Bruel & kjaer 1623 User manual

Instruction

Manual

Tracking Filter Type

1623

Filter

Center

Frequency

BrOel&

Kjaer

Tracking

Filter

Type

1623

Tachometer

Input

r

<;)

20mV

- 1

20V

033-0280

Trigger

level

Battery

'

Record

er

Sync

.

• • a • •

. .

.

On~

.

-

1V

+IV

r-

Manual

Tuning

/Preaet

•--,

200Hz

·I

20kHz

2Hz

1

200Hz

,----

Tracking

Mode

-._,

Tachm

. Filter Noise

In

put Input Manual Fiher

-r-1-r---

-.ndwtdth

6%

. 1

2%

23%

I

A small battery operated tracking

filter

which

can be synchronised

with

the funda-

mental frequency

or

any harmonic between

1

/99

and

99/1

of a periodic

tuning

signal.

Combined

with

a vibration meter. sound le-

vel meter,

or

measuring amplifier, the

1

623

allows

signal analysis

with

respect

to

a variable frequency reference signal, for ex-

ample vibration level

as

a function of shaft

speed. Frequency range covered is

2Hz

to

20kHz

with

filter

bandwidths

of

6%, 12%.

and 23%. Tuned frequency synchronisation

signals provided

for

the

Portable Level

Re-

corder Type

2306

and for X-V recorders.

Manual

tuning

of

the

filter

by means

of

a

front

panel

tuning

knob coupled to a

built-in

oscillator.

+ Bri.iel & Kjcer

TRACKING

FILTER

TYPE

1623

Revision

March

1

980

CONTENTS

1.

INTRODUCTION

AND

SPECIFICATIONS

(PRODUCT

DATA)

.................................................

1

2.

CONTROLS

....

........

..

.. .... ........

......

..

......

.

..

.....

..

....

........

..

........

.. ..

.. .... ....

....

........

..

........ 7

2.1.

FRONT PANEL

.......

..

....

........

....................................

......

..............

7

2.2

. REAR PANEL

..

..............

..

.........

.

..

..........

........

......

............

....

..

........

..

......

10

3.

PRELIMINARY

....................................................................................................................

;

12

3.1. MOUNTING

......................

.

........

.

.............................................................

12

3.2

. POWER SUPPLY

......

....

............................................................................

13

Rechargeable Cells

(8

& K no. QB

0008)

..

.

..

........

..

................

.. ..

......

..

....

..

.

..

. 13

Dry

Cells

1,5

V

.......

.

......................................

.......

......

..................

.

..........

14

External

DC

Supply

6

to

15 V ......

..

....

..

.

..

.

.. .. ..

....

..

.

.. .. .. ..

.........

..

.

..

...

..

...... 14

Power

Supply

Type

2808

..................

..

...

..

.

.. .. .. .. ..

.....

..

........... .. .... ............. 15

3.3.

CHARGING THE INTERNAL BATIERY FROM

THE

AC

MAINS

........................

15

3.4.

FUSE REPLACEMENT

..............................................................................

16

4.

OPERATION

....................................................................

.

...................................................

17

4.1. USING THE

1623

FILTER

...............................................................

.

.........

17

4.2.

SUITABLE TUNING SIGNALS

....................................................................

17

Photoelectric

Probe MM 001-2 ..............

..

.. .......

..

... .

..

.

..

.......

..

.

..

..... ...

.. .. ..

.... 18

Magnetic

Pickup

MM

0002

..

............... .

.. .. ..

....

..

... ...

..

.............

..

...............

18

4.3. SETIING THE TRIGGER LEVEL

.........

..

...............................................

.

..

.....

19

4.4.

MANUALLY

TUNING

THE

FILTER ....

.. ..

.......

.. .. .. .. ..

...

..

... .... .... ......... ..

..

.....

..

.

19

4.5.

SYNCHRONISATION WITH RECORDERS

....................................................

20

Synchronisation

with

the

'Portable Level Recorders Types

2306

and

2309

....

