E

VoltagedropSmall S

mall

currentVr

A/D

Digitaldisplay

8 8 8 8

Basics of Electrical Testing www.hioki.com

Inquiries

Magneticflux fromsecondarycurrent

Output

Measuredconductor

Shuntresistance

Magnetic

core

Magnetic flux frommeasured current

Secondarycurrent

Feedbackwinding

Measuredcurrent

Hall element AMP

MEASURESW

LR6 x 4

OFF

ON

AI

V=Rx×I

Rx=V/I

S(P)electrode

E electrode

HIOKI Calibration Certificate

HIOKI Data Sheet

H(C)electrode

ICurrent meter

Voltmeter

AC power

V

Measuring Instrument(Device under test)

Magnitude

Value

Input 10VCalibrated value 10.000 00V

Standard Instrument

Relationship

Verify

Intermediatestandards

Comparativestandards

Appliedstandards

National Instituteof Advanced

Industrial Scienceand Technology

Nationallyrecognizedstandards

MULTI-PRODUCTCALIBRATOR

FLUKE 5520A

POWER HiTESTER

HIOKI 3332

National Instituteof Information

and CommunicationsTechnology

Japan Electric MetersInspection Corporation

ManufacturerFLUKE

ManufacturerClarke-Hess

TelecomEngineering

Center

STANDARDRESISTANCE

FLUKE742A-1, 742A-10k

CALIBRATORFLUKE 5700A

AMPLIFIERFLUKE 5725A

STANDARDRESISTOR

AlphaElectronics Corp.

CSR

STANDARDRESISTOR

YOKOGAWA2792, 2794

CURRENTTRANSFORMER

TOKYOSEIDENCTS8-1(50A/5A)

CURRENTSHUNT

100Ω, 1kΩ

HIOKI

ACMEASUREMENT

STANDARD

FLUKE5790A

CURRENTSHUNT

FLUKEA40,A40A

DIGITALPHASEMETER

Clarke-Hess6000A

UNIVERSALCOUNTER

ADVANTESTTR5830D

MULTIMETER

HP/Agilent 3458A

A

Water will not flow.

Differencein water level

High +

BAT

Voltage (V)

Low −

ElectricPotential

Resistance (R)

Current

Waterflow

B A

B

Current (I)

current

DC (Direct Current) is the flow of electric charge in one direction.

Excessive overvoltage (impulse voltage) may also appear on power lines. The opening and closing of solenoid valves or loads at plants may cause high voltage spikes. Furthermore, since the wave peak value may be 10 times the power supply voltage or more in the case of inductive loads, etc., the IEC standard provides a correlation between the nominal system voltage (power supply line voltage), overvoltage level, and measurement category as an indication of transient overvoltage.

AC (Alternating Current) is electric charge that periodically varies in terms of direction and magnitude. A typical AC waveform is a sine wave, and commercial power supply is made of sinusoidal AC voltage signals.

Instantaneous : Level that occurs instantaneouslyMaximum and Minimum : The highest and lowest values Peak-to-Peak : Difference between the maximum and minimumAverage : Average of the instantaneous values that occur in half a cycleRoot Mean Square (RMS or True RMS) : Energy that is converted to a DC-equivalent valueFrequency : The number of times a point on a wave passes a fixed reference point in one second

In the average rectifying method, average values are measured using an internal circuit. The average values are multiplied by the sine wave’s waveform ratio of 1.11 and then converted to RMS values. In the RMS method, RMS values are measured using an internal circuit. With this method, even distorted waveforms can be properly displayed as RMS values.

Example: A crest factor 3 measuring instrument may not be able to accurately measure a waveform with crest factor of 3 or more with respect to the range. It is necessary to change the range or to use an instrument with a higher crest factor.

Example AC Waveforms

Voltagedrop

Large LargecurrentVr

Max

Max: 141.4V

Min: -141.4V

Full waverectified(×1.11)

LPF MEANValue

DC

Peak-to-Peak

Based on the IEC61010-1 international standard concerningthe safety requirements for electrical equipment formeasurement, control, and laboratory use

Drop connection

Service dropDistributionpanel

Distributionpanel

Fixedinstallation

Outlet OutletTransformer

Power meter

Min

Sine Square

Sawtooth Triangular

Pulse Distorted

Example DC Waveforms

Direct Ripple Pulsating

Peak-to-Peak: 282.8VAverage

Average: 90V

RMS: 100V

Example: 100V Commercial Power Supply

High surge voltages often occur when a solenoid valve opens and closes. The example above shows almost a 1000V surge on a 100V AC line.

