HT79 Clamp Meter User Manual

HT79 Clamp Meter

PRECAUTIONS AND SAFETY MEASURES

The instrument has been designed in compliance with directive IEC/EN61010-1 relevant to electronic measuring instruments. For your safety and in order to prevent damaging the instrument, please carefully follow the procedures described in this manual and read all notes preceded by symbol with the utmost attention.
CAUTION Failure to comply with the caution notes and/or instructions may damage the instrument and/or its components and be a source of danger for the operator.
Before and after carrying out the measurements, carefully observe the following instructions:

• Do not carry out any current measurement in humid environments.

• Do not carry out any measurements in case gas, explosive materials or flammables are present, or in dusty environments.

• Avoid any contact with the circuit being measured if no measurements are being carried out.

• Avoid contact with exposed metal parts, with unused measuring probes, etc.

• Do not carry out any measurement in case you find anomalies in the instrument such as deformation, substance leaks, absence of display on the screen, etc.

• Pay special attention when measuring voltages higher than 20V, since a risk of electrical shock exists
  In this manual, and on the instrument, the following symbols are used:

  • Warning: observe the instructions given in this manual; improper use could damage the instrument or its components.
  • Double-insulated meter.
  • AC current or voltage
  • DC current or voltage
  • Connection to earth
  • The instrument can operate on naked live conductors

PRELIMINARY INSTRUCTIONS

• This instrument has been designed for use in environments of pollution degree 2.
• It can be used for CURRENT and VOLTAGE measurements on installations with measurement category CAT IV 300V. For a definition of categories, see § 1.4.
• We recommend following the normal safety rules devised to protect the user against dangerous currents and the instrument against incorrect use.
• Only the leads supplied with the instrument guarantee compliance with the safety standards. They must be in good conditions and be replaced with identical models, when necessary.
• Do not test circuits exceeding the specified current and voltage limits.
•  Check that the battery is correctly inserted.
• Before connecting the test leads to the circuit to be tested, make sure that the switch is correctly set.
• Make sure that the LCD display and the rotary switch indicate the same function.

DURING USE

Please carefully read the following recommendations and instructions:
CAUTION Failure to comply with the caution notes and/or instructions may damage the instrument and/or its components or be a source of danger for the operator.

• Before switching on the clamp, remove the conductor from the clamp jaw.
• When the instrument is connected to the circuit being tested, do not touch any unused terminal.
• During current measurement, any other current near the clamp may affect measurement precision.
• When measuring current, always put the conductor as near as possible to the middle of the clamp jaw, as described in § 4.1.1, in order to obtain the most accurate reading.
• While measuring, if the value or the sign of the quantity being measured remain unchanged, check if the HOLD function is enabled.

AFTER USE

• When measurement is complete, switch off the clamp.
• If you expect not to use the instrument for a long period, remove the battery.

DEFINITION OF MEASUREMENT (OVERVOLTAGE) CATEGORY

Standard “IEC/EN61010-1: Safety requirements for electrical equipment for measurement, control and laboratory use, Part 1: General requirements”, defines what measurement category, commonly called overvoltage category, is. § 6.7.4: Measured circuits, circuits are divided into the following measurement categories:
(OMISSIS)

• Measurement category IV is for measurements performed at the source of the low-voltage installation.
  Examples are electricity meters and measurements on primary overcurrent protection devices and ripple control units.

• Measurement category III is for measurements performed on installations inside buildings.
  Examples are measurements on distribution boards, circuit breakers, wiring, including cables, bus-bars, junction boxes, switches, socket-outlets in the fixed installation, and equipment for industrial use and some other equipment, for example, stationary motors with permanent connection to fixed installation.

• Measurement category II is for measurements performed on circuits directly connected to the low-voltage installation.
  Examples are measurements on household appliances, portable tools and similar equipment.

• Measurement category I is for measurements performed on circuits not directly connected to MAINS.
  Examples are measurements on circuits not derived from MAINS, and specially protected (internal) MAINS-derived circuits. In the latter case, transient stresses are variable; for that reason, the standard requires that the transient withstand capability of the equipment is made known to the user.

