Brüel & Kjær 1026 User guide

Instructions
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Exciter Control
Type 1026
An all electronic , solid state
instrument generating sinusoidal
or
narrow band random outputs for
controlling vibration exciters in
a frequency range 1 Hz
to 10,000 Hz.
Built-in are two independent vibration
meters (with slave filters),
an
80 dB dynamic range compressor
amplifier, interlocking and trip
facilities.

EXCITER CONTROL TYPE 1026
February 1972

CONTENTS
1. INTRODUCTION ...................................... 7
2. CONTROLS .......................................... 9
2.1. Front Panel .................................. 9
Generator Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Vibration Meter Section . . . . . . . . . . . . . . . . . . . . . . . 13
Compressor Section
.......................... 16
2.2. Rear
Panel ................................. 17
Generator Section
............................ 18
Vibration Meter Section . . . . . . . . . . . . . . . . . . . . . . . 25
Compressor Section
.......................... 30
3. OPERATION ........................................ 32
3.1. Preliminary ................................. 32
Mounting
.................................. 32
Initial Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2. Operation
as a Vibration Meter . . . . . . . . . . . . . . . . . . 32
Mounting the Accelerometer . . . . . . . . . . . . . . . . . . .
33
Preamplifier ................................ 34
Vibration Meter (Mode and Level) ............... 34
Meter Rectifier Selection ...................... 36
Effective Averaging
Time ...................... 36
Set-up Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Summary
.................................. 37
3.3. Operation
as a Signal Generator ................. 37
With no Compressor Loop . . . . . . . . . . . . . . . . . . . . . 38
With Compressor Loop controlling the
Output Voltage .............................. 39
3.4. Operation
as a Vibration Exciter Control -
Sinusoidal Output ............................ 40
Generator Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Vibration Meter Section ....................... 41
Compressor Section . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Operation .................................. 43
Summary .................................. 45
3.5. Operation
as a Vibration Exciter Control-
Narrow Band Random ........................ 47
Generator Section
................... , ........ 47
Vibration Meter Section ....................... 48
Compressor Section . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Operation
.................................. 51
Summary .................................. 52
3.6. Sweep Control
.............................. 55
Output with swept frequency ................... 55
Summary .................................. 58
4. DESCRIPTION ....................................... 60
4.1. High Frequency Sources ....................... 62
1 - 2
MHz Oscillator ......................... 62
1.2- 1 MHz Oscillator ........................ 62
Narrow Band Random ........................ 62
4.2. Main Output ................................ 63
4.3. Frequency Readouts .......................... 64
Digital Outputs .............................. 64
Analogue Readout ........................... 65
DC o::f .................................... 65
DC ex: log f ......................... : ........ 65
4.4. Tuning Outputs ....... . ..................... 65
1.2 MHz and 1.2- 1 MHz ..................... 65
60 kHz and 60 - 50 kHz . . . . . . . . . . . . . . . . . . . . . . 65
100kHz and 100- 110kHz ................... 66
Constant Level Outputs ....................... 66
4.5. Sweep Control .............................. 66
4.6. Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Compressor Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Compressor
Control . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.7. Safety Limits and Interlock .................... 71
Safety Limits ............................... 71
Interlock ................................... 73
4.8. Vibration Meters ............................. 73
Attenuator and Mode ......................... 74
Dynamic Filter .............................. 75
Slave Filter ................................. 75
Meter Rectifiers
............................. 77

5. USE WITH LEVEL RECORDERS ........................ 78
5.1. Level Recorder Type 2305 ..................... 78
Synchronisation ............................. 78
Recording .................................. 79
5.2. Level Recorder Type 2307 ..................... 81
Synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Recording .................................. 81
6. PROGRAMMING SYSTEMS ............................ 84
6.1. Possible Combinations ........................ 84
6.2. Single Cross-Over Specifications
................. 85
6.3.
Multiple Cross-Over Specifications (Two Modes) .... 86
Interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
88
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
6.4.
Multiple Cross-Over Specifications (Three Modes) ... 91
7. REMOTE CONTROL .................................. 92
7.1. "Start", "Stop", "Reverse" of Frequency Scan ..... 92
7.2. External Voltage Controlled Sweep .............. 92
7.3. Phase Control of Output Voltage ................ 92
7.4. Compressor ................................. 93
External AC Compressor Control Signal ........... 93
External, Unsmoothed DC Compressor Control Signal 94
External, Smoothed DC Compressor Control Signal .. 95
7.5. Protection Circuitry .......................... 95
Remotely set to "Stand By" .................. ; . 95
Interlock Inhibited ........................... 95
Safety Limits Inhibited ........................ 95
8. MASTER-SLAVE SYSTEM ............................. 97
8. · 1. Interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
8.2. Setting
Up and Operation ..................... 101
8.3. Shut Down ................................ 101

