Basics of Electrical Testing www.hioki.com Basics of Electricity Measurement Basics Accuracy & Calibration

Electricity in Terms of Water Flow Measurement Category 1 Voltage Testing Resistance Testing Insulation Resistance Testing 4 How to Calculate Accuracy 1 Primary electrical circuits in equipment connected to an AC• electrical outlet by a • • Electricity can be likened to the flow of water. Connect to the circuit in parallel. Always conduct zero adjustment when measuring resistance. (Mechanical and Current CAT II power cord Measurement principle Digital Measuring Instruments Input impedance : low Input impedance : high electrical zero adjustment) Situations where voltage is being applied is hazardous Ohm’s Law Voltage = Current × Resistance High + Primary electrical circuits of heavy equipment (fixed installations) connected Analog Digital Switch from the transmission circuit, boost with a transformer to apply a high The accuracy and tolerance described in the product Instrument loss : large Instrument loss : small so separation is critical. specifications are given in terms of rdg., f.s., and dgt. CAT III directly to the distribution panel, and feeders from the distribution panel to outlets Max. voltage, then measure the current and convert it to a resistance value. Measurement uncertainty is often defined, and the uncertainty 300.0 V range BAT Electric External noise : low susceptibility External noise : high susceptibility displayed Potential The circuit from the service drop to the service entrance, and to the power meter Resistance measurement circuit of an analog meter Measurement terminal voltage characteristics (Hioki IR4000 series) limit is obtained from these values. MEASURE value Voltage Voltage EARTH A B A CAT IV and primary overcurrent protection device (distribution panel) SW 1,200 (1) f.s. (full scale: maximum displayed value, maximum scale, scale length)

