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Digital Voltmeter
Published in Mesut Sahin, Howard Fidel, Raquel Perez-Castillejos, Instrumentation Handbook for Biomedical Engineers, 2020
Mesut Sahin, Howard Fidel, Raquel Perez-Castillejos
This laboratory exercise will introduce the concept of analog-to-digital (A/D or ADC) converters and give a practical example of a specific A/D converter circuit built around AD7575. This particular A/D converter is primarily manufactured to be used as a peripheral to a microprocessor or a microcontroller. The control inputs, however, are simple enough that they can be emulated with a simple digital logic circuit. The output will be displayed on an LED display as opposed to be placed on the data bus to be read by the microprocessor. The third block in the circuit is a square wave generator that is built around an inverting Schmitt trigger gate (74HC14). This simple circuit will introduce the basic concept of a resistor-capacitor (RC) oscillator that is based on charging and discharging of a capacitor through a resistor. Overall, the circuit has three blocks; the A/D converter, the display decoder (CD4511) and the LED display, and the RC square wave generator.
Units and Measurements
Published in Daniel H. Nichols, Physics for Technology, 2019
RC Oscillator: The resistive capacitor oscillator or RC oscillator works by alternating charging and discharging of a capacitor through a resistor happens at a determined rate, dependent on the time constant τ = R × C. This can be used to measure time. One of the electronic industry’s standards that controls this charging and discharging is the 555-timer chip (Figure 1.30). It has a stability of 1%.
Design and Development of Instrumentation for Remote Detection of Hydrogen Using Metal Oxide Sensor
Published in IETE Technical Review, 2022
Ajay Kumar Keshari, J. Prabhakar Rao, A. Sree Rama Murthy, V. Jayaraman
The resistance of sensor changes with the change of concentration of hydrogen across the sensor. The resistance of the sensor was measured by the hardware based on a unique design of the XR-2206 function generator. The sensor (R1) and fixed capacitor (C) act as an RC oscillator in function generator configuration. The frequency of oscillation depends on the values of R1 and capacitor C. The value of capacitance, C is optimized and kept constant for a given range of sensor resistance measurement. Hence the frequency of oscillation of the function generator depends on the value of sensor resistance R1 only. The frequency of oscillation was measured and sent to a remote PC for the post-analysis of sensor response. The frequency of oscillation is determined by Equation (1) [34,41]. where C = fixed value of the capacitor, R1 = resistance of the sensor and R2 = fixed value of the resistor
Minimizing regain awareness time of the epileptic patient using a well-known phone ringtone
Published in Cogent Engineering, 2023
The ARM Cortex M4F LPC4330 model was chosen for its efficiency, small size, and low power consumption. It has an ARM M0 coprocessor. It is a central processing unit (CPU) that can run at speeds of up to 204 MHz. The LPC4330 is a 32-bit microcontroller. It has a low power consumption, improved debug features, a high level of block integration, on-chip memory up to 264 kB, and DSP (DSP). It supports floating points, which is critical for our image processing project. It can be programmed as a dual-core M4 and M0 for data control. The Internal RC oscillator (IRC) has a frequency of 12 MHz and an accuracy of 1.5 percent that varies with temperature and voltage. It has one Fast-mode Plus I2C-bus interface and can support data rates of up to 1 Mbit/s.