When a current flows, a magnetic field is generated concentrically. The magnitude of the magnetic field is proportional to the magnitude of the current. The direction of the magnetic field is the direction in which a screw is tightened if the direction of movement of the screw and the direction of current are matched. This law is called "Ampère's right-hand grip rule".

Input impedance : lowInstrument loss : largeExternal noise : low susceptibility

Example of Overvoltage atOpen/Close of Solenoid Valve

Ampère's right-hand grip rule

Resistance measurement circuit of an analog meter

A current clamp meter measures the voltage across a detection shunt resistor from the winding that forms the coil, the magnetic core that raises the sensitivity of the magnetic field, and the shunt resistor for measuring the induced current. The signal generated in the conductor is then calculated into current by the meter’s internal circuit and displayed.

For DC current, measurement is performed using a Hall element, whereby an induced current is generated by the change in magnetic field, and that magnetic field is proportional to the magnitude of the current to be measured.

Note) DC cannot be measured with a clamp tester dedicated for AC signals

Structure of a current clamp meter Insulation resistance is measured in order to ensure the safety of electrical equipment / parts and electrical facilities etc.1. Insulation between charged and non-charged parts → possible ground fault and electric shock if

insulation breakdown occurs2. Insulation between two or more charged parts → possible short circuit if breakdown occursThe higher the insulation resistance, the greater the effect.

Effective for TN earthing systems only 1. The voltage transducer injects a

defined voltage into the multi-grounded system.

2. From the defined voltage and measured current, the total circuit loop resistance is calculated in the following equation

IEEE 43-2013:Recommended Practice for Testing Insulation Resistance of Electric Machinery Typically referenced for motor maintenance, etc.

Objective

BS 7671: 200817th Edition of the IET Wiring Regulations

Switch from the transmission circuit, boost with a transformer to apply a high voltage, then measure the current and convert it to a resistance value.

Measurement principleThe accuracy and tolerance described in the product specifications are given in terms of rdg., f.s., and dgt. Measurement uncertainty is often defined, and the uncertainty limit is obtained from these values.

(1) f.s. (full scale: maximum displayed value, maximum scale, scale length)Generally, f.s. represents the range value currently used, and for analog displays, the maximum deflection of the needle.

(2) rdg. (reading: read value, displayed value, indicated value)Refers to the value actually being measured, i.e., the value that is currently indicated or displayed by the measuring instrument.

(3) dgt. (digit: resolution)Refers to the least significant digit of the digital display, i.e., the lowest digit in the displayed value, located at the far right of a string.

Calibration is the work to verify the relationship between values that is indicated by a meter or measurement system, to the true values provided by a given standard, standard sample, or other defined equipment

Calibration requirements stipulated byISO9001:2008:

7.6 Control of monitoring and measuring equipmenta) be calibrated or verified, or both, at

specified intervals, or prior to use, againstmeasurement standards traceable to international or national measurement standards; where no such standards exist, the basis used for calibration or verification shall be recorded

A data sheet is a document that describes the calibration and judgment results. It provides the indicated value for the input of each range, and a PASS if that value is within tolerance.

Traceability is the ability to link to national standards through a chain of seamless calibrations.

Accuracy specifications: ±1.0%rdg.±3dgt. (300V range)Measurement range: 300.0VMeasured value: 100V(A) Reading uncertainty: ±1.0% of 100.0V → 99.0 to 101.0V(B) Digit uncertainty: ±3dgt. → ±0.3VTotal uncertainty limits (range of true value) (A+B) = 98.7V to 101.3V

Digital Measuring Instruments

Example 1: Measuring voltage using the Hioki 3281 Clamp Meter

Accuracy specifications: ±0.2%rdg.±0.1%f.s. (voltage range)Measurement range: 300.0VMeasured value: 100V(A) Reading uncertainty: ±0.2% of 100.0V → 99.8 to 100.2V(B) Full scale uncertainty: ±0.1 f.s. → ±0.3V (300V x 0.001)Total uncertainty limits (range of true value) (A+B) = 99.5V to 100.5V

Example 2: Measuring voltage using the Hioki 3169 Clamp On Power Meter

How an earth resistance tester measures

Measurement Method : Clamp method

Voltage from the AC power supply is applied between the H(C) electrode and the E electrode, and the resulting AC current I is measured. In addition, an AC voltmeter is used to measure the voltage V between the S(P) electrode flowing with current and the E electrode. Earth resistance Rx of the E electrode is then calculated from the measured current and voltage.

Magnitude and values change as time passes (aging)

Earthing refers to the work of connecting the electric path to the ground. The ground is a stable potential, made possible by connecting the ground to an electric circuit. Earthing plays many roles, such as securing the outer case of equipment, the neutral point of an electric circuit, and the reference potential of electronic or communication devices.

What is earthing?

