BRUEL & KJAER 2694A User manual

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Local representatives and service organisations worldwide
16-channel DeltaTron Conditioning
Amplifiers Types 2694 A, 2694 B, 2694 C
and 2694 D
Volume 1: User Manual
English BE 1644 – 11
Cover.fm Page 1 Friday, May 18, 2001 11:56 AM

BE 1644−11 May 2001
16-channel Conditioning
Amplifier Type 2694
User Manual
Valid for version 1.0 (or higher) of the Type 2694 Embedded Software
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BE 1644−11 May 2001
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Trademarks
MS, Microsoft and Windows 95 are registered trademarks of Microsoft Corporation.
Copyright ©2001, Brüel& Kjær Sound & Vibration Measurement A/S
All rights reserved. No part of this publication may be reproduced or distributed in
any form, or by any means, without prior written consent from Brüel & Kjær
Sound & Vibration Measurement A/S, Nærum, Denmark
Safety Considerations
This apparatus has been designed and tested in accordance with IEC 61010 – 1 and
EN 61010 – 1 Safety Requirements for Electrical Equipment for Measurement, Con-
trol and Laboratory Use. This manual contains information and warnings which
must be followed to ensure safe operation and to retain the apparatus in safe condi-
tion. Special note should be made of the following:
Safety Symbols
The apparatus will be marked with this symbol when it is important that you
refer to the associated warning statements given in the manual.
Protective Earth Terminal Hazardous Voltage
Explosion Hazard
The equipment is not designed to be used in potentially explosive environments. It
should not be operated in the presence of flammable liquids or gases.
Warnings
• Switch off all power to equipment before connecting or disconnecting their dig-
ital interface. Failure to do so could damage the equipment.
• Whenever it is likely that the correct function or operating safety of the appara-
tus has been impaired, it must be made inoperative and be secured against
unintended operation.
• Any adjustment, maintenance and repair of the open apparatus under voltage
must be avoided as far as possible and, if unavoidable, must be carried out
only by trained service personnel.
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Table of Contents
CHAPTER 1
Introduction......................................................................................................... 1
Setup Using Control Software................................................................................................. 4
Setting up Type 2694 Amplifiers............................................................................................. 4
Serial Interface ......................................................................................................................... 7
CHAPTER 2
Controls and Connections .................................................................................. 9
Front Panel ............................................................................................................................... 9
EMC Immunity........................................................................................................................ 10
CHAPTER 3
Operation Overview......................................................................................... 11
Preliminary ............................................................................................................................. 11
CHAPTER 4
The Use of Control Software BZ 5291.............................................................. 15
Introduction ........................................................................................................................... 15
Transducer Setup ................................................................................................................... 20
CHAPTER 5
Maintenance, Service and Repair .................................................................... 25
General Maintenance ............................................................................................................ 25
Service and Repair.................................................................................................................. 25
CHAPTER 6
Specifications .................................................................................................... 27
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1
Chapter 1
Introduction
Conditioning Amplifier Type 2694 consists of four versions:
lType 2694 A −Standard version
lType 2694 B −Basic version; less functionality than Type 2694A
lType 2694 C −Customised version of Type 2694
lType 2694 D −All 16 channels delivered with single and double integration filters
For a simplified table showing the main features of the four units, see Table 1.2.
Types 2694 A, C and D conditioning amplifiers can always be updated/changed to
another configuration if required but, for calibration and reliability reasons, the unit
must first be returned to Brüel & Kjær for updating.
Note: Type 2694 B cannot be upgraded.
In addition to the various input configurations, you can also configure your amplifier
with special filters (see Table 1.1). Other filters are available upon request.
Table 1.1 Optional filters available to Type 2694
ZE 0848 Single and double integration filters
ZE 0847 A, B, C, D-weighting filters
WH 3278 900 to 1100 Hz band-pass filter
WH 3206 Whole-body vibration X, Y and Z-direction filters
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16-channel Conditioning Amplifier Type 2694 – User Manual2
Fig.1.1
16-channel IEPE
(DeltaTron) conditioning
amplifier
Fig.1.2 Block diagram of 2694 A. Note that it is identical to Type 2694 D except that
Type 2694 D has single and double integration on all channels
000280/1
Floating/Single
ended Input
Input
Protection
Voltage Mode
6mA Transducer Supply
IEEE 1451.4
0.1Hz H.p.
