Abstract
A new level recorder based on the SL-4 has been developed. The driving element of this recorder is a coil suspended in a magnetic field and controlled by a closed-loop servo system. The moving coil travels in a straight line and carries a pen which writes on a paper chart 4 in. wide. The circuits for this recorder have been completely transistorized, and a new magnetic structure has been used. As a result, the size, weight, and power consumption of the instrument have been reduced. Sensitivity has been increased 20 db. A “quasi-rms” detector circuit with adequate dynamic range for noise signals is used. A new, simplified method of construction for the logarithmic potentiometers has been developed and their resolution has been improved. The band width of the servo system which positions the pen is adjustable over a wide range. The effect of the servo band width, damping, and maximum writing speed on the transient response will be described. The corresponding effects upon the recording of reverberation and frequency-response curves will be discussed.
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