Wavetek 132 User Manual

MODEL 132
VCG/NOISE
GENERATOR
@ -
1981 - Wavetek
THIS DOCUMENT CONTAINS INFORMATION PROPRIETARY TO WAVETEK AND IS SOLELY FOR INSTRUMENT OPERATION AND MAINTENANCE. THE INFORMATION IN THIS DOCUMENT MAY
NOT BE DUPLICATED IN ANY MANNER WITHOUT THE PRIOR
APPROVAL IN WRITING OF WAVETEK.
SAN DIEGO
9045 Balboa Ave., San Diego, CA 92123
P. 0 Box 651,
Tel 7141279-2200 TWX 91 O-335-2007
San
Diego, Calif. 92112
Manual Revision: 10181
Instrument Release: U-l 0180
CONTENTS
Section One
Section Two
Section Three CIRCUIT DESCRIPTION
Section Four
Section Five DATA PACKAGE
SPECIFICATIONS
Physical and Electrical Specifications
OPERATION
Inspection Operating Controls Operation
General Description
MAINTENANCE
Introduction
Recommended Test Equipment Checkout and Calibration Troubleshooting
Introduction
Recommended Spare Parts List
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1
3 4 7
11
13 13 13 16
21
21
SCOPE OF MANUAL
This manual contains instructions for operating, test- The Model 132 is a source of analog and digital
ing, and maintaining the Wavetek Model 132 Noise Generator. The Wavetek product-improvement waveforms. Noise outputs, or waveforms can program ensures that the latest electronic developments are incorporated into the Wavetek instruments by the brated signal-to-noise and noise-to-signal ratios to addition of circuit and component changes as rapidly as development and testing permit. Due to the time re­quired to document and print this manual, it is not always possible to incorporate these changes into the manual. In this case, data will be found on engineering change sheets at the back of the manual. If there are no change sheets, the manual is correct as printed.
VCG/
SCOPE OF EQUIPMENT
as well as a precision source of sine, triangle and
individually, or combined to provide selectable, cali-
+60
dB. Waveforms can be varied over a frequency range of 0.2 Hz to 2 MHz. Length of the digital se­quence is selectable to a maximum of Clock rates, variable from 160 Hz through 1.6 MHz, give added versatility to the noise generator. These clock rates allow selectable noise bandwidths variable from 10 Hz to 100 kHz.
noise,
square
be used
220 - 1 bits.
SAFETY
Thi s
instrument i s
ss earth grou n
bYPa
BEFORE PLUGGING IN the instrument, comply with installation instructions.
wire dfor earth g r ounding via the ding w
ith two wir eextension cords,
facil i ty powe r
adapter setc.
plug
wiring.
Do not
MAINT
ENANCE
shoul d
be don e
WARNING operations.
CAUTION notes call attention to possible equipment damage in subsequent operations.
may requir epower on w i th th e
only by qualif
notes call attention t o
ied
personne l aware
possible injury or death hazards i n
instrumen t
of the elect
cover s
rica l
h a
removed.
zards.
subsequent
SECTIO N
1
SPECIFICATIONS
VERSATILITY
Waveforms Sine and analog noise
Frequency Range of Signal
0.2 Hz to 2 MHz in 6 decade ranges
Ranges x10 Xl00 X1K X10K XIOOK X1M
Function Outputs Sine with 60 dB step attenuator in 10
lapping calibrated vernier;
20 V p-p into open circuit and 10 V p-p into
load from
Sync Output
Greater than 1 V p-p square wave into open circuit at
6OOa
DC Offset
*5
V offset
from rear panel; peak amplitude limited by the dynam-
ic range of the amplifier output.
VCG
Frequency of the generator may be dc-programmed, or ac-modulated by external 0 to control circuitry is capable of 1000: 1 deviation. The
VCG amplifier has a 100 kHz bandwidth and a slew
rate of 0.1
result of the sum of the dial setting and the externally applied voltage.
Stability Short term
Long term Percentages apply to amplitude, frequency, and dc offset.
square
YJ
,
M.r
\
,
square f-l~
5Oa
source impedance.
output impedance.
(22.5
V offset into
-
Voltage Controlled Generator
V&s.
