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SC7657 Kit ($45 + postage): includes everything in the parts list a compact and simple ¬C Meter by Andrew Woodfield This little LC meter uses just 20 parts and delivers accurate results across a wide measurement range. Importantly, no costly or hard-to-find precision parts are needed. Compact, lightweight, inexpensive and easy to build Inductance range: <10nH to about 100mH Customer 3D-printed case M 62 Silicon Chip Capacitance range: <10pF to about 1μF Typical accuracy: ±2% any years ago, I built my first LC meter using the Atmel 89C8051 microprocessor. It worked very well, but it drained batteries fast. This was not really a problem because I rarely used it for more than a few minutes at a time. When I moved to another country several years later, I designed my own LC meter using one of the Microchip ATtiny microcontrollers and a twoline I2C alphanumeric LCD screen. It was powered by a standard 9V battery via an LP2951 low-dropout voltage regulator. While it drew very little current, unfortunately, just when I most wanted to use it, the 9V battery would require replacement. Returning home, I modified it to use a single 1.5V AA alkaline cell and a tiny boost converter. The AA battery version had a surprisingly good life. One reason was the complete absence of relays in the design. Some LC meters use anywhere from one to four (!) relays. This new version quickly became my ‘go-to’ LC meter. It was also borrowed periodically by friends because of its accuracy and ease of use. I was asked if I could design a smaller, cheaper, easier-to-make version. While I had expected the change to a single AA cell to bring about a reduction in the overall size of the LC meter, it was still constrained by the size and shape of the alphanumeric LCD Measures capacitor and inductor values Power supply: single AA cell screen and the added boost converter. That LCD was also a relatively costly device. These factors, along with the perceived need for 1% tolerance parts for calibration, were all seen as barriers by potential builders. The wide availability of smaller, inexpensive 0.91-inch OLED screens was the catalyst for a further redesign. It offered the opportunity to further reduce the size, cost and parts count. The product of this latest redesign is the LC meter described here. By finally doing away with any regulator and using any convenient USB-C 5V power supply, the LC meter has now been reduced to the volume roughly of a pair of AA batteries. Note that the 2-pin USB-C connector used is not standards-compliant and may not work with all USB-C/USB-C cables and power supplies. It should work with all USB-C/USB-A cables. A little LC meter theory Almost all LC meter designs use an LC resonant circuit in a simple oscillator. These typically operate around 500kHz (the ‘reference frequency’) when no actual inductors or capacitors are being measured. A 100μH inductor and a 1nF capacitor are the typical resonant circuit values used. When an unknown capacitor or inductor is added to this resonant circuit, the oscillator frequency drops. By Fig.1: an LM311 comparator is commonly used in the LC measurement oscillator in electronics most LC meters, but it requires a relatively high number of parts. Australia's magazine siliconchip.com.au measuring this reduction, the value of the unknown part can be determined. One variation of this approach uses two capacitors in the basic tuned circuit. The additional frequency measurements were claimed to give more accurate results. However, this additional capacitor proved unnecessary. Even the value of the reference inductor can be ignored when calculating the value of the capacitor or inductor being measured. For those interested in the details, refer to the panel titled “Only one capacitor is required”. Only one capacitor is required A simple LC resonant circuit, shown in Fig.a, lies at the heart of the LC meter. It sets the output frequency of the meter’s 74HC04 inverter-based oscillator. This LC circuit resonates at a frequency determined by the values of L and C: f1 = 1 ÷ (2π√LC). If another capacitor, Cx, is added in parallel with this circuit (Fig.b), the oscillator frequency falls to a lower frequency, f2 = 1 ÷ (2π√LC + LCx). If the value of capacitor C is known, we can calculate the value of the unknown capacitor, Cx, from the original frequency f1 and the