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The International Safety Standard IEC61010

This Safety Standard which is established for protecting operators and environment stipulates safety requirements for measuring instruments and electric equipment. The IEC standard defines the degree of pollution, measurement classification, barrier, material, spatial distance and creepage distance to assure safety. The impulse withstand voltage as transitional energy is estimated from the measurement category and main power supply voltage to conduct tests for measuring instruments.
Test voltage (impulse withstand voltage)
Nominal AC or DC line of main power
supply and neutral voltage
300V 2500V 4000V 6000V
600V 4000V 6000V 8000V
1000V 6000V 8000V 12000V
The output impedance of an impulse generator is 12Ω in the measurement category II, and 2Ω in measurement categories III and IV.

CE marking

CE marking is a safety mark which can be attached only on a product meeting the safety requirements of the Directive of Council of the European Union (EC Directive). A product attached with the CE mark is designed so as to meet the requirements of the "Low Voltage Directive" and "EMC Directive" of the EC Directive.
Low Voltage Directive: This Directive covers products of power supply voltage of 50V-1000V (AC) and 75V-1500V (D-C), and it defines electric safety requirements against shocks, burns, etc. The applicable standard is EN61010 corresponding to IEC1010 give on the left.
EMC Directive: This Directive stipulates conditions so as not to give out strong electromagnetic waves from equipment to the outer environment and to protect equipment from the effect of electromagnetic waves from the outside.

Measurement category (overvoltage category)

The IEC standard classifies measuring circuits according to measurement categories for the safe use of a measuring instrument in low voltage facilities. The measurement categories are classified into I to IV.
A larger number of the category denotes a spot involving higher transient energy. For safe measurement, wear protective gears such as insulated gloves and dust-proof glasses in an environment of CAT.III.

Measurement category IV (CAT. IV)

Equipment used for measurement in low voltage facilities.
Temporary overcurrent preventer, and electric measurement on ripple control unit, etc.

Measurement category III (CAT. III)

Equipment used for measurement in building facilities Distribution board, circuit breaker, wiring including cables, busbar, junction box, switch, receptacle, and industrial equipment located in fixed facilities, and other equipment such as a fixed motor connected to fixed facilities in a permanent manner.

Measurement category II (CAT. II)

Equipment used for measurement performed on a circuit directly connected to low voltage facilities Measurement on electric household appliances, portable tools and similar tools.

Measurement category I (CAT. I)

Equipment used for measurement on a circuit not directly connected to main power supply
Circuit not derived from the main power supply

For safe measurement - Method for safe use of measuring instrument


Voltage measurement
Never use a measuring instrument for a measurement category higher than specified. A tester not conforming to the international safety standard is for use with weak current. Never use these testers on a high power circuit of 250V or more (excluding VS-100). Referring to measurement categories defined in the IEC standard, use a measuring instrument of equivalent or higher category. For instance, when a measuring instrument is used on a motor of facility of 200V main power supply, which corresponds to Category III, use a measuring instrument of CAT.III or higher.
Current measurement
Use special caution not to input voltage to the current measuring terminal in measurement. In current measurement, a meter is connected in series with the measuring circuit. For this reason, impedance inside the meter is low, thereby possibly causing a short-circuit fault. To prevent such a short-circuit fault and assure safe operation, fuses are installed for protection. Check the protection capability of the fuses. RD700 uses a quick-breaking ceramic fuse of rated voltage 250V and breaking current 1.5kA for the milliamp measuring circuit, which causes the fuse to blow out to prevent short-circuit when the main power supply is 250V or less and short circuit current is 1.5kA or less.

Clamp meter

●Use all clamp meters for measurement of low voltage circuit of 600V or less. ●n choosing an appropriate model, special attention should be paid to the current measurement range and diameter of a conductor to be clamped.

Insulation resistance tester

●The insulation resistance tester cannot be used on an measuring object in live-wire status. ●If the measuring voltage is specified, choose a model of the specified voltage. It is a general practice to choose the measuring voltage equivalent to or a little higher than voltage usually applied to the measuring object. ●Since the insulating-resistance tester measures resistance values by applying DC high voltage on a measuring object, the measurement may damage the measuring object if voltage is directly applied on he electronic circuit including the IC and LSI. ●The insulating-resistance tester generates DC high voltage during measurement. If an electric shock occurs, a falling accident from a high altitude may follow. Use special caution in operation at a high altitude. ●If your measuring instrument is provided with a voltage measuring function, use it at no higher than the maximum measuring voltage.

Thermo Meter (Temperature Probe)

●The temperature sensor cannot be used for measurement in direct contact with a live part. ●Use caution in handling a sharp-edged probe to avoid an injury. ●The grip is heated in high temperature measurement. Use an appropriate jig to secure the probe in high temperature measurement.

Tachometer・Speed Meter

●In measurement on a rotating motor (measurement of speed for elevator in operation), risks are involved due to the strong force of the measuring object. Use special caution in measurement to assure safety. Never touch the rotating part during measurement.

Laser Power Meter

●Infrared semiconductor laser light is invisible to the naked eye. It may occasionally emit high power of 30mW or more, which may threaten vision if eyes are exposed to the light. Use special caution to avoid gazing at the light directly or exposing eyes to reflected light.