If you’re trying to simulate free-field acoustic conditions using a pulse technique, then you might be facing a bunch of noise, including a large 1st harmonic, where you’re trying to measure only the second harmonic. Using a lock-in amplifier to cut out the noise is a common solution, but it accepts all reflections as well, resulting in resonant peaks dependent on the container size.
The Basics of Lock-in Amplifiers
Firstly, let’s understand the basics of lock-in amplifiers. They are primarily used to measure small AC signals in the presence of noise. The noise can be effectively removed by combining a reference signal (usually a sinusoidal signal) with the input signal. The reference signal, typically generated by an oscillator, is set at a specific frequency and phase. The reference signal and the input signal are multiplied, resulting in a product signal. This product signal can then be filtered using a low-pass or band-pass filter to remove all unrelated frequencies. The filter is tuned to the reference frequency, and the output voltage is measured. This voltage is proportional to the signal amplitude at the reference frequency.
Measuring a Pulsed Signal with a Lock-in Amplifier
Measuring a pulsed signal with a lock-in amplifier is tricky, mainly because lock-ins are optimized for the steady-state measurements of periodic waveforms that have a defined frequency. Pulsed signals, however, are time-dependent and have a varying frequency spectrum.
One way to measure a pulsed signal with a lock-in amplifier is to employ a technique called time-domain gating. In this technique, only a specific segment or window of the pulsed signal is analyzed. The lock-in amplifier is used to calculate only the Fourier transform within the desired measurement window, and the unwanted data is excluded from the measurement.
Another approach is to use a digital oscilloscope along with a lock-in amplifier. The oscilloscope can be used to capture the pulsed signal in the time domain, while the lock-in amplifier can remove the noise from the measured signal in the frequency domain.
The Use of Zurich Lock-in Amplifier in Measuring Pulsed Signals
The Zurich Instruments HF2LI Lock-in amplifier is a versatile instrument that can be used to measure a wide range of signals, including pulsed signals. One advantage of this lock-in amplifier is its ability to be used in time-domain gating mode, allowing measurement of specific segments of a signal.
For instance, if one is interested in analyzing only the initial response of an acoustic pulse, they need to incorporate a time delay between the source’s emission and the recording of the signal. The Zurich Instruments HF2LI Lock-in amplifier can be programmed to detect and record signals only within the desired time window, eliminating the reflections and unwanted signals.
Conclusion
Lock-in amplifiers can be used to measure pulsed signals, but it is essential to keep in mind that pulsed signals are time-dependent and have a varying frequency spectrum. Therefore, using time-domain gating techniques or digital oscilloscopes can help remove unwanted data from the signal. Zurich Instruments HF2LI Lock-in amplifier, with its time-domain gating mode, can be particularly useful for capturing specific segments of a signal.
How (if Possible) Can I Measure a Pulsed Signal With a Lock-in Amplifier?
If you’re trying to simulate free-field acoustic conditions using a pulse technique, then you might be facing a bunch of noise, including a large 1st harmonic, where you’re trying to measure only the second harmonic. Using a lock-in amplifier to cut out the noise is a common solution, but it accepts all reflections as well, resulting in resonant peaks dependent on the container size.
The Basics of Lock-in Amplifiers
Firstly, let’s understand the basics of lock-in amplifiers. They are primarily used to measure small AC signals in the presence of noise. The noise can be effectively removed by combining a reference signal (usually a sinusoidal signal) with the input signal. The reference signal, typically generated by an oscillator, is set at a specific frequency and phase. The reference signal and the input signal are multiplied, resulting in a product signal. This product signal can then be filtered using a low-pass or band-pass filter to remove all unrelated frequencies. The filter is tuned to the reference frequency, and the output voltage is measured. This voltage is proportional to the signal amplitude at the reference frequency.
Measuring a Pulsed Signal with a Lock-in Amplifier
Measuring a pulsed signal with a lock-in amplifier is tricky, mainly because lock-ins are optimized for the steady-state measurements of periodic waveforms that have a defined frequency. Pulsed signals, however, are time-dependent and have a varying frequency spectrum.
One way to measure a pulsed signal with a lock-in amplifier is to employ a technique called time-domain gating. In this technique, only a specific segment or window of the pulsed signal is analyzed. The lock-in amplifier is used to calculate only the Fourier transform within the desired measurement window, and the unwanted data is excluded from the measurement.
Another approach is to use a digital oscilloscope along with a lock-in amplifier. The oscilloscope can be used to capture the pulsed signal in the time domain, while the lock-in amplifier can remove the noise from the measured signal in the frequency domain.
The Use of Zurich Lock-in Amplifier in Measuring Pulsed Signals
The Zurich Instruments HF2LI Lock-in amplifier is a versatile instrument that can be used to measure a wide range of signals, including pulsed signals. One advantage of this lock-in amplifier is its ability to be used in time-domain gating mode, allowing measurement of specific segments of a signal.
For instance, if one is interested in analyzing only the initial response of an acoustic pulse, they need to incorporate a time delay between the source’s emission and the recording of the signal. The Zurich Instruments HF2LI Lock-in amplifier can be programmed to detect and record signals only within the desired time window, eliminating the reflections and unwanted signals.
Conclusion
Lock-in amplifiers can be used to measure pulsed signals, but it is essential to keep in mind that pulsed signals are time-dependent and have a varying frequency spectrum. Therefore, using time-domain gating techniques or digital oscilloscopes can help remove unwanted data from the signal. Zurich Instruments HF2LI Lock-in amplifier, with its time-domain gating mode, can be particularly useful for capturing specific segments of a signal.