The Government Laboratory (GL), Hong Kong Council for
Testing and Certification (HKCTC), Open University of Hong Kong (OUHK) and
Standards and Calibration Laboratory of Innovation and Technology Commission (SCL)
jointly organized the online Metrology Symposium 2021 on 28th May 2021. The theme is “Metrology Around Us”. Hong Kong Society for Quality (HKSQ) was one
of supporting organizations. The seminar aimed to share selected several
interesting topics around our daily life and the recent development in the
transformation of the International System of Units (SI) to the digital world
led by the International Committee for Weights and Measures (CIPM). Group photo was took after welcoming address
and opening remarks.
The first speaker was Mr. Brian HT Lee (Electronics
Engineer, SCL) and his topic entitled “Can we use a smartphone as a luxmeter?”
In the beginning, he asked us to think a student proposed to measure the plant’s
growth rate against light condition using luxmeter. Is this measurement method
appropriate?
Then he introduced basic theory of photometry and
radiometry, as well as photometric units.
Some daily life examples of luminous flux were discussed.
Finally, Mr. Lee compared the key components in
smartphone and instrumental luxmeter.
The key difference was the acceptance angle that the smartphone luxmeter
reading is dropped by ~10% to the instrumental luxmeter.
The second speaker was Dr. Alvis CF Au Yeung
(Electronics Engineer, SCL) and his topic named “Is time running at the same
rate at different places in Hong Kong?”
Dr. Yeung shared the content including definition of second, Caesium and
optical clock as well as general relativity theory.
Firstly, Dr. Yeung briefed the definition of second,
SI base unit of time. It used the fixed numerical value of the caesium
frequency to express the unit Hz (s-1).
Then he briefed the general relativity theory and
Lorentz time dilation named after the Lorentz transformation that related the
space-time coordinates. And he
introduced the effect of the gravitational time dilation. He showed the
different altitude in Tai Mo Shan and Avenue of Stars.
Finally, Dr. Yeung calculated the atomic clock runs
9ns faster per day at Tai Mo Shan.