Lesson 6Lesson 6

VoltageVoltageDo we need to MEASURE it? ORDo we need to DETECT it?

Test LampsTest LampsNeon Test Pencils/ScrewdriversNeon Test Pencils/ScrewdriversVoltage ProbesVoltage ProbesSteinel Combi-CheckSteinel Combi-CheckAC Voltage ProbeAC Voltage Probe

VoltmeterVoltmeterMultimeterMultimeter

Clamp meterClamp meter

AnalogueAnalogue DigitalDigital Digital simulated AnalogueDigital simulated Analogue

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 open in time

Poor quality leads and probes led to injury.

Probe tips burned off

Fingerprints burned into probes

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

ProtectionHigh fault current rated fuses

Use meters / testers without current sockets

Protection

• Double insulated• Recessed / shrouded Plugs/Sockets• Finger guards• CAT III – 1000 V• Replace when damaged

Test Leads

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

• CAT III

• CAT II

• CAT I

“Origin of installation”Supply Authority level and any outside cable runs

Distribution wiring, including Consumer mainsand Sub-circuits; permanently installed loads.

Socket Outlets; plug-in loads.

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 III

CAT II

CAT IV – 600 V: 8 kV impulse

CAT III – 600 V: 6 kV impulse

CAT III – 1000 V: 8 kV impulse

CAT II – 600 V: 4 kV impulse

CAT II – 1000 V: 6 kV impulse

CAT III-600 V = 6 kV impulse 2 ohm test source

CAT II-1000 V = 6 kV impulse 12 ohm test source

The greater the source impedance, the lower the category:

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

CAT III-1000 V

OR

AND CAT IV 600 V ORCAT III-1000 V test leads

CAT III-1000 V CAT IV-600 VCAT III-1000 V

CAT III-600 V

No meter is safe when improperly used

Don’t let test leads be a weak pointCAT III-1000 V or CAT IV 600 V/CAT III 1000 V ratingDouble insulationShrouded connectorsFinger guardsInsulation not damaged: not melted, cut, cracked, stretchedConnectors: no insulation pulled away from end connectorsProbe 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.