The instantaneous frequency is the
triangle
I-I
,
or
digital noise
,
,
and triangle
5Oa
dB
output impedance,
5Ofi
*5
+0.05%
+0.25%
waveforms
2/
l-u--L
0.2 Hz to 20 Hz 2 Hz to 200 Hz 20 Hz to 2 kHz
200 Hz to 20 kHz 2 kHz to 200 kHz
20 kHz to 2 MHz
2/
selectable,
steps and over-
5Oa
load) controlled
V signal. Voltage
for 10 minutes
for 24 hours
HORIZONTAL PRECISION
Dial Accuracy
*2%
of full scale, 1 Hz to 2 MHz
Frequency Vernier
One
turn equals 1% of full scale.
Time Symmetry
*I
% through XIOOK range
VERTICAL PRECISION
Sine Wave Frequency Response Amplitude change with frequency less than:
dB
from 0.2 Hz to 200 kHz
0.1 dB
from 0.2 Hz to 2 MHz
0.5
PURITY
Sine Wave Distortion
Less than:
0.5% on X10, X100,
1.0% on XIOOK range All harmonics 30
Square Wave Rise and Fall Time Less than 50 ns terminated into
NOISE
outputs Pseudo-random analog or digital noise with a maximum of 20 V p-p excursion (open circuit) with 60 attenuator in 10
vernier.
Sequence Lengths Push buttons on the front panel provide a sequence
length of
dB steps and overlapping calibrated
21° -
1, 215 - 1, or 220 - 1.
X1K, X10K
dB
down on Xl MHz range
ranges
SOQ
dB
step
1
lock
Noise C Switchselectable noise
Clock Frequency
OPERATIONAL MODES
FUNC form atthe main
S/N Signal-to-Noise operation adds noise to a selected signal of constant amplitude. The signal-to-noise ratio is variable from 0 to
N/S Noise-to-Signal operation adds a selected signal to a constant amplitude noise. The noise-to-signal ratio is variable from 0 to
FM Frequency Modulation - Provides random modu­lation of the frequency of the generator. The S/N
(dB)
quency deviation.
Frequency
160 Hz
1.6 kHz 16 kHz
160 kHz
1.6 MHz
Function
ratio control also controls the amount of fre-
frequencies
Mode
-
Provides the selected
output.
+60
dB.
+60
dB.
NOTE
are listed
Analog Noise
Bandwidth
10 Hz 100 Hz
1 kHz 10 kHz 100 kHz
-
N/S
ENVIRONMENTAL
Temperature All specifications listed, except stability, are for
*5’C.
For operation from
specifications by factor of 2.
MECHANICAL
Dimensions
8%
incheswide,5% incheshigh,
Weight 8 Ibs net,
Power
105Vto125V
Less than 15 watts.
12 Ibs shipping
or
200
All
specifications apply for frequencies
obtained when dial is between 0.
2.0 and at 10 V p-p in to a 50 ohm load.
V
to
NOTE
O°C
250
to
V,
55’C,
derate all
11%
inches deep
50Hzto400Hz.
1
and
25’C
When noise is added to the signal output, specifications apply up to 200 the square wave rise time is dera ted by
a factor of 10. In the clock range of
1.6 MHz, the maximum calibrated
to-noise ratio is 30
dB
kHz
and
signal-
It is possible to stop the generator from oscillating by applying a negative VCG
voltage when the dial is already set at minimum frequency. VCG inputs up to 30 V will not permanently damage the
ins trumen t.
INSPECTION
The following procedures should be performed to as­sure the user that the instrument has arrived at its destination in satisfactory operating condition. Com­plete calibration and checkout instructions are pro­vided in Section 4 to determine compliance with elec­trical specifications.
Checking Visually
After carefully unpacking the instrument, visually in­spect the external parts for damage to knobs, dials,
indicators, surface areas, etc. If damage is discovered, file a claim with the carrier who transported the in­strument. Retain the shipping container and packing material for use in case reshipment is required.
Checking Electrically
NOTE
lnstrumen ts are normally shipped con­nected for 115 V power unless 230 V power is ordered. Refer to the end of this section for conversion instructions.