GENERAL DESCRIPTION

The instrument carries out the following measurements:

• DC and AC TRMS voltage up to 300V
• DC current from 0.1mA up to 10A
• AC TRMS current from 0.1mA up to 20A
• AC and DC leakage current
• Resistance and continuity test with buzzer

Each of these functions may be selected through a 6-position rotary switch, including the OFF position and a key for enabling the HOLD function. The instrument also has a “MAX/MIN, “ZERO” and “ ” key. For their use, please refer to § 4.2. The selected quantity appears on the LCD display with the indication of the measuring unit and of the enabled functions.

MEASURING AVERAGE VALUES AND TRMS VALUES

Measuring instruments of alternating quantities are divided into two big families:

• AVERAGE-VALUE meters: instruments measuring the value of the sole wave at fundamental frequency (50 or 60 Hz).
• TRMS (True Root Mean Square) VALUE meters: instruments measuring the TRMS value of the quantity being tested.

With a perfectly sinusoidal wave, the two families of instruments provide identical results. With distorted waves, instead, the readings shall differ. Average-value meters provide the RMS value of the sole fundamental wave; TRSM meters, instead, provide the RMS value of the whole wave, including harmonics (within the instruments bandwidth). Therefore, by measuring the same quantity with instruments from both families, the values obtained are identical only if the wave is perfectly sinusoidal. In case it is distorted, TRMS meters shall provide higher values than the values read by average-value meters.

DEFINITION OF TRUE ROOT MEAN SQUARE VALUE AND CREST FACTOR

The root mean square value of current is defined as follows: “In a time equal to a period, an alternating current with a root mean square value of 1A intensity, circulating on a resistor, dissipates the same energy that, during the same time, would be dissipated by a direct current with an intensity of 1A”. This definition results in the numeric expression

PREPARATION FOR USE

INITIAL CHECKS

Before shipping, the instrument has been checked from an electric as well as mechanical point of view. All possible precautions have been taken so that the instrument is delivered undamaged.
However, we recommend generally checking the instrument in order to detect possible damage suffered during transport. In case anomalies are found, immediately contact the forwarding agent. We also recommend checking that the packaging contains all components indicated in § 7.3.1. In case of discrepancy, please contact the Dealer.
In case the instrument should be returned, please follow the instructions given in § 8.

INSTRUMENT POWER SUPPLY

The instrument is supplied with 2×1.5V alkaline batteries type AAA IEC LR03, included in the package. When batteries are almost flat, the symbol “ ” appears on the display. Replace the battery by following the instructions given in § 6.2.
The instrument is also equipped with an Auto Power OFF function which automatically switches off the instrument approx. 30 minutes after the last operation was carried out.

STORAGE

In order to guarantee precise measurement, after a long storage time under extreme environmental conditions, wait for the instrument to come back to normal operating conditions (see § 7.2.1).

NOMENCLATURE

DESCRIPTION OF THE INSTRUMENT

CAPTION:

1. Openable flexible jaws
2. Hand protection
3. Key
4. Jaw trigger
5. Rotary selector switch
6. ZERO key
7. MIN/MAX key
8. HOLD key
9. LCD display
10. Input terminal COM
11. Input terminal
12. Battery cover fastening screw
13. Battery compartment cover

Hand protection
In order to meet the meter’s accuracy specifications, always put the conductor as close as possible to the middle of the jaws (see Fig. 2).

CAPTION:

1. Conductor
2.  Hand protection

Always keep your hands under the hand protection. This protection is always located in a suitable position to guarantee a correct safety distance from possible exposed live parts (see Fig. 2)

DESCRIPTION OF THE SYMBOLS SHOWN ON THE DISPLAY

Fig. 3: Display description

CAPTION:

1. Auto Power OFF symbol
2. AC quantities symbol
3. DC quantities symbol
4. Active HOLD function
5. Active ZERO function
6. Resistance measuring unit
7. Active continuity test
8. Voltage measuring unit
9. Current measuring unit
10. Active MAX function
11. Active MIN function
12. Low battery symbol
13. Polarity indication

DESCRIPTION OF FUNCTION KEYS

HOLD key
Shortly pressing the HOLD while measuring current allows holding the current value shown on the display. The symbol “HOLD” is shown on the display. Shortly pressing the HOLD key again allows quitting the function.

