This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.

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Each measurement cycle is divided into three phases. Auto-Zero Phase During auto-zero three things happen. Second, the reference capacitor is charged to the reference voltage.

Third, a feedback loop is closed around the system to charge the auto-zero capacitor CAZ to compensate for offset voltages in the buffer amplifier, integrator, and comparator. Since the comparator is included in the loop, the A- Z accuracy is limited only by the noise of the system. During signal integrate, the auto-zero loop is opened, the internal short is removed, and the internal input high and low are connected to the external pins.

This differential voltage can be within a wide common mode range: up to 1V from either supply. At the end of this phase, the polarity of the integrated signal is determined. De-Integrate Phase The final phase is de-integrate, or reference integrate.

Input low is internally connected to analog COMMON and input high is connected across the previously charged reference capacitor. Circuitry within the chip ensures that the capacitor will be connected with the correct polarity to cause the integrator output to return to zero. The time required for the output to return to zero is proportional to the input signal.

Specifically the digital reading displayed is:. The input can accept differential voltages anywhere within the common mode range of the input amplifier, or specifically from 0.

However, care must be exercised to assure the integrator output does not saturate. A worst case condition would be a large positive common mode voltage with a near full scale negative differential input voltage. The negative input signal drives the integrator positive when most of its swing has been used up by the positive common mode voltage. For these critical applications the integrator output swing can be reduced to less than the recommended 2V full scale swing with little loss of accuracy.

The integrator output can swing to within 0. Differential Reference The reference voltage can be generated anywhere within the power supply voltage of the converter. The main source of common mode error is a roll-over voltage caused by the reference capacitor losing or gaining charge to stray capacity on its nodes. If there is a large common mode voltage, the reference capacitor can gain charge increase voltage when called up to de-integrate a positive signal but lose charge decrease voltage when called up to de-integrate a negative input signal.

This difference in reference for positive or negative input voltage will give a roll-over error. However, by selecting the reference capacitor such that it is large enough in comparison to the stray capacitance, this error can be held to less than 0.

See Component Value Selection.


PDF ICL7107 Datasheet ( Hoja de datos )



PDF ICL7107 Datasheet ( Hoja de datos )


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