This project was made as part of my senior project at my university. The idea behind the device was to make a data logger that can be carried around a lab without the need to connect to a computer. In this segment, we will cover the components used for this project. Later, we’ll get into calibrating the sensors, setting up software programs, and running some experiments.
System Overview
What Does it Measure?
The following table shows the parameters to be measured and the sensors used to measure them.
S/N Measurement variable Sensor Range
1 Temperature Thermocouple(K-type) -250°C-1250°C
2 Mass Electronic load cell 0 – 1 Kg
3 Flow rate Hall Effect Flow meter 1 – 30 Litres/min
DAQ System Components
Data Transmission and Storage
This device is used to convert a parallel input to a serial output, and thus, it enables the use of fewer input pins in the microcontroller. It’s an 8-bit static shift register and therefore converts 8 parallel inputs to the serial transfer.
Arduino UNO
The microcontroller is used to link all the components, get the digital data from all the ADCs, process them, and store them on the memory card. It also distributes power to all of the sensors.
The communication between the microcontroller and the SD card uses SPI. The functions of the module are: Formatting and preparing the memory card, file naming, as well as opening and closing files.
Signal Conditioning
The MAX6675 performs cold-junction compensation and digitizes the signal from a type-K thermocouple. The data is output in a 12-bit resolution. It resolves temperatures to 0.25°C, allows readings as high as +1024°C. The chip can also detect an open thermocouple.
HX711 Load Cell
Sensors
It is a K type thermocouple with a Chromel {90% nickel and 10% chromium} Alumel {95% nickel, 2% manganese, 2% aluminium and 1% silicon} junction. It is has a temperature range of 0 to 800°C. It resistive to oxidation at higher temperatures but vulnerable to sulfur attacks.
Weighing Load cell
Flow sensor/Hall Effect Flow Meter
Integrating the Components
The integration of the system is done using the parts shown above. Integration is done first using simulation by Proteus Isis design suite for configuring and arranging the electronic components and developing a program that will be used for the device. The block diagram and schematic below show the general method used in the integration of the DAQ system.
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