micro controller based data acquisition system

2. Introduction
• It is PC based instrument designed using
industry standard PIC18F4550 from microchip
corp.
• It has idyllic GUI designed using visual C# .net
2005.
• It has 6 different modules.

3. Modules
• Electronic counter.
• Programmable function generator.
• Digital carrier modulation
• Digital Multi-meter.
• Weather station.
• Digital storage oscilloscope. (DSO)

4. Electronic counter
Digital frequency counter
Digital time period measurement
Digital pulse width measurement
Digital duty cycle measurement
Digital phase angle measurement
Digital ratio measurement

5. Digital frequency counter
Timer
At t = 0sec
Counter Counter
Timer
At t = 1sec
Synchronized Synchronized
Counter &
timer start at
t = 0sec.
Counter &
timer stop at
t = 1sec.
timer = 1 sec.
count =
frequency
count = 0
timer = 0 sec.

6. Digital time period measurement
Capture timer
Timer = X
Capture timer
Timer = Y
Time period = Y-X
Time period

7. Digital pulse width measurement
Capture timer
Timer = X
Capture timer
Timer = Y
Time period = Y-X
Pulse width

8. Digital phase angle measurement
+
_
+
_
X-OR gate
COMPARATOR
PHASEDIFFRANCE
INPUT WAVE

9. Digital Multi-meter
• Digital voltmeter
• Digital ohmmeter
• Digital Capacitance meter
• Digital Inductance meter

10. Digital voltmeter
A/D converterAnalog voltage Digital voltage

11. Digital Capacitance meter
+
_
R
c
ΔV=0.693VCC
E=VCC
Q=0 at t=0sec.
COMPARATOR
Putting values in Eq. below
ΔV=E(1-e-t/RC
)
Timer start Timer stop
R= constant
C= variable

12. Digital ohmmeter
+
_
R
c
ΔV=0.693VCC
E=VCC
Q=0 at t=0sec.
COMPARATOR
Timer start Timer stop
C= constant
R= variable
Putting values in Eq. below
ΔV=E(1-e-t/RC
)

13. Weather station
•Temperature measurement
•Humidity measurement
•Atmospheric pressure measurement

14. Temperature measurement
IC used: SHT11
Range: -40 to 123.8°C
Humidity measurement
IC used: SHT11
Range: 0 to 100%RH
Atmospheric pressure measurement
IC used: MPAX6115A
Range: 15 to 115kPa
Components used and ranges

15. Digital carrier modulation
 Binary Frequency shift keying generator
(BFSK)
 Binary Phase shift keying generator (BPSK)
 Binary amplitude shift keying generator
(BASK)

16. Binary Frequency shift keying
generator (BFSK)

17. Binary Phase shift keying
generator (BPSK)

18. Binary amplitude shift keying
generator (BASK)

19. Σ
PHASE-TO-
AMPLITUDE
CONVERSION
D/A CONVERSION
PHASE
REGISTER
TUNING WORD
PHASE
ACCUMULATOR
24 TO 48
BITS
14 TO 16
BITS
Programmable function generatorProgrammable function generator
SYSTEM CLOCK
fc

20. Working of Programmable function
generator
Frequency is determined by the eq.
fOUT = output frequency of the DDS
M = binary tuning word
fC = internal reference clock frequency (system
clock= 20 MHz)
n = length of the phase accumulator, in bits

21. Amplitude control in
Programmable function generator
+
_
Rf
R1
R2
Digital potentiometer
By varying input control word we can control output voltage

22. Digital storage oscilloscope (DSO)
• Single channel digital storage oscilloscope.
• Voltage range: 40V peak-to-peak
• Five User selectable time base.
• Nine user selectable voltage base.
• On screen rise time and total time display.
• On screen peak amplitude display.
• Waveform storage capability.

23. Thank you!