B&K 1621 User manual

Instruction Manual
Tunable Band Pass Filter Type 1621
TuMble B•mt Pua Fiher T~ 1821
Overload Power
033-0119
Filter
-20t
Hl
A small light-weight portable filter with se-
lectable bandwidths of 3% and 23% (third
octave), covering
the frequency range
0,2 Hz to 20kHz with a continuously vari-
able tuned frequency. Powered from inter-
nal batteries or an external DC voltage.
Suited for use with B & K Sound Level Me-
ters Types 2203, 2209. 2210 and 2218.
B & K Vibration Meter Type 2511. and the
B & K
Wow and Flutter Meter Type 6203.
Can be manually tuned. or tuned automati-
cally by, and synchronously with, the B & K
Portable Graphic Level Recorders Type
2306 and 2309 for recording spectra from
one of the above instruments.
+ BrUel &Kjaer

TUNABLE BAND PASS FILTER
TYPE 1621
Applicable to instruments with serial numbers from 6941 24
Revision September 1981

CONTENTS
1. INTRODUCTION AND SPECIFICATION (PRODUCT DATA) .................................................. .
2. CONTROLS ..... ..... .. .. .. .... .......... .. .... ....... ......... .. .. .. .... .......... .. .. .. .. .......... .... .. .............. .. .. ........ 3
2.1 . FRONT PANEL ......
.. .. ....... .... .. . .. .. ..... .. .. .. .. ......... .. .. . .. ... .. .... .. .. ... .. ..... .. . .. . .. 3
2.2 . REAR PANEL ............. . .. ... ....... .... ..... ............ . ........ . ...... ... ....... ............... .. 4
3. OPERATION .............................................. ................................................................... ....... . 7
3.1 . MOUNTING .... .. .. .. .. ... .. ......... .. .. .. .. .. .. ..... .. ... .. .. .. .. .. ... .. . .. .. .. .. .. .. .... .. .... .. .. .. 7
3.2 . POWER SUPPLIES AND THEIR USE ....... ...... ....... .. .. ..... .......... .. .............. .. .. 7
Internal battery supply .. ........................................................................... 7
Mains battery charger .................................... .. ........................................ 8
Mains power supply and battery charger Type ZG 0199 ....................... .. .... 9
Mains power supply Type 2805 ................................................................ 9
External DC supply ........................................................................... .. ..... 10
3.3. MANUAL OPERATION WITH SOUND LEVEL AND VIBRATION METER ETC ..... 11
3. 4. AUTOMATIC OPERATION WITH LEVEL RECORDERS
TYPES 2306 AND 2309 . ................................... .. ........ ....... .. .. ...... ........ .. . 12
4. MEASUREMENT CONSIDERATION .................................................................................... . 15
4.1 . FREQUENCY CHARACTERISTICS ......... . ..... . ....... . ....... ...... .. .. ....... .. ...... ....... 15
4.2 . PHASE CHARACTERISTICS ...... . ......... . .. ... .. .. ...... .................. .................... 16
4.3. FILTER SWEEP RATE CONSIDERATIONS ...... .............. ...... . ........ .. .............. 16
Selection of DC or AC recording ................................................................. 16
Choosing the meter and recorder settings .................................................... 17
5. SERVICE AND REPAIR . ....................................................................................................... 20

