How does one measure small inductances with a precision of at least two, and possibly three, significant digits A search of the literature produced scanty results. One interesting circuit was described in The 2001 ARRL Handbook on p 26. 22. I built a replica, and duplicated the results. Measurements with accuracy of ±10% can be made with that clever
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device from about 3 to 3000 µH, and that is good enough for many ham applications. A more accurate and direct reading device was described by Robert Vreeland, W6YBT, in QEX (May 1989); but an expensive Fluke DMM is required. Evidently, accuracy in the 3-5% range can be expected with W6YBT`s elegant method. Nonetheless, 1% accuracy and measurement of smaller inductors (down to about 0. 5 µH) was the goal, even if elusive. I attempted numerous approaches, including various unsatisfactory bridges and the old standby grid-dipper method. By forming a parallel resonant circuit with a known-value capacitor and finding the resonant frequency with a grid-dip meter, the value of the inductor can be estimated. At best, this yields ±10% accuracy. A serious shortcoming of this method is that coupling to toroidal inductors is nearly impossible since the magnetic field is concentrated in the core. (Did I miss something Has someone found a way to do this without influencing the unknown tuned circuit`s resonant frequency ) Finally, a simple solution occurred to me: the converse of the grid-dipper method. If we put the unknown inductor in parallel with a known capacitance in an oscillator and measure the frequency of oscillation with a counter or accurately calibrated receiver, we can calculate the inductance from the known tuned circuit capacitance and oscillator frequency. This method works very well, and I am convinced that it yields...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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