4. RECORDING OF FREQUENCY ANALYSES
For fully automatic recording of octave and third octave analyses on frequency graduated
paper, the 1618 may be used with the portable Level Recorders Types 2306 and 2309
or the main operated Level Recorder Type 2307. Switching of the Band Pass Filter cen-
tre frequency is accomplished using the filter shift pulses generated by the Level Recor-
ders. Operation depends on the particular Level Recorder used and is described in the
following sections.
4.1. USE WITH LEVEL RECORDERS TYPES 2306 AND 2309
The instrument arrangement for automatic recording of octave and third octave analyses
with the 2306 and 2309 Level Recorders is shown in Fig.4.1. Also indicated are the ne-
cessary remote control cables for application of the Level Recorder filter shift pulses to
the RECORDER CONTROL II socket of the 1618 Band Pass Filter in the arrangement.
Recorder Control II
Band Pass Filter
1618
nput
AO 0014/AO 0064
V
Ext. Output
Filter
Input
Signal -•f
Measuring
Amplifier
2606, 2607, 2608
AQ 0182
L AO 0034-----_—J
Level Recorder
2306
with common
Remote Control-
Ext. Supply socket
Level Recorder
2306 (or 23091
with separate
Remote Control
Ext. Supply sockets
AO 0064 790201
Fig.4.1. Use of Level Recorders Types 2306 and 2309 for auto-
matic recording of octave and third octave analyses
With 2306 Level Recorders before serial no. 576700 a 3,3 k0 resistor must be sold-
ered to print board XC 1 062 (see Fig.4.2) to permit correct synchronization. For access
to XC 1062, disconnect all power from the Level Recorder and remove the four screws
under the black snap-on caps at each corner of the rear panel. XC 1062 is located be-
hind print boards XC 1059 and 1060 which may be released by unscrewing the two
screws and two spacers at the top of the respective boards. Modification should be per-
formed only by persons qualified in the service and maintenance of electronic measuring
instrumentation.
The procedure for recording an octave or third octave analysis is given below. This is
given with reference to the 2306, however, a similar procedure may be used with the
2309 Level Recorder.
16
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