- #1
quantumfoam
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Hi guys,
I am working on a project that involves measuring the phase angle between two sinusoidal voltages. The circuit under examination is an RL type (the resistor was in series with the inductor), where the phase of voltage across the inductor is measured relative to the voltage input of the circuit (it has zero phase).
The oscilloscope I used to measure such was the Tektronix MDO3014 Mixed Domain Oscilloscope. The two probes in use were the Tektronix TPP0256 type. The probe connected to Channel 1 measured the voltage signal across the inductor while the probe connected to Channel 2 measured the voltage input signal of the circuit.
After obtaining the phase between the two signals, I realized that the measured phase was much smaller than expected. While using a resistor of 32.2 Ohms, an inductor of 10 mH, and an input voltage of 100 Hz, the oscilloscope gave a phase between 1-8°. After calculating the phase angle of the voltage across the inductor as shown in the attached image below, the phase angle was clearly off from that measured by the oscilloscope (I calculated it was supposed to be 79°.
Am I missing something in the set-up of the oscilloscope to measure phase between two voltage signals? I made sure to calibrate the probe on Channel 1, and I attempted to do so with the probe in Channel 2 as well. Since this discrepancy occurred for frequencies (100 Hz and higher) that were well within the measurement range of the oscilloscope, I am wondering if it has anything to do with a set-up I missed in executing.
I noticed that the measured frequencies for the input voltage and inductor voltage were the same, implying the frequencies weren't distorted. I measured the phase from the Channel 1 signal (inductor voltage) to that of the Channel 2 signal (input voltage). I also used both an Agilent Arbitrary Function generator and the Arbitrary Function Generator from the oscilloscope. When applying the two different function generators separately, both gave me the same wrong angle (1-8°).
I am working on a project that involves measuring the phase angle between two sinusoidal voltages. The circuit under examination is an RL type (the resistor was in series with the inductor), where the phase of voltage across the inductor is measured relative to the voltage input of the circuit (it has zero phase).
The oscilloscope I used to measure such was the Tektronix MDO3014 Mixed Domain Oscilloscope. The two probes in use were the Tektronix TPP0256 type. The probe connected to Channel 1 measured the voltage signal across the inductor while the probe connected to Channel 2 measured the voltage input signal of the circuit.
After obtaining the phase between the two signals, I realized that the measured phase was much smaller than expected. While using a resistor of 32.2 Ohms, an inductor of 10 mH, and an input voltage of 100 Hz, the oscilloscope gave a phase between 1-8°. After calculating the phase angle of the voltage across the inductor as shown in the attached image below, the phase angle was clearly off from that measured by the oscilloscope (I calculated it was supposed to be 79°.
Am I missing something in the set-up of the oscilloscope to measure phase between two voltage signals? I made sure to calibrate the probe on Channel 1, and I attempted to do so with the probe in Channel 2 as well. Since this discrepancy occurred for frequencies (100 Hz and higher) that were well within the measurement range of the oscilloscope, I am wondering if it has anything to do with a set-up I missed in executing.
I noticed that the measured frequencies for the input voltage and inductor voltage were the same, implying the frequencies weren't distorted. I measured the phase from the Channel 1 signal (inductor voltage) to that of the Channel 2 signal (input voltage). I also used both an Agilent Arbitrary Function generator and the Arbitrary Function Generator from the oscilloscope. When applying the two different function generators separately, both gave me the same wrong angle (1-8°).
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