openbench:lcrmeter
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openbench:lcrmeter [2008/04/23 19:38] geekabit + theory + characteristics |
openbench:lcrmeter [2008/04/24 12:49] geekabit + link + powersupply |
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| An LCR meter measures, among other things, the impedance, inductance, capacity and resistance of a Device Under Test. Usually the DUT is connected to an AC voltage source, then the voltage over and the current through the DUT are measured. The measured impedance consists of real and/or complex component. The phase angle (Φ) also is an important variable. | An LCR meter measures, among other things, the impedance, inductance, capacity and resistance of a Device Under Test. Usually the DUT is connected to an AC voltage source, then the voltage over and the current through the DUT are measured. The measured impedance consists of real and/or complex component. The phase angle (Φ) also is an important variable. | ||
| - | (This text is identical to the the article on Wikipedia because I wrote that as well) | + | So we need a sine generator, voltage and current measurement, microcontroller, user interface and power supply. |
| - | + | ||
| - | So we need a sine generator, voltage and current measurement, microcontroller and a user interface. | + | |
| ====== Characteristics ====== | ====== Characteristics ====== | ||
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| ====== Sine generator ====== | ====== Sine generator ====== | ||
| - | There are some 'instant' sine generators that are not suitable for the openbench function generator, but might be suitable for this application. All that is needed is a fixed output level and a couple of frequency presets (100Hz, 1kHz, 10kHz). | + | There are some 'instant' sine generators that are not suited for the openbench function generator, but might be suitable for this application. All that is needed is a fixed output level and a couple of frequency presets (100Hz, 1kHz, 10kHz). |
| ====== Voltage and current measurement ====== | ====== Voltage and current measurement ====== | ||
| - | Voltage is measured over the DUT, current is measured as voltage over a shunt resistor. The values are digitized and sent to the microcontroller. Because of the wide variations in voltage and current, a low noise amplifier is needed, preferable with programmable gain. An instrumentation amplifier is perfect for this. The analog values are then digitized using an A/D converter. | + | Voltage is measured over the DUT, current is measured as voltage over a shunt resistor. The values are amplified, digitized and sent to the microcontroller. Because of the wide variations in voltage and current, a low noise amplifier is needed, preferable with programmable gain. An instrumentation amplifier is perfect for this. The analog values are then digitized using an A/D converter. |
| What would be the voltage and current in case of the biggest or smallest capacitor or inductor or resistor? What resolution and sample rate do we need for the ADC? | What would be the voltage and current in case of the biggest or smallest capacitor or inductor or resistor? What resolution and sample rate do we need for the ADC? | ||
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| ====== User interface ====== | ====== User interface ====== | ||
| The display must be able to show inductor/capacitor/resistor, series/parallel configuration, L, C, R, Φ, Q and D readout. The user must be able to select measurement frequency, voltage bias and calibrate the meter. | The display must be able to show inductor/capacitor/resistor, series/parallel configuration, L, C, R, Φ, Q and D readout. The user must be able to select measurement frequency, voltage bias and calibrate the meter. | ||
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| + | ====== Power supply ====== | ||
| + | What voltages do we need? Probably digital 5V and analog +/- 5V. | ||
| ====== Existing (similar) examples ====== | ====== Existing (similar) examples ====== | ||
| * [[http://www.bkprecision.com/www/np_searchmodel7.asp?lf=LCR+Meters|B+K Precision LCR meters]] | * [[http://www.bkprecision.com/www/np_searchmodel7.asp?lf=LCR+Meters|B+K Precision LCR meters]] | ||
| * [[http://www.circuitcellar.com/microchip2007/winners/third.html|Full-feature LCR meter, very well documented]] | * [[http://www.circuitcellar.com/microchip2007/winners/third.html|Full-feature LCR meter, very well documented]] | ||
| + | * [[http://www.circuitcellar.com/psoc2002/winners/h3.htm|Another design challenge]] | ||
/home/ladyada/public_html/wiki/data/pages/openbench/lcrmeter.txt · Last modified: 2016/01/28 18:05 (external edit)
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