User manual

13
4 - DECIBELS
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■■
■ Reminder. The measurement of an AC voltage can be expressed
in decibels (symbol dB). The decibel is the ratio of two quantities or
levels. Level N, in dB, of a voltage U has the mathematical expression:
U
o
is the reference voltage of 0.775 V AC for a power P
o
of 1 mW
on a load of 600 Ω.
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■■
■ Use. Zero level of the red scale in dB corresponds to Uo = 0.775
for the 10 V AC range. The reading is direct in dB for the 10 V AC range
from 0 to +22 dB. For the other ranges, it is possible to read in dB (near
value) by adding respectively:
+10dB on the 30 V AC range +20dB on the 100 V AC range
+30dB on the 300 V AC range +40dB on the 1000 V AC range
3 - DC AND AC VOLTAGES
■ Connect the leads to the multimeter and connect in parallel to the
circuit to be tested.
■ When the order of magnitude is not known, place the switch on the
highest range then progressively lower to the appropriate range.
■ To get the voltage in V, multiply the value read on the appropriate
scale by the reading cœfficient shown in the table.
(1) Common to the 50 µA range (2) Direct reading in mV
(3) Specific R: 20 kΩ/V, except range 1000 V-R = 6.32 kΩ/V
(4) In % of the end of scale (5) For 15 seconds
(1) Specific R:
6.32 kΩ/V
(2) In % of
the end of scale
(3) From 20 Hz to ...
(4) For 15 seconds
()
NdB) UU(log=20
10 0
V AC 10 V 30 V 100 V 300 V 1000 V
Scale 100 30 100 30 100
Reading
cœfficient
x0,1 x1 x1 x10 x10
Internal
resistance
(1)
63,2 kΩ 200 kΩ 632 kΩ 2 MΩ 6,32 MΩ
Accuracy
(2)
3 % 2,5 %
Bandwidth
(3)
100 kHz 50 kHz 25 kHz 1 kHz
Permitted
overload
1000 V
(4)
1500 V
(4)
V DC 100 mV
(1)
1 V 3 V 10 V 30 V 100 V 300 V 1000 V
Scale 100 100 30 100 30 100 30 100
Reading
cœfficient
x1
(2)
x0,01 x0,1 x0,1 x1 x1 x10 x10
Internal
resistance
(3)
2 kΩ 20 kΩ 63,2 kΩ 200 kΩ 632 kΩ 2 MΩ 6,32 MΩ 6,32 MΩ
Accuracy
( 4)
2,5 % 1,5 %
Permitted
overload
440 V 1000 V
(5)
1500 V
(5)