Low − drop drop Boost Resistance under test 1000V & Smoothing &

Always separate Rectification 8 8 8 8 OFF V 1,000 Measured current Large current Small Generally, f.s. represents the range value currently used, and Large Based on the IEC61010-1 international standard concerning Small detection Digital ON V → I value Difference Current (I) the safety requirements for electrical equipment for 800 for analog displays, the maximum deflection of the needle. display Select HV in water level measurement, control, and laboratory use Vr Vr Zero range I2 600 (2) rdg. (reading: read value, displayed value, indicated value) Measuring 100V on the 300 V range LR6 x 4 (DC Voltage) 500V Drop connection Adjustment B When reading an instrument's specifications, a Distribution Distribution Rx Refers to the value actually being measured, i.e., the value that Water will not flow. Service drop panel panel A/D I1 400 voltage value will follow the measurement category, Fixed R value 250V is currently indicated or displayed by the measuring instrument. Water Voltage (V) Resistance (R) Power meter installation 200 Outlet Outlet display LINE 125V Resolution such as in “CATIII 600V” . Transformer flow Current 100 50V (3) dgt. (digit: resolution) This means that the instrument can measure up to detection Oscillating 0 25V Refers to the least significant digit of the digital display, i.e., the Oscillating 0 0.025 0.05 0.1 0.125 0.25 0.5 1 20 100 2,000 600V in a CAT III environment. control Measurement terminal voltage [V] ∞ lowest digit in the displayed value, located at the far right of a circuit circuit 0.1 V is the least significant digit Tester Equipment under test Measured resistance [MΩ] string. in the 300.0 V range What is DC ? Measurement Category and Rated Voltage Current Testing Low Resistance Testing• 1 Earth Resistance Testing• 1 How to Calculate Accuracy• 2 DC (Direct Current) is the flow of electric charge in one direction. to Ground Indication Direct wiring Serial connection to circuit Clamp Serial connection to circuit In order to measure without effects from wiring or contact resistance, What is earthing? Example 1: Measuring voltage using the Hioki 3281 Clamp Meter method Power line must be cut method No need to cut power line use the 4-wire measurement method in place of the 2-wire method Accuracy specifications: ±1.0%rdg.±3dgt. (300V range) Earthing refers to the work of connecting the electric path to the ground. The ground is a Measurement range: 300.0V stable potential, made possible by connecting the ground to an electric circuit. Earthing plays 2-wire method 4-wire method Measured value: 100V + many roles, such as securing the outer case of equipment, the neutral point of an electric (A) Reading uncertainty: ±1.0% of 100.0V → 99.0 to 101.0V CAT IV 600 V / CAT III 1000 V circuit, and the reference potential of electronic or communication devices. (B) Digit uncertainty: ±3dgt. → ±0.3V Constant Constant Measuring in the 0 current power current power Total uncertainty limits (range of true value) (A+B) = 98.7V to 101.3V 300.0 V range Main objectives Voltmeter I Voltmeter I Example 2: Measuring voltage using the Hioki 3169 Clamp On Power Meter - I I I I I The Hioki DT4280 Series is designed • Telecommunication and electronic equipment: to countermeasure electromagnetic waves, current current with a terminal shutter system to noise, and communication issues Accuracy specifications: ±0.2%rdg.±0.1%f.s. (voltage range) Measurement range: 300.0V • Building electrical equipment: to prevent electric shock prevent erroneous connections. Measured value: 100V Displayed r1 r2 r1 r3 r4 r2 • Lightning protection E E (A) Reading uncertainty: ±0.2% of 100.0V → 99.8 to 100.2V measured value Example DC Waveforms • Balance of potential Minute current direction Load current direction (B) Full scale uncertainty: ±0.1 f.s. → ±0.3V (300V x 0.001) Direct Ripple Pulsating Resistance Ro Resistance Ro The lower the earth resistance value, the greater the effect. Total uncertainty limits (range of true value) (A+B) = 99.5V to 100.5V What is AC ? Measurement Category •2 Measurement Principle of Low Resistance Testing• 2 Earth Resistance Testing• 2 What is Calibration ? Excessive overvoltage (impulse voltage) may also appear on power lines. AC (Alternating Current) is electric charge that Example AC Waveforms Current Clamp Meters 1 The resistance of copper wire changes according to the surrounding temperature. Earthing Systems (TN, TT and IT) Calibration is the work to verify the relationship between values that is indicated by periodically varies in terms of direction and The opening and closing of solenoid valves or loads at plants may cause high voltage spikes. a meter or measurement system, to the true values provided by a given standard, Ampère's right-hand grip rule • Magnetic field TN-S system TN-C system TT system Furthermore, since the wave peak value may be 10 times the power supply voltage or more magnitude. A typical AC waveform is a sine Resistance Generator / Transformer Generator / Transformer Generator / Transformer standard sample, or other defined equipment When a current flows, a magnetic field is generated concentrically. Rt = Rt0 ×{ 1 + αt0 × (t - t0) } L1 L1 L1 wave, and commercial power supply is made of in the case of inductive loads, etc., the IEC standard provides a correlation between the Current Grid and customer are The magnitude of the magnetic field is proportional to the magnitude L2 L2 L2 sinusoidal AC voltage signals. Sine Square nominal system voltage (power supply line voltage), overvoltage level, and measurement Rt L3 L3 L3 connected to the of the current. The direction of the magnetic field is the direction in Rt : Actually tested resistance [Ω] N PEN N Magnitude and values change as time passes (aging) category as an indication of transient overvoltage. which a screw is tightened if the direction of movement of the screw PE different earth and the direction of current are matched. This law is called "Ampère's Rt0 : Compensated resistance [Ω] Earth Consumer Earth independently. + Rt0 Earth Consumer Earth Consumer right-hand grip rule". High precision instruments generally exhibit Compensate t0 : Reference temperature [°C] Rated voltage to Recommended Impulse Withstand Voltage Magnitude Value little change over time 0 Sawtooth Triangular Measurement principle of current testing t : Current ambient temperature [°C] TN-C-S system IT system ground [V] CAT II CAT III CAT IV Current generated Generator / Transformer Generator / Transformer t0 t Temperature αt0 : Temperature coefficient at t0 Time When the magnetic field changes, a current is induced in the coil due to fluctuating L1 Connected to the L1 Grid is not connected to - 300 2500 4000 6000 L2 L2 through which it penetrates. The magnitude of the current is magnetic field L3 common earth through L3 the earth. 600 4000 6000 8000 determined by the magnetic fluctuation. By measuring the induced N By using a temperature-compensated resistance meter, PE grid. Safe against leakage. Low precision instruments generally exhibit I=0 I I=0 I I=0 current, the magnitude of the magnetic field is known as it flows in the Pulse Distorted 1000 6000 8000 12000 conductor, making it possible to measure the current at that time. you can automatically capture the temperature-converted resistance value. Earth Consumer Consumer Earth large change over time Describing AC Signal Measurement Category •3 Measurement Principle of Insulation Resistance Testing• 1 Earth Resistance Testing• 3 Why is Calibration Necessary ? Instantaneous : Level that occurs instantaneously 2 Calibration requirements stipulated by Example of Overvoltage at Example of Damage due Current Clamp Meters Objective Measurement principle of Current meter AC power Maximum and Minimum : The highest and lowest values Open/Close of Solenoid Valve to Misuse of Tester an earth resistance tester I ISO9001:2008: •Measured Insulation resistance is measured in order to ensure the safety of electrical equipment / parts and electrical facilities etc. I A Peak-to-Peak : Difference between the maximum and minimum Structure of a current clamp meter Magnetic flux from conductor +1000V measured current 1. Insulation between charged and non-charged parts → possible ground fault and electric shock if Voltage from the AC power supply is Average : Average of the instantaneous values that occur in half a cycle A current clamp meter measures the voltage across a insulation breakdown occurs 7.6 Control of monitoring and measuring detection shunt resistor from the winding that forms Output applied between the H(C) electrode and the Voltmeter equipment calibration time Root Mean Square (RMS or True RMS) : Energy that is converted to a DC-equivalent value the coil, the magnetic core that raises the sensitivity 2. Insulation between two or more charged parts → possible short circuit if breakdown occurs V=Rx×I of the magnetic field, and the shunt resistor for Secondary E electrode, and the resulting AC current I a) be calibrated or verified, or both, at traceability measuring the induced current. The signal generated The higher the insulation resistance, the greater the effect. Frequency : The number of times a point on a wave passes a fixed reference point in one second 0 Magnetic current Shunt V in the conductor is then calculated into current by the core resistance is measured. In addition, an AC voltmeter is specified intervals, or prior to use, against meter’s internal circuit and displayed. Feedback Non-charged used to measure the voltage V between the E S(P) H(C) measurement standards traceable to Peak-to-Peak 1 cycle Average Example: 100V Commercial Power Supply winding part electrode electrode electrode Max For DC current, measurement is performed using a L Insulated S(P) electrode flowing with current and the Peak-to-Peak: 282.8V Measured international or national measurement Hall element, whereby an induced current is current Power part L Charged part Max: 141.4V -1000V Magnetic Power Average: 90V generated by the change in magnetic field, and that flux from supply Insulated part E electrode. Earth resistance Rx of the E standards; where no such standards exist, magnetic field is proportional to the magnitude of the secondary E supply High surge voltages often occur when a solenoid 400V was mistakenly input while in the E electrode is then calculated from the current to be measured. current Charged part Charged part Rx=V/I the basis used for calibration or verification RMS: 100V valve opens and closes. The example above resistance function. The resistance function Hall element AMP measured current and voltage. shall be recorded shows almost a 1000V surge on a 100V AC line. carried a 250V protective circuit. Note) DC cannot be measured with a clamp tester Min Min: -141.4V dedicated for AC signals Ground HIOKI Calibration Certificate