The steps in this paragraph provide a quick checkout of the instrument operation. If electrical deficiencies exist, refer to the WARRANTY in the front of this
manual. The following test equipment is recommended
for performing this electrical inspection:
Name Required
Oscilloscope
Plug-l n Plug-l
n
Counter-Timer
1.
Turn
FREQ (This connects ac power to the unit and estab­lishes the frequency multiplier.)
HZ selector to the Xl K position.
Characteristics
To 30 MHz
Dual channel Peak mV measuring capability To 2 MHz with 5-digit resolution
SECTION
OPERATION
2.
Depress MODE - FUNC push button. Connect oscilloscope to the
3. tor with a
Set frequency dial to the 1.0 mark and
4. VERNIER to CAL position.
Set function selector to the
5.
Set OUTPUT
6.
NIER tion (no attenuation). Check for 1 kHz sine wave with at least 10 V
7. p-p amplitude on oscilloscope.
Select
8. and check for 10 V p-p amplitude on oscil­loscope.
9.
Turn frequency dial from maximum counter­clockwise (ccw) to maximum cw position and check for frequency change.
10.
Step OUTPUT
its range and verify attenuation at each step.
11.
Rotate OUTPUT VERNIER maximum cw to maximum ccw position and check for decreasing amplitude. Rotate
12. frequency change.
13.
Set FREQ VERNIER control at maximum cw and frequency dial at 0.02. Set frequency to
20 Hz with counter. Connect a 0 to +5 Vdc input to the VCG IN connector. Slowly increase
voltage input from 0 to +5 V and check that frequency of output waveform increases from approximately 20 Hz to 2 kHz.
14.
Depress SEQUENCE LENGTH button.
Set NOISE FREQ HZ selector to the
15. position and vernier control fully cw.
Connect a BNC cable from the NOISE SYNC
16.
connector (rear panel) to the external trigger
input of the oscilloscope. Rotate the function selector to
17.
to assure oscilloscope displays digital noise. Check to assure SEQUENCE LENGTH push
18. buttons vary the bits in the sequence length.
19.
Step NOISE FREQ HZ selector through its range and check to assure clock frequency changes. (Use NOISE CLOCK connector on rear panel.)
5Oa
terminator.
ATTEN
(dB)
to maximum clockwise
2/
and s with function selector
ATTEN (dB)
FREQ
VERNIER control and check for
5Ofi
(dB) and OUTPUT VER-
selector through
(dB)
m
OUT connec-
FREQ
yj
position.
(cw)
posi-
control from
2l* - 1
push
16K/160K
and check
l
3
Verify that NOISE FREQ HZ vernier control
20. provides approximately IO: 1 variation in clock frequency at the NOISE CLOCK connector (rear panel). Rotate function selector to
21. check to assure oscilloscope displays analog noise. Check to assure SEQUENCE LENGTH push
22. buttons vary the length of the sequence of analog noise. (Use NOISE SYNC connector on rear panel.) Connect oscilloscope external trigger cable to
23.
FUNCTION SYNC connector (rear panel) and set function selector to Set S/N - N/S
24. and vernier control fully ccw. Depress MODE
25. to assure square waveforms are frequency modu­lated by analog noise. Release MODE
26. MODE square wave and analog noise are mixed.
27.
Depress MODE
-
N/S
S/N position, checking for reduction in signal level.
28.
Verify that the S/N ates the signal approximately 10 each step of the S/N
OPERATING CONTROLS
The operating controls and electrical connections for the Model 132 are shown in Figures of the following paragraph numbers corresponds to a number appearing in Figure 2-1, front panel, or Figure 2-2, rear panel. The listing below discusses each control and its function.
FRONT PANEL
1.
FREQ HZ/PWR OFF - Selects one of six dec­ade ranges from X 10 to frequency. quency dial setting (3) gives the output frequen­cy of the generator. Extreme ccw rotation will place the switch in the PWR OFF position, turn­ing off all power to the function and noise generators. This control has no affect on the noise frequency.
