In this episode Shahriar builds a magical charger circuit that has an efficiency of tens-of-thousands of percent! But not to worry, it is a trick and the trick is revealed in the video. The purpose of the video is to discuss the nature of the scientific method and our society’s need for free education.
Archive for August 23, 2015
In this episode Shahriar gets a hold of a National Instruments VirtualBench! This instrument combines a mixed-signal oscilloscope, function generator, digital multimeter, programmable power supply and digital I/Os in one compact and portable unit. The teardown of the unit reveals a two-board construction with a core single processor which handles all instrument functionality simultaneously.
The unit software (which is embedded inside the instrument memory) is examined in detaile before performing any experiments. Using the VirtualBench, a Si5351 multi-synthesizer clock generator IC is characterized including output signal analyses and I2C decoding. Next by using the function generator and oscilloscope the response of a band-pass 15MHz filter is measured.
In this episode Shahriar takes a detailed look at the new Keithley DMM7510 7.5-Digit Multimeter. Boasting Keithley’s touchscreen GUI interface, 100mV, 1-Ohm and 10uA ranges makes this multimeter a precision instrument for a variety of applications. The multimeter is also capable of 1MS/s digitization functionality.
The teardown of the unit reveals the complex multi-board construction and analog board design intricacies. After a brief performance verification and GUI overview the multimeter is used in several experiments including measuring the conductivity of a flame, digitizing a large dynamic range multi-tone signal and DC-DC converter noise analysis. Furthermore, the scripting capability of the unit is employed to estimate the location of a short in an Ethernet cable and measure the dielectric constant of a parallel plate capacitor.
In this episode Shahriar examines a faulty R&S FSH3 100kHz – 3.0GHz Portable Spectrum Analyzer. This exceptionally dirty unit does not power on and is missing a power supply and battery. After verifying the correct operation of the battery charger circuit and keypad the problem is traces to a damaged SOT-23-6 MOSFET device which is part of a fly-back DC-DC converter. A replacement MOSFET with a lower current rating proves to be a failure as the device fails on startup. A higher rated MOSFET resolves the problem and device begins to operate correctly.
The block diagram of the system as well as a detailed block diagram of the RF section is presented and correlated with the teardown of the RF section. The super-heterodyne down-conversion circuits and components are examined.