13
4 - DECIBELS
■
Reminde
r. 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
.
■
Use
. Zero level of the red scale in dB corresponds to U
o
= 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 coefficient shown in the table.
(1) Common to the 50
µ
A DC range
(2) Direct reading in mV DC
(3) Specific R: 20 k
Ω
/V, except range 1000 V-R = 6.32 k
Ω
/V
(4) In % of the end of scale
(5) For 15 seconds
(1) Specific R:
6.32 k
Ω
/V
(2) In % of
the end of scale
(3) From 10 Hz to ...
(4) For 15 seconds
(
)
N dB)
U U
(
log
= 20
10
0
V AC
10 V
30 V
100 V
300 V
1000 V
Scale
100
30
100
30
100
Reading
coefficient
x0,1
x1
x1
x10
x10
Internal
resistance
(1)
63,2 k
Ω
200 k
Ω
632 k
Ω
2 M
Ω
6,32 M
Ω
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
coefficient
x1
(2)
x0,01
x0,1
x0,1
x1
x1
x10
x10
Internal
resistance
(3)
2 k
Ω
20 k
Ω
63,2 k
Ω
200 k
Ω
632 k
Ω
2 M
Ω
6,32 M
Ω
6,32 M
Ω
Accuracy
(4)
2,5 %
1,5 %
Permitted
overload
440 V
1000 V
(5)
1500 V
(5)
Summary of Contents for C.A 5001
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