In this episode, Shahriar presents the theory, design and characterization of Nyquist Digital to Analog Converters (DACs). After a brief overview of DAC operation and theory, the schematic of an 8-Bit R-2R DAC is presented. The R-2R DAC, which is driven by a dsPIC30F6014A Microchip microcontroller is capable of producing ramps and arbitrary waveforms uploaded through an RS232 interface. The static integral non-linearity (INL) and differential non-linearity (DNL) is measured by using a Rigol DM3068 Multimeter through a Matlab interface program. The dynamic performance of the DAC is characterized using an Analog Devices AD6645 105MSps 14-Bit ADC evaluation board coupled with a USB FIFO interface board. By using the 'Visual Analog' software, the spectrum of the DAC output as well as the signal to quantization and distortion ratio (SQNDR) is calculated. Finally, the impact of component mismatches, operational amplifier non-linearity and timing uncertainty on the INL/DNL and SQNDR (ENOB) of the DAC is examined.
Archive for Videos
TSP #19 – Teardown, Repair and Calibration of a Keithley 220 Programmable Current Source
In this episode Shahriar investigates the cause of failure of a Keithley 220 Programmable Current Source. Despite being manufactured in the mid-1980's, the Keithley 220 is still a very popular programmable current source. Alongside the repair efforts, the schematic of various analog, digital and power supply boards are also presented. By interpreting the failure mechanism, the fault is traced and corrected. The Keithley 220 is then calibrated and the calibration procedure of the sub-100nA range is explained. Finally, the performance of the calibrated unit is verified using a Rigol DM3068 Multimeter.
The Signal Path
http://www.TheSignalPath.com
TSP #18 – Teardown and Repair of a Fluke 196B Handheld ScopeMeter
In this episode Shahriar goes through the teardown and repair process of a Fluke 196B Handheld ScopeMeter. This unit, which has been purchased as a "dead" unit from eBay, is examined for faults. During the teardown, various PCB components, architecture and design is presented. The performance and functionality of the unit is verified with a few brief experiments. Finally, the schematic and block diagram of the Fluke 196B is explored for the finer details of its design and operation.
TSP #17 – Rigol DSA1030A-TG3 Spectrum Analyzer Review and Experiments
In this episode Shahriar extensively reviews the Rigol DSA1030A-TG3 Spectrum Analyzer. A wide variety of experiments are performed using the Rigol spectrum analyzer to serve both as a tutorial to use the instrument and to demonstrate its capabilities. Some measurement results are also performed using other calibrated instruments to verify the accuracy of the spectrum analyzer. The Rigol DSA1030A-TG3 can be purchased directly from Rigol Inc.
The Signal Path
http://www.TheSignalPath.com
TSP #16 – Teardown and Repair of an HP 8648C Synthesized Signal Generator
In this episode Shahriar attempts to repair an HP 8648C Synthesized Signal Generator from a dumpster dive. The cause of failure is investigated and traced. Alongside the repair efforts, the internal construction and components of the synthesizer are also presented. Various component teardowns are shown and described including the structure of the VCO used in the generator assembly. The functionality of the repaired unit is verified using an Agilent Power Meter and Rigol Spectrum Analyzer. Finally, the overall unit block diagram is presented and the principle of operation is described in detail.
The Signal Path
http://www.TheSignalPath.com
