1 Khz Inductance Meter ATTINY861

Posted on Jul 20, 2012

1 kHz is a commonly used test frequency, and I resolved to see if I could make an inductance meter that uses a 1 kHz test signal at a low level. I also wanted to use a low level test signal so that the test current would have a minimal effect on the measurement. Magnetic cores, and soft ferrites in particular, change in permeability as a function of the current through the winding. I chose 1.0 milliamps peak-to-peak as a test current. Given that I wanted to be able to measure inductance down to 100 uH, my attention turned to the problem of how to accurately measure the amplitude and the phase of as little as 63 millivolts across a 100 uH inductor.

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

Looking around on the web a little more, found the user's manual for an M3 Electgronix Digital LCRZ Meter kit, which, aside from spelling out the meter's impressive capabilities, also explained a few short paragraphs explained how the meter worked. That was enough to convince me to give this technique a try. By the way, if case you are starting to get the idea that this project is a quick and dirty knock-off of the M3 design, its not. The M3 kit has much more range, measures lot more than just inductance, and seems to be quite a bit more accurate. My project is just an exploration of circuit and firmware techniques, mostly to see what it would take to get such an instrument operating. I think that if you have the time to build the kit, the M3 kit is an excellent way to get a full function LCRZ measurement capability that rivals that of some of the most expensive factory built instruments, but at fraction of the cost. You might want to have a look at the M3 Electgronix webiste, and in particular at the web page for their meter kit. You can even download the manual for their kit on the page at this link: http://www.m3electronix.com/lcr.html. The result of this investigation is some circuit concepts, some firmware techniques, and some learning. Notably, the internal reference impedances are switched on and off without the use of electromechanical relays or switches, and a comparatively low parts count version can be...

Visit page

Leave Comment

characters left:

Related Circuits

Clock multiplier circumvents PLL

Using a standard PLL circuit, such as the CMOS 4046B with some passive components, is a well-known way to design a clock multiplier. Unfortunately, using a PLL in a digital circuit has two...

Polarity Indicator Circuit

This circuit consists of a tri-color LED, a resistor, wire, and a coin-size test plate. You will have to build two such circuits one for each black clamp on a set of auto battery jumper cables....

Bi-Color Indicator Circuit

With SI open, base bias is supplied to Q2 through a voltage divider (formed by R2 and R3), thus turning on the green element in the LED. That indicates that power is being supplied to the project....

Visual Continuity Tester Circuit

By judging the rate at which a particular LED flashes, you`ll be able to estimate the resistance. The circuit consists of two IC`s (1 4011 CMOS quad 2-input, NAND gate, Ul; and a 4024 binary...

Rc Decade Box Circuit

This decade box can be set for any resistance value between 10 and 11.1 in 10- stops. A switch can be used to configure several RC configurations. Use close tolerance components in the circuit....

Cable Tester Circuit

At the heart of the cable tester are two op amps, which are used as a window- comparator to indicate a short- or open-circuit condition. A third op-amp comparator is used to indicate a good...

Transistor Checker Circuit

The circuit is built around a 741 general-purpose op amp that is configured as a voltage follower; with the components shown, the op amp has a voltage gain of one. The output of the 741 is used to...

Audible Logic Tester Circuit

The tester provides an audible indication of the logic level of the signal presented to its input. A logic high is indicated by a high tone, a logic low is indicated by a low tone, and oscillation...

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.....