9. ANALOGUE AND DIGITAL OUTPUTS .................. 102
9.1. Analogue Outputs ........................... 102
DC
cx:f •..........••..•........••.....•... 102
DC
ex: log f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Constant Level Outputs . . . . . . . . . . . . . . . . . . . . . . 102
9.2. Digital Outputs ............................. 103
Digital Coded Frequency
Output ............... 103
Bandwidth Control .......................... 104
10. APPENDIX ......................................... 106
11. SPECIFICATIONS ................................... 108
11. 1. Generator Section . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
11.2. Vibration Meter Section . . . . . . . . . . . . . . . . . . . . . . 111
11.3. Compressor Section . . . . . . . . . . . . . . . . . . . . . . . . . 112
11.4. General
................................... 113

1. INTRODUCTION
The Exciter Control incorporates a signal generator (sinusoidal and
narrow band random), a compressor amplifier, and two vibration me ters in
the same instrument. There is also full function interlocking and safety limit
circuitry.
The sinusoidal generator is of high stability, low distortion, and wide
range.
The output is derived by mixing together the outputs from a fixed
and a variable oscillator working in the high frequency range. The variable
oscillator
is voltage controlled. Digital and analogue readouts are provided.
This mixing process gives a capability down to 1 Hz and up to 10.000 Hz in
a single range. Manual or automatic sweep is provided. Automatic sweeping
can be linear or logarithmic.
Four bandwidths of Rayleigh distributed
narrow band random noise are also available. The centre frequency of the
band is as indicated in the readouts and full sweep capability is retained.
The compressor amplifier has a dynamic range of 80 dB and a pro-
grammable compressor speed. The compressor speed can be set to be
continuously variable with frequency thus optimizing the stability and
distortion conditions. The signal supplied to the compressor speed circuitry
can be selected to be wide band RMS rectified, wide band average rectified
or narrow band average rectified. Internal slave filters can be switched
into the vibration meters. This gives considerable assistance when working
with poor signal to noise ratio signals in a feedback loop; the slave filters
then extract the fundamental from the noise components.
Two independent vibration meter channels are fitted, either of which can
be used as control channel. Separate meters are provided for level readout,
and the signal supplied to the meter can be selected as for the compressor
signal. A comparator can be switched into circuit so that the larger of the
two vibration meter channel signals can be selected as control signal, thus
preventing overtesting or providing a built-in cross-over.
Full interlocking between the various controls is included. In the event of
a critical switch being moved during a test the Exciter Control is electroni-
cally switched to "Stand By", i.e. full compression is applied.
7

To provide full protection for the test specimen or the shaker the Exciter
Control has built-in pre-selectable safety limits. If the variation of level on
the shaker table exceeds ±1, 3 or 6 dB the trip circuitry of the 1026 is
initiated. This also covers for possible loss of feedback- as in the case of an
accelerometer cable breaking.
The
test specification levels, sweep speeds, sweep lim its, etc. can be set
up prior to the test. The compressor is designed to reduce the loop com-
pression sufficiently slowly
at the beginning of a test to allow the Exciter
Control to increase the test level automatically from the stand-by condition
to the full pre-set level, thus simplifying the switch-on procedure.
The
1026 can be used with the Level Recorder Type 2305. No
synchronization
is needed because of the continuously variable, and
accurate, sweep speeds. These can be arranged
to match the paper speeds of
the Level Recorder, retaining the calibration of the paper in use. The Level
Recorder
Type 2307 has voltage steered paper speeds and this can be driven
from a rear panel
output of the 1026.
Full
remote control is possible of sweep functions, interlock, phase, and
compressor amplifier.
The removal of rear panel and circuit board short circuiting links allows
Master-Slave operation between many 1026s. Each Exciter Control retains
its own phase
control. The 1026 is thus very useful for multiple shaker
app
Iications.
Test specifications derived from practical measurements often require
multi-level and multi-mode control. This can be achieved using the Exciter
Control Type 1026 together with the Vibration Programmer Type 4413.
Using one 4413 gives four frequency subranges (three cross-overs). These
Vibration Programmers are simple
to connect in cascade for implementation
of test specifications with more than three cross-overs, or to give a "notch-
ing" capability.
8

