BRUEL & KJAER 2237 User manual

Brüel BK
7/6-'89
& Kjær
BI5031–11
Technical
Documentation
WORLD HEADQUARTERS: DK-2850 Nærum • Denmark •
Telephone: [phone] •Telex: 37316 bruka dk • Fax: [phone] •e-mail: [email protected]
Sound Level Meter Type 2237
– Version A + B
Service Manual

0−2Brüel & KjærSound Level Meter Type 2237A+B
Service Manual

August 1998
BI5031–11
Brüel & Kjær Sound Level Meter Type 2237A+B
Service Manual
Sound Level Meter
Type 2237
Versions A + B
Service Manual
Valid from serial number 1 896 028

0−2Brüel & KjærSound Level Meter Type 2237A+B
Service Manual
Safety Considerations
This apparatus has been designed and tested in accordance with IEC Publication
348, Safety Requirements for Electronic Measuring Apparatus, and has been supplied
in safe condition. This Guide contains information and warnings which must be fol-
lowed by the user to ensure safe operation and to retain the apparatus in safe
condition. Special note should be made of the following:
Safety Symbols
See the associated warning statements given in the User Guide.
Chassis Terminal
Safety Earth Terminal
Hazardous Voltage
Warnings
This is a CISPR II, Class A product. In a domestic environment this product may
cause radio interference in which case the user may be required to take adequate
measures
Switch off all power to equipment before connecting or disconnecting their digital
interface. Failure to do so could damage the equipment.
Whenever it is likely that the correct function or operating safety of the apparatus
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.
Copyright © 1997, Brüel & Kjær Sound and 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 consent in writing from Brüel & Kjær Sound
and Vibration Measurement A/S, Nærum, Denmark.

Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 0−3
Contents
1. General Information.................................................................................................. 1–1
1.1 Edition Number........................................................................................................... 1 – 2
1.2 Safety ........................................................................................................................... 1 – 2
1.3 Instrument Versions ................................................................................................... 1 – 2
1.4 Service Policy............................................................................................................... 1 – 3
Exchange Scheme................................................................................................... 1 – 3
Mechanical Spare Parts ......................................................................................... 1 – 3
Serial Numbers....................................................................................................... 1 – 3
1.5 Repair........................................................................................................................... 1 – 4
1.6 Field Replaceable Parts .............................................................................................. 1 – 4
1.7 Special Tools and Equipment ..................................................................................... 1 – 4
2. Service Note...................................................................................................................... 2 – 1
2.1 General......................................................................................................................... 2 – 2
3. Checking Procedure ................................................................................................... 3 – 1
3.1 Introduction................................................................................................................. 3 – 2
Results not achieved............................................................................................... 3 – 2
Special Tools and Equipment ................................................................................ 3 – 2
3.2 Preparation.................................................................................................................. 3 – 3
3.3 Checking Procedure .................................................................................................... 3 – 4
Visual Inspection of the Microphone..................................................................... 3 – 4
Initial Setting ......................................................................................................... 3 – 4
AC Output............................................................................................................... 3 – 4
Serial Interface....................................................................................................... 3 – 4
Frequency Weighting ............................................................................................. 3 – 5
Attenuator Accuracy............................................................................................... 3 – 5
Noise........................................................................................................................ 3 – 6
Overall Check ......................................................................................................... 3 – 6
4. Calibration and Adjustment............................................................................... 4 – 1
4.1 Introduction................................................................................................................. 4 – 2
4.2 Power Supply............................................................................................................... 4 – 2

Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær
0−4
Power Supply Board ZD 0393 ................................................................................ 4–2
Battery Voltage and Current................................................................................. 4 – 3
Back-up Battery ..................................................................................................... 4 – 3
Input Stage ............................................................................................................. 4 – 4
No supply to the Digital Board.............................................................................. 4 – 4
The Display............................................................................................................. 4 – 4
Battery Low ............................................................................................................ 4 – 4
4.3 Adjustment Procedure ................................................................................................ 4 – 4
ZD 0814 Digital Board Reference Voltage............................................................. 4 – 7
ZZ 0233 Analogue Board ........................................................................................ 4 – 7
RMS Detector Gain and Offset.............................................................................. 4 – 7
Peak Detector Gain and Offset.............................................................................. 4 – 8
5. Mechanical Parts.......................................................................................................... 5 – 1
5.1 Exploded View............................................................................................................. 5 – 2
5.2 Dismantling Kit WZ 0065 ........................................................................................... 5 – 3
5.3 Dismantling................................................................................................................. 5 – 3
5.4 Reassembly.................................................................................................................. 5 – 4
5.5 Service Parts List........................................................................................................ 5 – 5
6. Theory of Operation................................................................................................... 6 – 1
6.1 Introduction................................................................................................................. 6 – 2
6.2 Functional Description ............................................................................................... 6 – 2
Signal Flow ............................................................................................................. 6 – 2
Internal Control...................................................................................................... 6 – 2
Interfaces ................................................................................................................ 6 – 3
Power Supply.......................................................................................................... 6 – 3
6.3 Block Diagram............................................................................................................. 6 – 4
A. Appendix – Type 2237 B ........................................................................................ A–1
A.1 Introduction................................................................................................................ A – 2
A.2 Upgrade ...................................................................................................................... A – 2
A.3 Special Tools and Equipment .................................................................................... A – 2
A.4 Repair.......................................................................................................................... A – 2
A.5 Field Replaceable Parts ............................................................................................. A – 2
A.6 Preparation................................................................................................................. A – 3
A.7 Checking Procedure ................................................................................................... A – 4
Initial Checks ........................................................................................................ A – 4
A.8 Initial setting.............................................................................................................. A – 4
A.9 Checking Outputs ...................................................................................................... A – 4
AC output............................................................................................................... A – 4
Digital output ........................................................................................................ A – 4
A.10 Frequency Weighting................................................................................................. A – 5

Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 0−5
A.11 Noise............................................................................................................................ A–5
A.12 Calibration.................................................................................................................. A – 6

Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær
0−6

Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 1−1
Chapter 1
General Information

Chapter 1 — General Information
Edition Number
Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær
1−2
1.1 Edition Number
If any major changes are made to the instrument and/or Service Manual, a new
edition of the Service Manual will be released. Any new edition can be recognised
by the Literature Number (BI 5031-xx) given at the bottom of odd numbered pages,
where xx is the edition number.
The serial number from which each edition is valid is printed in the frontispiece of
this Service Manual.
Information concerning minor changes will be released in the form of a Service
Note which is dealt with in Chapter 2.
1.2 Safety
The equipment and modules in Type 2237 have been designed and tested in accord-
ance with IEC Publication 348, Safety Requirements for Electronic Measuring Ap-
paratus, and has been supplied in safe condition.
Any work done on the instrument when open must be done by a qualified person
who is aware of the hazards involved, particularly ESD protection.
Note: The word WARNING denotes a hazard. It calls attention to a procedure,
practice, or like, which, if not correctly performed or adhered to, could result in
personal injury.
1.3 Instrument Versions
Hardware
When Type 2237 is switched on, the hardware version number appears in the in-
strument’s display.
The letter following the Type number indicates whether the instrument is an “A”
version or a “B” version. For example, the “A” version is shown as “Type 2237 A”.
The “A” version is designed to be used with a microphone input – that is, sound
measurement.
The “B” version is designed to be used with an accelerometer input – that is, vibra-
tion measurement.
There is only a little difference between the “A” and “B” versions, therefore the
main part of this service manual is based on the “A” version. The differences that
affect the “B” version are given in Appendix A.

Chapter 1 — General Information
Service Policy
Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 1−3
Software
The software version number is shown on the instrument’s display when it is
turned on, for example “Version n.mm”
The first number (n) indicates the main software version. Main versions only
change when major changes are made to the software.
The two numerals after the decimal point (mm) indicate if any minor upgrades are
implemented. If none, the numbers are 00.
1.4 Service Policy
1.4.1 Exchange Scheme
Type 2237 and its preamplifier are part of the Field Replaceable Part (FRP)
scheme. The microphone is a spare part. The FRP exchange scheme enables Brüel
& Kjær to offer a price reduction on FRP’s. To assure economical reuse, it is impor-
tant that no attempt is made to repair an FRP locally. If such an attempt is made
and the part subsequently needs to be exchanged, the price of an exchange FRP is
100% the price of a new one.
Therefore, DO NOT ATTEMPT ANY REPAIR to a Type 2237.
1.4.2 Mechanical Spare Parts
Mechanical spare parts can be ordered from Brüel & Kjær, see Chapter 5, Mechani-
cal Parts, for details of the parts available and their part numbers.
1.4.3 Serial Numbers
If an part in Type 2237 is found to be faulty, the only way to repair it is to send it
to Brüel & Kjær headquarters in Nærum. The faulty part will then be dealt with in
one of two ways, depending on how the instrument’s serial number is to be handled.
1. If a customer wants to receive exactly the same unit in return from repair, then
the whole instrument must be sent to Nærum. A repair time of up to 10 days
+ transport time must be allowed, however...
2. ...if there is no concern about the unit’s serial number, then “repair” can be done
in 2 days + transport time, since one choice Nærum has is to exchange the
faulty unit with another one. This type of “repair” must be ordered using the
FRP order form.

