$999.0 Buy It Now or Best Offer
free,30-Day Returns
Seller Store jemz4094
(139) 100.0%,
Location: Marlton, New Jersey
Ships to: US,
Item: 186172902241
Restocking Fee:No
Return shipping will be paid by:Buyer
All returns accepted:Returns Accepted
Item must be returned within:30 Days
Refund will be given as:Money Back
General Radio Company:General Radio Company
MPN:1521B
This General Radio Company 1521-B Sound Level Meter Graphic Level Chart Recorder is a reliable tool for measuring sound levels. With its precise readings, it is perfect for those in the business and industrial sector who require accurate sound measurements. Made by General Radio Company, this piece of equipment is of the highest quality and is built to last. The meter comes in a used condition and has been well-maintained. It is ideal for those working in test, measurement, and inspection and is specifically designed for sound level measurement. With its exceptional brand reputation and high-quality performance, this sound level meter is a great investment for anyone looking for a reliable and accurate tool. 1.1 PURPOSE. The Type 1521-B Graphic Level Recorder (Figure 1.1) produces a permanent ink record of the level of ac voltages, at frequencies from 7 ps to 200 kc. The trace, which is proportional to the logarithm of changes in input level, and hence linear in decibels, may be plotted as a function of time, on translucent chart paper. When the recorder is set up to drive the dial of an external oscillator, it automatically plots level vs frequency, yielding a permanent record with minimum time and effort. The translucent paper permits superposition of one recording over another for compari-son. Recording width is four inches. Fast writing speed in conjunction with a wide servo bandwidth enables the Type 1521-B to record rapidly changing signal levels from the outputs of various electrical and electroacoustic devices. Writing speed is high enough for most reverberation-time measurements. The Type 1521-B can also be used as a de re-corder, with an input-voltage range of 0 to 0.8 volt. 1.2 GENERAL DESCRIPTION. (See Figure 1.2.) The Type 1521-B is a servo-type recorder. The input signal is fed through an input step attenuator to a potentiometer which is automatically positioned to maintain a constant 1-mv ac signal at the wiper arm output. This output voltage is amplified and then rectified by a quasi-rms detector (refer to paragraph 4.3). The detector's de output voltage is compared with a 1-volt reference, and the difference (error) voltage is amplified by a de am-plifier. The push-pull output current from the de amplifier passes through the drive coil, which is suspended in a magnetic field. The interaction between the coil current and the magnetic field moves the wiper arm to reduce the error voltage to zero (null condition), and also positions the pen mounted on the coil assembly. Since potentiometer output is a constant 1 mv at null, the attenuation of the input potentiometer is directly proportional to the level of the input signal. By suitable shaping of the potentiometer, a scale linear in db is achieved. A feedback voltage, proportional to velocity, is subtracted from the error signal at the input to the de amplifier. This voltage provides damping so that the drive coil will not oscillate, and varies the servo bandwidth and maximum writing speed. The moving drive coil, then, responds to changes in the input level of a voltage applied to the recorder, and a pen fastened to the coil will trace out these changes on paper. For instance, if the input level increases by 10 db, the drive coil (along with the pen) moves the potentiometer wiper arm to restore the voltage in the arm to about 1 mv. Since the potentiometer is logarithmic, the wiper arm moves downscale 10 db, in – dicating a level change of 10 b directly on the chart paper. The Type 1521-B responds to the rms level of the ac waveform, and is less influenced by the waveshape of the input signal than it would be with a peak- or average-response detector. The rms response is particularly useful in noise measurements, where peak response would cause large errors in measurement. When used as a level recorder, the Type 1521-B has an input impedance of 10,000 ohms. This impedance can be increased, at a sacrifice of sensitivity, by the addition of a series resistor at the input. When the recorder is used as a dc recorder, the ac amplifier is bypassed and a linear potentiometer is used. The input impedance of the de recorder is 1000 ohms. 1.3 WRITING SPEED. The maximum writing speed (saturated pen velocity) is 20 in./sec for 0.1 inch over-shoot. The corresponding servo bandwidth for small-amplitude variations is from de to 10 cps. This bandwidth determines the ability of the recorder to follow changes in input level, and is net related to the frequency of the ac input signals. With a fast writing speed, the pen should follow any level variations normally encountered in level recording. Such fast speed can, however, present too much information, as, for instance, in a loudspeaker frequency-response curve recorded in a small reverberant room. Filtering can be added to smooth the rapid level fluctuations to obtain an averaged response of the loudspeaker. This filtering is accomplished by reduction of the servo bandwidth and maximum writing speed. 1.4 PAPER SPEED. The paper is driven by a synchronous motor, at speeds of 2.5, 7.5, 25, or 75 in./min. (Two alternate motors are available: a slow-speed motor for speeds from 2.5 to 75 in./hr and a medium-speed motor for speeds from 0.5 to 15 in./min.) The direction of paper drive can be reversed. Tested for basic function. Unit turns on, works in forest and reverse, and light turns on. Will be shipped promptly and professionally. Enjoy!
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