• Telecommunication and electronic equipment: to countermeasure electromagnetic waves, noise, and communication issues

• Building electrical equipment: to prevent electric shock• Lightning protection• Balance of potentialThe lower the earth resistance value, the greater the effect.

Main objectives

Measuring Leakage Current

When the magnetic field changes, a current is induced in the coil through which it penetrates. The magnitude of the current is determined by the magnetic fluctuation. By measuring the induced current, the magnitude of the magnetic field is known as it flows in the conductor, making it possible to measure the current at that time.

Measurement principle of current testing

Example of Damage due to Misuse of Tester

CAT II

Ohm’s Law

Average Rectified Method

True RMS Method

Comparing Distorted Current Values Such as Inverter Signals

Voltage = Current × ResistanceCAT III

CAT IV

Full waverectified Sq Avg √ LPF RMS

Value

RMS Processing IC

Average methodcurrent clamp

Max. value

RMS value

True RMS methodcurrent clamp

DC

Crest Factor (CF) =RMS

Max Value (Peak)

Always conduct zero adjustment when measuring resistance. (Mechanical and electrical zero adjustment) Situations where voltage is being applied is hazardous so separation is critical.

Connect to the circuit in parallel.

In order to measure without effects from wiring or contact resistance, use the 4-wire measurement method in place of the 2-wire method

Earthing Systems (TN, TT and IT)The resistance of copper wire changes according to the surrounding temperature.

Rt = Rt0 ×{ 1 + αt0 × (t - t0) }

RtRt0t0tαt0

Actually tested resistance [Ω]Compensated resistance [Ω]Reference temperature [°C]Current ambient temperature [°C]Temperature coefficient at t0

:::::

By using a temperature-compensated resistance meter, you can automatically capture the temperature-converted resistance value.

Current clamp meters are roughly classified into those that measure load current, leakage current, direct current, as well as wide frequency band meters. If only measuring load current, basically clamping 1 line is sufficient. Current clamp meters only measure 1 line at a time.

When measuring leakage current, two wires may be clamped simultaneously. Leakage current is current that flows to the ground through the insulation resistance of the load, and can be several tens of μA if many loads are connected. By using a clamp meter, the minute difference flowing in both directions can be detected and identified as leakage current.

The currents of the two go- and return- lines are in the opposite direction, and a magnetic field of the same magnitude is generated. Therefore, since the two magnetic fields cancel each other out, the fields become zero when summed. In short, zero is displayed when the two wires are clamped at the same time.

The UK standard required for distributionConfirm the standard/requirement of your country.

Analog Input impedance : highInstrument loss : smallExternal noise : high susceptibility

Digital

Serial connection to circuitPower line must be cut

Minute current direction Load current direction

Direct wiringmethod

Serial connection to circuitNo need to cut power line

High voltage:100 V AC

Allowablecurrent:158mA

Allowablecurrent:

50μA

10A(1/4W resistance)

Rs = 10Ω rv = 5kΩ Damage due toovercurrent

Approx. 63x overcurrent

20mAApprox. 400x overcurrent

The tip of the test lead also melted due to the shorted current.

-1000V

+1000V

0

Compensate

Magnetic field

Current

Current generateddue to fluctuating

magnetic field

current

Insulationresistance

Leakagecurrent

The Hioki DT4280 Series is designedwith a terminal shutter system toprevent erroneous connections.

CAT IV 600 V / CAT III 1000 V

Rt

Resistance

Rt0

t0 t Temperature

Oscillatingcircuit

Oscillatingcontrolcircuit

1,200

1,000

800

600

400

200100

00 0.025 0.05 0.1 0.125 0.25 0.5

Measured resistance [MΩ]

Measurement terminal voltage characteristics (Hioki IR4000 series)

1000V1000V

500V500V

250V250V125V125V50V50V

Mea

sure

men

t ter

min

al v

olta

ge [V

]

1 20 100 2,000 ∞

Select HVrange

R valuedisplay

Currentdetection

LINE

V → IV

detection

Boost

I1

I2

(DC

Voltage)

Resistance under test

25V25V

■ 3-pole methodMeasured resistance = Rx[Ω]

■ 2-pole method (simple method)Measured resistance = Rx + Ro [Ω]

10m 10m

Rx

C P E E P C

Minimum 5m

RxRo

E C

300.0 V range

0.1 V is the least significant digitin the 300.0 V range

Measuring 100V on the 300 V range

Measuring in the 300.0 V range

Displayedmeasured value

Max.displayed

value

Measuredvalue

calibration timetraceability

Resolution

Pin Tip

Sleeve

Nationalstandards

ReferenceTraceability Appliedstandards

Equipmentunder

calibration

300600

1000

Rated voltage toground [V] CAT II CAT III

Recommended Impulse Withstand VoltageCAT IV

250040006000

400060008000

60008000

12000

2-wire method 4-wire method

r1 r3 r4

I

r2

Constantcurrent power

Voltmeter

r1 E

I

r2

Resistance Ro

Non-chargedpart

Powersupply

LL

E E

Ground

Insulatedpart

Powersupply

Charged part

Charged partCharged partInsulated part

EARTH

MagnitudeValue

Time

High precision instruments generally exhibit little change over time

Low precision instruments generally exhibitlarge change over time

Electricity can be likened to the flow of water.