2.1. FRONT PANEL
POWER
SET-UP CONTROL
2. CONTROLS
p Control and Output Volt age 2TI2P:J
Fig.2. 1. Front panel of 1026
Single-pole single-throw switch used to
apply mains power to the instrument.
When switched "On" the digital read-
out of frequency and the meter scales
are illuminated.
A five-position switch allowing the fre-
quency sweep "Upper Limit" and
"Lower Limit'' to be set up. The requir-
ed vibration "Level" on the table can be
9

OUTPUT VOLTAGE
pre-set before the output of the Exciter
Control is connected to the associated
Power Amplifier in the "Operate"
position. The fifth position, "Stand
By", holds the Exciter Control output
at >sodB below the maximum level.
A single-turn potentiometer mounted
on the
same axis as the SET-UP CON-
TROL and controlling the generator
output level. Turn the control fully anti-
clockwise for minimum output voltage.
When operating with the Compressor
off the generator must first be reset by
returning this control fully anticlock-
wise (click position).
The remainder
of the controls can most conveniently be grouped under
three
function headings.
2.1.1. Generator Section
GENERATOR FUNCTION
FREQUENCY DISPLAY
(Digital)
FREQUENCY DISPLAY
(Analogue)
10
A five-position switch selecting either a
1 - 10.000 Hz
"Sine" or a Rayleigh
distributed "Narrow Band Random"
output signal. The "Narrow Band Ran-
dom" output can have a ( -3 dB) spec-
tral width of "3. 16", "1 0", "31.6" or
"100" Hz with abandwidth accuracy of
5%.
A six-figure numerical read-out using
neon display valves. The display
reads
the output frequency to ± 0.1 Hz and
up-dates every 0.5 second.
A moving-coil meter
with a logarithm i-
cally calibrated scale. The scale is
calibrated directly in frequency (Hz)
from 1 - 10.000 Hz, and in octaves

SWEEP CONTROL
SWEEP
LOWER LIMIT
UPPER LIMIT
(oct.), using 1 Hz as a reference. The
meter
has an accuracy of 5% after
warm-up (15 min).
This
row of six push-button switches
selects either manual
or automatic
sweep modes, and controls parts of the
sweep function. "Manual" control of
the output frequency is switched to the
MANUAL FREQUENCY CONTROL
and associated VERNIER control. The
automatic
sweep mode chosen can be
"Single" or repetitive sweeping ("Re-
peat").
To commence a sweep the "Start"
switch is used. All sweeps commence in
the frequency increasing direction (up)
unless commencing
from the upper limit
of the sweep. At any point during a
sweep, either going up or down in fre-
quency, the
sweep direction can be re-
versed by the "Reverse" button. The
sweeping
is halted by the "Stop" but-
ton.
Two indicator lamps showing the
direction
of the frequency sweep. The
"Up" lamp is lit for increasing frequen-
cy
and the "Down" lamp is lit for de-
creasing frequency.
A ten-turn potentiometer,
used with the
SET-UP CONTROL in position "Lower
Limit", to define the minimum frequen-
cy
of afrequency sweep.
A ten-turn potentiometer,
used with the
,SET UP CONTROL in position "Upper
Limit", to define the maximum fre-
quency
of a frequency sweep.
t1