FEATURES:
• Tunable band pass
frequency
• Frequency range 0,2 Hz to
20kHz in 5 sub-ranges
• Selectable bandwidths 3%
or 23% ( 1/3 Oct.)
• Two alternative input
voltage ranges
• Manual tuning or tuned
automatically from Level
Recorders 2306 and 2309
• Internal battery or external
DC power supply
• Small size and light weight
for ready portability
USES:
• In
portable systems for
narrow band frequency
analysis of vibration with
the General Purpose
Vibration Meter 2511
• In portable systems for
narrow band frequency
analysis of sound and
vibration with the Sound
Level Meters 2203, 2209,
2210and 2218
• Recording frequency
spectrograms with one of
the above instruments plus
the Portable Level
Recorders 2306 or 2309
The Tunable Band Pass Filter
Type 1 621 is a variable frequency
band pass filter intended for use as
an external filter with Bruel and
Kjrer measuring instruments, to
which it gives the ability to perform
narrow band frequency analysis. It
is particularly suited for use with
the General Purpose Vibration Me-
ter 2511 for narrow band fre-
quency analysis of vibration, and
with the Sound Level Meters 2203
2209, 221 0 and 2218 for narrow
138-81
type 1 621
Tunable Band Pass Filter
Tunable Band Pass Filter Type 1621
Overload Power Filter
, Frequency Tuning •
On
12
Frequency Range
20-200
14 2 - 2~ •
0,2 - 2
• -
2k
-2 0k
Hz
Manual
Auto e
Start •• Briiei&Kjaar
band frequency analysis of sound
and vibration. Its light weight and
battery power supply make the
1 621 the ideal portable instrument
for applications away from fixed
power sources.
Description
The 1 621 consists of a tunable
single pole butterworth filter with
switchable bandwidths, its own
power supply, and the necessary
control circuits.
The FILTER selector allows the fil-
ter bandwidth to be switched to
"3%" or to "23%", which are
the bandwidths · between the half
power points, i.e. 3 dB down from
the peak. The selector also has a
"Linear" position, that by-passes
the filter .
Five contiguous frequency sub-
ranges can be selected from the in-
strument's overall frequency range
between 0,2 Hz and 20kHz, each
sub-range covering one order of
magnitude. The frequency may be
swept manually through the sub-
range by a large control knob hav-
ing an attached pointer that sweeps
a scale showing the filter centre fre-
quency, and the preferred centre fre-
quencies of 1/ 3 octaves according
to ISO R 266 .
Alternatively, the Filter 1 621 may
be tuned automatically from the Por-
table Level Recorders 2306 or
2309 when they are interconnected
by a suitable cable (see specifica-
tions). The required paper speed,
which controls the sweep rate, is
F i htr!~UI
Medel In Oenmartc:
-
Fig .1. Rear view of the Type 1621

