Oscillator with an inductance with nonzero resistance

In summary, the individual needs to measure the change in inductance of a loop with a resistance of 30-200 ohms. They have tried building an oscillator but it only works well with a low resistance inductor. They are now looking for alternative circuits, such as one using negative resistance or a transformer, to detect the change in inductance. The desired approach is to use an oscillator with TTL output and measure the frequency with a microcontroller. However, it may be difficult to measure the in-phase and quadrature components of the AC voltage waveform with a common microcontroller. The desired inductance range is 100-300 microH with a pure resistance of 30-200 ohms.
  • #1
meereck
13
0
Hello,
I need to measure ONLY a change in inductance of a loop (long wire) which has got resistance about 30-200 ohms.
I have tried to build the oscillator according to this schematic : http://ironbark.bendigo.latrobe.edu.au/~rice/lc/
but the problem is it works well with an inductance with almost zero resistance only.
If I connect my loop, it behave wrongly. I guess because of the energy disappation?

Therefore, I need to modify that circuit, or use another another one. Unfortunately, I haven't found anything about how to make an oscillator with an resistive inductor.

I read about using a negative resistance circuit but I have no clue how to employ that.
I have also heard about using a transformer (perhaps it is called tapped inductors?).

To summarize my approach:
I only need to detect a change in inductance of a wire loop.
I prefer to have an oscillator with TTL output and to measure therefore the frequency (in a microcontroller)

May I ask you for some hints on that?
Thanks in advance,
Best regards Meereck
 
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  • #2
What is the range of inductance that you are trying to measure, in addition to the 30-200 Ohms of real resistance?

I would probably approach it by driving a signal from a known source impedance, and measuring the in-phase and quadrature components of the divided AC voltage waveform. That will give you values for both the real resistance and the reactive inductive impedance.
 
  • #3
berkeman said:
What is the range of inductance that you are trying to measure, in addition to the 30-200 Ohms of real resistance?

I would probably approach it by driving a signal from a known source impedance, and measuring the in-phase and quadrature components of the divided AC voltage waveform. That will give you values for both the real resistance and the reactive inductive impedance.

thanks for a reply.
The inductance will be about 100-300 microH, its pure resistance will be 30-200Ohm.
>>measuring the in-phase and quadrature components of the divided AC voltage waveform.
Right, but this will probably be quite difficult to measure by a common microcontroller such as a PIC. Would you have any supporting circuit for that?

cheers M.
 

1. What is an oscillator with an inductance with nonzero resistance?

An oscillator with an inductance with nonzero resistance is a type of electrical circuit that generates a continuous, alternating current (AC) without the need for an external power source. It is made up of an inductor, a resistor, and a capacitor, and produces a sinusoidal waveform that can be used for various applications.

2. How does an oscillator with an inductance with nonzero resistance work?

An oscillator with an inductance with nonzero resistance works by storing energy in the inductor and capacitor, and then releasing it back and forth in the form of an AC signal. The resistor is used to limit the current and prevent the circuit from overheating. This continuous flow of energy results in a stable oscillation.

3. What is the purpose of using an inductance with nonzero resistance in an oscillator?

The inductance with nonzero resistance is used in an oscillator to provide a frequency-selective element. This means that it helps to control the frequency of the oscillation, making it more stable and predictable. It also helps to prevent the circuit from becoming too sensitive to external factors like temperature changes.

4. What are the advantages of using an oscillator with an inductance with nonzero resistance?

One of the main advantages of using an oscillator with an inductance with nonzero resistance is its ability to generate a continuous and stable AC signal without the need for an external power source. It is also relatively simple and inexpensive to construct, making it a popular choice for various electronic applications.

5. How is an oscillator with an inductance with nonzero resistance different from other types of oscillators?

An oscillator with an inductance with nonzero resistance is different from other types of oscillators, such as LC oscillators or RC oscillators, in that it uses both an inductor and a resistor in its circuit. This helps to provide better frequency stability and makes it less sensitive to external factors. Additionally, its output waveform is more sinusoidal compared to other types of oscillators, which may produce square or triangular waveforms.

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