new, lower, oscillator frequency f2 using this formula: The LC meter backstory Most current LC meter designs are derived from the original AADE design published by Neil Heckt in Electronics Now magazine, June 1996, or variations based on a later design and software by Phil Rice, VK3BHR. However, the approach used in these LC meters is actually much older. For example, the Tektronix model 130 LC meter first released in 1959 (June-­August 2020; siliconchip.au/ Series/346) used the same method, although using an analog display. Some thirty years later, Bill Carver, K6OLG, used a FET-based oscillator and some Pascal software in a design described in Communications Quarterly magazine in Winter 1993 to achieve a similar result. But it took until 1998 for these ideas to be integrated into Neil Heckt’s compact design, complete with a digital display. Fig.a: a simple parallel resonant LC network. This means that the unknown capacitor value may be calculated directly using the value of the reference capacitor (C) and the two oscillator frequencies (f1 and f2). It is also possible to measure an unknown inductor with the LC circuit. In this case, the unknown inductor (Lx) is added in series with the existing inductor L, as shown in Fig.c. The frequency again falls from f1 to f2. Fig.c: adding inductance in series with the original L also lowers the resonant frequency. Design optimisation The oscillator at the heart of many of these designs uses a fast comparator such as the LM311 (see Fig.1). While it can work very well, it uses a relatively high number of parts. Also, at times, I’d found the LM311 hard to find and/ or relatively expensive. We’ve also heard from some people who’ve built these circuits and they fail to oscillate. Swapping the LM311 usually fixes it. Few details were typically given about the best parts to use for the main oscillator components (L1 and C1 in Fig.1). A few builders suggested that this oscillator required low-ESR coupling capacitors. Several internet forums mentioned problems with specific types of inductors. Details based on measurements and testing, however, were scarce. Since I wanted to identify the best parts to use for L1/C1, I also used this siliconchip.com.au Fig.b: adding more parallel capacitance (externally) lowers the resonant frequency. Once again, this equation calculates the value of the unknown inductor Lx based only on the value of the two resonant frequencies, the first (f1) with only L and C in circuit and the second (f2) with the addition of the unknown inductor. The only other parameter needed is the value of the reference capacitor, C. Therefore, the value of unknown capacitors and inductors can be measured by knowing the value of just the reference capacitor, C. opportunity to look at a simpler and less costly alternative oscillator. Based on some previous work with 74HC04 CMOS hex inverters in oscillators, this device looked like a good candidate. This choice might address another problem. The LC meter’s accuracy relies on a very accurate clock source. Australia's electronics magazine Most LC meters use the chosen microcontroller’s internal oscillator and an external crystal. Unfortunately, by opting for a small 8-pin ATtiny processor in my LC meter, only one pin remained free for an external clock. That meant I had to use a separate external crystal oscillator. May 2026  63 Initially, I used a discrete single-­ transistor oscillator based on a Jim Williams design (in Linear Technology Application Note 12, October 1985) which also offered temperature compensation, but this took more parts as well as PCB real estate. The availability of several spare gates in the 74HC04 allowed me to build a suitable crystal oscillator with just a crystal and three extra passives. Fig.2: the value of MKT capacitors can change significantly with frequency, making them a poor choice for an LC meter reference capacitor. Source: Ostrava MKT datasheet. Resonant circuit components Since the reference frequency is determined almost entirely by the value of the inductor and capacitor used, it is important that their values are stable during any measurement(s). In practice, as with any analog oscillator, the reference frequency changes slightly with changes in temperature. It’s a sensitive circuit. Simply switching on the LC meter and passing the tiny current through the LC circuit as it starts oscillating results in a slight