Starting this time, under the title "Fundamentals of Digital Measurement," we will be covering topics such as basic knowledge about physical quantity measuring instruments and frequently asked questions from our customers. Since this is a measurement column, we will try to write in a way that is as easy to understand and interesting as possible, so we hope you will read it without feeling any pressure.
Now, as the name suggests, electrical/electronic measuring instruments are mainly used to measure electromagnetic quantities such as voltage, current, resistance, power, and electromagnetic waves. However, instruments intended to measure other physical quantities (for example, length, shape, displacement, thickness, mass, pressure, force, torque, rotational speed, frequency, sound, vibration, flow rate, temperature, humidity, heat, light, concentration, etc.) are sometimes called "physical quantity measuring instruments." Strictly speaking, light is also an electromagnetic wave, so it is sometimes excluded from physical quantity measurement.
Furthermore, in recent years, there has been a growing need for measuring instruments that measure quantities and information corresponding to human sensory perception (the so-called five senses). Specifically, in the fields of light and sound (i.e., vision and hearing), illuminometers and sound level meters have been put into practical use, but in the fields of taste and smell, practical applications are lagging behind. This is probably because these quantities are more chemical than physical, making sensing and quantitative evaluation of sensations more difficult than for the former.
To develop or understand this physical quantity measuring instrument
- Understanding and sensing physical phenomena
- Electrical/Electronic Circuit Technology
- Digital signal processing technology
- Software Technology
This column will require knowledge and skills in areas such as those mentioned above. In this column, I will try to explain the basics of these topics as clearly as possible. (Please do not expect highly specialized content, as this is limited to my own abilities.)
Now, in order to sense physical quantities, physics formulas are fundamental.
Regarding that fundamental physics formula, there's something my high school physics teacher taught me that I still remember vividly.
(Causative quantity) = (Constant of proportionality) × (Resulting quantity) .... (Equation 1)
This is the formula.
For example, in Newton's equations of motion,
F=ma (force) = (proportionality constant: mass) x (acceleration)
In Ohm's law for electrical circuits,
V = Ri (Voltage) = (Proportionality constant: Resistance) × (Current)
In elastic bodies, Hooke's Law
F = kx (Force) = (Constant of proportionality) × (Strain)
And so on.
Taking Hooke's Law as an example, it can be described as "the extension or compression of a spring is proportional to the force applied to it."
If you put it this way
(Resulting quantity) = (Constant of proportionality) × (Causative quantity) .... (Equation 2)
It seems to me that this is the appropriate way to express it... I would be grateful if someone could explain why (equation 1) is a common way of expressing physics formulas.
Another point that (Equation 1) implies is that, within a certain range, physical phenomena can be considered to be in a proportional relationship, that is, they can be viewed as a linear system.
Sensors used for measuring physical quantities essentially convert physical phenomena within the range where linearity holds into electrical signals by applying appropriate physical laws.
This post has turned into more of a casual chat, but from next time I'd like to write about more specific topics.
(Excerpt from the email newsletter issued on October 18, 2007)