set on the level recorder, and the
sweep is initiated from the 1 621 .
The
filter is then advanced one com-
plete decade synchronously with
the recording paper (QP 01 20, OP
0124, QP 0143, QP 0224, QP
21 00 and QP 21 20). During this
process, the 1 621 tuning knob
does not move, its position being ir-
relevant. After one decade, the
1 621 frequency range is changed
manually, and another decade is
swept .
Alternative input voltage ranges
can be chosen by a rear panel
switch . "1 V RM S" matches the 1 V
level that the Vibration Meter 2 51 1
delivers to external filters when op-
erating in RMS mode . "0,2 V RMS"
should be selected for use when
the 2 511 operates in Peak mode,
or for use with the Sound Level Me-
ters. An "Overload" lamp lights if
these ranges are exceeded.
The 1
621 is powered by either in-
ternal batteries or by al"l external
DC supply . The alkaline cells sup-
plied with the instrument give about
25 to 30 hours continuous, while
rechargeable NiCd cells will give 16
Frequency Range:
0,2 Hz to 20kHz in 5 sub-ranges
Pass bandwidth:
Switchable 3% or 23% (1/ 3 oct .)
Attenuation at 1/ 2 and 2 times selected
frequency:
Switchable 34 dB or 16 dB
Dynamic Range :
> 40 dB RMS with 3% bandwidth be-
tween 0, 2Hz and 6kHz
> 35 dB RMS with 3% bandwidth be-
tween 6kHz and 20kHz
> 40dB RMS with 23% bandwidth be-
tween 0, 2Hz and 20kHz
Accuracy of indicated frequency:
± 1,5% at 25 °C, with additional ±0 , 04 %
per °C
Input:
BNC socket
1 V RMS with crest factor 5
0,2 V RMS with crest factor 5
Input impedance:
1 V input: approx. 1 MO in series with
10pF
0,2 V input: approx. 200 kO in series
with 1 OpF
Output:
BNC socket
Impedance: < 0,5 0 in series with
100pF
load Impedance: ;;. 25 kO
to 20 hours of continuous opera-
tion.
A DC voltage can be applied to the
1621 to recharge batteries, and/ or to
power the instrument. External sup-
plies can be between +4 and + 15 V,
or alternatively ± 14 V DC, which can
be obtained
from a Battery Charger
ZG
0133, a Power Supply ZG 0199
or a car battery. When the ZG 0 113
or ZG 0199 is used the instrument
can be operated and the batteries re-
charged (at a reduced rate
with
ZG 0 113) simultaneously.
Portable Vibration Analyzer
The comp.Jetely self-contained Por-
table Vibration Analyzer Type 351 3,
shown in Fig.2, consists of a Vibra-
tion Meter 2511A and a Filter
1621 installed in a rugged hard-
foam plastic Carrying Case KA
2000 that can contain 1 2/1 2 of a
19
inch rack module . Other items
included in addition to the standard
accessories are two connection
cables AO 0133, six rechargeable
NiCd cells QB 0008 and a Battery
Charger ZG 011 3 for the 1621 .
Fig.2 . Portable Vibration Analyzer Type 3513
Specifications 1 621
Gain at se ected frequency :
0 dB± 1 ,0 dB
Hum and noise:
Max.
Volt -
age
0.2 Hz - 6 k
1 v
10mV
0. 2V
2mV
Distortion :
< 1%
3%
Hz
6kHz - 20kHz
18mV
3. 6mV
Environmental conditions :
23 %
0 .2 Hz - 20kHz
10mV
2 mV
The instrument performs within specifica-
tions under the following conditions
Operating temperature: - 1 0° to
+ 50°C ( 14° to 122°F)
Humidity: 0 to 90% relative humidity ,
non condensing
Electromagnetic: Field strengths up to
100A / m
Power Consumption:
Typically 200 mA at 8 V
External power supply :
+ 4 V to + 15 V, or ± 14 V, approx . 2 W
Internal power supply:
6 x 1,5 V cells (IEC TypeR 20)
Battery life :
25 to 30 hours continuous operation
with alkaline batteries (supplied)
16 to 20 hours continuous operation
with NiCd cells
Charging time for fully discharged batter -
ies
approx . 14 hours, 12 V 400 mA
Dimensions:
Height: 132,6 mm (5,2 in)
Width: 139,5 mm (5,5 in)
Depth: 200 mm (7,9 in)
(B & K module cabinet KK 0024 , 4/ 12
of 1 9" rack module)
Weight:
2,2 kg (4 ,91b) with batteries
Accessories included :
6
Batteries QB 0004
7 -pin DIN plug JP 0703
8-pin DIN plug JP 0802
2 BNC plugs JP 0035
Accessories Available :
Synchronization cable for 2306 and
2309 :
AQ 0034 for 2306 from serial no .
718058 and for 2309
AQ 0182 for 2306 before serial no .
718058
Rechargeable NiCd cells QB 0008
Battery Charger ZG 011 3
Power Supply ZG 0199

2.1. FRONT PANEL
Overload
Overload In dicator --:---JII., .
Frequency
Tuning Knob
Sweep
Control
Sweep Control --~-
2. CONTROLS
Tunable Band Pass Filter Type 1621
Frequency Tuning
Power Filter Power On
·-----------:1--- Indicator
On
1----e -- Filter Selector
fJ811'""'cy Range
20-200
14
2- 2~ • ;oo -2k
0 ,2-2
•
Brilel & K;.t
Frequency
,-----c--- Range Selector
Fig.2.1 . Front Panel of the Tunable Band Pass Filter Type 1621
POWER ON INDICATOR: This lamp lights when there is a sufficient voltage supply to the instru-
ment, from internal and external power supplies.
FILTER SELECTOR:
Note: It does not light when the instrument is powered from a ± 14 V
DC source .
A
4-position rotary switch for switching the instrument on and off, and
for selecting the required filters. "Linear", "23%", and "3%" are avail-
able.
In
the "Off" pos1t1on, the power is off, but the input signal is directly
transmitted to the FILTER OUTPUT socket.
In the "Linear" position, the output signal is unfiltered, but the input
signal is also applied to the 23% bandwidth filter. Thus, when the
23% filter bandwidth is selected, there is no "settling time" for the fil-
ter; the filtered signal is instantly available.
3