Chapter 1 — General Information
Repair
Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær
1−4
1.5 Repair
1.6 Field Replaceable Parts
Table 1.1 Field replaceable parts in Type 2237
1.7 Special Tools and Equipment
To perform the complete checking procedure, troubleshooting, adjustment and up-
grade of Type 2237, the following special tools and equipment must be available:
Type 1049/51 Sine Generator
Type 4231 Sound Level Calibrator, alternatively a Multifunction Acoustic
Calibrator Type 4226
AO 0403 LEMO to BNC
AO 0404 Interface cable for Type 2318
AO 1386 9-pin cable including 25-pin adaptor
JJ 2614 ½″Microphone Adaptor (with 4.7 nF capacitor) to B & K coaxial
plug
JP 0144 Adaptor, B & K coaxial plug to BNC
JP 0169 Short circuit for WA 0302
QX 0859 Tool for removing PLCC-circuits in sockets
WA 0302 Microphone Simulator with 13 pF capacitor
WB 1368 Set of 3 special tools for complete dismantling
115011 Decade Attenuator or equivalent (optional)
Power Supply with variable voltage (3–15 VDC)
Digital Voltmeter
Frequency Counter, accuracy ≥5 ppm
Part No. Description REF No.
Type 2237A Sound Level Meter – same serial numbera
a. see section 1.4.3
2237–A–REF
Part No. Description FRP No.
Type 2237A Sound Level Meter 2237–A–FRF
ZC0027 Preamplifier ZC0027––FRF

Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 2−1
Chapter 2
Service Note

Chapter 2 — Service Note
General
Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær2−2
2.1 General
From time to time some minor changes may be made to improve the performance
and serviceability of Type 2237. All information concerning these changes, or any
other changes to the Service manual, will be released in the form of a Service Note.
Note: The Service Note is renewed as a whole, meaning:
Discard the previous Service Note every time you receive a new one
The new edition of the Service Note must be placed in the binder in this section.

Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 3−1
Chapter 3
Checking Procedure

Chapter 3 — Checking Procedure
Introduction
Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær3−2
3.1 Introduction
The following Checking Procedure for Type 2237 is a subset of the final factory test.
The Checking Procedure verifies that the performance of the Type 2237 conforms to
the main specifications as given in the Product Data Sheet. To calibrate the Type
2237 to international standards IEC 651 and 804, the Sound Level Meter Calibra-
tion System Type 9600 can be used.
The result and validity of the following Checking Procedure is closely related to the
calibration status of the special tools and equipment.
It is recommended only to use a instrumentation calibrated to international stand-
ards.
The Checking Procedure is intended to be performed on a fully assembled instru-
ment, except that the microphone must be removed for some of the checks, or for
the noise check replaced by a equivalent electrical impedance.
The sub-headings in section 3.3 refer to the issues in the specifications given in the
Product Data Sheet. The order of the issues is different. Issues not covered by this
procedure are:
— Microphone Frequency Range
— Records
— Logged Results
— Electromagnetic Compatibility
— Batteries
3.1.1 Results not achieved
If the expected result is not achieved when a certain check is done, you should do
the calibration/adjustment procedure given in Chapter 4. If the instrument still
fails the checking procedure, it must be replaced using the FRP scheme (see Chap-
ter 1).
3.1.2 Special Tools and Equipment
See Chapter 1.

