FBT 37483_VAIE2550_manual1.pdf - Manuale (Pagina 115)

8-29
USING THE SYSTEM
UK
8.7.1 IMP. ACQUISITION
Line impedance acquisition
Panel for acquiring and storing the impedance levels of the speaker
unit lines. This information is necessary for system initialisation and
diagnostics.
• Loudspeaker line impedance acquisition
Foreword
Before acquiring the impedance values, make sure that the following
steps have been completed:
• Preliminary check of the impedance of the lines using a suitable
instrument (IMPEDANCE-METER) and of the loading conditions
as prescribed in the SIZING Section.
The new impedance values acquired will be stored automatically in the system and shown on the labels of each zone. They are in Ohms
and refer to both lines, A and B, connected to the output of each zone. The impedance values residing in the memory will be compared by
the monitoring system with the values measured subsequently during the diagnostics routine.
Note: To measure the impedance of the speaker unit lines, the monitoring system provided in the VAIE 2250 uses an inaudible 20 kHz
tone. Due to the inductance of the loudspeaker coils, the impedance at 20 kHz may be considerably different from that measured with an
impedance meter, which usually uses a 1 kHz measuring tone. The value acquired by the VAIE 2250 is therefore usually indicative only as a
comparative value for diagnostic purposes. For this reason, when calculating the power absorbed by the speaker unit lines for the purpose
of sizing the system it is recommended to use the value measured with an impedance meter.
Press ESC to return to the CONFIGURATION menu.
Upon completing the procedure, carry out a MANUAL RESET of the FAILURE SIGNALLING, as described under point 8.6.5.1.
N.B.: For a 12-zone system, repeat the procedure on both VAIE 2250 units.
8.7.2 SET TOLERANCE
Setting the line tolerance
Panel for setting the tolerance for checking the line impedance.
If the diagnostic system detects a difference between the impedance
measured in real time and the value stored in the system greater than
the tolerance that was set: an “Impedance Low” or “Impedance Hi”
“Fault Warning Condition” will be activated. For details about signalling
of failures, see the “LOUDSPK. LINE FAULT” panel (point 8.5.1.3).
• Setting the tolerance for measuring the lines
Foreword
The measurement tolerance must be set after completing acquisition
of the line impedance (see point 8.7.1):
After selecting the “Set> IMP. TOLERANCE” option from the CONFIGURATION menu, the “SET TOLERANCE” panel will show the current
tolerance settings for each output zone.
• Hold the numerical key corresponding to the zone (1-6) down.
• Turn the +/- knob to choose the required value.
>Values from 5% to 100%: tolerance above or below the stored value.
>Test Disabled: Impedance check disabled. Testing for short circuits and GND faults will in any case be carried out.
Press ESC to return to the CONFIGURATION menu.
Upon completion of the procedure, if appropriate carry out a “Manual reset of a Failure Signal” as described under point 8.6.6.1.
N.B.: For a 12-zone system, repeat the procedure on both VAIE 2250 units.
After selecting “Acquire> IMPEDANCE” from the CONFIGURATION menu, the “IMP. ACQUISITION” panel will show the impedance values
stored at the time of the previous acquisition:
•
press the OK key
• Connection of the speaker unit lines as indicated in the CONNECTIONS Section.
• Setting of music to “OFF” in the output zones and no service announcements being sent out by any PA sources. For details, consult the
MUSIC Menu (see point 8.3.4).