MIN/MAX key
Pressing the MIN/MAX key once activates the detection of maximum and minimum values of the quantity being tested. Both values are constantly saved and displayed cyclically every time the same key is pressed again. The display shows the symbol associated with the selected function: “MAX” for maximum value and “MIN” for minimum value. This function is not active for resistance measurement and continuity test. Press and hold the MIN/MAX key or turn the rotary switch to quit the function. With the rotary switch in position , press the MIN/MAX key to select resistance measurement or continuity test.

ZERO key
Pressing the ZERO key once allows zeroing the displayed value and carrying out a relative measurement of the quantity being tested. When pressing the ZERO key, the value of the quantity is saved as offset for the following measurements. The message “ZERO” appears on the display. The instrument shows the relative value obtained as current value – offset. This function is not active for resistance measurements and continuity test and with enabled MIN/MAX function. Press the ZERO key again or turn the rotary switch to quit the function.

Key
Press the key to activate/deactivate display backlight. This function automatically deactivates after approximately 30 seconds after being activated, in order not to discharge the batteries.

Auto Power OFF function
In order to preserve internal batteries, the instrument switches off automatically approximately 30 minutes after it was last used. The symbol “ ” indicates that the Auto Power OFF function is activated. To disable the function, proceed as follows:

• Switch off the instrument (OFF)
•  Press and hold the HOLD key and switch on the instrument by turning the rotary switch. The symbol “ ” disappears from the display
• Switch off and then on again the instrument to enable the function.

OPERATING INSTRUCTIONS

DC VOLTAGE MEASUREMENT

CAUTION The maximum input DC voltage is 300V. Do not measure voltages exceeding the limits given in this manual. Exceeding these limits could result in electrical shocks to the user and damage to the instrument.

1. Select the position.
2. Insert the red cable into input terminal V and the black cable into input terminal COM.
3. Position the test leads in the desired spots of the circuit to be measured (see Fig. 4). The display shows the value of voltage.
4. Symbol “OL.” appearing on the display indicates the overload condition of the instrument.
5. To use the HOLD, MIN/MAX and ZERO functions, please refer to § 4.3.

AC VOLTAGE MEASUREMENT

CAUTION The maximum input AC voltage is 300Vrms. Do not measure voltages exceeding the limits given in this manual. Exceeding these limits could result in electrical shocks to the user and damage to the instrument.

1. Select the position.
2. Insert the red cable into input terminal V and the black cable into input terminal COM.
3. Position the test leads in the desired spots of the circuit to be measured (see Fig. 5). The display shows the value of voltage.
4. Symbol “OL.” appearing on the display indicates the overload condition of the instrument.
5. To use the HOLD, MIN/MAX and ZERO functions, please refer to § 4.3.

RESISTANCE MEASUREMENT

CAUTION Before attempting any resistance measurement, remove power from the circuit under test and discharge all capacitors, if present.

1. Select the position.
2. Insert the red cable into input terminal V and the black cable into input terminal COM.
3.  Position the test leads in the desired spots of the circuit to be measured (see Fig. 6). The display shows the value of resistance.
4. Symbol “OL.” appearing on the display indicates the overload condition of the instrument.
5. To use the HOLD function, please refer to § 4.3.1.

CONTINUITY TEST

CAUTION Before attempting any resistance measurement, remove power from the circuit under test and discharge all capacitors, if present.

1. Select the position.
2. Press the MIN/MAX key until the symbol “ ” is displayed.
3. Insert the red cable into input terminal V and the black cable into input terminal COM and carry out the continuity test on the object to be tested (see Fig. 7). An buzzer sounds when the measured value of resistance is lower than 100.
4. Symbol “OL.” appearing on the display indicates an open circuit condition.

DC CURRENT MEASUREMENT

CAUTION Before attempting any measurement disconnect all the test leads from the circuit under test and from the meter’s input terminals.

1. Select the position.
2. Press the ZERO key to zero residual magnetization current.
3. Insert the cable in the middle of the clamp jaws (see Fig. 8), in order to obtain accurate measures (see Fig. 2). The display shows the value of DC current.
4. The symbol “-” appearing on the display indicates that the instrument is connected in the opposite direction with respect to the current direction indicated by the arrow located on the side of the jaws.
5. Symbol “OL.” appearing on the display indicates the overload condition of the instrument.
6. To use the HOLD, MIN/MAX and ZERO functions, please refer to § 4.3.