FREQ VERNIER - Allows precision electronic
2. control of the signal output frequency. A full turn of the control is approximately equal to 1%
(dB)
selector to -10 position
-
FM push button and check
-
FM push button and depress
-
S/N push button. Check to assure
-
N/S push button and rotate
(dB)
selector ccw through each
This value multiplied by the fre-
/‘=ltif’
I
_I
position.
-I
-
N/S
(dB)
vernier attenu-
-
N/S (dB) selector.
2-I
X1M
for generator
position and
dB
between
and 2-2. Each
of full scale. When turned to the full cw position (CAL), settings on the main dial will be cali­brated.
-
Frequency Dial signal output frequency.
Frequency Index setting (3) by reading the dial position opposite the scribe line on the frequency index. The in­dex is illuminated when power to the unit is on.
Function Selector or noise output. To select waveforms, or J/-IL_ or push button (7) must be depressed.
OUTPUT VERNIER (dB) control of 0 through -20 ATTEN (dB) justment for the output signal and will attenuate signal and noise.
MODE
FUNC - When depressed, this control allows the selected waveform or noise, as determined by the position of the function selector (5), to
be present at the This push button must also be in the depressed position for the frequency modulation mode
(10).
S/N - Depressing this push button allows a calibrated amount of analog noise to be added to the selected signal, either
r
wave. The signal-to-noise ratio (S/N) is determined by the S/N control (13). When in this mode, the peak to peak signal amplitude is reduced internally, since adding noise to the signal would overdrive the output amplifier.
-
Depressing this push button allows a
N/S
calibrated amount of the selected signal, either
i
L
Ad
analog noise. The noise-to-signal ratio (N/S) is determined by the S/N control (13). When in this mode, the peak to peak signal amplitude is reduced internally, since adding the signal to the noise would overdrive the output amplifier.
Allows coarse control of the
-
Indicates the frequency dial
-
Selects the desired function
‘1,
,
/‘-‘iv‘
noise, the FUNC
-
Provides vernier
dB
from the OUTPUT
setting (12). This is the fine ad-
5Oa
OUT connector (11).
-
N/S (dB) attenuator
, or
wave, to be added to the
‘L
-
N/S (dB) attenuator
i*\./
2/
,
, or
2/
I,
, or
4
7
I
WAVETEK
Figure 2-l. Operating Controls, Front Panel
10.
FM - Depressing this push button along with the FUNC push button (7) allows the selected signal, either
/‘\
u
, v
A
,
or
z
pseudo-randomly frequency modulated, or jit­tered. The modulating signal is provided by pseudo-random analog noise, and the S/N N/S
(dB)
controls frequency deviation. The
bandwidth of the modulating signal is controlled
FREQ
by the NOISE
HZ selector (15) and
vernier (16).
11.
5Oa
OUT - Provides the selected generator out­put function. The generator may operate into an open circuit providing 20 V peak to peak maxi-
5Oa
mum, or into a
load providing a
to peak output.
12.
OUTPUT
ATTEN
(dB) - Attenuates the output
(both signal and noise) from 0
dB
six calibrated 10
steps according to the fol-
lowing table:
wave, to be
10
dB
to -60 dB in
V peak
, ,,
MO~EI..
VCG!NQISE
Step
132
GENERATOR
Output peak to peak into
Attenuator
Position
Maximum Minimum
Vernier Vernier*
fully cw
­dB
0
dB
-10
-20
dB dB
-30 dB
-40 dB
-50 dB
-60
10V
3V
IV 0.1 v
0.3 v 0.03 v
0.1 v
0.03 v 0.003 v
0.01 v 0.001 v
* The values in this table are approximate. The OUT-
(dB)
PUT VERNIER approximately 20
S/N
-
13.
N/S (dB) - I n
(6) will reduce the output
dB
in all cases, as shown.
the S/N
mode, this control
attenuatesthe analog noise from
dB
five calibrated 10
steps. The selectable signal
0.01 v
0 to
5Ofl
IV
0.3 v
-50 dB in
Load
5
amplitude remains constant, thus giving cali­brated 0 to -50
N/S
mode, the signal is attenuated with the
noise remaining unchanged, thus giving to-signal ratios from 0 to -50 this control are indicated in black numerals the front panel.
14.
15.
16.
17.