change in temperature. One measurement method can largely negate the impact of this drift. By measuring the reference frequency prior to connecting the unknown part, then quickly measuring the oscillator’s frequency once the part is connected, the impact of drift can be mitigated. The best solution, however, is to select stable components. The reference inductor and capacitor should ideally be perfectly stable with temperature. An inductor wound on a high-Q ferrite toroid might appear ideal. However, the typical temperature coefficient (TC) for this type of inductor is up to 10,000ppm/°C (!), making it unsuitable. Similarly, a silver mica capacitor would appear the ideal choice for the reference capacitor. These have excellent temperature stability and, while relatively expensive, ±1% tolerance parts can be obtained. My tests showed that the optimal solution is to balance the TCs of the reference capacitor and inductor. This is a similar approach to that used in legacy analog RF variable frequency oscillators (‘VFOs’). After testing a variety of inductors, this design uses a cheap and widely available axial choke inductor and a polystyrene capacitor. The axial choke has a positive TC of about 300-500ppm/°C, while the polystyrene capacitor has a TC of around -150ppm/°C. While it’s tempting to suggest substituting a polyester (-200ppm/°C to 600ppm/°C) or Mylar (-300ppm/°C) capacitor, they can suffer from changes in capacitance with frequency, especially the MKT types that come in rectangular packages. Some polyester/Mylar capacitors may be suitable, but it’s hard to know which without checking the data sheets. For example, one manufacturer’s specifications for an MKT capacitor (Fig.2) shows a variation in capacitance of around 4% from 1kHz to 1MHz. Circuit details The resulting circuit is shown in Fig.3. It is built around two inexpensive devices: the 8-pin ATtiny85 microcontroller and a 74HC04 CMOS hex inverter. Three inverters in the 74HC04 provide the measurement oscillator and buffer. It uses less current and requires fewer parts than the more familiar LM311-based oscillator. This is configured as a Franklin oscillator using two of the gates of Fig.3: an inexpensive CMOS hex inverter (74HC04) is used in the two oscillators required in this LC Meter, while a Microchip (Atmel) 8-pin ATtiny85 calculates the value of the unknown inductors or capacitors and drives the OLED display. 64 Silicon Chip Australia's electronics magazine siliconchip.com.au the 74HC04 (IC1f & IC1e). The third gate (IC1d) buffers the oscillator and connects the output to the ATtiny85 microcontroller (IC2). Relay switching is avoided through the use of a simple two-pole changeover slide switch, S1. Contacts on this switch also tell the processor whether the user wants to measure inductance or capacitance. It’s simple, inexpensive and reliable. It also has the considerable advantage of drawing no current. The Microchip ATtiny85 8-pin microcontroller with its 8kiB of internal flash program memory is the brains of the meter. It measures the frequency of the LC reference oscillator, monitors the user LC mode selection and calibration switch inputs, and drives the OLED display. The software is written in Bascom-­ AVR, and it consumes 99% of the 8kiB memory, although a few hundred bytes are consumed for the arguably cosmetic ‘splash screen’ image that’s shown when power is applied. There are three further inverters available in the 74HC04 used for the crystal oscillator circuit. HCxx inverters are not usually considered suitable for crystal oscillators. However, by configuring these gates again as a Franklin oscillator with minimal feedback coupling, the resulting crystal oscillator delivered a reliable solution while further reducing the parts count, current drain and cost. Incidentally, this circuit was tested with a variety of 1-30MHz crystals from several sources and it proved quite reliable. Using this circuit with other crystal frequencies for other designs will require a change to the value of the coupling capacitors to ensure reliable operation. Each line in an I2C interface (SDA & SCL) usually requires a pull-up resistor to the supply rail. Usefully, these are already on the OLED module, saving another two parts. This LC meter draws about 25mA during operation. The OLED screen is responsible for about 70% of that. The earlier I2C LCD version drew less than 15mA, but