measuring inductance

Description: Choose the circuit that best suits your needs, although the one utilizing the LM339 is preferable. Both capacitors are 1 µF metallized film, but any non-polarized capacitor will suffice, provided it is close to 2 µF. Avoid using a capacitor that designates a connection as ground. It is important to note that the LM741 is designed for analog computing, which necessitates a negative voltage on its V- pin. If a power supply that provides this is unavailable, two AA batteries can be used to achieve 3 V below ground as illustrated. The LM339 does not require this, and it can accept a negative voltage without issue. It should be noted that the LC circuit will oscillate both above and below ground.

Since the waveform is a true sinusoidal wave, it spends equal time above and below zero volts. This characteristic allows the comparator to convert it into a square wave with a 50% duty cycle. The function pulseIn(pin, HIGH, 5000); measures the time in microseconds from the rising edge to the falling edge. This measurement can be doubled to determine the period, and the inverse of the period yields the frequency. Given that the circuit is resonating, this frequency corresponds to the resonant frequency.

The circuit described involves two primary components: the LM339 comparator and the LM741 operational amplifier. The LM339 is favored due to its capability to handle both positive and negative voltages without the need for additional power supply configurations, making it more versatile for various applications. In comparison, the LM741 requires careful attention to the power supply, specifically the necessity for a negative voltage, which can complicate the circuit design.

The capacitors used in the circuit play a crucial role in filtering and stabilizing the voltage levels, ensuring that the waveforms remain consistent during operation. The choice of a 1 µF metallized film capacitor is appropriate due to its low equivalent series resistance (ESR) and stability across temperature variations. It is essential to select non-polarized capacitors to avoid potential damage or malfunction, which could arise from incorrect polarity connections.

The behavior of the sinusoidal wave is pivotal in the operation of the comparator, which transforms the analog signal into a digital square wave. The 50% duty cycle indicates that the output signal is high for half of the time and low for the other half, making it suitable for various digital applications. The pulseIn function is critical for measuring the output frequency, as it provides accurate timing measurements that can be used for further analysis or control purposes.

Understanding the resonant frequency of the LC circuit is vital for applications such as signal processing, oscillators, and filters. The resonant frequency is determined by the values of the inductance and capacitance in the circuit, and it plays a significant role in defining the circuit's behavior and performance. This frequency can be fine-tuned by adjusting the capacitor values, allowing for precise control over the output waveform characteristics.Pick whichever circuit is better for you, but the one using the LM339 is better. Both the capacitors are 1uf metalized film, but anything that is non polar will work. It will need to be very close to 2 uF though. You can not use a capacitor that marks which connection is ground. One thing you may notice is that the LM741 is geared for analog computing. This means that it requires a negative voltage on it’s V- pin. If you don’t have a power supply that offers this, use two AA batteries to go 3v below ground as shown. The LM339 doesn’t need this and there is no problem inputting a negative voltage. Remember that the LC circuit will vary above and below ground. Since our wave is a true sinusoidal wave, it spends equal time above zero volts and below zero volts. This means that the comparator will turn it into a square wave with a duty of 50%, and pulseIn(pin, HIGH, 5000); will measure the time in microseconds elapsed from rising edge to falling edge.

This measurement can then be doubled to get the period and the inverse of the period is the frequency. Since the circuit is resonating, this frequency is the resonating frequency.