Many devices have been built for measuring electric charge. One of the first was the gold-leaf electroscope. When a charged object touches the metal knob at the outer end of the rod, the charge flows down to the leaves. The leaves diverge due to the repulsion of like charges they have received. The degree of […]
What’s all this double-slit photon stuff?
Newton’s corpuscular theory of light was the accepted model of light propagation in the 17th and 18th centuries. The double-slit experiment, first performed by Thomas Young in 1801, seemed to revive the wave theory of light. In the modern version of this experiment, a coherent light source such as a laser is aimed at an […]
When oscillators didn’t contain op amps
Examine a discrete oscillator circuit today and you’ll likely find an operational amplifier with components in a feedback loop that cause the oscillation. In many cases, oscillators implemented with op amps are updated versions of designs that formerly used odd-ball components such as neon bulbs and delay lines to get the required phase shift needed […]
The difference between amplifier gain and antenna gain
Amplifier and antenna gain may sound the same, and both may be expressed in decibels, but they actually are measures of two different things. In an amplifier, gain is simply the ratio of the output divided by the input. Gain has no units as it is a ratio. However, amplifier gain is often expressed in […]
Going parabolic: The difference between a Ronchi, Foucault, and a Caustic test
Amateur astronomers like to build their own telescopes, sometimes to the point of even grinding the objective mirrors. This is doable, but involves purchasing the mirror blank plus various grades of grinding abrasives, polishing compounds and specialized tools. The lens must have a precise parabolic profile. It takes special test instruments to figure out whether […]
What’s all this triplen harmonics stuff?
Unless your background is in ac power, it’s possible you haven’t run into the term triplen harmonic. Triplen harmonics have to do with the third harmonic. Even-numbered harmonics do not normally exist in power systems due to symmetry between the positive and negative halves of the ac cycle. It is the odd-numbered harmonics that engineers […]
The difference between LED and OLED displays
Despite some initial difficulties, it is reasonable to think that OLED (organic light emitting diode) displays will replace LCDs, making possible low-power flexible screens relatively inexpensive to manufacture. OLEDs have several advantages. For one thing, they can be made onto a suitable substrate by means of silk screen-printing or an inkjet printer. Roll-to-roll vapor deposition […]
Now THAT’S a test instrument: Inside the Webb space telescope
The Hubble telescope, despite its initial optics crisis, was an enormously successful undertaking that answered far more questions about the universe than originally posed. Now comes the Webb space telescope, the most powerful telescope ever put into space and a successor to Hubble. If successful, it will look farther back in time, image fainter objects […]
Measuring CMOS power use
Virtually all digital, analog and mixed-signal ICs are now done in CMOS due to the technology’s extremely low power consumption, small size and immunity to noise. Low power consumption arises from the use of a two-transistor configuration resulting in zero power consumption except during brief transitions. Interestingly, the bulk of CMOS power dissipation arises because […]
Measuring resonance with a scope and signal generator
One of the first things EE students learn in their ac circuits course is resonance. Electrical resonance, to quickly review, arises in an electric circuit at a frequency called the resonances frequency when the impedances or admittances of circuit elements cancel each other. In some circuits, resonance happens when the impedance between the input and […]