those LCDs are also more expensive and harder to find than OLED displays now. The ±1% reference capacitor Practically every DIY LC meter or capacitor meter design seems to demand one (or more!) ±1% tolerance capacitors, at least for the capacitor siliconchip.com.au Measuring capacitance accurately This simple method can measure capacitor values within about ±1.5%. It requires a lowcost function generator with a low impedance output (eg, 50W), an oscilloscope and a digital multimeter. A frequency counter may be required if your function generator does not have a digital display (and you don’t have one built into your oscilloscope). The measurement setup is shown below. The oscilloscope is used to measure the magnitudes of Vin and Vout. A digital AC millivoltmeter is a better choice if you have one (we’ve published several suitable designs). If the output voltage Vout is exactly half that of the input voltage Vin then C = √3 ÷ 2πfR. Let’s assume the function generator (used as the signal generator) is set to generate a sinewave at about 10kHz. Ideally, the frequency used should allow the resistor value (R) to be accurately measured with at least 3½ digit accuracy using the multimeter, eg, 123.4W or 1234W. Let’s say the capacitor to be measured is labelled “10nF” (although we don’t yet know its precise value), and f = 10kHz. In that case, R = √3 ÷ (2π × 10kHz × 10nF) = 2757W. The nearest standard value is 2.7kW. Reach into your parts bin and take out a 2.7kW resistor, then measure its actual value with the digital multimeter. My old Fluke Model 75 multimeter has a stated accuracy of ±0.7% when measuring resistors, although the typical Model 75 actually had an accuracy closer to ±0.3% ex-factory. The “2700W” resistor I selected measured 2762W. Use that resistor as “R” in the circuit below. The “unknown” capacitor C is the 10nF value to be accurately measured. Set the function generator initially to 10kHz. Measure the frequency with a frequency counter if the function generator’s display is not sufficiently accurate. You should be able to set the function generator frequency with an accuracy better than ±50Hz (±0.5% <at> 10kHz). Most function generators will display the frequency much more accurately than this without the need to use a frequency counter. Connect your oscilloscope to measure Vin and Vout. Many modern oscilloscopes have a digital measurement function that will report these values to three-digit accuracy. Adjust the frequency of the function generator so that the output voltage (Vout) is exactly half that of Vin as measured on the oscilloscope. Some adjustment of the generator’s output level may be required to measure both voltages accurately to achieve the best result. Measuring this 2:1 ratio accurately is the source of the greatest measurement error in this process, so care is required. I found the generator had to be set to 9611Hz, so C = √3 ÷ 2πfR = √3 ÷ (2π × 9611Hz × 2762W) = 10.385nF. The scope probe’s tip capacitance is in parallel with the Vout measurement. This capacitance is typically stated on the probe; mine was specified as 15pF. Deducting this from the calculated capacitance gives 10.37nF. This is the exact value of the How to accurately measure a capacitor’s capacitor. With the test equipment value using a function generator, and procedure described, the result frequency meter and multimeter (for can be shown to be accurate to measuring the R value). ±1.5%. in the main resonant circuit. Some require another for calibration. These parts can be difficult to find, and they can be expensive to buy. One solution used in the past by the home builder was to measure several ±5% or ±10% tolerance capacitors, selecting one that is as close as possible to the desired value. This worked at a time when many parts were not sorted by tolerance bands, so selecting one from many parts yielded a value close to the desired value. Australia's electronics magazine This approach also required a very accurate capacitance meter. The lack of such a meter is often the reason for building an LC meter in the first place! While a few constructors may have access to a suitable meter through work or a friend, this problem can be a significant barrier for potential builders. One solution to this ‘chicken and egg’ capacitor problem was described by retired Hewlett Packard engineer Jim McLucas in an article entitled “Circuit measures