20

Synchronisation

with

an X-Y Recorder

......

..

................................

.....

..

........

22

4.6

. USING

THE

TRACKING FREQUENCY MULTIPLIER

....................................

.

..

23

4.7. USING THE SPECIAL NOISE FILTER ....

......................................................

23

4.8.

FILTER SWEEP RATE LIMITATIONS

...........................................................

24

4.9

. TUNING FROM THE FILTERED OUTPUT SIGNAL

.........................................

25

FEATURES:

•

Battery

operated

• Frequency range 2

Hz

to

20kHz

• Three selectable

filter

bandwidths

6%, 12%,

23%

(1

/3

Octave)

•

Tunable

from

practically

any

periodic

signal

•

Manual

tuning

facility

•

Filter

frequency/tuning

signal

frequency

ratio

adjustable

between

99/1

and

1/99

•

Synchronization

signals

for

level

and

X-Y recorders

•

Wide

dynamic

range,

>60

dB,

with

crest

factor

capability

4

• Large

digital

display

of

filter

centre

frequency

•

Low-pass

noise

filter

for

tuning

signal

USES:

•

Synchronous

vibration

analysis

of

rotating

machinery

•

Harmonic

analysis

of

vibration

and

electroacoustic

signals

•

Filtering

of

response

signals

in

vibration

testing

set-ups

•

Harmonic

distortion

measurements

on

gramophone

pick-ups

19-300

type 1

623

Tracking Filter

Filter Center Frequency Trigger

level

Betterv

- -

~

--

~------~

------

Recorder

Sync.

~

11',:,//

~

L

___

- -

---------

On

Tracking

Filter

Type

1623

Introduction

The

fully

portable,

battery

oper-

ated, Tracking Filter Type 1

623

is a

narrow

bandwidth

filter

whose

cen-

tre

frequency

automatically

locks

onto

and

follows

the

fundamental

frequency,

or a

harmonic,

of

a peri-

odic

tuning

signal

originating

from,

for

example, a

tachometer

or

vibra-

tion

transducer

. Its

small

size and

built-in

battery

power

supply make

it ideal

for

field

operation

with

the

general purpose

Vibration

Meter

Type

2511.

When

combined

with

a sound lev-

el

meter,

vibration

meter,

or mea-

suring

amplifier,

sound,

vibration,

and

other

signals

which

can be con-

verted to electrical

waveforms,

can

be analyzed

as

a

function

of

a vari-

able

frequency

reference signal.

As

a typical example, can be quoted

the

synchronous

vibration

analysis

of

an

engine

being

run

up in speed;

the

vibration

level measured can be

plotted as a

function

of engine

speed, and

the

development

of re-

r Menual Tuning/Preaet '

e

2

00

Hz

20kH

z

2H

z

200H

z

,----

Tracking

Mode

~

Tachm. Filter Nol18

Input Input Manual Filter

sonances excited by

the

fundamen-

tal rotation

frequency

and its var-

ious

harmonics

can

then

be

stud-

ied.

Filters

Both

the

tuning

signal frequency

and

the

filter

frequency

ranges

cover

2Hz

to

20kHz

in one range

with

automatic

tuning.

Three con-

stant

percentage

bandwidth

filters

are provided

with

"white

noise"

bandwidths

of

6%, 12% and

23%

(

1/3

Octave)

of

the

tuned fre-

quency.

Constant

percentage band-

width

filters

give a

constant

resolu-

tion

on a

logarithmic

frequency

scale and are

therefore

able to give

a

relatively

quick

analysis over a

wide

frequency

range.

The

filter,

which

has a dynamic

range

of

about

70

dB, consists of a

digitally

tuned

pair

of two-pole

But-

terworth

filters

that

give good selec-

tivity

with

an

attenuation

of

12

dB/octave.

Characteristic curves

for

the

filters

are

shown

in Fig .1.