AC CURRENT MEASUREMENT

CAUTION Before attempting any measurement disconnect all the test leads from the circuit under test and from the meter’s input terminals.

1. Select the position.
2.  Insert the cable in the middle of the clamp jaws (see Fig. 9), in order to obtain accurate measures (see Fig. 2). The display shows the value of AC current.
3. Symbol  appearing on the display indicates the overload condition of the instrument.
4. To use the HOLD, MIN/MAX and ZERO functions, please refer to § 4.3.

AC/DC LEAKAGE CURRENT MEASUREMENT

CAUTION Insert the cable(s) in the middle of the clamp jaws, in order to obtain accurate measures (see § 4.1.1).
Measuring with direct method on earth leads

1. Select position (AC current) or (DC current)
2. To measure DC current, press the ZERO key to zero residual magnetization current.
3. Open the clamp jaws and connect the instrument as shown in Fig. 10 for DC systems or single-phase/three-phase 4-wire AC systems. The display shows the value of leakage current.
4. To use the HOLD, MIN/MAX and ZERO functions, please refer to § 4.3.

Measuring with indirect method

1. Select position (AC current) or (DC current)
2. To measure DC current, press the ZERO key to zero residual magnetization current.
3. Open the clamp jaws and connect the instrument as shown in Fig. 10 for DC systems or single-phase/three-phase 4-wire AC systems. The display shows the value of leakage current.
4. To use the HOLD, MIN/MAX and ZERO functions, please refer to § 4.3.

MAINTENANCE

GENERAL INFORMATION

1. While using and storing the instrument, carefully observe the recommendations listed in this manual in order to prevent possible damage or danger during use.
2. Do not use the instrument in environments with high humidity levels or high temperatures. Do not expose to direct sunlight.
3. Always switch off the instrument after use. In case the instrument is not to be used for a long time, remove the battery to avoid liquid leaks that could damage the instrument’s internal circuits.

REPLACING THE BATTERIES

When the LCD display shows symbol ”, batteries must be replaced.
CAUTION Only expert technicians should perform this operation. Before carrying out this operation, make sure you have removed the cable being tested from inside the clamp jaw.

1. Switch off the instrument by turning the rotary switch to the OFF position.
2. Remove the cable being tested from the clamp jaw.
3. Loosen the fastening screw of the battery compartment cover (see Fig. 1 – part 12) and remove it.
4. Remove all batteries and replace them with new batteries of the same type (see § 7.1.3), respecting the indicated polarity.
5. Restore the battery compartment cover into place and fasten it by means of the relevant screw.
6. Do not scatter old batteries into the environment. Use the relevant containers for disposal.

CLEANING THE INSTRUMENT

Use a soft and dry cloth to clean the instrument. Never use wet cloths, solvents, water, etc.

END OF LIFE

WARNING: the symbol on the instrument indicates that the appliance and its accessories must be collected separately and correctly disposed of.

TECHNICAL SPECIFICATIONS

TECHNICAL CHARACTERISTICS

Accuracy indicated as [%reading + (number of digits*resolution)] at 23°C±5°C, <80%RH

• DC Voltage (Autorange)
  Range| Resolution| Accuracy| Input impedance| Protection against overcharge
  ---|---|---|---|---
  50.00V| 0.01V| ±(1.0%rdg + 2digits)| 1MW| 300VDC/ACrms
  300.0V| 0.1
• AC TRMS Voltage (Autorange)
  Range| Resolution| Accuracy| Bandwidth| Protection against overcharge
  ---|---|---|---|---
  50.00V| 0.01V| ±(1.2%rdg+5digits)| 40Hz ÷ 1kHz| 300VDC/ACrms
  300.0V| 0.1V
• DC Current (Autorange)
  Range| Resolution| Accuracy| Protection against overcharge
  ---|---|---|---
  300.0mA| 0.1mA| ±(1.0%rdg+10digits)| 10ADC
  3,000A| 0,001A
  10.00A| 0.01A| ±(3.0%rdg+10digits)
• AC TRMS Current (Autorange)
  Range| Resolution| Accuracy| Bandwidth
  ---|---|---|---
  300.0mA| 0.1mA| ±(1.0%rdg+5digits)| 50Hz ÷ 60Hz
  3,000A| 0,001A
  20.00A| 0.01A
• Resistance and Continuity test (Autorange)
  Range| Resolution| Accuracy| Buzzer| Protection against overcharge
  ---|---|---|---|---
  500.0W| 0.1W| ±(1.0%rdg + 2digits)| <100W| 300VDC/ACrms
  5.000kW| 0.001kW
  50.00kW| 0.01kW
  500.0kW| 0.1kW

