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CONTRÔLEUR DE TERRE
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EARTH TESTER
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ERDUNGSPRÜFER
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CONTROLLORE DI TERRA
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CONTROLADOR DE TIERRA
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C.A 6421
ENGLISH
User's Manual
1
i
English
Meaning of the symbol :Caution! Read the instruction manual before using the
instrument.
In this manual, safety instructions prefixed with this symbol will, if not observed or followed,
bring hazardous conditions for the operator or for the instrument and installation.
You have just acquired an Earth Tester and we thank you for your confidence.
To get the best service from your instrument:
- read carefully this user’s manual,
- respect the safety precautions in it,
- stick the label corresponding to your language on the back of the instrument.
SAFETY IN USE
■ Before connecting the C.A 6421, check for any hazardous voltage in the earth
connection to be tested.
■ Before opening the battery trap-door, check that no test lead is connected to the
insrument.
■ Before performing a resistance measurement, check the galvanometer rating (the
pointer must stop at 0.5 Ω).
WARRANTY
Unless notified to the contrary, our instruments are guaranteed from any manufacturing
defect or material defect. They do not bear the specification known as the safety specification.
Our guarantee, which may not under any circumstances exceed the amount of the invoiced
price, goes no further than the repair of our faulty equipment, carriage paid to our workshops.
It is applicable for normal use of our instruments, and does not apply to damage or
destruction caused, notably by error in mounting, mechanical accident, faulty maintenance,
defective use, overload or excess voltage.
Our responsability being strictly limited to the pure and simple replacement of the faulty parts
of our equipment, the buyer expressly renounces any attempt to find us responsible for
damages or losses caused directly or indirectly.
Our guarantee is applicable for twelve (12) months after the date on which the
equipment is made available. The repair, modification or replacement of a part during the
guarantee period will not result in this guarantee being extended.
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SUMMARY
Page
1. PRESENTATION .......................................................................................................................................................................... 16
2. DESCRIPTION ...................................................................................................................................................................... 17
3. OPERATING MODE ......................................................................................................................................................... 18
3.1. Earth connection resistance measurement ........................................................................... 18
3.2. Resistance measurement ...................................................................................................................... 20
3.3. Fault indications ............................................................................................................................................. 20
4. CHARACTERISTICS ........................................................................................................................................................ 21
5. MAINTENANCE ................................................................................................................................................................... 25
5.1. Routine maintenance ................................................................................................................................. 25
5.2. Calibration ........................................................................................................................................................... 26
5.3. Repair ...................................................................................................................................................................... 26
6. TO ORDER ............................................................................................................................................................................... 27
1. PRESENTATION
This self-powered and watertight tester was designed for measuring earth connection
resistances in outdoor sites. It is particulary adapted to harsh environments and may be used
in all weather conditions.
It is very easy to use thanks to:
■ a single pushbutton for triggering your measurements
■ a large galvanometer, directly graduated in Ω
■ three lights indicating any fault liable to vitiate test results
■ a low-battery indicator built in the galvanometer
■ three color-coded screw-on terminals making test connections easier
■ one captive bar
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2. DESCRIPTION
1 Test input terminal E (green))
2 Test input terminal S (blue)
3 Test input terminal H (red)
4 Captive bar S - H for two-wire resistance measurements
5 Moving-coil galvanometer, logarithmic scale: 0,5....1000 Ω
6 Low-battery indicator
7 Galvanometer calibration screw
8 Fault indicator - current circuit (E - H)
9 Fault indicator - voltage circuit (E - S)
10 Parasitic voltage indicator - voltage circuit (E - S)
11 Pushbutton for triggering measurements
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3. OPERATING MODE
3.1 EARTH CONNECTION RESISTANCE MEASUREMENT
Two rod-based methods let you measure earth connection resistances with the C.A 6421.
The Tagg-method (said “ of the 62% ”) is indiscutably the best. It requires an unhindered stretch
of land at least 100 m in length, close to the earth connection to be tested.
The triangular method also provides suitable results, although test results may be vitiated in
the event of overlapping vicinitiy areas.
3.1.1. Measurements using the method “ of the 62% ”
Switch off the installation and disconnect it from the ground by opening the
earthing rod!
1. Connect terminal E to the earth connection to be tested.
2. Check that the bar 4 was not installed between terminals S and H.
3. Push down the rod H into the earth as deeply as possible, at a distance “a” from the earth
connection (E).
Note: this distance will be proportional to the depth of the earth connection (wider vicinity area).
4. Similarly, push down the rod S by lining it up with the earth connection E and the rod H,
at a distance of about 62% of “a”.
5. Connect the test leads between the rods and their respectives terminals.
6. Press the pusbutton 11 till the galvanometer pin stabilizes. Make sure none of the three
indicators is blinking, otherwise check the connections (see § 3.3: FAULT INDICATION)
and repeat the measurement.
earth bar
E
earth
point
0 % 72 % 100 %
E S H
S'' S'
S
52%62
%
Earth resistance measurement using the method of the 62%
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H
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