-
S/N fine adjustment of the S/N tenuator (13). This control is continuously vari­able over at least a 10 the coarse control total S/N or N/S ratio. Approximate values of attenuation are indicated in red numerals on the front panel.
NOISE FREQ HZ the clock frequency, or bandwidth for the digi­tal, or analog noise, respectively. When using the digital noise function, clock frequencies from
160 Hz through 1.6 MHz (indicated in black
numerals and letters on the front panel) are available. When using analog noise or the S/N, N/S modes, the bandwidth of the analog noise may be selected from 10 Hz to 100 kHz (in­dicated in red numerals and letters on the front panel). In the FM mode, this control establishes the bandwidth of the analog noise used for fre­quency modulation. There are four detent posi­tions with an overlapping vernier control (16). With the vernier in the full cw position, the clock frequency, or bandwidth, is equal to the value printed to the right of the detent mark.
NOISE FREQ HZ Vernier
number 15, this control provides a continuous,
fine control between the detent positions of
thecoarse control. When in the full cw position,
the clock frequency, or bandwidth, is equal to
the value appearing at the right of the detent
mark. As the knob is rotated ccw, the clock frequency, or bandwidth, is decreased. In the full ccw position,the actual value will be at
least 10: 1 (and as much as 100: the value to the right of the detent mark.
VCG IN age control of function generator frequency. Up
1000:1
to A positive voltage increases frequency and a negative voltage decreases frequency. Refer to “Operation as a Voltage Controlled Generator.”
dB
signal-to-noise ratios. In the
dB.
N/S (dB) Vernier - Allows a calibrated
-
N/S
dB
range. When added to
(13),
this amount equals the
-
This range control selects
-
As mentioned in
-
This connector
frequency change may be obtained.
allows
noise-
The steps for
(dB)
1)
lower than
external volt-
on
step at-
SEQUENCE LENGTH
-
18.
19.
20.
REAR PANEL
21.
22.
23.
24.
1 - Depressing this push button will
21°
provide 1,023 counts of the selected clock fre­quency,
NOISE generation of a digital, or analog noise pattern. At the end of each sequence, the pattern is automatically repeated.
215
provide 32,767 counts of the selected clock frequency, NOISE generation of a digital, or analog noise pattern. At the end of each sequence, the pattern is automatically repeated.
220 -
provide frequency, NOISE FREQ HZ controls (15 and generation of a digital, or analog noise pattern. At the end of each sequence, the pattern is automatically repeated.
DC OFFSET base line above or below ground
into vertical symmetry. Peak amplitude is limited by the dynamic range of the amplifier output.
FUNCTION SYNC synchronizing signal output at the same fre­quency of the main generator; that is, at the same frequency as the sine, triangle or square wave. The amplitude is greater than 1 V peak to peak square wave into open circuit at output impedance.
NOISE SYNC chronizing output signal for monitoring the dig-
ital or analog noise. A sync signal is generated at the beginning of each repetitive cycle for the selected sequence length of digital or analog noise.
NOISE CLOCK external output of the basic clock frequency used to generate the digital sequence and analog noise.
or bandwidth, determined by the
FREQ
HZ controls (15 and
-
1 - Depressing this push button will
or bandwidth, determined by the
FREQ
HZ controls (15 and 16), for
1
-
Depressing this push button will
1,048,575
5Oa
load). The OFF position gives normal
counts of the selected clock
or bandwidth, determined by the
-
This control adjusts the *5 V
-
This connector provides a
-
This connector provides a syn-
-
This connector provides an
(k2.5
16),
for
16),
for
V offset
6OOa
_
SAN OILGQ
l
CALfFORNfA
PAT. NO X268.738 OTHER
PAT
PEND.
MAN fp1 tt.S,A.
115
23OVAC 7htAMP
Figure 2-2. Operating Controls, Rear Panel
VAC
114
AMP
OPERATION
No preparation for operation is required beyond com­pletion of the initial installation previously stated in this section. It is recommended that a one-half hour warm-up period be allowed for the associated equip­ment to reach a stabilized operating temperature and for the Model 132 to attain stated accuracies.
Operation as a Function Generator
1.
