HT instruments HT78 User Manual

ENGLISH

User manual

HT78

Table of contents:

1. SAFETY PRECAUTIONS AND PROCEDURES ..........................................................2

1.1. Preliminary ........................................................................................................................ 2

1.2. Before use......................................................................................................................... 3

1.3. After use............................................................................................................................ 3

1.4. Measuring (overvoltage) categories definitions................................................................. 3

2. GENERAL DESCRIPTION ...........................................................................................4

2.1. TRMS and MEAN VALUE measuring instruments............................................................ 4

2.2. TRUE ROOT MEAN SQUARE VALUE and CREST FACTOR definitions........................ 4

3. PREPARATION FOR USE ...........................................................................................5

3.1. Initial.................................................................................................................................. 5

3.2. Power supply..................................................................................................................... 5

3.3. Calibration ......................................................................................................................... 5

3.4. Storage.............................................................................................................................. 5

4. OPERATING INSTRUCTIONS.....................................................................................6

4.1. Instrument description....................................................................................................... 6

4.1.1. Front panel.................................................................................................................................. 6

4.2. Description of parts ........................................................................................................... 7

4.2.1. Range and ON/OFF selector...................................................................................................... 7

4.2.2. D-H key....................................................................................................................................... 7

4.2.3. FILTER selector.......................................................................................................................... 7

4.2.4. LOCK selector ............................................................................................................................ 7

4.2.5. AutoPowerOFF........................................................................................................................... 7

4.2.6. DC analogical output .................................................................................................................. 8

4.3. How to perform the measurements ................................................................................... 9

4.3.1. AC Current measurement........................................................................................................... 9

4.3.2. Leakage current measurement on Single phase system ......................................................... 10

4.3.3. Leakage current measurement on Three phase system.......................................................... 11

5. MAINTENANCE .........................................................................................................12

5.1. General informations....................................................................................................... 12

5.2. Batteries replacement ..................................................................................................... 12

5.3. Cleaning .......................................................................................................................... 12

5.4. End of life ........................................................................................................................ 12

6. TECHNICAL SPECIFICATIONS ................................................................................13

6.1. Characteristics.................................................................................................................13

6.1.1. Safety........................................................................................................................................ 13

6.1.2. General data............................................................................................................................. 13

6.2. Environmental conditions ................................................................................................ 14

6.2.1. Climatic conditions.................................................................................................................... 14

6.3. Accessories.....................................................................................................................14

6.3.1. Standard accessories ............................................................................................................... 14

7. SERVICE....................................................................................................................15

7.1. Warranty conditions......................................................................................................... 15

7.2. Service ............................................................................................................................ 15

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HT78

1. SAFETY PRECAUTIONS AND PROCEDURES

This meter complies with IEC/EN61010-1. For your own safety and in order to avoid damaging the instrument, you’re recommended to keep to the instructions contained in this

manual and read carefully all the notes preceded by the symbol .

Take extreme care for the following conditions while measuring:

• Do not measure voltage or current in humid or wet environment.

• Do not use the meter in presence of explosive gas (material), combustible gas

(material), steam or dust.

• Insulate yourself from the object to be tested.

• Do not touch exposed metal (conductive) parts such as sockets, fixing objects, circuits,

etc.

• If you detect anomalies of testing end (metal part) and attachment of the meter such as

breakages, deformations, foreign substances, no display, etc., do not take any measurement.

The followings symbols are used on meter and user’s manual

Caution: refer to the instruction manual. An incorrect use may damage the tester or its components.

High Voltage ranger: electrical shock risk.

Double insulated instrument.

AC Current

DC Voltage

1.1. PRELIMINARY

• This apparatus has been designed for use in an environment of pollution degree 2.

Indoor use

• It measures AC CURRENT on CAT II 600V or CAT III 300V plants. For overvoltage

and categories please see § 1.4

• You must comply with the usual safety regulations aimed at: protecting you against the

dangerous electric current and protecting the instrument against an incorrect operation

• Do not test or connect to any circuit whose current exceeds the specified overload

protection

• Make sure that the batteries are installed correctly

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HT78

1.2. BEFORE USE

Always keep to the instructions contained in this manual:

CAUTION

Non compliance with the warnings and/or the instructions may damage the tester and/or its components or injure the operator.

• When the clamp is connected to the circuits to be tested, never touch unused terminals

• When measuring current, any strong current near or close to the clamp jaw will affect

the accuracy

• When measuring current, always put the tested conductor in the middle of the clamp

jaw in order to obtain a more accurate reading

• If the reading value or the sign indication remains unchanged during the measurement,

check if the HOLD function is active

1.3. AFTER USE

• Once the measurements are completed, turn OFF the meter

• If you expect not to use the clamp for a long time, remove the batteries

1.4. MEASURING (OVERVOLTAGE) CATEGORIES DEFINITIONS

The norm IEC/EN61010-1: Safety requirements for electrical equipment for measurement, control and laboratory use, Part 1: General requirements, defines what measuring category, usually called overvoltage category, is. On § 6.7.4: Measuring circuits, it says:

(OMISSIS)

circuits are divided into the following measurement categories:

• 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 in the building installation.

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 norm requires that the transient withstand capability of the equipment is made known to the user.

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HT78

2. GENERAL DESCRIPTION

HT78 meter can performs the herewith features:

• AC TRMS current measurement up to 3000A

• AC leakage current measurement with 0.1mA resolution

• DC voltage analogical output for connection with external data loggers

• 150Hz low-pass filter for reduce harmonic components of input signal

Each feature can be selected by using rotation selector on meter’s front panel. The Data HOLD, FILTER and LOCK functions are still available (see § 4.2). The selected quantity appears on a LCD display with indication of measurement units and functions. Analogical bargraph it’s also displayed on meter. The meter disposes of an Auto Power Off function consisting in an automatic switching off 10 minutes after last operation.

2.1. TRMS AND MEAN VALUE MEASURING INSTRUMENTS

Safety testers for alternate quantities are divided into two big families:

• MEAN VALUE instruments: instruments which measure only the value of the wave at

the fundamental frequency (50 or 60 Hz).

• TRUE ROOT MEAN SQUARE instruments, also defined as TRMS: instruments which

measure the true root mean square value of the quantity under test. In presence of a perfectly sinusoidal wave, both families provide identical results. In presence of distorted waves, instead, the readings are different. Mean value instruments provide only the value of the fundamental wave while True RMS instruments provide the value of the entire wave, including harmonics (within the passband of the instrument). Accordingly, if the same quantity is measured with both kinds of instruments, the measured values are identical only if the wave is purely sinusoidal. Should it be distorted, True RMS instruments provide higher values than medium value instruments.

2.2. TRUE ROOT MEAN SQUARE VALUE AND CREST FACTOR DEFINITIONS

The current effective value is defined as follows: “In an interval of time equivalent to a period, an alternate current with effective value having an intensity of 1A, by passing on a resistor, disperses the same energy which would be dispersed in the same period of time by a direct current having an intensity of 1A”. From this definition comes the numerical

+Tt

expression: G=

The Crest Factor is defined as the ratio between the Peak Value of a signal and its

effective value: CF (G)=

for a purely sinusoidal wave it’s worth 2 =1.41. In presence of distortions the Crest Factor assumes higher values as long as the wave distortion is higher.

dttg

)(

∫

The effective value is indicated as RMS (root mean square).

. This value varies according to the waveform of the signal,

RMS

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