FREQUENCY RANGE
SELECTOR:
FREQUENCY
TUNING KNOB:
OVERLOAD INDICATOR:
SWEEP CONTROL:
SWEEP CONTROL INDICATOR:
THUMBWHEEL:
2.2. REAR ' PANEL
FILTER INPUT:
FILTER OUTPUT:
4
A 5-position rotary switch for selecting the decade required for
analysis. Two scales are shown, the upper scale giving the decade
for selection and the lower scale giving the factor by which the
scales on the FREQUENCY TUNING KNOB should be multiplied to
give the actual frequency or RPM value.
A continuously variable tuner covering a range of one decade select-
ed by the FREQUENCY RANGE SELECTOR. The outer scale shows
the centre frequency of the band being swept and the inner scale
shows the RPM value. To obtain the actual frequency or RPM value
the scale values should be multiplied by the factors given on the
lower scale of the FREQUENCY RANGE SELECTOR. The small black
circular marks in between the scales indicate the prefered centre
frequencies of the 1I 3 octave bands according to ISO R 266.
The FREQUENCY TUNING KNOB has no effect when the SWEEP
CONTROL switch is set to Auto.
This lamp lights whenever too large a voltage is applied to the FILTER
INPUT socket; depends on
the setting of the VOLTAGE RANGE SELEC-
TOR
on the rear panel.
A 3-position paddle switch to select the method of tuning the filter,
with positions as follows:
"Manual": In this upper position, the filter is tuned manually by the
FREQUENCY TUNING KNOB.
"Auto": In this central position the filter is tuned automatically from
the Portable Level Recorder· Type 2306 or 2309 when a suitable
cable connects the two instruments. The sweep will always start at
0,2 Hz (or a decade multiple thereof) and will sweep one decade.
"Start": When the switch is depressed to this spring-loaded self re-
turning position and released (so that it comes back to "Auto"), the Por-
table Level Recorder Type 2306 or 2309 will start, when the rele-
vant cable connects the 1 621 and the appropriate recorder and will
sweep the filter synchronously with the recording paper over one com-
plete decade (selected by the FREQUENCY RANGE SELECTOR) and
then stop. During this process, the position of the FREQUENCY TUN-
ING KNOB is irrelevant, and it does not move.
This lamp lights when the filter is actually being swept synchronously
by the Portable Level Recorder Type 2306 or 2309. At the end of de-
cade,
when the sweep stops, the lamp goes out.
The knurled knob at the bottom centre of the front panel is to release
the baseplate to enable the 1 621 to be mounted in a rack or portable
carrying case. Turn it anticlockwise to release, clockwise to tighten.
A BNC socket for feeding the signal into the instrument.
A BNC socket for feeding the filtered signal out of the instrument.

In put
Voltage
Se lector
Power Selector
FiIter Output
G ro un ding Po in t
Fig.2 .2.
POWER SELECTOR:
INPUT VOLTAGE SELECTOR:
EXTERNAL POWER SUPPLY:
External Power
Charge Input
+ 15 V DC
Battery Cover
Release Screw
External
Power Supp ly
Filter In put
Synchronization
Rear Panel of the Tunable Band Pass Filter Type 1621
A 2-position slide switch for selecting internal or external power sup-
ply.
A 2-position slide switch for selecting the maximum input voltage.
"0,2 V RMS" and "1 V RMS" are available.
A 7-pin DIN socket for accepting an external DC power supply voltage
for powering the instrument and for recharging its internal cells. The
pin
connections are shown in Fig.2.3. See also section 3.2 .
& WARNING! Never apply a charge voltage to alkaline or conventional
dry cells: there is a danger of explosion.
External Power
---+------- - --Drive Input
Dual Polari
ty
External Power
Drive Input
+ 4 to + 15 V DC
7 90 77 4
Fig.2.3. Pin Connections of EXT. POWER SUPPLY Socket. External
view
5