1Hz H.P.
Disable
-10dB
0dB
+10dB
+20dB
+30dB
+40dB
Optional
Filter Module
Overload
Ch1
Ch2-16 MUX
Output
Filter
Module
Processor
Board RS-232
RS-232
Multiplexed
Output
Zout: 50 // 470pF
Output
Zout: 1M // 300 pF (Voltage)
100 k // 300 pF (DeltaTron®)
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CHAPTER 1
Introduction 3
Table 1.2 Type 2694 family functionality
Functions Type
2694 A
Type
2694 B
Type
2694 C
Type
2694 D
High-pass Filter 0.1 Hz ✓✓✓
High-pass Filter 1 Hz ✓
(2nd order)
✓
(1st order)
✓
(2nd order)
✓
(2nd order)
Floating/Single-ended
Input ✓✓✓✓
Gain: –10 dB ✓✓✓
Gain: 0 dB ✓✓✓✓
Gain: +10 dB ✓✓✓
Gain: +20 dB ✓✓✓✓
Gain: +30 dB ✓✓✓
Gain: +40 dB ✓✓✓
IEPE (DeltaTron) Input ✓✓✓✓
Voltage Input ✓✓✓✓
IEEE P1451.4 Transducer
Support ✓✓✓✓
Optional Filters Possible Yes No Yes Yes
Filters Installed, e.g., A-,
B-, C-, D- or single and
double integration in 1 to
16 channels
✓
Filters Installed: single
and double integration in
all 16 channels
✓
Multiplexer Functionality ✓✓✓✓
Signal Overload ✓✓✓✓
Transducer Voltage
Overload ✓✓✓
Channel Disable/Enable ✓✓✓
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16-channel Conditioning Amplifier Type 2694 – User Manual4
Setup Using Control Software
All parameters are set up using control software BZ 5291 via the RS–232 interface
(refer to User Manual Volume 2: Interface).
The Windows-based control software program is supplied with Type 2694. The soft-
ware enables the conditioning amplifier to be configured for specific measurement
tasks. Type 2694 always retains the last setup used before it is switched off. The
control software also performs the important function of monitoring overloads and
collecting transducer data during measurements. The minimum system requirement
is a PC capable of running Windows and Internet Explorer 5.0 or later.
Fig.1.3 Type 2694 conditioning amplifiers can be daisy-chained to at least 16 Type 2694 units
per COM port. The more COM ports that are used, the faster the RS–232 interface
becomes. Communication flow is as indicated
Setting up Type 2694 Amplifiers
The Type 2694 family of conditioning amplifiers is automatically detected by the
software and displayed in the ‘File’ and ‘Link’ views (see Fig.1.4). You designate the
port(s) used for the range of conditioning amplifiers yourself. You can select or
deselect each Type 2694 amplifier for specific tests, which can be convenient in
fixed test setups.
You can also arrange the setup of a Type 2694 conditioning amplifier using just the
software, even the amplifier itself is not physically present. This can be done from
the Type 2694 configuration files that you have previously saved to disk for later use
in measurement situations. By dragging the icon of the Type 2694 conditioning am-
plifier you are to use into the ‘Setup view’, the detailed setup of the amplifier and
transducer settings can be performed.
Alternatively, you can load stored setups from the file view and adapt them to the
current configuration by dragging and dropping previously saved configurations of
Type 2694 conditioning amplifiers from the File view to the Link view.
COMMUNICATION FLOW
RS–232 cables
Amplifier Setup Overload, Status
and Transducer
Information
com 1
com 2
000279
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CHAPTER 1
Introduction 5
Fig.1.4
Type 2694 File, Link and
Setup views
Setting up Channel-dependent Parameters
The individual parameters of the selected Type 2694 conditioning amplifier(s) can be
shown in the Setup view (see Fig.1.4). These are shown in the ‘amplifier setup’ and
the ‘transducer setup’ tabs, where parameters that belong to the amplifier and trans-
ducer, respectively, are grouped. Both the amplifier and transducer setups can be
modified to include, or exclude, setup and monitoring parameters in any order or
type of setup.