Average Rectified vs RMS 1 Safety Standards for Test Probes How to Measure Using Current Clamp Meters 1 Insulation Resistance Testing 2 Earth Resistance Testing 4 What is a Data Sheet/Test Report ?

Full wave • • • • Use the pin sleeves at the tips to prevent short-circuit accidents. Current clamp meters are roughly classified into those that measure load current, leakage BS 7671: 2008 A data sheet is a document that describes the Average Rectified Method DC How an earth resistance tester measures rectified LPF MEAN current, direct current, as well as wide frequency band meters. If only measuring load current, calibration and judgment results. It provides the Assuming a pure sinusoidal waveform with no (×1.11) Value 17th Edition of the IET Wiring Regulations basically clamping 1 line is sufficient. Current distortions (at a single frequency), waveforms are ■ 3-pole method ■ 2-pole method (simple method) indicated value for the input of each range, and a converted to RMS values and displayed. Distorted clamp meters only measure 1 line at a time. Nominal circuit voltage (AC) Test voltage (DC) Minimum resistance Measured resistance = Rx[Ω] Measured resistance = Rx + Ro [Ω] PASS if that value is within tolerance. waveforms will result in measurement values with Measuring Instrument large errors. 0 V to 50 V 250 V 0.5 MΩ Standard Instrument (Device under test) 50 V to 500 V 500 V 1 MΩ CPE EPC Magnitude Magnitude EC True RMS Method 500 V to 1000 V 1000 V 1 MΩ Value Relationship Value Full wave DC RMS Verify Sq Avg √ LPF Sleeve The currents of the two go- and return- lines are in the Rx Waveforms that include harmonic and rectified Value opposite direction, and a magnetic field of the same The UK standard required for distribution Ro Rx other components are converted to RMS magnitude is generated. Therefore, since the two RMS Processing IC values and displayed. magnetic fields cancel each other out, the fields Confirm the standard/requirement of your country. 10m 10m Input 10V RMS = Root Mean Squared become zero when summed. In short, zero is displayed Minimum 5m Calibrated value 10.000 00V Pin Tip when the two wires are clamped at the same time. HIOKI Data Sheet

