This document describes the design and development of a single multifunction tester for insulation resistance, earth resistance, and RCD (residual current device) testing based on a PIC (programmable interface controller) microcontroller. The objectives were to design circuits, PCBs, program the PIC, and test the functionality. The tester was designed to provide accurate and affordable testing compared to commercial options. Testing showed the insulation and RCD measurements were over 90% accurate compared to commercial units, while earth resistance was over 80% accurate. The total development cost was about Rs. 22,188.50, much lower than individual commercial units or a single multifunction unit.

1. DESIGN & DEVELOPMENT OF
INSULATION RESISTANCE TESTER
,EARTH TESTER & RCD TESTER
BASED ON PIC
PRESENTED BY : RATNAYAKA S.D.T.D.
SUPERVISED BY : ENG. GAMINI D. NANAYAKKARA
DATE : 07/20/2014

2. OBJECTIVES………..
The aim of this project is to design and build a
single equipment for insulation testing, earth
resistance testing and RCD testing based on PIC
(programming integrated circuit) programming.

3. A microcontroller is a microprocessor which has
I/O circuitry and peripherals build-in, allowing it
to interface more or less directly with real-world
devices.
PIC

4. The Megger insulation tester is a small, portable
instrument that gives us a direct reading of
insulation resistance in ohms or megohms. For
good insulation, the resistance usually reads in
the megohm range.
INSULATION TESTER (MEGGER)

5. The purpose of insulation around a conductor
is much like that of pipe carrying water, and
ohm’s law of electricity can be more easily
understood by a comparison with water flow.
INSULATION TESTER (MEGGER)……..

6. EARTH RESISTANCE TESTER
Earth resistance
tester has been
develop for
routine testing of
the earthing or
grounding systems
resistance to
ground.

7. RCD TESTER
An RCD detects fault currents flowing to earth
that are too small to trip over-current protection
devices (such as fuses), but are still sufficient to
cause a dangerous electric shock or an electrical
fire.

8. Design circuits
Design PCBs
Programming PIC
microcontroller
Testing and
operation of circuits

9. DESIGN OF RCD TESTER

10. DESIGN OF INSULATION TESTER……

11. DESIGN OF INSULATION TESTER……

12. DESIGN OF INSULATION TESTER……

13. DESIGN OF INSULATION TESTER……

14. DESIGN OF EARTH RESISTANCE TESTER

15. CONTROL BOARD

16. PCB OF CONTROL BOARD

17. PCB OF CONTROL BOARD

18. PCB OF INSULATION TESTER & RCD

19. PROGRAMMING OF PIC

20. TESTING

21. TESTING

22. TEST RESULTS
MCB Rating (A) KYORITSU 3131A (MΩ) New equipment (MΩ)
20 100 90
20 100 95
16 100 86
6 100 91
6 100 89
6 100 96

23. TEST RESULTS
DB No. KYORITSU KEW 5410 (ms) New equipment (ms)
1 30 28
2 30 29
DB No. KYORITSU 4105A (Ω) New equipment (Ω)
1 13.5 11
2 11 9

24. ACCURACY
Insulation resistance measuring accuracy = 92%
RCD tripping time accuracy = 95%
Earth resistance measuring accuracy = 81.6%

25. COST
ITEM No. DESCRIPTION UNIT QTY. PRICE (Rs.) AMOUNT (Rs.)
1.0
For insulation tester.
Dual pole relay. No. 3 225.00 675.00
12V DC 220V AC Inverter module. No. 1 500.00 500.00
IN 4148 Diode. No. 4 2.00 8.00
Resistors. No. 7 0.50 3.50
Variable resistors. (100kΩ & 500kΩ) No. 6 5.00 30.00
Op-amps. No. 4 30.00 120.00
Transistors. No. 3 3.00 9.00
LEDs. No. 3 6.00 18.00
Connectors. No. 1 25.00 25.00
Zenor diodes. No. 4 8.00 32.00

26. COST……
2.0
For RCD tester & Earth tester.
220V - 12V Step down transformer. No. 1 150.00 150.00
Single pole relay. No. 3 40.00 120.00
IN 4148 Diode. No. 4 2.00 8.00
Op-amps. No. 2 30.00 60.00
Resistors. No. 6 0.50 3.00
Zenor diodes. No. 2 8.00 16.00
Variable resistors. No. 4 5.00 20.00
Transistors. No. 2 3.00 6.00
LEDs. No. 2 6.00 12.00
Connectors. No. 1 25.00 25.00

27. COST……
3.0
For Control board.
PIC 16F887 Microcontroller. No. 1 400.00 400.00
74HC4051 Multiplexer. No. 1 250.00 250.00
Power regulator IC. No. 2 30.00 60.00
Dual pole relay. No. 1 225.00 225.00
IC base for PIC. No. 1 30.00 30.00
IC base for multiplexer. No. 1 20.00 20.00
16 X 9 LCD display. No. 1 500.00 500.00
Push buttons. No. 5 20.00 100.00
Connectors. No. 4 25.00 100.00
Capacitors. No. 4 10.00 40.00
Resistors. No. 16 0.50 8.00
LEDs. No. 8 6.00 48.00
Variable resistors. No. 1 5.00 5.00

28. COST……
3.0
Other costs.
Printing copper boards. No. 3 2,000.00 6,000.00
Soldering. No. 3 2,000.00 6,000.00
Battery packs. No. 2 2,000.00 4,000.00
Enclosure. No. 1 1,500.00 1,500.00
13A Socket. No. 1 162.00 162.00
Chemicals for etching No. 3 300.00 900.00
Total cost Rs. 22,188.50

29. COST COMPARISON
Insulation tester KYORITSU 3131A = Rs. 75,900/=
RCD tester KYORITSU KEW 5410 = Rs. 38,200/=
Earth tester KYORITSU 4105A = Rs. 56,300/=
Total cost for three testers = Rs. 170,400/=
Multifunction tester KEW 6016 = Rs. 236,160/=
PIC based multi tester = Rs. 22,188.50/=