Terminate
5Oa
OUT connector with
5Oa *I%,
2 watt termination. Select the desired waveform by setting function
2. selector to
\
, 2/
,
or
?_1
,
Set frequency dial and FREQ HZ range multi­plier for desired output frequency.
-
Depress MODE
FUNC push button. Select output signal amplitude by setting OUT­PUT
ATTEN (dB)
control to appropriate attenu­ation position and fine adjusting signal to de­sired amplitude with OUTPUT VERNIER
(dB) control. A positive or negative dc offset may be applied to the waveform by setting the DC OFFSET
(Rear Panel) to the desired level. The peak
k5.0
signal value plus the offset cannot exceed
V
into 50 ohms.
Operation as a Voltage Controiled Generator
The VCG input connector can be used to externally control the frequency of the generator. If a positive voltage is applied to the VCG input terminal, the frequency will increase from the dial setting, A nega­tive voltage will cause the frequency to decrease from
the dial setting. The VCG range of the Model 132 is
1000:1.
Terminate 5Oct OUT connector with 50 ohm
1.
+l%,
2 watt termination.
Select the desired waveform by setting function
2. selector to Set FREQ HZ selector to desired multiplier.
3.
4.
Connect external voltage source (dc program-
$
,
/YJ ,
or
‘1~
.
ming or wideband ac signal) to VCG IN con­nector.
NOTE
%
VCG input requires 0 to
volts for operation over full-scale range, but can withstand many times maximum input.
5.
Set frequency dial as follows: a.
For frequency modulation with ac input, set dial for center frequency.
7
b. For increasing frequency sweep with positive
dc input, set dial to lower frequency limit.
c. For decreasing frequency sweep with nega-
tive dc input, set dial to upper frequency limit.
To sweep the audio range from 20 Hz to 20 kHz,
6. set the controls to 20 Hz as follows: a. Set the main dial to 0.02. b. Set the frequency vernier to the full ccw
position.
c. Introduce a 0 to +5 V ramp into the VCG
inputconnector.
The maximum frequency which may be obtained, when using the VCG input, is the range multiplier times the value at the top of the dial (2.0). The minimum fre­quency is the range multiplier times the value at the bottom of the dial (0.002 be in ccw position). Verify this using the nomograph
in Figure 2-3.
MAIN DIAL
SETTING
A
Figure 2-3 - VCG Voltage-to-Frequency Nomograph
-
frequency vernier must
VCG IN
VOLTAGE
B
5Ofi
OUT
FREQUENCY
.4
1.6
1.8
2.0
C
.02
.2
.6
.8
In example 1, the dial is set at 1.0 and 0 voltage is
applied to the VCG input. Extend a straight line from
1.0 (dial setting) through 0 voltage (VCG voltage) and obtain a dial frequency of 1.0. For the total output frequency, multiply the range by 1 with the same dial setting. Example 2 shows the results of using a ramp
+2.5
from -1 volt to results in a swept output from 0.6 to 2.0 on the dial.
Remember to multiply the dial times the range.
Operation as a Calibrated Signal-to-Noise Source
1.
Select the desired signal waveform by setting function selector to
2.
Set frequency dial and FREQ HZ range multi-
plier for desired signal output frequency.
3.
Depress MODE - S/N push button.
4.
Select noise bandwidth by setting NOISE FREQ
HZ control to desired range and fine adjusting
bandwidth by turning the noise frequency Hz vernier control. Select desired SEQUENCE LENGTH by de-
5. pressing appropriate push button.
Select signal-to-noise ratio by setting S/N - N/S
6. (dB) control to appropriate attenuation position
and fine adjusting attenuation to desired value with S/N
7.
Select total output amplitude by setting OUT-
ATTEN (dB)
PUT uation position and fine adjusting signal to de­sired amplitude with OUTPUT VERNIER (dB) control.
Operation as a Calibrated Noise-to-Signal Source
Select the desired signal waveform by setting
1.
function selector to
2.
Set frequency dial and FREQ HZ range multi­plier for desired signal output frequency.
3.
Depress MODE
4.
Select noise bandwidth by setting NOISE FREQ HZ control to desired range and fine adjusting bandwidth by turning the noise frequency Hz vernier control.