SYNCHRONIZATION:
BATIERY COVER RELEASE
SCREW:
6
An 8-pin DIN socket to enable the filter frequency to be swept by the
Portable Level Recorder Type 2306 or 2309 synchronously with its re-
cording paper. For
details of connections, synchronization, sweep rate,
and
operation , see section 3.4.
This retained screw enables the top plate of the instrument to be rem-
oved for battery replacement.

3.1. MOUNTING
3. OPERATION
The 1 621 can be used free standing on its four feet or, to enable better viewing, the
front may be raised using the metal stand attached to the underside of the instrument .
For easy
transportation the 1 621 can be fitted into a hard foam plastic carrying case
Type
KA 2000, capable of carrying three instruments the size of the 1621.
3.2. POWER SUPPLIES AND THEIR USE
There are several methods of supplying power to the 1 621 . Although it is primarily a
small lightweight portable Filter which is powered by its own internal batteries, it may
also be driven - from an external power supply. The choice of power supply depends on
whether it has to be capable of recharging the internal cells of the Filter, and also
whether it has to power other instruments in the measurement chain at the same time.
The various possibilities are outlined in the following sections.
3.2.1. Internal Battery Supply
Six 1,5 V alkaline dry cells (conforming to IEC R 20) are supplied with the 1621, with a
battery life of 25 to 30 hours continuous operation (8 & K stock No. QB 0004). Other
1,5V standard dry cells may also be used, these however, will only have a battery life of
approximately 6 to 8 hours.
150516
Fig.3.1. Position of Cells in Battery Compartment of 1621
7

The 1 621 may also be powered using six rechargeable nickel-cadmium batteries (B &K
Stock No. QB
0008), which can be supplied as accessories. The cells recommended are
SAFT VOLTA BLOCK Type VR 40 which have a voltage and charge rating of 1,2 V and 4
amp.
hours respectively. (Any rechargeable cell with equivalent ratings may be used,
however). SAFT,
the cell manufacturers specify that with normal use the cells have a
minimum of 500 charge cycles before replacement is necessary. The need for replace-
ment is indicated by the cells failing to reach a fully charged condition after having been
on charge
for 14 hours or more. The battery life will be between 16 ar:'ld 20 hours con-
tinuous operation.
& WARNING! Never attempt to recharge alkaline or conventional dry cells · or batteries
with poles reversed: there is a danger of explosion. Similarly never mix different types of
battery, or batteries that have been used in other instruments or battery packs. This can
cause
internal reversal of battery polarity.
The cells may be fitted as follows:
1. Loosen the battery cover release screw (see Fig.2.2) and.slide the top plate of the in-
strument off towards the rear. (The screw is captive, so it cannot be lost).
2. Place the cells in the compartments with the polarities indicated. (See Fig.3.1 ).
3. Replace the top panel.
4. Select "Internal Battery" witt"l the POWER SELECTOR switch on the rear of the
1621.
5. Select "Linear" with · the FILTER SELECTOR, and check that POWER INDICATOR
lamp is
lit to ensure the batteries have sufficient power.
6. Switch the 1 621 off after the battery check.
7. Label the instrument, stating which type of cells have been installed. If alkaline or
standard dry cells have been fitted, then also include the warning "EXPLOSION
RISK -NOT TO
BE RECHARGED".
3.2.2. Battery Charger ZG 0113
8
A Battery Charger ZG 0113 (Fig.3.2) is available as an ·accessory on separate order for
recharging the cells QB 0008, the recharge time being approx. 14 hours for fully dis-
charged cells. The
charger is merely plugged into the mains supply, and connected to
the EXTERNAL POWER SUPPLY socket of the 1 621 . Colour coding of the connections
for the different mains voltages is:
Blue 0 V (Neutral)
Black
100- 130V AC
Brown 200 - 240 V AC
& WARNING! Clip back and insulate the line not in use.
The
charger may also be used to power the instrument at the same time as recharging
the cells. In this situation, however, the battery recharge time will be longer.