Electrical characteristics

• Conversion type: TRMS
• Sampling frequency: 2 times per second

Reference standards

• Safety: IEC/EN61010-1
• EMC: IEC/EN61326-1
• Insulation: double insulation
• Pollution level: 2
• Max operating altitude: 2000m (6562ft)
• Measurement category: CAT IV 300V

General characteristics

• Mechanical characteristics
  • Dimensions (L x W x H): 206 x 76 x 34mm (8 x 3 x 1in)
  • Weight (batteries included): 262g (9ounces)
  • Clamp jaw opening: 23mm (1in)
  • Max. cable diameter: 23mm (1in)
  • Mechanical protection: IP20
• Pow er supply
  • Battery type: 2×1.5V batteries type AAA IEC LR03
  • Low battery indication: symbol “ ” on the display
  • Battery duration (without backlight): ca. 15 hours (DC current)
  • ca. 60 hours (AC current and voltage)
  • ca. 100 hours (DC voltage and resistance)
  • Auto Power OFF: after 30 minutes’ idling

Display

• Characteristics: 4 LCD, 5000 dots plus decimal point and backlight
• Out of range indication: message OL. on the display

ENVIRONMENT

Environmental conditions for use

• Reference temperature: 23°C ± 5°C (73°F ± 41°F)
• Operating temperature: 0°C ÷ 40°C (32°F ÷ 104°F)
• Operating humidity: ≤ 80%RH
• Storage temperature: -10°C ÷ 60°C (13°F ÷ 140°F)
• Storage humidity: <80%RH

This instrument satisfies the requirements of Low Voltage Directive 2014/35/EU (LVD) and of EMC Directive 2014/30/EU This instrument satisfies the requirements of European Directive 2011/65/EU (RoHS)  2012/19/EU (WEEE).

ACCESSORIES

Accessories provided

• Couple of test leads
• Carrying bag
• Batteries (not inserted)
• User manual

ASSISTANCE

WARRANTY CONDITIONS

This instrument is warranted against any material or manufacturing defect, in compliance with the general sales conditions. During the warranty period, defective parts may be replaced. However, the manufacturer reserves the right to repair or replace the product. The manufacturer declines any responsibility for injury to people or damage to property.
The warranty shall not apply in the following cases:

• Repair and/or replacement of accessories and battery (not covered by warranty).
• Repairs that may become necessary as a consequence of an incorrect use of the instrument or due to its use together with non-compatible appliances.
• Repairs that may become necessary as a consequence of improper packaging.
• Repairs which may become necessary as a consequence of interventions performed by unauthorized personnel.
• Modifications to the instrument performed without the manufacturer’s explicit authorization.
• Use not provided for in the instrument’s specifications or in the instruction manual.

The content of this manual cannot be reproduced in any form without the manufacturer’s authorization.
Our products are patented and our trademarks are registered. The manufacturer reserves the right to make changes in the specifications and prices if this is due to improvements in technology.

ASSISTANCE

If the instrument does not operate properly, before contacting the After-sales Service, please check the conditions of the batteries and replace them, if necessary. Should the instrument still operate improperly, check that the product is operated according to the instructions given in this manual. Should the instrument be returned to the After-sales Service or to a Dealer, transport will be at the Customer’s charge. However, shipment will be agreed in advance. A report will always be enclosed to a shipment, stating the reasons for the product’s return. Only use original packaging for shipment; any damage due to the use of non-original packaging material will be charged to the Customer.

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