USB Data Acquisition Card

Abstract

The aim of this invention is to have a new data acquisition device that is compatible with the USB (Universal Serial Bus) standard. The USB Data Acquisition Card (USB DAQ) is connected to personal computer (PC) through a normal USB cable. The circuit is built on a compact printed circuit board (PCB) and it requires no external power supply. The heart of USB DAQ is a Microchip's USB microcontroller (IC # PIC18F4550), firmware of which is programmed in C-language. The USB DAQ has eight digital outputs (8-DO), eight digital inputs (8-DI), two pulse- width modulated or PWM outputs (with frequency range of up to 2.9 KHz) and eight high impedance analog inputs (8-AI) with unipolar voltage span (0-5 V). The USB DAQ supports full speed data transfer operation which makes its' communication speed faster than serial and parallel ports. Owing to high impedance, the analog input signals can be directly connected to the analog input channels without any signal conditioning, if these are within the range of 0-5 Volts. The graphical user interface (GUI) of USB DAQ is developed in LabVIEW and Visual C++ for Windows OS. The USB DAQ is a flexible general purpose device that works well in a variety of applications. Some applications are in lab experiments, embedded systems, data logging, industrial data acquisition etc. The performance of the USB DAQ is verified by employing it in a thermocouple calibrator. The calibrator was especially designed and developed for this purpose. The results of the designed calibrator were compared and found in conformity with an industrial standard thermocouple "Temperature Calibrator" of National Instruments.