capacitance or May 2026  65 Photo 1: the prototype PCB without the OLED fitted. The socket for IC2 differs slightly from the approach described in the text. The USB-C connector is mounted at upper-right. Photo 2: a side-view of the prototype shows how the OLED sits just above or on the ATtiny85. This construction method reduces the overall height of the meter. Photo 3: the PCB sits in the lower half of the 3D-printed case. The pressed-in nuts can be seen at upper left and lower right. Photo 4: the Simple LC Meter measuring a 47μH test inductor. Photo 5: this simple jig makes it easier to measure the value of small SMD components. Fig.4: only a few parts are mounted on the board; this PCB overlay shows clearly their locations and the orientations of IC1 and IC2. 66 Silicon Chip Australia's electronics magazine inductance” from Electronic Design magazine, October 21, 2010 (see the panel on “Measuring capacitance accurately” above). Careful measurements using several methods and meters showed this technique was as accurate as claimed. The procedure is also relatively easy, especially when measuring a single capacitor value such as 1nF (1000pF). In this LC meter, the capacitor in question needs only to be approximately 1000pF. Using one of these methods, it is possible to accurately establish the value of the chosen reference capacitor. Write the value down, because this value will be programmed into the ATtiny85 later. It actually doesn’t matter if your capacitor is actually 5% or more away from the preferred or ideal value. For example, one version of this meter used an 820pF polystyrene capacitor to accurately measure inductors and capacitors for years! In short, in this design, provided the value of your chosen capacitor is accurately measured and saved in the LC meter’s EEPROM memory, the LC meter software takes care of the rest. Construction The LC Meter is built on a double-­ sided PCB coded 04103261 that measures 67 × 20mm. Start by fitting the resistors and capacitors, then the 74HC04 IC, using the overlay diagram (Fig.4) as a guide. Proceed to fit the USB-C connector and the 8MHz crystal. You’re almost 50% of the way through construction already (by parts count, anyway)! Next, mount the IC socket for the ATtiny85 to the PCB. It is drilled to allow the socket to fit down into the PCB to reduce the overall height of the assembly. The excess pin length can be trimmed from the IC socket after it is soldered into place. Fit the four-way female pin strip for the OLED display on the PCB. OLED screens often come with standard square pin headers (sometimes soldered, sometimes separate) but the LC meter’s size can again be usefully reduced if machined IC socket pin strips are used. So, if your screen has a header soldered to it, remove it and re-fit the round-pin machined header. Photos 1 & 2 show the general arrangement. The OLED display should be fitted with a matching connector, in this case siliconchip.com.au a four-way machined IC male-male pin strip. As Photo 2 shows, when the display is attached to the PCB, it will rest on or very slightly above the top surface of the ATtiny85 (IC2). Solder the DPDT slide and pushbutton switches in place, then proceed to mount the reference capacitor, followed by the inductor. Space both about 1mm above the PCB to allow them to be more easily bent over at a slight angle. This is to allow the PCB to be mounted in the compact 3D-printed enclosure. Do not fit the crocodile clips yet. This will be done as part of the 3D-printed enclosure assembly. Before final assembly, you’ll need to program the ATtiny85 unless you purchased a pre-programmed chip. The instructions for this are in the text box “Programming the ATtiny85”. Once programmed, carefully fit the ATtiny85 into the IC socket, making sure the chip is correctly orientated. Pin 1 of the ATtiny85 is usually marked with a tiny circle. The orientation can also be checked against the component overlay on the PCB (Fig.4). Now plug the OLED screen into place. Final assembly the soldering iron doesn’t go anywhere near the 3D-printed parts! Slide the LC meter PCB into the base and arrange it so it is flat and the USB socket aligns with the matching hole in the base. Check that your USB-C cable can connect with the PCB-mounted connector. Leave it in place briefly while adding a couple of drops of hot glue to the edges of the PCB to keep it firmly in place, if