MANUAL FREQUENCY and
VERNIER
SWEEP RATE RANGE and
SWEEP RATE
PHASE
12
Two potentiometers, coaxially mount-
ed, one of which has ten-turns from end
to end, giving coarse frequency settings,
and the other
is a single turn poten-
tiometer giving VERNIER (fine) con-
trol. The controls can be used to set up
the starting frequency
of an automatic
sweep,
to manually scan the frequency
range
of interest or to set up spot fre-
quencies.
A
range of sweep speeds (Hz/min. or
Oct./m in.) can be selected by the
SWEEP RATE RANGE and the exact
sweep speed within that range is set up
by the SWEEP RATE potentiometer.
The SWEEP
RATE is a ten-turn,
calibrated
potentiometer giving con-
tinuous adjustment. The SWEEP RATE
RANGE can select one
of four linear
sweep ranges or one of three logarithmic
ranges.
The linear ranges are "1 - 10", 10-
1 00", " 1 00 - 1 000" and " 1 000 -
10.000" Hz/min. The maximum fre-
quency sweep available in the"1 -10"
Hz/min. range is from 1 - 200Hz and
in the
"10- 100" Hz/min range is from
1-2000 Hz.
The logarithmic
ranges are "0.1- 1",
1- 10'', and "10- 100'' octaves/min
with a maximum upper limit frequency
of 2000Hz, and "0.1- 1", "1- 10"
and "10- 100" octaves/min with a
minimum lower limit frequency of
5Hz.
A screwdriver control of output signal
phase giving more than 360° change.

2.1.2. Vibration Meter Section
EFFECTIVE AVERAGING TIME A five-position switch choosing the aver-
aging time of the vibration meters. The
switch
is common to both meters and
the available averaging times
are "0.3",
"1", "3", "10'', and "30" seconds.
All other meters and controls are duplicated in each channel; thus only
one channel will be described.
CHANNEL A (B)
OVERLOAD
MODE
Indicator lamps lighting when Channel
A (or
B) is chosen as the control chan-
nel and the SET-UP
CONTROL is at
"Operate" or "Level".
An indicator lamp that indicates the
amplifier in the vibration meter section
is overloaded and that the input range
must be increased by changing the
LEVEL switch.
The vibration meters
can measure or
control different input functions, select-
able by the MODE switch. The meters
are calibrated for input acceleration
signals normalized
to 10 mV/g.
"Accel." The vibration meter is used as
a direct measuring amplifier indicating
the value
of the acceleration signal
applied.
"Vel." One stage of integration is intro-
duced
into the normal measuring ampli-
fier thus converting all acceleration
readings
to velocity readings.
"Displ." A further integrator is added
into the measuring amplifier thus con-
verting all acceleration readings to dis-
placement readings.
13

LEVEL
14
"Accel. Grad." A -3 dB/octave filter is
introduced into the measuring amplifier
to give a decreasing RMS value with fre-
quency.
"Ext. Filter". Switches in any external
filters connected
to the rear panel EXT.
Fl LTE R socket that may be required to
give special amplifier characteristics.
The filter will then be connected in
series with the amplifier.
"-6 dB/oct." This position also
switches to any external filters used but
includes a -6 dB/octave filter (the
Velocity Integrator) at the input to the
measuring amplifier.
The LEVEL control consists of a multi-
position switch and a coaxially mounted
potentiometer. The switch works in
conjunction with the MODE control.
When "Accel." or "Vel." is selected on
the MODE switch the LEVEL control
can select a Full Scale Deflection of
II 1 tr 1 "3" 1 II 1 0" 1 "30" 1 II 1 00" 1 "300" 1
or "1 000" g or inches/sec. When
"Displ." or "Accel. Grad." is selected
the LEVEL control can select a FSD of
"0.01"1 "0.03"1 "0.1"1 "0.3"1 "1"1 "3"
or "10" inches or g{SeC. These calibra-
tion figures will be found around the
switch in large lettering. The small
lettering refers
to the corresponding
metric units.
The potentiometer is used to control
the level of the chosen table vibration
mode and
is adjusted in either the
"Level" or "Operate" positions of . the
SET-UP CONTROL.

METER A moving-coil
meter with am irror scale
to reduce parallax error. The meter face
is marked for five scales, two (0- 10
and 0- 30) for measurements in the
f.p.s. system, two (0- 25 and 0- 75)
for measurements
in the metric system
and
one is lettered in dB.
If the GENERATOR FUNCTION is
"Sine", the meter is calibrated to read
the peak value of Sinusoidal Accelera-
tion, Velocity and Acceleration Gradi-
ent signals, and the peak to peak value
of Sinusoidal Displacement signals.
If
the GENERATOR FUNCTION
switch is in one of the "Narrow Band
Random" positions, the meter is
calibrated to read RMS.
The meter rectifier (not meter calibration which is always as above) is
selectable by three push-buttons.
"RMS"
"Average"
"Track"
A true RMS wide band rectifier is select-
ed as the meter rectifier.
Selects a rectifier that will give the aver-
age value
of the input signal.
Connects a bandpass filter whose centre
frequency is slaved to the generated fre-
quency or to the centre frequency of
the noise band generated.
In GENERATOR FUNCTION "Sine"
the filter is a 6% constant relative band-
width filter and in GENERATOR
FUNCTION "Narrow Band Random" it
is a constant bandwidth filter with the
same bandwidth as the noise bandwidth
selected.
15

