We recently bought some new test equipment for the workbench, and decided to share the experience.
We love test equipment at DIYODE but we certainly don’t have everything. With a maker rather than engineering and production focus, we buy equipment as we need it and often, we make do without.
Sure, we have multimeters and a couple of oscilloscopes, and we thought about a signal generator for a while before we bought one, but so far that’s it. Rather, it was until recently. Just before Christmas, we ordered an ESR meter, LCR meter, and semiconductor analyser from Element 14, and they arrived overnight, too.
We’ll go into why we bought these items at the end of the reviews where relevant, and cover the alternatives such as DIY methods or approximations that can be gained other ways. This will help you decide whether or not you might need or want one.
For now though, we’ll take a look at the Peak Atlas LCR40, glance at its specifications, then see why it’s so much more user-friendly than other options.
Peak Electronic Design have been making electronic instruments for quite some time. All parts come from within Europe and all manufacturing is done in the UK, which is a rarity indeed. The microcontroller-based units use the popular PIC series as the brains, with an easy to use, two-button interface and a 2 x 16-character LCD display.
While not backlit, this screen is high-contrast and very clear, making it easy to read in many lighting conditions. The whole thing fits in the palm of your hand, and connection is by two spring-clips on a practical but not excessively long test lead. Helpfully, the clips attach via 2mm banana plugs, so you can get other leads or extensions to plug in.
In terms of specifications, this area is one where the LCR40 has an advantage over cheaper units. This tester has the capacity to measure very low inductances and resistances, even displaying inductance in decimals of a microhenry. Capacitance is between 0.5pF and 10,000μF, which is much better than the cheaper LCR meters available. Most of those have a 2nF or 4nF lower range. While most meters will read 0.5pF on a 2nF range, 0.5pF is lower than those ranges will be accurate at.
|Component Type Selection||Automatic|
|Test Frequencies||DC, 1kHz, 15kHz, 200kHz|
|Range and Scaling Selection||Automatic|
|Resistance Range||1Ω to 2MΩ|
|Capacitance Range||0.5pF to 10,000μF|
|Capacitance Resultion||0.2pf to 0.5pF|
|Inductance Range||1μH to 10H|
|Inductance Resolution||0.4μH to 0.8μH|
|Test Voltage, Peak||1.05V|
|Test Current, Peak||3.25mA|
Inductance is also similar. The stated range is 1μH to 10H, and although some of the cheaper handheld LCR meters can go to 20H, they are not accurate in the lowest ranges. Ten Henries is still quite a lot for most of us. In any case, the LCR40 has a special ‘low range’ function, whereby it will analyse components differently if they show very low inductance or DC resistance.
While the specifications of the LCR40 are good, they’re not good enough to justify a doubling of price over the cheaper options on their own. The real key to the utility of the LCR40 is its operation. Being a microcontroller-based product, you don’t need to choose a range like the base-level LCR meters.
However, the LCR40 goes further: You don’t even have to choose a function. Control is achieved by two buttons: ‘On, Test’; and ‘Scroll, Off’. When the ‘on/test’ button is first pressed, the display reads ‘Analysing in 5 seconds’, then begins counting down.
In this time, you can connect your test component to the spring clips. That’s all there is. If you miss the timing window, you can just press the button again, and pressing the button during countdown will start the test straight away.
Now, the device analyses the component connected to it. The device decides if the component is a capacitor, resistor, or inductor, and tests it accordingly. It also decides the best test frequency to use. After the test, the top line of the display labels a parameter, while the bottom line shows the value.
There may be one, two or three values: The resistance for pure resistors; the test frequency and the capacitance for pure capacitors; and test frequency, inductance, and DC Resistance for inductors.
On the capacitor subject, the device chooses either AC impedance or DC charge analysis as appropriate, depending on the value and construction of the capacitor. Additionally, because the unit uses a 1V test signal, polarity is rarely an issue.
