Merilne naprave

Pri fizikalnih eksperimentih pogosto uporabljamo merilne naprave, s katerimi želimo potrditi teoretične principe in fizikalne pojave. V šolskem prostoru najpogosteje uporabljamo Vernier-jevo merilno napravo LabQuest Hardware @LabQuest30:online , ki nam omogoča raznovrstne meritve.

Vernier’s DAQs

Poglejmo si nekaj podatkov o napravi:

• Display
  • 11.2 cm x 6.7 cm (13.1 cm diagonal) screen
  • 00 x 480 pixel color display at 188 dpi
  • ED backlight
  • ortrait or landscape screen orientation
  • igh-contrast mode for outdoor visibility
• Processor
  • 800 MHz Application Processor
• Connectivity
  • Wi-Fi 802.11 b/g/n @ 2.4GHz
  • Bluetooth Smart for WDSS and Go Wireless Sensors
• User Interface
  • Resistive touch screen
  • Touch and stylus navigation for efficiency and precision
• Data Acquisition
  • 100,000 samples per second
  • 12-bit resolution
  • Built-in GPS, 3-axis accelerometer, ambient temperature, light, and microphone
• Environmental Durability
  • Operating Temperature: 0 + 45°C
  • Storage Temperature: -30 + 60°C
  • Splash resistant
  • Rugged enclosure designed to withstand a fall from lab bench
• Size and Weight
  • Size: 8.8 cm x 15.4 cm x 2.5 cm
  • Weight: 350 g
• Ports
  • 5 sensor channels
  • USB port for sensors, flash drives, and peripherals
  • USB mini port
  • DC power jack
  • MicroSD/MMC slot
  • Audio in and out
• Storage
  • 200 MB
  • Expandable with MicroSD and USB flash drive
• Power
  • Rechargeable, high-capacity battery
  • DC charging/powering through external adapter (included)
• cena:
  • $455

Seveda pa morate dokupiti še senzorje, ki tudi niso cenovno ugodni, saj se njihova cena giblje od $30 … naprej.

Arduino Data Acquisition System

On the market we can find different DAQ systems which are hi-end products and often expencive (from 100 € .. n k€). Buy we can use Arduino (Uno, nano, …) as low-cost data acqusition system if we do not need scientific accurate data (for pedagogical purposes).

<– Parts of DAQ[[NationalInstruments]] –>

Na plošči vsebuje mikrokrmilnik Atmega328, ki lahko opravi podobne naloge, kot smo jih opisali v poglavju Merilne naprave.

Poglejmo si nekaj karakteristik tega mikrokrmilnika [@ATmega328P_Datasheet:online]:

• Advanced RISC Architecture
  • 131 Powerful Instructions
  • Most Single Clock Cycle Execution
  • 32 x 8 General Purpose Working Registers
  • Fully Static Operation
  • Up to 20 MIPS Throughput at 20MHz
  • On-chip 2-cycle Multiplier
• High Endurance Non-volatile Memory Segments
  • 32KBytes of In-System Self-Programmable Flash program Memory
  • 1KBytes EEPROM
  • 2KBytes Internal SRAM
  • Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
  • Data Retention: 20 years at 85°C/100 years at 25°C(1)
  • Optional Boot Code Section with Independent Lock Bits
    • In-System Programming by On-chip Boot Program
    • True Read-While-Write Operation
  • Programming Lock for Software Security
• Atmel® QTouch® Library Support
  • Capacitive Touch Buttons, Sliders and Wheels
  • QTouch and QMatrix® Acquisition
  • Up to 64 sense channels
• Peripheral Features
  • Two 8-bit Timer/Counters with Separate Prescaler and Compare Mode
  • One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode
  • Real Time Counter with Separate Oscillator
  • Six PWM Channels
  • ADC
    • 8-channel 10-bit ADC in TQFP and QFN/MLF package
    • Temperature Measurement
    • 6-channel 10-bit ADC in PDIP Package
    • 10-bit Resolution
    • 0.5 LSB Integral Non-Linearity
    • ±2 LSB Absolute Accuracy
    • 13 - 260us Conversion Time
    • Up to 76.9kSPS (Up to 15kSPS at Maximum Resolution)
    • Six Multiplexed Single Ended Input Channels
    • Two Additional Multiplexed Single Ended Input Channels (TQFP and VFQFN Package only)
    • Temperature Sensor Input Channel
    • Optional Left Adjustment for ADC Result Readout
    • 0 - VCC ADC Input Voltage Range
    • Selectable 1.1V ADC Reference Voltage
    • Free Running or Single Conversion Mode
    • Interrupt on ADC Conversion Complete
    • Sleep Mode Noise Canceler
  • Two Master/Slave SPI Serial Interface
  • One Programmable Serial USART
  • One Byte-oriented 2-wire Serial Interface (Philips I2C compatible)
  • Programmable Watchdog Timer with Separate On-chip Oscillator
  • One On-chip Analog Comparator
  • Interrupt and Wake-up on Pin Change
• Special Microcontroller Features
  • Power-on Reset and Programmable Brown-out Detection
  • Internal Calibrated Oscillator
  • External and Internal Interrupt Sources
  • Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby, and Extended Standby
• I/O and Packages
  • 23 Programmable I/O Lines
  • 28-pin PDIP, 32-lead TQFP, 28-pad QFN/MLF and 32-pad QFN/MLF
• Operating Voltage:
  • 1.8 - 5.5V
• Temperature Range:
  • -40°C to 105°C
• Speed Grade:
  • 0 - 4MHz @ 1.8 - 5.5V
  • 0 - 10MHz @ 2.7 - 5.5V
  • 0 - 20MHz @ 4.5 - 5.5V
• Power Consumption at 1MHz, 1.8V, 25°C
  • Active Mode: 0.2mA
  • Power-down Mode: 0.1uA
  • Power-save Mode: 0.75uA (Including 32kHz RTC)

Requirements

(Checked is required, unchecked is optional)

Hardware:

• Computer
• Arduino board (Arduino UNO, Arduino LEONARDO, Arduino NANO, clone products )
• basic electronics components for sensors
• arduino set starter for example use this kit
• arduino sensors set for example use this kit

Software:

• Arduino IDE download here
• Python (>=3.0)
• pyserial
• Ms Excel

Pros & Cons

| Pros | Cons | |————————————–|—————————| | + Price (Arduino ~3€, sensors ~2-5€) | - work in progress | | + Accessibility | - no plug&play solutions | | + Versatility | - DIY project | | + Easy importing data into MS Excel | - low sampling rate ~6kHz | | + točne časovne meritve | - 10-bi resolutuin |

More about DAQ you can read in further reading…

Kaj ko bi si lahko naredili svojo merilno napravo?

V ta namen smo ustvarili nekaj vsebin na portalu GitHub…