Picoampere Level Current Detection for Ultraviolet Photoelectron Spectroscopy Instrument

In today's scientific research and industrial applications, the microstructure, chemical composition, and physical properties of materials are very important. In order to acquire this information accurately, the key is to detect the low photoelectron current sensitively. In view of this, the ultra-low noise operational amplifier ADA4530-1 produced by ADI is used in this paper, which has a shallow noise level and can process low current signals from samples effectively. We build a multi-task processing platform by combining the mighty computing power and efficient data processing function of the STM32F103C8T6 microprocessor. In addition, in order to ensure the reliability and environmental protection of the detection system, the introduction of guarding environmental protection technology. By forming an insulating layer between the cable and the equipment, the technology dramatically reduces the influence of electromagnetic interference on the detection process. At the same time, the shielded cable technology further strengthens the system's anti-interference ability and makes signal transmission more stable and reliable. In the circuit design, the I-V conversion method is adopted, and the ADS1256 is used as the back-end interface of the ADC device to achieve high-resolution current detection. The ADC has a 24-bit analog-to-digital conversion rate that provides more accurate current measurements. In order to verify whether the designed detection circuit achieves the desired effect, we use the Keithley 6221 standard current source for testing. The experimental results show that the designed circuit performs excellently. The relative error of low current measurement is only 2%, which is far below the technical requirements. Moreover, the linearity of the whole system performs well, with a determination coefficient R2 of 0.99997. The resolution is also ideal at 0.1 pA.