necessary. Finally, secure the cover in place with the two M2 machine screws. Inductor & capacitor testing A wide variety of methods have been tried for connecting the components being tested. The LC test inputs on the PCB allow for various builder preferences. The approach shown here uses a pair of small alligator (crocodile?) clips on short lengths of stranded hookup wire. I find this the easiest, most practical and robust approach. SMD parts may prove troublesome to clip onto, though. For the occasional test, the clips are fine, if a little clumsy at times. One alternative for testing SMD parts I tested is shown in Photo 5. I cut a very thin slot into the copper side of a scrap of single-sided PCB substrate. A further blank PCB scrap was milled to match the dimensions of the most commonly used SMD parts: M2012/0805 (2.0 × 1.2mm), M3216/1206 (3.2 × 1.6mm) etc. This was glued on top of the first PCB so Parts List – Simple LC Meter 1 double-sided PCB coded 04103261, 67 × 20mm 1 3D-printed enclosure [STL files: Silicon Chip SC3581] 1 3D-printed pushbutton extender [STL file: SC3581] 1 74HC04 SMD hex inverter IC, SOIC-14 (IC1) 1 ATtiny85-20PU microcontroller programmed with 0410326A.HEX/EEP (IC2) [Altronics Z5105 or Jaycar ZZ8721 (both unprogrammed)] 1 128×32-pixel 0.91-inch I2C OLED display module [AliExpress 1005003743893780, Silicon Chip SC7484] 1 pair of small red & black crocodile/alligator clips (CON1a/CON1b) [Jaycar HM3020] 1 female machined 4-pin strip (CON2) [cut from Altronics P5400A or Jaycar PI6470] 1 4-pin machined male-to-male header strip (for the OLED) [AliExpress 1005007564228387] 1 USB-C Type C-05 PCB-mount 2-pin socket (CON3) [AliExpress 1005005371954812] 1 100μH axial RF choke (L1) [Jaycar LF1534] 1 SS22H02-G5 5mm miniature PCB-mounting vertical DPDT slide switch (S1) [AliExpress 1005009907089109] 1 4-pin PCB-mounting tactile pushbutton switch with 6mm-long actuator (S2) [Altronics S1124, Jaycar SP0603] 1 8MHz crystal, HC-49U (X1) [Altronics V1249A or Jaycar RQ5287] 1 8-pin DIL machine pin IC socket (for IC2) 2 M2 × 5mm countersunk head machine screws and hex nuts 2 short (~100mm) lengths of medium-duty hookup wire Capacitors (all SMD M2012/0805-size 50V X7R unless noted) 1 1μF 1 100nF 1 1nF 50V polystyrene [AliExpress 1005006112435371] 2 4.7pF NP0/C0G Resistors (all SMD 0805-size ±1%) 1 1MW 1 22kW 1 100kW 1 5.6kW These next steps assume the use of the 3D-printed enclosure designed for this meter, although the PCB can be mounted into almost any suitable enclosure. The 3D-printed case usefully avoids the need for precision drilling and cutting of the various holes required. There is also a little pushbutton shaft extender, also 3D-printed. This is suitable for 6-10mm shaft length miniature pushbuttons. This is placed over the top of the pushbutton shaft just prior to screwing on the top cover. Begin final assembly by inserting the two M2 nuts into the base using a soldering iron. Locate them in place and press them into the base with a light and very brief press of the soldering iron tip. They should lie just at or slightly below the mating surface of the base and cover. Attach the red and black miniature crocodile clips to two 55mm lengths of stranded hookup wire. Strip 4mm of insulation from the free ends and tin the stranded wire with solder. Pass these ends through the hole located on the left-hand side of the lower half of the enclosure and carefully solder them to the LC test pin inputs. Ensure Figs.5-7: the enclosure and pushbutton cap may all be 3D-printed with PLA filament. The prototype was printed with grey PLA for the case, while the pushbutton cap was printed in a contrasting blue. siliconchip.com.au Australia's electronics magazine May 2026  67 Programming the ATtiny85 Download the HEX and EEP files for the LC meter from siliconchip.au/Shop/6/3580 The EEP (EEPROM) file provided contains a nominal value of 1000pF for the reference capacitor. If you have an in-circuit programmer like the USBasp, you will also need a way to connect the correct lines to the pins on the chip. This is most easily done using an adaptor board. It saves adding a 6-pin programming socket to each PCB. My 8-pin adaptor was published in the September 2020 issue (page 47; siliconchip. au/Article/14563) and the PCB is still available (siliconchip.au/Shop/8/5642) Once you have the chip plugged into an adaptor, connect the programmer to your