Accurate Measurement of Small Inductances

Posted on Feb 7, 2014

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

Accurate Measurement of Small Inductances

Click here to download the full size of the above Circuit.

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...

Leave Comment

characters left:

Related Circuits

METAL DETECTOR Circuit

Metal Detector DIY

The heart of this DIY metal detector circuit is CS209A. The metal detector is build with one 100 µH coil. CS209A has one oscillator which forms a LC circuit, the inductance of the coil will change...

homemade Geiger counter with UGP interface

It uses very common building blocks. The high voltage power supply is a classical oscillator circuit used in many places where a low current and high voltage is needed. TR is a step-up transformer...

English Amiga Board

Digital Clock

The complete circuit diagram is shown in Fig. 1. Heart of the system is lC2, National`s MM5402 clock chip. It is an MOS monolithic large scale integrated circuit. It`s pin configuration is shown in...

Digital High/Low Logic Tester Circuit diagram

When the input signal is logic 1, the display shows `H` and the loudspeaker emits a note which is an octave higher than the `low` tone. Operation of the circuit can be seen from the circuit diagram...

Digital Voltmeter and Ammeter Circuit Module

This V/I display module is eminently suitable for building into an existing DC power supply, where it gives a precise indication of the set voltage or the current consumption of the load. In the...

Electronic Voltmeter Ammeter Circuit Using Single IC 741

Simple Electronic Multimeter High cost deters many hobbyists from buying a conventional multimeter. Since it is difficult to obtain cheap 50 uAor 100uA meters which are essential for a highly...

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

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....
Ultrasonic distance finder circuit

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....
Simple Metal detector circuit with CD4030

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....
Fully automatic watering circuit for flower pots

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....
Simple deep searching metal detector circuit

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....
Sub-Harmonic Bass Converter for Electric Guitars

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,....
Echo Depth Sounding Sonar for Boats

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....
100W HiFi Audio Amplifier Circuit

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....
Plant-Pot Water Level Indicator Circuit

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.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Mic Phantom Supply

This is a very simple design for a phantom supply. This design will work with microphones that...

CMOS PLL circuit

One of the most interesting projects to work with is that of a synthesizer that can accurately...

Arduino controlling a DC Motor

When controlling motors with a microcontroller (like shown), the snubber is really pretty...

Simple receiver with microvolt sensitivity

The three-transistor circuit in Fig 1 costs less than $10 to build, uses commonly available...

Multi-Melody Generator With Instrumental Effect

This melody generator can generate various English and Hindi tunes as also instrumental effects....

DIY Mini Tesla Coil

This coil operates from 12V or 24V SLA batteries. A pair of car ignition coils are used to...