Amplifier Setup
In the amplifier setup (see Fig.1.5), you can specify the settings of filters and gain for
each channel. This includes high-pass filters, optional filters, gain in steps of 10 dB,
multiplexer channel, tachometer, and whether single-ended or floating inputs are
used.
During measurement, the amplifier setup monitors overloads in the overload col-
umn, representing them by means of a change in colour.
Transducer Setup
In the transducer setup (see Fig.1.6), you can key in transducer sensitivities and
transducer types, or they can be read automatically for IEEE P1451.4-capable trans-
ducers with standardised TEDS. This includes transducer type number, serial
number and sensitivity. Full alphanumeric descriptions can also be attached to each
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16-channel Conditioning Amplifier Type 2694 – User Manual6
channel if required.
Note: Transducer sensitivities can only be read from TEDS. The amplifier gain is not
affected by the sensitivity read. Data is only for use in the analyzers or data-acquisi-
tion systems accompanying the conditioning amplifier. Sensitivities from other, non-
TEDS transducers cannot be entered manually in the Sensitivity field. The
Position(Trans) field can also be used for making test notes or other test documen-
tation.
Fig.1.5
The amplifier setup
Fig.1.6
The transducer setup
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CHAPTER 1
Introduction 7
Serial Interface
All functions can be controlled via the serial RS–232 interface. Controlling all the
parameters via the interface allows you to use Type 2694 amplifiers in automated
test environments.
Up to 16 Type 2694 units can be daisy-chained in a single setup on one COM port on
a PC. Each unit is automatically addressed from the PC program, Setup and Control
software BZ5291, which is included with each Type 2694 unit. One other, serially
controlled instrument (for example, a DAT recorder) may be connected to a chain of
Type 2694 units (or a single Type 2694 unit) but it must be connected as the last
instrument in the chain.
The commands and use of the interface are fully treated in Volume 2 of this manual.
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16-channel Conditioning Amplifier Type 2694 – User Manual8
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9
Chapter 2
Controls and Connections
Front Panel
Fig.2.1 Front panel of Signal Conditioning Amplifier Type 2694
On/Off button: When off, all circuits in the instrument are switched off. It is
still possible to switch on via the RS–232 cable.
Status LED: Green – Channel OK; Red – Signal Overload; Green and Red – Trans-
ducer/Cable failure; Neither – Channel disabled
Input: there are 16 analogue input plugs on the front panel. 15 are BNC input
plugs and the 16th channel is a BNT which also supports a tachometer probe.
Output: Any one of the 16 inputs can be monitored via this output. The selection
is made using the control software.
DC 10 – 33 V: Coaxial DC-socket for connection to an external 10 to 33 V DC source.
Complies with ISO DP 7637/1 and DP 7637/2, 24 V.
Warning: The DC-socket/cable ground is not connected to chassis ground. The
internal power supply is isolated from the rest of the instrument for voltages up to
±10 V.
Status LED
Green: Channel OK
Red: Signal overload
Green & Red: Transducer/ Cable failure
Neither: Channel disabled Chassis
RS–232 interface
to next 2694 unit
(daisy-chain capability) RS–232 interface
to host On/Off button
LED
Power
Connected
Isolated DC input
16 ch. analogue
output, analogue
Tacho out, TTL
Tacho out
Multiplexer
output on
1 out of 16
16 analogue BNC input plugs. Ch.16 is a BNT which also supports a tacho probe
000236
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16-channel Conditioning Amplifier Type 2694 – User Manual10
Chassis ground and RS–232 interface ground are the same. Both are isolated
from the power ground.
EMC Immunity
Type 2694 amplifiers do not require ferrite cable clamps to comply with EMC Emis-
sion standards EN 50081–1 and EN 50081–2.
The ferrite cable clamps are only required for compliance with EMC Immunity stand-
ards EN50082–1 and EN 50082–2. No problems should occur under normal use and
it is therefore only necessary to fit the clamps when the instrument is used in elec-
trically hostile environments such as powerful electrical fields.