computer. Download and open a programming application (such as Extreme Burner) and load the HEX and EEP files into this program. It is almost certain you will need to modify the contents of the EEP file with the precise value of your reference capacitor. The value is saved in picofarads, eg, 1.015nF is saved as 1015 (pF). EEPROM values are usually edited as two-digit hexadecimal bytes (in this case, two bytes, making up a four-digit hex value). You can use the following website to convert the value to hex: www.rapidtables.com/convert/number/decimal-to-hex.html One of my LC meters used a 995pF capacitor; 995 is 03E3 in hexadecimal. This value was entered into cells 02 and 03 in the first line of the EEPROM tab in Extreme Burner (see Screen 1). Just click your mouse on the cell to be changed and enter the new value. Note that the least significant byte (E3 in this case) comes first, in cell 02, and the most significant byte (03) goes in cell 03. Now program your ATtiny85 with the HEX file, then the EEP file. Click on the “Write” tab in Extreme and select the file you are sending to the ATtiny85. Next, program the hardware configuration fuses in the ATtiny85. Table 1 shows the required fuse settings. You need to set these after loading the HEX and EEP files before the LC Meter will work. To set the fuses, click on the Fuse Bits/Setting tab (Screen 2), enter the values shown, and click on the Write selection boxes for the Low and High fuses (the others may safely be ignored). When you have done this, write the fuse settings to the ATtiny85 by clicking on the Write button at the lower right of this tab. That’s it! If you need more information about the programming procedure, there are some helpful tutorials on this topic that can be found on the Adafruit and Instructables websites. Table 1 – ATtiny85 fuse settings Fuse Hex value Comment Lock byte FF Flash not locked Extended byte FF Self-programming disabled High Byte 5F Defaults except RSTDISBL=0 Low byte E0 Defaults except CKDIV8=0 & CKSEL1=0 Silicon Chip Operation A simple sign-on message is displayed when the meter is powered up. Once the measurement mode (inductance or capacitance) has been selected with the LC switch, the meter must then be calibrated. Press CAL and wait a moment. You will see a display prompting you to short the test leads together (for inductance measurements) or leave them open (for capacitance measurements). Once calibrated, the component can be connected, and the meter will then display its value. The meter also reports the oscillator frequency during the measurement. This allows invalid results to be easily detected; for example, if a faulty component is tested or one with a value outside the range of the meter. The prototype will measure values from less than 10nH to about 100mH and from less than 10pF to about 1μF. If the reference capacitor has been carefully measured, the results can be expected to be within ±2%. Final remarks Screen 2: another tab in Extreme allows the fuse bits to be set and then written. Do this after you have written the HEX and the EEP files to the ATtiny85. This meter, in one form or another and with minor variations in the software, has been in continuous use on my bench for well over a decade. The latest version described here has been in use for over 18 months. It is, by far, the most compact and convenient to use. The only problem has been that it is also small enough to become buried under other stuff on my workbench! It is quick, simple & inexpensive to build, and so convenient to use that I find myself taking its convenience and accuracy for granted. I have long since forgotten just how time-­consuming the alternative methods were prior to the arrival of such LC meters. Even if you already have an LC meter, I encourage you to take the time to build this one. Once built, you’ll find yourself reaching for it all SC the time, too. Australia's electronics magazine siliconchip.com.au Screen 1: the value of the reference capacitor entered into the EEPROM tab in the application. 68 that the slot sat midway in this gap (see Photo 5). The SMD part can easily be placed into this assembly for testing and measurement. The arrangement can then be connected to the LC meter using the alligator clips. Another version used miniature pin connectors, which allowed the assembly to be plugged into a different version of the LC meter when required.