5.
Select desired SEQUENCE LENGTH by depres­sing appropriate push button. Select noise-to-signal ratio by setting S/N
6. (dB) control to appropriate attenuation position and fine adjusting attenuation to desired value with S/N
Select total output amplitude by setting OUT-
7.
ATTEN
PUT uation position and fine adjusting signal to
volts for the VCG voltage. This
\
,
2/
, or
-
N/S vernier control.
control to appropriate atten-
Q
,
2/
, or
-
N/S push button.
-
N/S vernier control.
(dB) control to appropriate atten-
-
z
z
N/S
de-
.
,
sired amplitude with OUTPUT VERNIER (dB) control.
Operation as a Random FM Source
Before using the generator as a random FM source, please note the following.
Select desired SEQUENCE LENGTH by depres-
4. sing appropriate push button.
5.
Select noise amplitude by setting OUTPUT ATTEN
(dB) control to appropriate attenuation
position and fine adjusting noise to desired
amplitude with OUTPUT VERNIER (dB) con-
trol.
The frequency of the generator is being varied or
modulated by a changing voltage in the same way as described in “Operation as a Voltage Controlled Gen­erator.”However, instead of using a dc ramp, or ac signal, a random analog voltage is used. When the FM push button is depressed, the analog noise is injected internally into the VCG circuit; therefore, the modu­lation is created by random noise. The S/N knob controls the maximum amount of frequency deviation, since it controls the amplitude of the noise. Bandwidth of the FM signal is controlled by the NOISE FREQ HZ control. Using the generator in the FM mode may be accomplished as follows:
1.
Select the desired signal waveform by setting function selector to
2.
Set frequency dial and FREQ HZ range multi­plier for desired center output frequency. Depress MODE
3. Select the bandwidth by setting NOISE FREQ
4. HZ control to desired range and fine adjusting frequency by turning the noise frequency Hz vernier control.
5.
Select desired SEQUENCE LENGTH by depres­sing appropriate push button.
Select signal frequency deviation by setting
6.
7.
-
N/S
(dB)
S/N
tion position and fine adjusting attenuation to desired deviation with S/N Select output signal amplitude by setting OUT-
ATTEN
PUT
uation position and fine adjusting signal to de­sired amplitude with OUTPUT VERNIER control.
control to appropriate attenua-
(dB) control to appropriate atten-
‘b
, 2/ , or
-
FUNC and FM push buttons.
-
N/S vernier control.
-
N/S
(dB)
‘1J .
(dB)
Connect Signal and Chassis Grounds
The instrument is shipped from the factory with the signal ground floating above chassis ground, unless otherwise specified. A common signal/chassis ground can be obtained as follows:
1.
Remove power cord. Loosen two captive thumb screws on rear panel
2. and remove panel.
3.
Solder a jumper wire between the ground lugs
(green wires) of the SYNC OUT connector and
the power connector (Figure 2-4).
ADD JUMPER
A/
POWER TRANSFORMER OUT T1
POWER CONNECTOR
SYNC
CONNECTOR J3
J1
BRACKET
DC OFFSET R
172/SW4
Operation as a Digital or Analog Noise Source
1.
Set function selector to digital or analog noise position.
2.
Depress MODE Select clock frequency for digital or bandwidth
3. for analog noise by setting NOISE FREQ HZ control to desired range and fine adjusting fre­quency by turning the noise frequency Hz ver­nier control.
-
FUNC push button.
Converting Output Impedance to 600 Ohms
Unlessotherwise specified, this instrument was shipped with 50 ohm output impedance, but can be converted to 600 ohm output if needed. Place a
in series with the wire leading from the center tap of
the
Figure 2-2. Common Ground Connection Diagram
55Oa
resistor
5Ofi
OUT BNC and the attenuator control.
9
Converting to
instruments are shipped from the factory with the power transformer connected for unless ordered for 230-volt use. Converting a 115-volt unit for 230-volt operation is a simple matter.
1.
230-Volt
Remove power cord.
Line Power
1 15-volt
line power,
2.
Loosen two captive thumb screws on rear panel and remove panel. The conversion switch is located on the chassis.
