HT HT712 User manual

©Copyright HT ITALIA 2012 Release EN 1.02 - 23/02/2012
ENGLISH
User’s manual

HT712
EN - 1
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

HT712
EN - 2
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.

HT712
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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.

HT712
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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
expression: G= ∫
+Tt
t
dttg
T
0
0
)(
12The effective value is indicated as RMS (root mean square).
The crest factor is defined as the ratio between the peak value of a signal and its effective
value: CF (G)=
RMS
p
G
G. This value varies according to the waveform of the signal, for a
purely sinusoidal wave it’s worth 2=1.41. In presence of distortions, the higher the wave
distortion is, the higher the crest factor values get.

HT712
EN - 5
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.

HT712
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4. OPERATING INSTRUCTIONS
4.1. INSTRUMENT - DESCRIPTION
4.1.1. Front panel
Fig. 1: Instrument description
LEGEND:
1. Test probe
(accessory)
2. V+/Ωinput terminal
3. DISP key
4. HOLD key
5. Metallic pad
6. COM input terminal
7. Rotary selector
8. MEAS key
9. LCD
4.2. FUNCTION KEYS
Once pressed, the relevant symbol appears on the display and the buzzer beeps. Every
time the selector is rotated all functions activated by means of the function keys are
cancelled.
Fig. 2: Function keys
4.2.1. HOLD
The data HOLD function key holds the displayed value. Press “ ” to activate or
deactivate. When the data HOLD function is active the symbol “H” is displayed.
4.2.2. DISP
Press “ ” key to display voltage and frequency values during AC voltage
measurements.
4.2.3. MEAS
Press “ ” key to clear the display after phase sequence and phase conformity
measurements, and prepare the instrument for further operations.
4.3. SPECIAL FUNCTIONS
4.3.1. Turning on
When the instrument is turned on, all display segments and the LEDs are lit for just one
second. Then the instrument is ready for operation.
4.3.2. Auto power off
The instrument automatically turns off 5 minutes after last pressure of keys or last selector
rotation. To resume operation turn the selector on OFF and turn on the instrument again.

HT712
EN - 7
4.4. MEASUREMENTS - DESCRIPTION
4.4.1. DC voltage measurement
CAUTION
The maximum input for DC voltage is 600V. Don’t try to measure higher
voltages to avoid risks of electrical shocks or serious damages to the
instrument.
Fig. 3: DC voltage
measurement
1. Turn the selector on .
2. Insert the black test lead in the COM jack and the red
probe in the V+/Ωjack (Fig. 3).
3. Connect the red probe and the black test lead
respectively to the positive and negative poles of the
circuit under test; the voltage value will be displayed
(automatic range detection).
4. Should you get the message "O.L" it means that the
detected voltage exceeds the limits which the
instrument can measure. In this case stop the
measurement by disconnecting the test leads from the
circuit under test to avoid risks for yourself and for the
instrument.
5. Should you get a symbol "-" it means that the detected
voltage has an opposite direction compared to the
connection shown in Fig. 3.
6. If you want to activate the HOLD function refer to
chapter 4.2.

HT712
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4.4.2. AC voltage and frequency measurement with 2 test leads
CAUTION
The maximum input for AC voltage is 600V. Don’t try to measure higher
voltages to avoid risks of electrical shocks or serious damages to the
instrument.
Fig. 4: AC voltage and frequency
measurement with 2 test leads
1. Turn the selector on .
2. Insert the black test lead in the COM jack and the
red probe in the V+/Ωjack (Fig. 4).
3. Connect the red probe and the black test lead to
the poles of the circuit under test; the voltage value
will be displayed (automatic range detection).
4. By pressing the “ ” function key you can
display the frequency value instead of the voltage
one and vice-versa.
5. Should you get the message "O.L" it means that
the detected voltage exceeds the limits which the
instrument can measure. In this case stop the
measurement by disconnecting the test leads from
the circuit under test to avoid risks for yourself and
for the instrument.
6. If you want to activate the HOLD function refer to
chapter 4.2.

HT712
EN - 9
4.4.3. AC voltage and frequency measurement with 1 test leads
CAUTION
The maximum input for AC voltage is 600V. Don’t try to measure higher
voltages to avoid risks of electrical shocks or serious damages to the
instrument.
L1
Fig. 5: AC voltage and frequency
measurement with 1 test lead
1. Turn the selector on .
2. Insert the red probe in the V+/Ωjack (Fig. 5).
3. Keep the instrument gripped correctly by touching
the metallic pad with a finger.
4. Connect the red probe to the desired position of
the circuit under test; the voltage value of that point
to earth will be displayed (automatic range
detection).
5. By pressing the “ ” function key you can
display the frequency value instead of the voltage
one and vice-versa.
6. Should you get the message "O.L" it means that
the detected voltage exceeds the limits which the
instrument can measure. In this case stop the
measurement by disconnecting the test leads from
the circuit under test to avoid risks for yourself and
for the instrument.
7. If you want to activate the HOLD function refer to
chapter 4.2.
CAUTION
The instrument detects and displays
the AC voltage value between the
measuring point and the potential
where the operator is located. Such
value is typically the earth potential, but
in some cases it may differ from it. DO
NOT TOUCH THE PHASE CABLE IF
YOU ARE NOT SURE WHETHER
VOLTAGE IS PRESENT OR NOT.