In this episode Shahriar takes a close look at a faulty Agilent E4433B 4.0GHz signal generator and vector modulator. This instrument is equipped with many of the most useful options such as dual arbitrary waveform generator and high-power output.
The instrument does not generate any error messages, however the output signal is ~20dB below specifications. After presenting the system block diagram and observing the output power characteristics, it becomes clear that the issue is with the mechanical attenuator. The teardown of the attenuator reveals faulty o-rings on the 5dB attenuation pad which has to be repaired with some flexible epoxy.
After the repair the instrument’s functionality is verified by measuring the output power with a power meter, frequency accuracy with a Rubidium frequency counter and the modulation accuracy with a vector signal analyzer.
In this episode Shahriar investigates a malfunctioning E3646A Dual Channel Programmable Power Supply. The power supply provides the correct output voltage on one channel. However, the second channel produces no output and continuously reads 0V and 0A.
Applying an external voltage to the malfunctioning channel produces the correct readout from the instrument display suggesting that most of the channel circuitry is functional. After a close examination of the power supply schematics, the problem is traced to a failed solder joint. The DAC output amplifier is disconnected from the output transistor and after repairing the colder joint, the power supply is fully functional.
In this episode Shahriar demonstrates the capabilities of a Waveshare 7.5-Inch tricolor e-Paper display. By combining the display with a Raspberry Pi Zero, the SPI interface of the mini-computer can be used to program and configure the e-Paper display using Python scripts. Furthermore, the Python script takes advantage of the available API of a few website to provide relevant information such as the current date, calendar, task list with due-dates as well as the current weather and weather forecast all in a clean user interface.
The complete Python code is presented and analyzed and the principle operation of the display is also presented. Do not forget to check Applied Science’s video on this topic as well. Finally, the individual pixels are examined under the microscope while the screen undergoes a refresh which demonstrated how various colors are displayed.
The complete code can be downloaded here. You can also buy the e-Paper display here and the Raspberry Pi Zero kit here. If you are interested in using an ESP WiFi module with Arduino to interface with the e-Paper display, it can be found here. You can chose any picture frame to complete the project. The Task Manager and Weather APIs can be found here and here.
In this episode Shahriar goes over the operation and principle theory behind Lock-in Amplifiers. The SRS SR530 is one of the most iconic lock-in amplifiers ever made and since it offers two channels it can be used to perform very interesting experiments across many domains. After reviewing the block diagram and equations governing the theory of operation, a brief instrument teardown is presented.
Two unique and interesting experiments are also presented. In the first experiment the instrument is used to measure the speed of light. This is accomplished by measuring the wavelength of sound at 20kHz using a pair of speakers and a function generator. The distance between the speakers can be carefully adjusted and the relative signal strength from each lock-in channel is measured and thus the wavelength can also be measured.
In the second experiment the sensitivity of a red LED to blue laser light is measured. Due to the semiconductor composition of the red LED as well as its red plastic casing, the responsibility of the LED to blue light is extremely low. A chopper is therefore used to lock the light to the lock-in amplifier’s reference input. The measured induced current is measured down to very low optical level in the order of hundreds of fempto (10^-15) amps.
The Signal Path (TSP) is an electrical engineering video blog for industry professionals, students and hobbyists. TSP is a non-for-profit website dedicated to provide free education spanning a wide range of electrical engineering topics. Equipment reviews, tutorials and repair videos are posted regularly.