Chapter 3 — Checking Procedure
Preparation
Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 3−3
3.2 Preparation
1. Check the battery compartment and contacts, and clean if necessary. Put in new
batteries.
2. Connect the equipment as shown below:
3. When you are asked to ’Preset the Type 2237’ in the following procedures, the
setup for the Type 2237 must afterwards be:
— Time Weighting: F
— Display Parameter: SPL and Peak
— Measuring Range: 50 – 120 dB RMS
Please refer to the User Manual for detailed guidance on the meaning of the
symbols on the keypad, how to set-up the Type 2237, etc.
4. The input signal to the Type 2237 from the generator is supplied through the
JJ 2614 ½″Microphone Adaptor. The input signal must be a sine signal, and the
voltage unit is dBµVRMS.
Note: The sensitivity for the Microphone Type 4137 is typically 31.6 mV/Pa.
Note: When the input signal to the ZC 0027 Input Stage is applied through the JJ 2614
½" Microphone Adaptor, the microphone capacitance (12 pF) is replaced by 4.7 nF,
causing 0.6 dB higher signal to the input (input capacitance approx. 1 pF).
5. Check of the Instrumentation
Before starting the Checking Procedure, it is advisable to check that the intend-
ed output from the Sine Generator Type 1049/51 match the read-out on the
voltmeter by connecting the output from the generator to the input of the volt-
meter. In the following procedure the generator Type 1049/51 is the reference.
Fig.3.1 The fundamental setup for performing the Checking Procedure
970028/1e
Sine/Noise Generator
1049 AC Multimeter
2237
JP 0144
JJ 2614
Serial Output
AC Output
0
Brüel&Kjær Type2236

Chapter 3 — Checking Procedure
Checking Procedure
Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær3−4
3.3 Checking Procedure
The following procedure must be performed in the order given in this manual as
certain parts are interactive.
3.3.1 Visual Inspection of the Microphone
Remove the protection grid from the microphone, inspect and remount
No visual holes, corrosion, scratches or other damage to the diaphragm
should be visible.
3.3.2 Initial Setting
Press the “Calibrate” and “Settings” buttons while turning the power on. This per-
forms a master reset which clears the contents of the RAM and the calibration
factor.
The display should show:
****************
Master Reset
****************
The calibration factor is 0.0 dB and the Type 2237 is in a well defined state.
3.3.3 AC Output
Adjust the input voltage to give a 120 dB display reading at 1kHz
The measured AC Output should be 500 mV ±1dB (±approx. 55 mV).
3.3.4 Serial Interface
Check the digital output according to the description in the User Manual.

Chapter 3 — Checking Procedure
Checking Procedure
Sound Level Meter Type 2237A+B
Service Manual
BI5031–11 3−5
3.3.5 Frequency Weighting
Set the output from the generator until the display reads 118 dB at 1000 kHz.
The SPL value in the display must be within the tolerances relative to the refer-
ence value as given in Table 3.1:
Table 3.1 The frequency response tolerances
3.3.6 Attenuator Accuracy
Using a display reading of 110 dB as the reference, change the range and input
levels as given in Table 3.2. Check the output display is as shown:
Table 3.2 Attenuator linearity
Generator
Frequency
Hz
Display
Reading
10 –
19.95 67.5±1.8
31.62 78.6±1.0
125.9 101.9±0.5
Ref 1000 118.0
2512 119.3±0.5
3981 119.0±0.5
10.000 115.5±1.5
Range
dB Generator Output level
relative to referencea
a. ‘The reference signal is one that gives a display reading of 110dB when the range is set to 50–120
and the input signal is 1kHz
Display
dB SPL
70
– 140 +20dB @ 1kHz 130.0±0.4
30
– 100 –20dB @ 1kHz 90.0±0.4

Chapter 3 — Checking Procedure
Checking Procedure
Sound Level Meter Type 2237A+B
Service Manual Brüel & Kjær3−6
3.3.7 Noise
1. Remove the JJ 2614 ½″ Microphone Adaptor
2. Mount the WA 0302 Microphone Simulator with the short circuit JP 0169
3. Set the Range to 30 – 100 dB
4. The result should be “Underrange”
3.3.8 Overall Check
1. Apply 89.4 dBµVRMS, 1kHz, to the JJ 2614 adaptor
2. Perform a 'Calibration' as described in the User Manual, Chapter 4.
3. Set 'Calibr. Level' to 94.0 dB
4. The difference from last calibration must be ≤0.2 dB
5. Remove the JJ 2614 adaptor, and remount the Type 4137 Microphone.
6. Perform a 'Calibration' as described in the User Manual, Chapter 4.
Use the calibration level given on the actual calibrator's calibration chart
The overall check can also be performed with the Multifunction Acoustic Calibrator
Type 4226. By using the Type 4226 the frequency response for the microphone can
be checked.