Waveforms that include harmonic and other components are converted to RMS values and displayed. RMS = Root Mean Squared

Crest factor is the ratio of a waveform's peak value to its RMS value.

In the specifications of an RMS measuring instrument, its crest factor is defined. This value represents the type of waveform that can be measured.

Primary electrical circuits in equipment connected to an AC electrical outlet by a power cord

Primary electrical circuits of heavy equipment (fixed installations) connected directly to the distribution panel, and feeders from the distribution panel to outlets

The circuit from the service drop to the service entrance, and to the power meter and primary overcurrent protection device (distribution panel)

When reading an instrument's specifications, a voltage value will follow the measurement category, such as in “CATIII 600V” . This means that the instrument can measure up to 600V in a CAT III environment.

400V was mistakenly input while in the resistance function. The resistance function carried a 250V protective circuit.

Example: mA range (analog tester)

The resistance range was used to test the voltage in this 200V electrical panel, causing severe damage.

Use the pin sleeves at the tips to prevent short-circuit accidents.

Clampmethod

Constantcurrent power

Voltmeter

Resistance Ro

Rectification

& S

moothing

Magnitude

Value

Nominal circuit voltage (AC) Test voltage (DC) Minimum resistance

0 V to 50 V 250 V 0.5 MΩ

50 V to 500 V 500 V 1 MΩ

500 V to 1000 V 1000 V 1 MΩ

Rated voltage (AC) Insulation resistance test voltage (DC)

< 1000 500

1000 to 2500 500 to 1000

2500 to 5000 1000 to 2500

50001 to 12000 2500 to 5000

> 12000 5000 to 10000

Rx R1 R2 R3 R4

Assuming a pure sinusoidal waveform with no distortions (at a single frequency), waveforms are converted to RMS values and displayed. Distorted waveforms will result in measurement values with large errors.

Measurement principle ofan earth resistance tester

*The True RMS method can measure even distorted waveforms correctly

Rx +Many R are connected.

=+R1

1 +R21

1

+R31 ...

R41 I

V Rx =IV

TN-S system

TN-C system

Consumer

Generator / Transformer L1L2L3N

Earth

PE

Consumer

Generator / Transformer L1L2L3PEN

Earth

Consumer

Generator / Transformer L1L2L3

Earth

IT system

Consumer

L1L2L3N

Earth

PE

TT system

Consumer

Generator / Transformer L1L2L3N

Earth Earth

Grid and customer are connected to the different earth independently.

Grid is not connected to the earth.Safe against leakage.

Connected to the common earth through grid.

Generator / Transformer TN-C-S system

-

0

+

I I I I I

1 cycle

-

0

+

I=0 I=0 I=0I I

Zero Adjustment

Rx

Tester Equipment under test

Always separate

Electricity in Terms of Water Flow

What is DC ?

What is AC ?

Describing AC Signal

Average Rectified vs RMS •1

Average Rectified vs RMS •2

What is Crest Factor ?

Measurement Category •1

Measurement Category •2

Measurement Category •3

Do Not Input Voltageto the Current Measurement Circuit

Do Not Input Voltageto the Resistance Measurement Circuit

Safety Standards for Test Probes

Voltage Testing

Current Testing

Measurement Principle of Current Clamp Meters •1

Measurement Principle of Current Clamp Meters •2

How to Measure Using Current Clamp Meters •1

How to Measure Using Current Clamp Meters •2

Resistance Testing

Low Resistance Testing •1

Low Resistance Testing •2

Insulation Resistance Testing •1

Insulation Resistance Testing •2

Insulation Resistance Testing •3

Insulation Resistance Testing •4

Earth Resistance Testing •1

Earth Resistance Testing •2

Earth Resistance Testing •3

Earth Resistance Testing •4

Earth Resistance Testing •5

How to Calculate Accuracy •1

How to Calculate Accuracy •2

What is Calibration ?

Why is Calibration Necessary ?

What is a Data Sheet/Test Report ?

What are Reference Instruments ?

Measurement Category and Rated Voltageto Ground Indication

Basics of Electricity Measurement Basics Accuracy & Calibration