Here is a simple way to measure an unknown inductance by forming a resonance LC circuit and measure it using an oscilloscope. Glen Chenier writes:
One of our technicians recently asked for help determining the value of an SMT inductor. It was unmarked, and was many turns of very fine wire on a ferrite core. The resistance measured 26Ω, which for some reason gave our ancient LCR bridge a conniption, and read 30mH along with a blinking error message. The tech rightfully felt that such a small inductor could not possibly be 30mH.
Texas Instruments (TI) announced the world’s first multichannel inductance-to-digital converters (LDCs). The four new devices in the LDC1614 family expand the innovative LDC portfolio, a data converter category that TI first introduced in 2013. The devices offer two or four matched channels and up to 28-bit resolution in a single integrated circuit (IC).
The combination of precision and multichannel functionality will allow engineers to design high dynamic range position and motion sensing solutions with simpler system designs and reduced cost. Unlike other technologies, LDC-enabled inductive sensing employs low-cost, high-reliability inductors as sensors, which can be located remotely from the IC. By integrating up to four channels in a single IC, the LDC1614 family allows designers to distribute sensors throughout a system, while centralizing electronics on fewer printed circuit boards (PCBs). This can benefit precision linear or rotational sensing and metal detection in a variety of end equipment including white goods, printers, cameras and automotive infotainment consoles.
TI introduces world’s first multichannel inductance-to-digital converters – [Link]
This project uses an entirely different microcontroller: A PIC 16F1932 instead of the Atmel Atmega328
This code is written in C (for the MikroC for PIC compiler by Mikroelektronika), not Arduino-style C++
The display I’m using here comes with a I2C interface rather than the familiar Hitachi interface
Lukas of Soldernerd built a DIY Arduino-based inductance meter:
I’ve just finished a little Arduino project. It’s a shield for the Arduino Uno that lets you measure inductance. This is a functionality that I found missing in just about any digital multi meter. Yes, there are specialized LCR meters that let you measure inductance but they typically won’t measure voltages or currents. So I had to build my inductance meter myself.
I had a bunch of random inductors in some random drawers and I wanted to know what values they were. These values are quite often not obvious by looking at the device. Colour codes for old ones were not standardized and some of the coloured rings on inductors can be faded or discoloured so that its impossible to tell what they are. Others may be unmarked and any that are hand-wound are just guess work without a meter. So I decided to make an inductance and capacitance meter which would be fairly accurate and work over several decades of value from a few nano-Henries to a few milli-Henries and also from a few pico-farads to about a micro-farad (hopefully). Sounded easy – what could go wrong?
This beehive weight scale uses a TI LDC1000EVM inductance processor circuit to measure the weight of a Beehive, by detecting the the change in resonance due to a change in inductance, as the change in weight on the scale occurs. The processor sensed and measured differences; outputs are sent to a collocated laptop computer via a USB port and displayed by the TI software GUI on the screen. For this design concept, it was decided to design for a maximum of 160 lbs. The detailed PDF available below shows a range scale of desired performance, however the LDC1000 was not well understood by me at first, so this concept was a design to fit the unknown performance of the LDC1000, but adjusted to make it work.
Inductive Loop Detector is detecting the inductance change of a buried wire coil and thus it can be used to detect metal objects. by elektronika.ba:
Inductive Loop Detector works by detecting an inductance change in wire loop (coil) that is buried in road. It does that by measuring the frequency of the internal oscillator which powers the mentioned coil. When a metallic object moves over the coil it changes its inductance and that in turn changes the oscillator frequency which is measured by the microcontroller.
It is used for vehicle access control at door and barrier controls, for monitoring the occupancy and for vehicle counting in parking garages, traffic light installations and traffic controllers, direction and speed detection of vehicle traffic (if dual channel version is used), in car-wash plants, etc.
Texas Instruments designers have developed an entirely new data converter with the LDC1000 inductance-to-digital converter (LDC) designed specifically for inductive sensing applications.
The LDC uniquely combines all of the external circuitry on chip that is normally required to simultaneously measure the impedance and resonant frequency of an LC resonator. It then regulates the oscillation amplitude in a closed loop to a constant level, while it monitors the dissipated energy of the resonator. This leads the accurate measurement of inductance of the front-end LC circuit, which enables precise measurement of linear/angular position, displacement, motion, compression, vibration, metal composition and new applications which will be conceived by designers. All of this can be done in the presence of oil, dust, dirt and moisture unlike most other solutions.
LDC1000 – Texas Instruments inductance to digital converter (LDC) – [Link]
Bipolar junction transistors transfer a current from a lower-resistance emitter to a higher-resistance collector. You can use this property to measure inductance by connecting a series inductance/resistance circuit in the emitter and biasing on the transistor long enough for the current to reach a maximum value that is at least five LR time constants. When the transistor’s off time is equal to its on time but is still biased by a silicon diode, the LR current decays exponentially toward 0A. Using the transistor’s current-source property, you can measure this current without hindering the decay process in the LR circuit.
Use a transistor and an ammeter to measure inductance – [Link]
An LCR meter is an extremely useful device for measuring three basic impedance elements, namely, Inductance (L), Capacitance (C), and Resistance (R). Recently, I got a TENMA 72-8155 digital LCR meter from Newark for review. I was very excited to receive it as I didn’t have a dedicated LCR meter in my home lab. Here’s my quick review of this product.