Specifications

4
Specifications
DISPLAY
11 x 28 array of red light emitting diodes
27 channels on ISO 1/3 octave centers from 40 Hz
to 16 kHz plus one broad band channel
Either one dB or two dB steps for display range of
10 dB or 20 dB, plus over-range indication on each
channel
40 dB dynamic range via adjustment of attenuators
FILTERS
Two pole-pair bandpass response (see below)
Meets ANSI Sl.11-1971 Class II
Each channel individually converted and smoothed
Smoothing time constants selected to accommodate
statistics of pink noise.
Each channel trimmed for overall response of ±1dB
with pink noise in from 40 Hz to 16 kHz.
FRONT END
Microphone input
2000 ohms to accommodate standard 200
ohm dynamic microphone
Transformer coupled
Standard XLR connector
Input range from dynamic microphone: 40 dB-SPL to
110 dB-SPL (2.6 uVrms to 2.6 mVrms)
Calibrated for microphone with sensitivity of -56 dBM
or 0.13 mV/microbar (1 microbar = 74 dB-SPL)
Internal gain adjustment for other sensitivities
Line level input: 20 kilohms input impedance; input
range of 2.6 mVrms to 2.6 Vrms; standard phone
jack
Input attenuator: 10 dB steps from 40 dB to 90 dB
DISPLAY VERNIER
2 dB steps
Allows centering of 1/3 octave channels to
accommodate approximately 16 dB difference in
energy between 1/3 octave channel and broad band
channel
NOISE GENERATOR
Output level may be selected for 20 mVrms or 0.5
Vrms maximum with front panel switch
Level varied via front panel vernier
Low level suitable for driving microphone input
High level suitable for driving impedances of 5
kilohms or greater
Transformer coupled
XLR connector
Noise generated by digital shift register technique
with word length of approximately 32 megabits at a
50 kHz clock rate
MISCELLANEOUS
Rear panel terminal strip
Line input connection
Scan output for remote oscilloscope display
Noise output
POWER REQUIREMENTS
115/230 Vac, 50 Hz to 400 Hz, 15 watts
MECHANICAL
3-1/2 inch by 19 inch standard rack mount
7
inches required behind panel
Supplied in wood grained formica covered carrying
case with space in lid for accessories
Can be supplied without case and with dust shrouds
for rack mounting
OPTIONAL MICROPHONE MULTIPLEXER
Accepts inputs from three dynamic microphones
Gain of each input independently adjustable
Low impedance, high level output for driving line
level input of Model 140 via unshielded pair
Self-contained: uses two 9 volt transistor batteries
Scan rate carefully selected to minimize "aliasing"
effects
Carried in lid of Model 140 carrying case