Mea

s

uring

Object

:

__

_

DDDDDD

DO

DDDO

D O O

OODOOOOOO

0

dB

Dat

e:

10

dB

20 dB

30dB

40dB

50 dB

100

200

Lower

Lim

. Freq

.:

Potentiomet

er: Zero Lev

% Bandwidth =

12%

Bandwidth =

3%

Bandwidth =

500

1

000

2000

5000

10000

Hz

Writ

ing

Sp

eed:

mm

l s

760855

Fig.1.

Typical

filter

characteristics

of

Track

-

ing

Filter

Type

1623

The

large

digital

display

on

the

front

panel,

showing

the

frequency

to

which

the

filter

is

tuned

, is

easily

readable in

daylight

conditions

.

Filter

Tuning

Practically

any

well

defined

peri-

odic

signal

with

a level

between

20

mV

(noise

free)

and 1

20

V peak-

to-peak

and

a

noise

level less

than

20

mV

peak-to-peak,

is

suitable

for

tuning

the

filter.

The

signal

can,

for

example,

be

obtained

from

a ta-

chometer,

photo-electric

transdu-

cer, eddy

current

probe,

accelerome-

ter,

microphone,

force

transducer,

magnetic

transducer,

capac1t1ve

transducer

etc

.

(with

suitable

pream-

plifier

where

necessary)

which

will

give a

signal

in

synchronization

with

some

periodic

motion

of

the

measuring

object.

A

manually

set

trigger

level en-

ables

the

periodicity

of

the

tuning

signal

to

be

detected

in

the

most

su-

itable

portion

of

the

waveform

;

this

adjustment

together

with

the

hyster

-

esis

effect

exhibited

by

the

trigger,

makes

it

possible

for

a

reliable

con-

trol

pulse

to

be

obtained

from

al-

most

any

periodic

waveform

.

In

addition

to

the

"tachometer"

in-

put

,

two

other

possibilities

exist

for

automatically

tuning

the

filter:

(1)

Where

the

signal

to

be

filtered

has

a

well

defined

periodic

content

it-

self,

this

can

also

provide

the tun

-

ing

signal.

(2) In cases

where

a peri-

odic

component

of

the

signal

to

be

filtered

is

not

clearly

defined,

the

fil-

ter

can be

tuned

through

any

single

decade

using

the

filter

's

own

output

as a

tuning

source.

In

this

case,

the

tracking

frequency

multiplier

facil-

ity,

of

course,

cannot

be used.

One

2

would

normally

expect

this

closed

loop

control

system

to

be

unstable,

but

with

the

un

i

que

digitally

tuned

filter

used in

the

1623,

this

is

not

the

case.

Note

that

for

ordinary

frequency

analysis

work

the

1

623

can be

auto-

matically

tuned

by

the

Sweep

Unit

Type

5555.

Photo-Electric

Transducers

for

"Tachometer

Tracking"

For analyses on

rotating

machin

-

ery, a reliable

method

of

tuning

the

filter

is by

means

of

a

photoelectric

transducer

which

gives a

well

de-

fined

pulse

each

time

a

photo-diode

or

transistor

is

triggered

by an

inter-

rupted

light

source

.

The

B &K

Photoelectric

Tachome-

ter

Probe

MM

0012

is a

combined

infra-red

light

source

and

pickup

de-

vice

built

into

a

common

housing

,

which

is ideal

for

triggering

the

1

623.

It is

positioned

up

to

15

mm

from

a

convenient

rotating

machine

part

so

that

the

light

beam

is

ref-

lected

back

from

a

contrasting

band

attached

to

the

part

. A

white

paper,

or

aluminium

foil

strip

glued

onto

a

black

background

is ideal. The de-

vice is

fitted

with

a red

filter

to

re-

duce

interference

from

mains-oper-

ated

lights.

Power

for

the

MM

001

2 is

derived

directly

from

an

extra

shield

in

the

tachometer

input

socket

(BNC)

of

the

1

623.

Fig.2.