2.1.3. Compressor Section
COMPRESSOR CONTROL
COMP. RATE
MAX. COMP. SPEED
COMPRESSION
16
A set of nine push-button switches
selecting which of the vibration meters
controls the compressor loop and the
type of rectifier used.
Either Channel A
or Channel B can be
selected to control the compressor by
pushing button "A" or "B". A ttiird
possibility is the button "Larger,"
which selects the larger output of the
two channels as the compressor control
signal. Each compressor control channel
can have a "RMS", "Average" or
"Track" rectifier, similar to the avail-
able
meter rectifier choice. The rectifier
for Channel A compressor control is
chosen by the buttons to the left of the
row and Channel B rectifier control is
selected by those to the right.
A five-position switch used
to select the
slope of the continuously variable com-
pressor speed. The available slopes are
"0.1", "0.3", "1", "3", and "od' dB/
second per Hz.
A switch
to select the maximum com-
pressor speed or to switch off the com-
pressor and have an unregulated genera-
tor. The compressor speed increases
with the slope chosen by the COMP.
RATE to the frequency where the
selected maximum speed is reached.
Above
that frequency the compressor
speed is kept constant at the maximum
value (Fig.4.7). The available max.
speeds are:
"1", "3", "10", "30",
"1 00", "300", and "1 000" dB/sec. -
A small moving coil meter, calibrated in
dB, and used
to indicate the amoun .t of
compression applied at any instant.

Associated with the compressor control loop is a safety circuit.
SAFETY LIMITS
STAND-BY
SAFETY CONTROL IN
2.2. REAR PANEL
Meter
Comp.
Channel
Selector
Switch
A four-position switch. The chosen
variation
in pre-set level above which
the safety circuit is triggered can be
"± 1", "±3", or "±6" dB. If the safety
circuit
is triggered the generator auto-
matically switches back
to "Stand-by"
and the STAND-BY lamp is lit. The
safety circuit is switched off when the
SAFETY LIMITS switch is at "Off".
When the safety circuit is operative the
SAFETY CONTROL IN lamp is lit.
Ground
Fig.2.2. Rear panel of 1026
MAINS VOLTAGE SELECTOR
and CARTRIDGE FUSE The generator can be set to operate on
100, 115, 127, 150, 220, and 240 V
mains voltages
(50 to 60Hz). A cart-
17

CHASSIS/SIGNAL GROUND
ridge fuse is integrally mounted with the
voltage selector and can be removed by
turning the selector centre with a wide
bladed screwdriver or a small coin.
Choice
of equipment CHASSIS or
SIGNAL GROUND as reference is avail-
able
as required by these two screw-in
terminals and the associated shorting
plate.
The remainder of the rear panel can be sub-divided into sections as for
the front panel.
2.2.1. Generator Section
OUTPUT L1 NEAR
OUTPUT HIGH PASS
CONSTANT
LEVEL OUTPUT
18
An isolated BNC connector used to con-
nect the sine
or narrow band random
outputs to external loads. The frequen-
cy
range available is from
1 - 10.000 Hz at levels between
0- 3 V RMS. The maximum load is
10 kD. shunted by 3 nF.
An isolated BNC connector similar to
the LINEAR connector except with a
high
pass filter in series. A simple RC
filter is used (1 nF, 22 kD., f3 dB =
45 Hz). See also section 4.2. This gives
inherent matching
to shaker low fre-
quency characteristics.
An isolated BNC connector whose out-
put is a constant amplitude 1 V RMS
sinusoidal signal
of the same frequency
as the OUTPUT LINEAR socket. A
further constant amplitude output, also
1 V RMS, but 90° leading in phase to
that of the CONSTANT LEVEL OUT-
PUT L
0° socket can be obtained at the
CONSTANT LEVEL OUTPUT L90°
socket. The maximum load at either of