ffi WARNING! Never apply a charging voltage to the 1621 when non-rechargeable cells
are fitted : There is a danger of explosion.
Fig .3 .2. ZG 0113 Battery Charger
3.2.3. Mains Power Supply and Battery Charger Type ZG 0199
The Power Supply Type ZG 0199 is capable of providing a driving voltage of + 7,5 V DC and
a charging
voltage of + 12 V DC simultaneously or separately, controlled by a switch on its
front panel. One instrument may be charged while three (e.g. a 1621, a 2511 Vibration
Meter, and a 2306 I 2309 Level Recorder) may be powered simultaneously from the
ZG 0199. The output socket of the ZG 0199 is connected to the EXTERNAL POWER
SUPPLY socket of the 1621 with the connections shown in Fig.3.3. Cable AQ 0035
(available as an accessory on serarate order) is suitable for this connection even though all 7
of its pins are connected 1 to 1, 2 to 2 etc.; there is no need to disconnect pins 4 to 7. For
powering the other instruments from a ZG 0199, consult their Instruction Manuals. Provided
the total combined drive current does not exceed 1 ,25 A, the ZG 0199 is a very useful
power supply. With such a set-up, however, a ground loop is formed by the 0 V line of the
power supply and the sreening of the signal cables. This may prove troublesome when
measuring small vibration levels, and in this case it is recommended that the screening be dis-
connected from the plug at one end of each of the signal cables.
Power Supply
ZG 0199
Output S ocket
+7,5 V DC
ov
JP 0703
+12 V DC
Ch arge
+12 V DC
ov
JP 0703
Driv e
+7,5 V DC 1621
Exte rn al Power
Supply S ocke t
750449 / 1
Fig. 3.3 . Connections for external power to, and for recharging inter-
nal batteries of, 1621 . External view of sockets, soldering
side of plugs shown
3.2.4. Mains Power Supply Type 2805
The Power Supply Type 2805 contains two channels, each of which can supply either
+28 V DC or ±14 V DC . When either channel is switched to ±14 V it is suitable for pow-
ering the 1 621, but not for charging the internal cells as its current rating is not suffic-
iently high. Connection of the Bulgin socket on the rear panel of the 2805 to the EXTER-
NAL POWER SUPPLY socket on the 1621 is shown in Fig. 3.4. Ensure that the CHAN-
NEL 1 switch on the front of the 2805 is set to "±14 V", i.e. the switch should be up. (If
channel 2 is used, then pins 4, 5, 6 of the 2805 socket should be used instead of pins
9

