Frequency and Pulse Generation Features in a Multifunctional Field Calibrator

The aim of the Thesis was to investigate improvements that could be made for frequency and pulse generation features of a next-generation multifunctional field calibrator as well as to suggests how the found improvements could be implemented. The improvement investigation was done by reviewing the frequency and pulse generation specifications of multifunctional calibrators that were on the market during the writing process of the Thesis. In addition to that, a customer needs analysis was performed by interviewing experts, and by analyzing customers’ feedback. Based on the results of the investigation, it can be concluded that the frequency and amplitude range and resolution of the current solution by Beamex is competitive and do not require alternation. However, the selection of generatable waveforms could be improved by adding a sine wave generation possibility into the frequency generation function. The current solution is only capable of generating symmetric and positive square waves. Furthermore, some requests for dual pulse generation were found during the investigation. The main focus in the solution design process was the sine wave generation because the dual pulse generation can be utilized easily if the next-generation multifunctional field calibrator has a modular structure. In that case, the number of frequency and pulse generation channels in the calibrator can be increased by adding multiple frequency and pulse generation modules into the calibrator. On the other hand, adding a sine wave generation option to the system is more complicated. Two possible solution suggestions for sine wave generation were designed and evaluated in the present thesis. One solution is based on direct digital synthesis and another one on usage of timer, registers, and direct memory access feature of a microcontroller. In theory, both of the solution suggestions should be able to generate square, pulse, and sine waves. However, by evaluating the solution suggestions, it can be said that the option to generate sine waves increases the complexity and cost of the system. In addition to that, the demand for sine wave generation might not be that high. Hence, it should be re-evaluated if it is profitable to add a sine wave option to the frequency generation

Design and Analysis of a Low Cost Wave Generator Based on Direct Digital Synthesis

Signal generators are widely used in experimental courses of universities. However, most of the commercial tests signal generators are expensive and bulky. In addition, a majority of them are in a fixed working mode with many little-used signals. In order to improve this situation, a small sized and highly accurate economic signal generator based on DDS technology has been developed, which is capable of providing wave signals commonly used in experiments. Firstly, it is introduced the basic principles of DDS and is determined the overall scheme of the signal generator. Then, it proposes a design of the hardware, which include power supply module, display module, keyboard module, waveform generating module based on DDS chip, and the minimum system module based on C8051F010. The signal generator was designed to output sine and square waveforms, and the other achieved performances included the frequency range 0.1 Hz–12.5 MHz, the frequency resolution 0.05 Hz–0.1 Hz, the output amplitude 1.0–4.5 V, the frequency accuracy Kfmin=94.12% and Kfmax=99.99%, and the signal distortion RTHDmin=0.638% and RTHDmax=11.67%