信念Apogee在开发其新的MQ-500 PAR表之前,我们别无选择,但是由于某种原因,我们的测试underwaterPAR measurements were not lining up.
We kind of put the issue aside for the time being but yesterday Apogee reached out to us with an explanation和解决水下质量标准杆问题的解决方案。Apogee Mark Blonquist的首席科学家解释说,不同的测量值是“沉浸式效应”,对其不同的传感器的影响不同。显然,由于扩散材料,半透明,折射和光散射之间的相互作用以及从“Measurements of Spectral Irradiance Underwater” by Tyler & Smith:
‘当一种半透明的,扩散的材料被浸入水中时,散射材料边界处的折射率变化会导致散射到水中的入射辐射通量的比例更大,而不是散落在空气中。这种沉浸式效应是内部和外部界面反射变化的结果,结合了扩散材料中的多个散射。’
Apogee的PAR仪设计用于露天,即使某些型号具有防水传感器。但是,随着水族馆的爱好成为其客户群的越来越多的一部分,Apogee考虑了这些水下沉浸式因素,并提出了一个校正因素,似乎可以纠正我们的预期PAR值。
When measuring PAR with the old MQ-200 or similar sensors, a correction factor of 1.07 should be added to all light readings. Meanwhile if you have the new Apogee MQ-500, the correction factor is much higher at 1.32, basically increasing the underwater light measurements by 32%.
This new correction factor gives us much more accurate measurements of PAR value underwater, and it brings the MQ-500 meter to read light at about 3% higher than the old PAR meter. Measuring light intensity is a tricky task, and it gets even more complicated when the interplay of light and refraction is brought into consideration.
这只是表明你应该neverblindly trust the readings of ANY parameter for your aquarium, simply because you believe your electronic sensors or meters are more ‘advanced’ than some other method of measurement – this goes for refractometers, pH probes, ORP, temperature and especially Photosynthetically Active Radiation.
Big thanks to Apogee for working on to make their meters as accurate as possible, and we look forward to a forthcoming whitepaper from the company which more formally explains the immersion effect and how to correct for it.