Posts by James Wei

Characterization of Dye-Sensitized Solar Cell Impedance at Low Frequencies with HF2IS Impedance Spectroscope

on 03.07.2015 at 12:29 by James Wei on Blog of James Wei
Co-author and main contributor: Dr. Antonio Braga Introduction The electrical impedance spectroscopy (EIS) technique is used to characterize the physical-chemical processes of the dye-sensitized solar cells (DSSC) using different types of metal oxides semiconductors, dyes or electrolytes [1]. The EIS […]

Deep Level Transient Spectroscopy Using HF2LI Lock-in Amplifier

on 23.05.2015 at 10:58 by James Wei on Blog of James Wei
Co-author and main contributor: Dr. Antonio Braga Introduction A very small concentration of lattice point defects, or simply defects, such as vacancies, impurities, dislocations, grain boundaries or cavities, are responsible for creating many different properties in semiconductors. Defects play a crucial […]

Measuring the I-V Characteristic of PN Junction Devices with HF2LI Lock-in Amplifier

on 13.05.2015 at 09:24 by James Wei on Blog of James Wei
Co-author and main contributor: Dr. Antonio Braga Introduction The p-n junction is the fundamental building block of semiconductor material electronics device such as transistors, diodes, sensors, laser, light emitting diodes, as well as solar cells. If one wants to know […]

Detecting a small fraction of impedance changes with improved sensitivity

on 16.09.2014 at 13:54 by James Wei on Blog of James Wei
Introduction There are normally two types of impedance measurement. The first type is the dynamic impedance measurement where impedance can change rapidly over time. This is the case in electrical impedance spectroscopy (EIS) in microfluidics for cell counting and cell discrimination […]

Reduce Ground Disturbances when using HF2TA Transimpedance Amplifier in a Measurement Setup

on 26.02.2014 at 18:13 by James Wei on Blog of James Wei
Ground loops can potentially pose a serious problem in many measurement setups. Due to the multiple connections to and from the HF2TA current amplifier and other external components, several ground loop related issues can pop up in the signal being […]

Taking Your Microfluidics EIS Measurement to the Ultra-High Frequency Domain

on 08.01.2014 at 13:28 by James Wei on Blog of James Wei
Introduction The HF2IS Impedance Spectroscope from Zurich Instruments is a versatile tool suitable for label-free electrical impedance spectroscopy (EIS) of single cells in the domain of cell counting and discrimination. The high frequency range, from DC to 50 MHz, and the […]

Using HF2IS Impedance Spectroscope for FRA, 2-Terminal and 4-Terminal Measurements

on 19.09.2013 at 14:14 by James Wei on Blog of James Wei
Often there are questions from our HF2IS Impedance Spectroscope users on how to configure the HF2IS for frequency response analysis (FRA), 2-Terminal impedance measurement, or 4-Terminal impedance measurement. This short blog will clarify the proper physical connections as well as […]

Guide to Tuning the HF2LI-PID Controllers

on 17.09.2013 at 10:54 by James Wei on Blog of James Wei
On the Zurich Instruments website, there are a few advanced examples of using HF2LI-PID controllers in different feedback control applications. However, I often get questions from first time users on how to properly tune the PID gain parameters. I am […]

Operate HF2LI dual-channel lock-in amplifier with one reference frequency

on 24.05.2013 at 11:43 by James Wei on Blog of James Wei
This blog quickly described how to synchronize the lock-in reference for both lock-in channels of HF2LI lock-in amplifier. HF2LI lock-in amplifier comes with two independent lock-in channels which offers HF2LI users substantially more flexibility compared to the single lock-in setup. With […]

Optimize Your Frequency Sweep for Static Impedance Measurement

on 28.02.2013 at 08:20 by James Wei on Blog of James Wei
Very often people want to measure very large static impedance (e.g. small capacitance, large resistance) over a wide frequency range. In the very low frequency region, one may notice that measured curve is not smooth but rather “jiggly”, just like […]

ω/2 Demodulation for a Parametric Oscillator

on 27.02.2013 at 10:04 by James Wei on Blog of James Wei
We often get questions from HF2LI lock-in amplifier customers who characterize MEMS and sometimes from those doing AFM scans on how to measure at half reference frequency using a lock-in amplifier. Half reference frequency lock-in measurement is often necessary when […]

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