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