3. Use a thin-bladed screwdriver to move the 115­230 switch to the 230 position.
4. of the same type.
Replace
1/4-ampere
fuse with a
1/8-ampere
fuse
10
SECTION
3
CIRCUIT DESCRIPTION
GENERAL DESCRIPTION
Refer to the block diagram of the Model 132 Noise Generator, Figure 3-l.
Basically, a square wave is applied to the input of an integrator composed of a wide-band differential dc
amplifier, integrating resistor and capacitor. Output
VCG/
VCG
VCG
Cl RCUIT
POWER
SUPPLIES
<
I
+5
v
+15 v
-15 v
I
DIGITAL
I
FILTER
I I
I I
HYSTERESIS
OUTPUT
SWITCH
.
+
CONVERTER
23
SINE
of the integrator is fed into the hysteresis switch. The hysteresis and output switches function like a Schmitt trigger with the limit points set at the form extremes, firing when the triangle wave reaches +1.25
volts and-1.25 volts. When firing occurs, the hysteresis and output switches are set, reversing the square wave fed into the integrator. Reversal of the square wave causes the triangle wave to reverse direc-
wave-
FUNC
)
SYNC
OUT
x
L
I
.
MODE
%
L
r
b b
SWITCHING
c
CIRCUIT
ATTENUATOR
9
4
t
I
--~-~---~---
-_-
Figure 3-l. Functional Block Diagram
.
NOISE
l
SYNC
b
NOISE
CLOCK
11
tion. The result is simultaneous generation of a square wave and triangle wave of the same frequency with the positive half cycle of the square wave coincident with the negative slope of the triangle wave.
The magnitude of the capacitor across the integrator and amplitude of the current into the integrator deter-
mine the frequency of oscillation. Capacitance across
the integrator is changed by rotating the frequency Hz
selector. Amplitude of the current into the integrator is determined by four parameters which are summed
(1)
in the VCG circuit: the frequency voltage, (4) the VCG analog voltage input and (5) the analog noise when in the FM mode.
The sine wave is produced by feeding the triangle wave into a shaping network composed of resistors and diodes. As the triangle wave voltage passes through zero, loading of the triangle wave is minimal and thus the slope is maximum.As the triangle voltage in­creases, diodes with current limiting resistors conduct and successively cause the slope of the output to be
reduced.
Since the diode break points are mathematically com-
puted and fitted to the true sine shape, the resultant waveform resembles a pure sine wave. Using a com­plementary pair of diodes on each break point, the circuitry is completely symmetrical about ground. The sine wave, produced by shaping, is considerably less
in amplitude than the triangle wave input and is thus amplified to be equal to the triangle wave.
hysteresis switch output, (2)
dial
voltage, (3) the frequency vernier
Either square, triangle, or sine waveforms can be se­lected as a signal from a digital filter. A clock oscillator of 160 Hz to
1.6 MHz range functions as a trigger source for the digital pseudo-random sequence generator (P RSG). Output of the PRSG is a random binary signal that can function as digital noise. The number of bits in each sequence can be selected by the SEQUENCE
LENGTH controls. Parallel data is fed from the PRSG to the digital-to-analog converter where the informa­tion is summed and filtered to provide a random analog noise signal.
The selected sine, triangle, square, analog noise, digital noise signal is routed to the mode control circuitry where one of the following modes of opera­tion is selected: Function tion (FM); signal-to-noise (S/N)
(N/S). I n the signal-to-noise and noise-to-signal modes, one signal is fed to the S/N attenuator and then mixed with the other signal in the S/N summing amplifier in a known
put of the mode switching circuit is coupled to the output amplifier. From the output amplifier the signal
is fed to the precision output attenuator and finally to a
All circuits, except for the hysteresis switch, output amplifier, and PRSG, operate from The hysteresis switch and power amplifier require
*6
PRSG requires a +5 V supply.
dB
5Ofl
output connector.
volts and
source.
The noise source is derived
(FUNC);
frequency modula
;
or noise-to-signal
ratio selected by the S/N attenuator. Out-
+I5
volt supplies.
*22
volts, respectively. Operation of the
or
12
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