Average Rectified vs RMS 2 Do Not Input Voltage How to Measure Using Current Clamp Meters 2 Insulation Resistance Testing 3 Earth Resistance Testing 5 What are Reference Instruments ?

National Institute Nationally National Institute • • • • of Advanced recognized of Information In the average rectifying method, average values are measured using an internal IEEE 43-2013: Traceability is the ability to link to national Industrial Science standards and Communications to the Current Measurement Circuit Measuring Leakage Current Measurement Method : Clamp method and Technology Technology circuit. The average values are multiplied by the sine wave’s waveform ratio of 1.11 standards through a chain of seamless Recommended Practice for Testing Insulation Resistance of Electric Machinery Telecom Example: mA range (analog tester) Japan Electric Meters Manufacturer Manufacturer Effective for TN earthing systems only Inspection Corporation Engineering and then converted to RMS values. In the RMS method, RMS values are measured When measuring leakage current, two wires Typically referenced for motor maintenance, etc. calibrations. FLUKE Clarke-Hess Center AC 1. The voltage transducer injects a STANDARD CALIBRATOR CURRENT DIGITAL UNIVERSAL MEASUREMENT Comparative FLUKE 5700A SHUNT PHASE COUNTER using an internal circuit. With this method, even distorted waveforms can be may be clamped simultaneously. RESISTANCE STANDARD METER standards FLUKE AMPLIFIER FLUKE FLUKE Clarke-Hess ADVANTEST defined voltage into the 742A-1, 742A-10k FLUKE 5725A 5790A A40,A40A 6000A TR5830D properly displayed as RMS values. (1/4W 10A 20mA Leakage current is current that flows to the National Approx. 63x Approx. 400x overcurrent Rated voltage (AC) Insulation resistance test voltage (DC) multi-grounded system. standards STANDARD STANDARD resistance) RESISTOR RESISTOR ground through the insulation resistance of Alpha Insulation Electronics Corp. YOKOGAWA overcurrent CSR 2792, 2794 Comparing Distorted Current Values Such as Inverter Signals the load, and can be several tens of μA if resistance < 1000 500 2. From the defined voltage and Intermediate MULTIMETER measured current, the total circuit Applied standards HP/Agilent 3458A High voltage: Damage due to many loads are connected. By using a Leakage Traceability Reference Rs = 10Ω rv = 5kΩ CURRENT CURRENT current 1000 to 2500 500 to 1000 TRANSFORMER loop resistance is calculated in standards SHUNT 100Ω, 1kΩ Average method 100 V AC overcurrent clamp meter, the minute difference flowing TOKYOSEIDEN Rx R1 R2 R3 R4 the following equation CTS8-1(50A/5A) HIOKI current clamp in both directions can be detected and 2500 to 5000 1000 to 2500 Applied MULTI-PRODUCT Allowable Allowable CALIBRATOR identified as leakage current. Equipment standards *The True RMS method can 50001 to 12000 2500 to 5000 1 V V FLUKE 5520A True RMS method current: current: Rx + 1 1 1 1 = Rx = under measure even distorted + + + ... I I POWER HiTESTER current clamp > 12000 5000 to 10000 R1 R2 R3 R4 Many R are connected. calibration waveforms correctly 158mA 50μA HIOKI 3332

What is Crest Factor ? Do Not Input Voltage Crest factor is the ratio of a waveform's peak value to its RMS value. to the Resistance Measurement Circuit Inquiries The resistance range was used to test the voltage in this 200V electrical panel, Max Value (Peak) Crest Factor (CF) = causing severe damage. RMS Max. value

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

Example: A crest factor 3 measuring instrument may not be able to accurately measure a waveform with crest factor of 3 or more with The tip of the test lead also melted respect to the range. It is necessary to change the range or to use an instrument with a higher crest factor. due to the shorted current.