RCF 13360089, User Manual, Page: 10 / 12

10
ENGLISH
NOTES ABOUT THE TESTER USE
READ THE SAFETY NOTES BEFORE PROCEEDING.
1
Make sure the system to be tested is not alive.
2
If the symbol appears on the display, replace all batteries (by new ones).
3
Connect both the test leads to the load (loudspeaker or line) to be tested.
Set the proper range (among 20 Ω, 200 Ω, 2000 Ω), by choosing the first higher than
the expected value (if known) of the load to be tested, then press the TEST button
to start the impedance test.
4
It is useful to get (/ make) a wiring drawing of the system that has to be tested.
5
Power calculation of a constant voltage sound system.
P =
V²
—
Z
P = power; V = line voltage; Z = total load impedance
Example: on a 100 V system, if the load measured impedance is 200 Ω, the power
delivered by the amplifier (connected to that line) is 50 W.
P =
100²
——
200
= 50W
It is possible to test the impedance up to 2 kΩ (corresponding to P = 5 W on 100 V
systems).
6
Loudspeaker impedance test
A single loudspeaker has usually a nominal impedance
value in the range 2 ÷16 Ω: select the 20 Ω range by
means of the FUNCTION selector (5).
7
100 V line impedance test
Example: 3 loudspeakers (with transformer) are
connected to the line and their power values are
respectively 10 W, 50 W, 200 W.
The line total impedance (assuming the wire impedance
negligible) is:
Z =
V²
—
P
=
100²
————————
(10+50+200)
= 38,46Ω
a.
If the measured impedance is about 38 Ω, the line
is OK.
b.
If the measured impedance is significantly lower
or higher, check for possible:
• accidental short-circuits (impedance close to 0);
• wrong loudspeaker power settings;
• wires wrongly connected;
• loudspeaker (or transformer) faults.
10W
50W
200W