The Level Recorder - BRUEL & KJAER 1022 Instructions And Applications

The Level Recorder.
The Level Recorder has been designed to record signal levels in the frequency
range 10 c/ s to 200ooo c/ s as well as d.c. The operation of the instrument
is based on the servo-principle. Fig. 4.3 shows a block diagram of the
instrument.
159398
Fig. 4.3. Block diagram of the Level Recorder.
Fundamentally the Recorder consists of an interchangeable range potentio-
meter; a direct coupled amplifier; the special B & K rectifier circuit which
gives RMS, Average or Peak detection of the input signal, a DC chopper
amplifier and an electro-mechanical writing system.
When the magnitude of the voltage applied to the input terminals is changed
a current will flow through the df>iving coil of the writing syste!m thus
n'loving the stylus, which is mechanically coupled to the range potentiometer.
By the movement of the stylus the voltage delivered from the potentiometer
to the AC amplifier will be altered until a stable condition is regained. In
this way it is possible to obtain different ranges of voltage variations
which can be recorded, by employing different range pontentiometer' S . Loga-
rithmic range potentiometers are available for voltage level range' s of 10, 25,
50 or 75 dB. Two linear po-tentiometers cover the ranges 10 to 35 m V and
10 to 110 1 1 nV respectively.
The recorder is capable of writing on two different widths of recording
paper, 50 mm and 100 mm. To change from one width to the other it is
only necessary to release a snap-lock arrangement on the moving arm
which holds the stylus.
The writing speed is determined by the amount of damping applied to the
writing system which is selectable by the rotary switch "Writing Speed".
This is variable in 15 spot settings shown by the figures outside the switch.
45