2805
Output
Socket
JP 4705 JP
0703
750448
Fig.3.4. Connections from the 2805 to the 1621 for power supply.
External view of sockets, soldering side of plugs shown
3, 2, 1 respectively, and the CHANNEL 2 switch should be set to "±14 V".) One instru-
ment may be powered from each channel.
Any other ±14 V DC source should be connected to the same three pins on the 1 621,
i.e. -14V, OV and +14'1 DC. All three pins must be connected.
Note: The POWER ON INDICATOR does not light when the instrument is powered from
a ±14 V DC source.
3.2.5. External DC Supply, 4 to 15 V
10
A car battery, or other DC source of between 4 V and 15 V with a capacity of 2 W or
more, may be used to power the 1 621. The source is applied to the 1621 via the EXTER-
NAL POWER SUPPLY socket on its rear panel as shown in Fig.3.5.
4 to 15 V DC
ov
JP 0703
+4 to
+15 V DC
1621
External Power
Supply Socket
750446 /1
Fig.3.5 . Connections for external DC source connection to 1621.
External view of socket, soldering side of plug shown
If recharging or powering of the 1 621 is carried out in a car that has a positive - earth
system, and the car's own battery is being used, then the 1621 should be isolated from
the car's chassis and bodywork. The rest of the instrumentation chain should also be sui-
tably isolated from the car, since the signal cables are connected to a common ground.
This is important since the metal case of the 1 621 and of other connected instruments
will have a potential 12 V below that of the car chassis/body when connected to the
battery, and the battery could be short-circuited if the instruments are allowed to touch
the car chassis/body. If it is impossible to isolate the instruments effectively the battery
should be disconnected from the car's chassis.
For simultaneous powering of the 1 621 and charging of its internal cells, a 15 V DC
source may be connected to the EXTERNAL POWER SUPPLY socket of the i 621 as
shown in Fig.3.6. If charging only is required then pin 1 need not be connected.

15 V DC
+15 V DC
ov
JP 0703
1621
External Power
Supply Socket
750447 / 1
Fig.3.6. Connections for simultaneous operation, and charging
cells, of 1621. External view of socket, soldering side of
plug shown
3.3. MANUAL OPERATION WITH SOUND LEVEL AND VIBRATION METER ETC
To
Ext.
Filter
Vibration
Meter
2511
The 1 621 is ideally suited for use as an external filter to portable instruments such as a
Vibration Meter or a Sound Level Meter.
Fig.3.7 shows some examples of how the instruments may be set up.
Sound Level
Meters
2203/2209
2210/2218
In Out
To
Ext.
Filter
·~ · ~In_....,....,
. -- ;_ ·-_ .- Out
-, ..... ..
Flutter
Meter
6203
Level
Recorder
2306
~ - - ,· ·~ 1-------S..;..y_nc_hr_o_nisa_t_io_n ___________ __,
·. -~~-------------------------,
Tunable Band
Pass Filter
1621 Level
Recorder
2309
AO 0182 (For 2306 with
serial N° below
718058)
AO 0034 (For 2306 with
A00034
serial N° above
718058)
790775
Fig.3. 7. Combination of the 1621, Tunable Band Pass filter, with
Sound, Vibration and Flutter meters
The 162 1 is used as follows:
1. Select "Internal Battery" or "External Power" as required. See Section 3.2.
2. Using the INPUT VOLTAGE SELECTOR, select the maximum input voltage range to
be used. The actual noise level is lower in the "0,2 V RMS" position, so this should
be used whenever a small signal is to be filtered. With the 2511 set to "RMS", the
1 621 should be set to "1 V RMS". With the 2511 set to "Peak - to Peak", or with
instruments 2203, 2209, 2210, 2218 or 6203, the 1621 should be set to "0,2 V
RMS".
11

