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Friday, December 20, 2013

LCR Meter



LCR Meter

LCR meter is very common measurement equipment in R&D centers or manufacturing floors. Even some more the more professional DIYer will have 1 at home, but of course, it will not be as common as the multi-meter due to the price. 

A simple low end LCR meter will be able to measure at fixed frequencies of maybe 100Hz, 1kHz, 10kHz and 100kHz. This will be good for sanity check but for real analysis, a precision unit that can do continuous sweep from 20Hz to 100kHz would be required and it is usually in price range of USD$2,000 and above. 

With continuous sweep, one would be able to measure the components value at the actual working frequency. It can even measure transformer impedance and that’s why it’s very effective tool to have to analyze the various input, output and inter-stage transformers we have in the market, single ended or push-pull. 
Different inputs for different measurement range.
With DC bias option that some of the LCR meters have, it can even bias the components and transformer at designated operating condition for more accurate measurement.  This is especially useful for single ended output transformer where it would be gapped for a certain DC on the primary winding. When DC is injected, the core will be loaded and the electrical characteristics will change drastically. The data gathered will be closer to what the real operating condition is.

Common LCR meter will be able to bias the components to around 30Vdc @ ~200mA maximum, depending on the quality level of the equipment used. With impedance measurement function on transformer, user will be able to know how good the transformer is at various frequencies to plot the frequency response chart. 

For capacitor measurement, other than the capacitance, it can measure the Q factor and the D factor, which are equally important. D – Dissipation factor, the lower the better. Q – Quality factor, the higher the better. So, with this data being available, one will know whether the capacitor under test is really fitting the applications or not, rather than just trusting the marketing materials.
Agilent E4980AL Screen
As for inductor measurement, with the frequency sweeping function, one can really know whether the inductor is good for only power supplies working at the range of 50Hz to 120Hz, or it can be used for anode / plate load function (plate choke), or even the grid choke function. The inductance will need to hold steady at higher frequencies for plate or grid applications. With LCR meter capable of doing so, one can only trust their ears. 

Even for power supply filtering applications, it will be applicable too. Say one wants to filter a 1MHz noise using inductor and capacitor. If both the inductor and capacitor have good values at 1MHz measured with the LCR meter, users will be able to ensure that the filter will be effective. Without such data, one will never know. 

The Agilent E4980AL Precision LCR Meter is one that you can consider for audio applications.
Agilent E4908A LCR Meter


It can measure from 20 Hz to 300 kHz/500 kHz/1 MHz, with 4-digit resolution in any range. Now that’s really SOMETHING! Of course, one can go higher end but this unit is more than sufficient. It sells for around USD$6,000 a unit. 

J&K Audio Design
21/12/2013

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* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.

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