Application Cases

Experiment Name: Application of Voltage Amplifier in Reflective Miniature Optical Electric Field Sensor

Experiment Objective:
To simultaneously measure DC, alternating, and transient electric fields, a theoretical sensing model for a reflective optical electric field sensing probe based on the Pockels effect was established using Jones matrix calculations. The effects of lithium niobate crystal length, crystal cut type, temperature, and packaging stress on the sensing performance of the probe were analyzed.

Experimental Equipment:
Function generator, voltage amplifier (Aigtek, ATA-7030), electrode plates, light source, polarization-maintaining circulator, photodetector, data acquisition card, LabVIEW signal analysis and display software, probe.

Experimental Procedure:

Alternating Electric Field Experiment:
The operating principle of the system is as follows: A function generator produces a voltage signal with adjustable frequency and amplitude. The voltage amplifier amplifies this signal by a factor of 0 to 1000 and delivers it to the electrode plates to generate an alternating electric field. The probe converts the electric field information into light intensity via the Pockels effect. The photodetector then converts the light intensity back into a voltage signal. A data acquisition card simultaneously captures the reference voltage (attenuated by a factor of 1000 from the amplifier output) and the output voltage from the photodetector. The signals are analyzed and displayed using LabVIEW software.

Figure: Experimental Setup for Alternating Electric Field Measurement

The function generator was set to output square waves with frequencies of 10 Hz and 5000 Hz and an amplitude of 3 V. The voltage amplifier applied a 1000× gain. The acquired square wave signal waveforms are shown in the figure. In the figure, $A_{\text{Ref}}$ represents the amplitude of the reference signal, and $A_{\text{OES}}$ represents the amplitude of the signal measured by the probe. It can be observed that as the frequency increases, the waveform curve (Ref) representing the reference signal exhibits distortion, which is attributed to the performance limitations of the voltage amplifier. However, the waveform curve (OES) representing the signal measured by the probe remains consistent with the output Ref waveform. This indicates that the detected signal faithfully reflects the actual electric field signal.

Experimental Results:
From the relationship curve between $A_{\text{OES}}$ and the electric field strength $E$, it can be seen that the probe's response amplitude to the electric field increases linearly with the electric field strength across different frequencies. Moreover, the linear trend remains essentially consistent within the 10–5000 Hz range. Preliminary analysis suggests that the slight differences in the measured amplitude-electric field strength curves at different frequencies may be caused by systematic errors, including variations in the photodetector's conversion efficiency at different frequencies and discrepancies between the actual output voltage of the amplifier and the reference voltage at different frequencies.

Figure: ATA-7030 High-Voltage Amplifier Specifications and Parameters