3. Use the FILTER SELECTOR knob to choose the required analysis bandwidth. The
POWER ON lamp should light - if not, check the power supply. (Remember, how-
ever, that the lamp does not light for a ± 14 V DC source).
4. Select EXT. FILTER on the Sound Level Meter or Vibration Meter in use and apply a
signal to the 1 621 .
5. Set the SWEEP CONTROL switch to "Manual".
6. Using the FREQUENCY RANGE SELECTOR, choose the first decade of interest for an-
alysis.
7. Using the FREQUENCY TUNING KNOB, select the frequencies of interest, and note
the Meter reading and the frequency.
8. If the OVERLOAD indicator lamp lights, the signal input to the Filter is too large -
either adjust the signal input amplitude or change the INPUT VOLTAGE SELECTOR
from "0,2 V RMS" to "1 V RMS" as appropriate.
9. Repeat 6 and 7 as necessary.
If the frequencies of interest are not known, the FREQUENCY TUNING KNOB may be
turned slowly across the complete range in the "23%" position (changing the FRE-
QUENCY RANGE SELECTOR as necessary)
until high levels are indicated on the Meter.
These levels and frequencies should be noted, and then a 3% bandwidth analysis can be
made later if necessary to give improved resolution around those frequencies.
3.4. AUTOMATIC OPERATION WITH LEVEL RECORDERS TYPE 2306 OR 2309
12
It is often a great advantage if a hard copy of a spectrum can be plotted out while the an-
alysis is proceeding. The 1621 has been designed for use in conjunction with Portable
Level Recorders Type
2306 or 2309 for that purpose. When the 1 621 and 2306/2309
are connected together with the appropriate cable, and the . 1621's SWEEP CONTROL
switch is set to "Auto", the 2306/2309 will sweep the filter synchronously with its re-
cording paper as soon as the "Start" button has been depressed. The synchronization
cable to be used depends upon the type of Level Recorder being used. For those with a
8-pin DIN socket, i.e. a 2306 with a serial number 718058 or higher and all 2309's,
then a cable AQ 0034 should be used with the pins connected 1-1, 2-2, ... 8-8.
For a 2306 before number 718058, which had a 7-pin DIN socket for synchronization,
cable AQ 0182 should be used. (see Fig.3.8 for pin connections).
2306
Remote
Control Socket
JP 0703 JP 0802
1621
Sync.
Socket
770776
Fig . 3.8. Cable AQ 0182 for frequency synchronization between
1621 Filter and 2306 Level Recorder (before serial no.
718058). External view of sockets, soldering side of plugs,
shown

The procedure for using the 1 621 and 2306/2309 combination is as follows:
1. Connect the 1621 and 2306/2309 into the instrumentation line as required (see
also
section 3. 3) with the 1621 connected to the Level Recorder by cable AQ 0034
or AQ 0182 as required.
2. On the 1621 select "Internal Battery" or "External Power" as required. See section
3.2.
3. Using the INPUT VOLTAGE SELECTOR, select the maximum input voltage to be
used.
4. Use the FILTER SELECTOR knob to choose the required analysis bandwidth.
5. Set the SWEEP CONTROL switch to "Auto".
6. Check that the batteries are fully charged in the appropriate Level Recorder and fit
the correct paper. For the 2306 frequency calibrated paper Type QP 0120, QP
0124, QP 0143 or QP 0224 should be used and for the 2309 Type QP 2100 or QP
2120 .
Set on the 2306:
PAPER DRIVE
POWER
PEN DRIVE
or on the 2309:
PAPER
PEN
PAPER DRIVE
POWER
"In"
"On"
"In"
''Forward''
"Down"
"Cont ."
"On"
7. Calibrate the pen deflection of the recorder (see the 2306 or 2309 Instruction Man-
ual).
8. Using the FREQUENCY RANGE SELECTOR of the 1621 choose the first decade of in-
terest for analysis.
9. Adjust the position of the recording paper until the pen lies directly over the begin-
ning of the frequency decade to be swept. (The position of the FREQUENCY TUNING
KNOB
of the 1 621 is irrelevant when tuning is controlled by the 2306/2309, and
it does
not move during the sweep.
1
0. Select the required recording paper speed, bearing in mind that this will control the
filter sweep speed (see section 4.3).
11 . Select the required writing speed, bearing in mind that this will also affect the aver-
aging time (see section 4.3). If DC recording is being used, averaging time must be
set on the meter to which the 1 621 is connected.
12. Depress the 1 621 SWEEP CONTROL switch to "Start" and release it to the "Auto"
position. The 2306/2309 will now sweep the filter synchronously with its record-
ing paper
over one decade from "2" to "20" on the 1 621 scale (without the pointer
moving whilst this happens). The SWEEP CONTROL INDICATOR lamp of the 1621
13

14
will light during the sweep. When the decade has been swept, the Level Recorder
and the filter sweep will stop and the SWEEP CONTROL INDICATOR lamp will go
out.
13. Repeat steps 8 - 13 as necessary for the next decades of interest. Synchronization
will be maintained during the process, and from one chart to the next.
I