In such cases, the cables for the power supply, the RS–232 interface and all floating
inputs/outputs must be fitted with the appropriate ferrite cable clamps. Clamp
LK 0013 is used for BNC cables, accelerometer cables, RS–232 cables and the power-
supply cable. The clamps must be fitted as close to the input/output sockets of the
instrument as possible. Cables for single-ended inputs/outputs and for the chassis
ground must not be fitted with ferrite cable clamps. When using the clamps with
accelerometer cables, the cable must be wound around the ferrite core so that two
loops are formed.
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11
Chapter 3
Operation Overview
Preliminary
Environmental
Temperature
Type 2694 conditioning amplifiers are built for portable, outdoor use and can be
used over a wide temperature range extending from –10 to +55°C (14 to 131°F) at a
maximum humidity of 90% RH at 40°C (104°F) (non-condensing).
Electromagnetic Compatibility
Type 2694 amplifiers meet the European EMC requirements EN 50081–1/2 (Emission)
and EN 50082–1/2 (Immunity). With special reference to the harsh electrical environ-
ment in cars, they also meet the strict ISO 7637–1 “Road Vehicles — Electrical
disturbance by conduction and coupling” requirements.
Power Supply
External Power
The conditioning amplifier is powered from an external DC supply which must pro-
vide a voltage between 10 and 33 V. A certain amount of 50 or 60 Hz ripple on the DC
supply voltage is allowed.
The power output required from the external supply depends on the amplifier type.
The maximum power consumption for a conditioning amplifier with 16 channels
driving 16 Type 2671 Microphone Preamplifiers via 100 m long cables (worst case)
amounts to 25 W. The typical consumption for a 16-channel version with a 5 m cable
is 20 W.
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16-channel Conditioning Amplifier Type 2694 – User Manual12
The mains adaptor (ZG 0426) supplied is a wide-range input type, which can be
safely used over the following voltage and frequency ranges:
90 – 264 V AC, 40 – 65 Hz
Protection against Excessive Current
The power supply is equipped with an protection circuit that will turn off the ampli-
fier if excessive currrent is drawn, such as when multiple outputs occur simultane-
ously. If this occurs, remove loads and turn on the amplifier by pressing the on/off
switch.
Rack Mounting
Type 2694 amplifiers can be used free-standing on their rubber feet. For more per-
manent installations, various rack mountings are available.
A rack-mounting kit (KS 0046) allows Type 2694 amplifiers to be mounted in 19″
instrumentation racks.
For automotive use, a special portable 19″rack (KQ 0158) is available.
Grounding
Ground loops are a common problem in large vibration-measurement installations.
There are different ways of avoiding this problem.
If the transducer is grounded to the test structure, the potential difference VCM
between the structure ground and the amplifier chassis ground (perhaps a few volts)
may cause a current to flow through the shield of the accelerometer cable and
through the amplifier circuits, introducing an error voltage which adds to the input
signal.
Fig.3.1 Avoiding ground loops
010010
Test Equipment
Conditioning
Amplifier
2694
If DeltaTron accelerometer is not isolated, then select "floating input mode"
If DeltaTron accelerometer is isolated (floating), then select "single-ended mode"
VCM
~
Type
2694
145
678910
11 12 13 14 15 16 Chassis RS232 Next Unit RS 232 Host
Output
Multiplexed
Output AllSockets !
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CHAPTER 3
Operation Overview 13
Loops can be formed by signal cables and RS–232 cables or output cables connect-
ing to accompanying analyzers or data-acquisition systems.
To avoid this, the accelerometer can be isolated from the structure with an isolated
stud and a mica washer, when single-ended DeltaTron input is used. Most DeltaTron
accelerometers have built-in insulators and thus are always isolated from the test
structure and grounded through the amplifier (see Fig.3.1).
In multichannel applications, ground loops will occur if more transducers (for exam-
ple, triaxial accelerometers) are connected to the same ground structure. In such
setups, magnetic fields will induce current into the loop, causing noise signals. In
such cases, the best solution is to select floating inputs, except for the most sensi-
tive one which must be single-ended. As a result, the noise signals at all the floating
inputs are suppressed with the ≥50 dB common-mode rejection and the single-ended
input is not exposed to any ground potential difference and subsequent noise signal.
Ground loop problems can also occur with microphones, for example, with a mul-
tichannel microphone array where the frame of the array is an electrical conductor
that is not at ground potential and makes contact with the housing of the micro-
phone preamplifiers.
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