HT instruments HT712 User Manual

ENGLISH

User’s manual

HT712

Content:

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

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

1.2. During use ......................................................................................................................... 3

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

1.4. Overvoltage categories - definitions .................................................................................. 3

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

2.1. TRMS VALUE and MEAN VALUE - DEFINITIONS .......................................................... 4

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

3. PREPARATION TO USE .......................................................................................................... 5

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

3.2. Supply voltage ................................................................................................................... 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. Function keys .................................................................................................................... 6

4.2.1. HOLD .......................................................................................................................................... 6

4.2.2. DISP ........................................................................................................................................... 6

4.2.3. MEAS .......................................................................................................................................... 6

4.3. Special functions ............................................................................................................... 6

4.3.1. Turning on ................................................................................................................................... 6

4.3.2. Auto power off ............................................................................................................................ 6

4.4. Measurements - description .............................................................................................. 7

4.4.1. DC voltage measurement ........................................................................................................... 7

4.4.2. AC voltage and frequency measurement with 2 test leads ........................................................ 8

4.4.3. AC voltage and frequency measurement with 1 test leads ........................................................ 9

4.4.4. Phase sequence test and phase conformity test ...................................................................... 10

4.4.5. Resistance measurement and continuity test ........................................................................... 12

5. MAINTENANCE ...................................................................................................................... 13

5.1. General information ......................................................................................................... 13

5.2. Battery replacement ........................................................................................................ 13

5.3. Cleaning .......................................................................................................................... 13

5.4. End of life ........................................................................................................................ 13

6. TECHNICAL SPECIFICATIONS ............................................................................................. 14

6.1. Technical features ........................................................................................................... 14

6.1.1. Electrical ................................................................................................................................... 15

6.1.2. Safety ........................................................................................................................................ 15

6.1.3. General data ............................................................................................................................. 15

6.2. Environment .................................................................................................................... 15

6.2.1. Environmental conditions ......................................................................................................... 15

6.3. Accessories ..................................................................................................................... 15

6.3.1. Standard accessories ............................................................................................................... 15

7. SERVICE ................................................................................................................................ 16

7.1. Warranty conditions ......................................................................................................... 16

7.2. Service ............................................................................................................................ 16

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HT712

1. SAFETY PRECAUTIONS AND PROCEDURES

This instrument complies with EN 61010-1 concerning electronic measuring instruments. For your own safety and to avoid damaging the instrument follow the procedures described in this instruction manual and read carefully all notes preceded by this symbol

When taking measurements:

• avoid doing that in humid or wet places - make sure that humidity is within the limits

indicated in section “environmental conditions”.

• avoid doing that in presence of explosive gas, combustible gas, steam or excessive

dust.

• do not touch exposed metal (conductive) parts such as test lead ends, sockets, fixing

objects, circuits etc.

• avoid doing that if you notice anomalous conditions such as breakages, deformations,

fractures, foreign substances, blind display etc.

• avoid measuring higher voltages than 20V as you may risk electrical shocks.

The following symbols are used:

Caution: refer to the instruction manual; an improper use may damage the instrument or its components

Danger high voltage: risk of electrical shocks

Double insulated meter

AC voltage

DC voltage

DC/AC voltage

1.1. PRELIMINARY

• This instrument has been designed for use in environments of pollution degree 2.

• It can be used for VOLTAGE measurements on installations of CATIV 600V.

• Only the original test leads supplied along with the instrument guarantee compliance

with the safety standards in force. They must be in a good conditions and, if necessary, replaced with identical ones.

• Do not test nor connect to any circuit exceeding the specified overload protection.

• Do not take measurements under environmental conditions exceeding the limits

indicated in chapter 6.2.1.

• Make sure that batteries are correctly installed.

• Before connecting the test probes to the installation make sure that the rotary selector

is positioned on the right function.

• Make sure that LCD and rotary selector indicate the same function.

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HT712

1.2. DURING USE

CAUTION

An improper use may damage the instrument and/or its components or injure the operator.

• Before changing the range, first disconnect the test leads from the circuit under test in

order to avoid any accident.

• When the instrument is connected to circuits never touch an unused terminal.

• When measuring resistors do not add any voltage. Although there is a protection

circuit, excessive voltage would still cause malfunctioning.

• If values remain unchanged on the display during measurement check if HOLD

function is on.

1.3. AFTER USE

• Once measurements are completed turn off the instrument.

• If you expect not to use the instrument for a long period remove batteries.

1.4. OVERVOLTAGE CATEGORIES - DEFINITIONS

EN 61010-1 (Safety requirements for electrical equipment for measurement, control and laboratory use, Part 1: General requirements) defines what a measurement category (usually called “overvoltage category”) is. At paragraph 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 low

voltage installations.

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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HT712

2. GENERAL DESCRIPTION

The instrument performs the following measurements:

● DC and AC TRMS voltage

● AC voltage with 1 test lead

● Frequenza

● Frequency with 1 test lead

● Phase sequence test

● Phase conformity test

● Resistance

● Continuity test

selectable by means of a 5-position rotary selector. Three function keys are also available. The selected measurement is displayed with indication of active functions. In order to save batteries the instrument automatically switches off 15 minutes after last pressure on keys or last selector rotation. To resume operation turn the rotary selector on OFF position and switch it on again.

2.1. TRMS VALUE AND MEAN VALUE - DEFINITIONS

Safety testers for alternate quantities are divided into two categories:

• MEAN VALUE instruments: instruments measuring only the value of the wave at

the fundamental frequency (50 or 60Hz)

• True Root Mean Square (TRMS) instruments: instruments measuring the true root

mean square value of the quantity under test. In presence of a perfectly sinusoidal wave, both categories provide identical results. But in presence of distorted waves, readings are different. Mean value instruments provide only the value of the fundamental wave while TRMS 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 instruments, the measured values are identical only if the wave is purely sinusoidal. Should it be distorted, TRMS instruments provide higher values than mean 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 we get 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)=

purely sinusoidal wave it’s worth distortion is, the higher the crest factor values get.

dttg

)(

∫

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

RMS

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

2 =1.41. In presence of distortions, the higher the wave

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HT712

3. PREPARATION TO USE

3.1. INITIAL

This instrument was checked both mechanically and electrically prior to shipment. All possible cares and precautions were taken to let you receive the instrument in perfect conditions. Notwithstanding we suggest you to check it rapidly (eventual damages may have occurred during transport). Make sure that all standard accessories mentioned in paragraph 6.3.1 are included. Should you have to return back the instrument for any reason please follow the instructions mentioned in paragraph 7.

3.2. SUPPLY VOLTAGE

The instrument is powered by batteries (refer to paragraph 6.1.3 for details on model, no. and battery life). When batteries are low, a low battery indication is displayed. To replace/insert batteries follow the instructions indicated in paragraph 5.2.

3.3. CALIBRATION

The instrument complies with the technical specifications contained in this manual and such compliance is guaranteed for 1 year. Afterwards the instrument may need recalibration.

3.4. STORAGE

After a period of storage in extreme environmental conditions exceeding the limits mentioned in paragraph 6.2.1 let the instrument return to normal measuring conditions before using it.

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