Transcript Electromagnetic Applications

Lesson 6
Voltage
Do we need to MEASURE it?
OR
Do we need to DETECT it?





Test Lamps
Neon Test Pencils/Screwdrivers
Voltage Probes
Steinel Combi-Check
AC Voltage Probe
 Voltmeter
 Multimeter
 Analogue
 Digital
 Digital simulated Analogue
 Clamp meter
Last known earthly
residence of automotive
fuse used to replace
original fuse
Test leads survived intact
13.8 kV arced over
to test probes
Test leads destroyed
250V fuse
didn’t into
openprobes
in time
Fingerprints
burned
Poor quality leads and
probes led to injury.
Probe tips burned off
 Arc from transients (lightning, load switching)
 Voltage contact while in continuity or resistance
 Measuring voltage with test leads in current sockets
 Shock from accidental contact with live components
 Using meter or tester above rated voltage
Protection
Independent certification to meet
CAT III-1000 V or CAT IV 600 V
Protection
Overload protection in Ω up to the meter’s volt rating
Protection
High fault current rated fuses
Use meters / testers without current sockets
Protection
Test Leads
•
•
•
•
•
Double insulated
Recessed / shrouded Plugs/Sockets
Finger guards
CAT III – 1000 V
Replace when damaged
IEC 61010
 New standard for low voltage “test, measurement and
control equipment”.
 Provides much improved protection against “overvoltage
impulse transients” - voltage spikes.
 Basis for:
 ANSI/ISA-S82.01-94 (US)
 CAN C22.2 No. 1010.1-92 (CAN)
 EN61010-1:1993 (EUR)
 AS 61010.1:2003 (Testers)
 AS 61010.031:2004 (Leads)
The closer the location is to the power source, the higher the
available fault current, the higher the category
 CATEGORIES: CAT I to CAT IV
 The greatest danger from transients is in the high categories, because they
could trigger an arc blast
 IMPULSE TESTING: No failure allowed
 Meters must be tested by being hit with a specified number of transients,
with specified peak voltages
• CAT IV
“Origin of installation”
Supply Authority level and any outside cable runs
• CAT III
Distribution wiring, including Consumer mains
and Sub-circuits; permanently installed loads.
• CAT II
Socket Outlets; plug-in loads.
• CAT I
Protected electronic circuits
WITHIN each Category:
 There are designated “working voltages”
(50, 150, 300, 600, 1000 V).
 A higher voltage has a higher transient withstand
 CAT IV
CAT IV – 600 V:
 CAT III
CAT III – 600 V: 6 kV impulse
CAT III – 1000 V: 8 kV impulse
 CAT II
8 kV impulse
CAT II – 600 V: 4 kV impulse
CAT II – 1000 V: 6 kV impulse
The greater the source impedance, the lower the category:
 CAT III-600 V = 6 kV impulse
 2 ohm test source
 CAT II-1000 V = 6 kV impulse
 12 ohm test source
A CAT III-600 V 6k V test impulse has 6 times the
current of a CAT II-1000 V 6 kV test impulse!
First know the category you are working in, then choose the
appropriate voltage rating
If you ever measure power circuits, you should use:
CAT III-600 V
OR
CAT IV 600 V
OR
CAT III-1000 V
AND CAT IV 600 V ORCAT III-1000 V test leads
No meter is safe when improperly used
CAT III-1000 V
CAT IV-600 V
CAT III-1000 V
CAT III-600 V
Don’t let test leads be a weak point
 CAT III-1000 V or CAT IV 600 V/CAT III 1000 V rating
 Double insulation
 Shrouded connectors
 Finger guards
 Insulation not damaged: not melted, cut, cracked, stretched
 Connectors: no insulation pulled away from end connectors
 Probe tips: not loose or broken off (too short)
Safe practices include but are not limited to:
 Whenever possible, work on de-energized circuits.

Follow proper Isolation procedures.
 Use well maintained tools and appropriate safety gear
 Safety glasses, insulated tools, insulating gloves,
flash suits, insulating mats, etc.
 Don’t work alone.
 Practice safe measurement techniques.
 Always connect the EARTH FIRST, ACTIVE SECOND.
 Disconnect the ACTIVE lead first, EARTHED lead second.