Measurement 65BLACK RED 3 3 2 2 1 1 (^10)
1
2
2
^3
^3
^5
^5
^7
^7
^10
^10
^20
^20
0
0
20
20
40
40
60
60
80
80
100
100
BLACK
BLACK
VU
VU
RED
(a) Recording and test equipment
(b) Broadcast monitoring
Figure 2.14 : Volume indicator instrument scales.
18 dBm, you are in danger of distortion with any signal indicating more than 8 VU on
the VI instrument ( 18 dBm – [ 10 dB] peaking factor or meter lag equals 8 VU).
Figure 2.15 shows an example of commercially available VI instrument panels used in
the past that included the VI instrument and 3900- Ω attenuator, which also contains the
3600-Ω build-out resistor.
2.19.2 How to Read the VU Level on a VI Instrument
A VI instrument is used to measure the level of a signal in VU. In calibration:
0 V U 0 dBm and a 1.0-VU increment is identical to a 1.0-dB increment. The true level
reading in VU is found by
True VU levelApparent level Impedance correction^ (2.41)