As hinted, the LCR40 has a special function for when capacitance and inductance are both very low. This is because their behaviour may be similar under test conditions, so the device just gives the data along with the label ‘Low Resistance and Inductance’. Then, test frequency, resistance, and inductance can be accessed by the ‘scroll/off’ button.
That’s it really. No calculations, no formula, no multiple measurements or adjustments; just one button. It is this that makes the LCR40 very worth its asking price for anyone who is going to work with inductors or coils on any regular or semi-regular basis.
Despite the simplicity, the product still comes with a very clear and comprehensive manual, which includes step-by-step testing procedures; hints, notes, and warnings; probe compensations steps; troubleshooting; and specifications.
Peak Electronic Design also make a range of alternative connectors. You can get spring clips, alligator clips (which are gold plated), SMD tweezers, and probes. All of these terminate with 2mm banana plugs so you can share them between test units.
POINTS TO NOTE
The LCR40 is rugged but not bullet-proof. Capacitors should be discharged before measuring, and that’s even more critical for high-voltage capacitors. Components should always be measured out of circuit, but that goes without saying in any component test situation.
We tried measuring one of our Slayer Exciter coils while the low end of the secondary was still connected to the circuit, because one end hangs in free air and there is no direct current path.
However, even this caused the characteristics to change to the point where the LCR40 thought it was measuring a capacitor. As soon as the low end of the secondary coil was disconnected, it read as an inductor.
WHY AN LCR METER?
When researching for our recent Sparking Ideas Tesla coil project in Issue 41, one of the things that stopped us deciding on a genuine Tesla coil is that it is necessary, for decent performance, to know the inductance of the coils involved so that the resonance can be calculated.
We didn’t have a suitable piece of test equipment on hand, but knowing the inductance turned out to be the smallest of the problems with a genuine Tesla coil.
Dangerous voltages, noisy and fiddly spark gaps, the need for big power supplies, and the potential for burns and other damage were the main reasons we elected to go with a Slayer Exciter design.
However, it wasn’t the first time we had wanted to know the inductance of a coil. You can calculate the inductance of a coil you’ve made if you know all the factors (not the case with the Tesla coil development), but if you don’t know, or haven’t made the coil, you’ll need to measure it.
The best way to do this is with an inductance meter, but the few multimeters which have an inductance function don’t do it very well. You can measure inductance with a function generator and an oscilloscope. If you do have a function generator, which will set you back more than $700 for a decent quality entry level one, then you’re likely very electronics-minded and the calculations involved probably don’t bother you.
If you do have a function generator and oscilloscope, you can connect a resistor in series with your chosen inductor, then attach the oscilloscope and generator. The generator has to be one with two outputs that can be synchronised. You also have to adjust the function generator output frequency so that the voltage at the test point is half of the voltage at the output of the function generator, as displayed on the oscilloscope screen.
Sounds fun, right? For some makers, yes it is. For others, not so. Because there’s a lot more to it than this, and several other methods which are no less involved, we’ve dedicated this month’s Classroom to the topic.
So, that leaves the choice of a dedicated LCR meter. Options abound, but even the cheapest handheld units from reliable suppliers cost around $80. They work just fine, but functions are basic and the lowest ranges aren’t always the best. The budget end of the scale often starts with a minimum range of 2mH. That’s millihenries, not microhenries. Of course the meter reads lower, but ranges exist for both accuracy and resolution, and both suffer when reading three factors of ten below the range. These meters usually measure resistance and capacitance too, with similar caveats.
We didn’t have to go far before we found the product we ended up choosing: The Peak Atlas LCR40, which we bought from Element 14. This product retailed at $166.64 including GST at the time of our order, but prices vary a little with shipments, depending on fluctuating international currency rates. That’s only a bit over double the cheapest units, but you get a whole lot more. We certainly don’t regret the choice!
The Peak Atlas LCR40 is available from Element 14: https://element14.com.au
- Peak Atlas LCR40 2843468 $166.64