Photoelectric

Tachometer

Probe

MM

0012,

available

as an

accessory

for

the

Tracking

Filter

Type

1623

Manual

Tuning

By

means

of

a

tuning

knob

on

the

front

panel,

the

1

623

can be

manu

-

ally

tuned

and

used as an

ordinary

tunable

bandpass

filter

for

fre

-

quency

analysis

work

in

the

field

.

The

tunable

range

from

2Hz

to

20kHz

is covered

in

this

mode

in

two

ranges

(2Hz

to

200Hz

and

200Hz

to

20kHz)

. The

frequency

tuning

knob

is also used

to

preset

the

filter

centre

frequency

to

the

ap-

proximate

starting

frequency

of

the

tuning

signal.

This

significantly

re-

duces

the

time

taken

for

the

filter

to

automatically

lock

onto

the

tuning

signal

,

especially

at

lower

frequen

-

cies.

Auxiliary

Sweep

Unit

An

alterna-

tive

to

manual

tuning

of

the

1

623

for

ordinary

frequency

analysis

work

is

the

Frequency

Sweep

Unit

Type

5555

available

on

special

order

from

the

B & K

Systems

Engineer-

ing

Group

.

The

5555

connects

to

the

tachometer

input

of

the

1

623

and

facilitates

automatic

frequency

sweep

between

two

preset

frequen-

cies selected on

the

front

panel

of

the

5555.

Start

frequencies

of

2,

20,

200,

and

2000Hz

may

be

chosen

while

the

upper

frequency

may

be set

to

20

,

200

, 2 K, and

10kHz

. Coverage

up

to

20kHz

is

possible

by

using

the

frequency

mul-

tiplier

facility

in

the

1

623

.

It

may

be seen

from

Fig.5

that

for

a

given

filtered

signal

accuracy

the

sweep

speed is

limited

at

high

fre

-

quencies

by

the

writing

speed

of

the

recorders, Types

2306

and

2309

.

At

low

frequencies

the

limit

-

ing

factor

is

the

1

623

filter

settling

time

which

in

turn

depends

on

the

filter

bandwidth

chosen

. These val-

ues are set on

the

front

panel

of

the

5555

so

that

changeover

from

one

limiting

parameter

to

the

other

is au-

tomatic

during

sweep

thus

ensuring

the

shortest

possible

analysis

time

.

The

5555

is

equipped

with

a

built-

in NiCd

battery

which

may

be re-

charged

in-situ

by

battery

charger

ZG

0113

which

is

supplied

as an

accessory

to

the

1623

.

Battery

con-

dition

is

indicated

on a

meter

.

Tracking

Frequency

Multiplier

This

facility

enables

the

filter

to

be

tuned

to

any

ratio

combination

between

1/

99

and

99

/ 1

times

the

tuning

signal

frequency,

thus

allow-

ing

any

harmonic

or

sub-

harmonic

(between

these

limits

and

within

the

frequency

limits

of

the

instru-

ment)

of

the

fundamental

of

the

measured

signal

to

be

examined

.

This

feature

makes

the

vibration

an-

Filter

Bandwidth

6% 12%

23

%

(?(?

(y

G

M

Filter

Input

Amplitude

(oot~o!l'l

Overload

!-

Detector

0 Manual

D

E

Manual

Tuning/

Auto

-Cut-

r---

out

f >

200Hz

~

LP

Noise

Fi

lter

6

{ Noise

4~

fFilter

Schmitt

Trigger

Preset/

Digitally

Tuned

Analogue

Filter

Output

J"\

~Frequency

~

(out

of

range)

Tuning

Range

.__

_________

~

Change Recorder

Logic

Control

/

Range

Changing -

r--------<--1

Synchron-

.-------+---i

isation

-----o

Pulse

a:

Log f

(for

2306)

and 2309

Memory

~-----iTFimej

.,._

_____

,Frequency

requency Display

Logic

~

Battery Charger

-

!---(included)

12 V,

-

400mA

Preset

e---------1

~Preset

Power

Track

~Track

-Supply

0

1--

External Power Supply

Logic -

T

6Vto15VDC(4W)

J

I

t Denomina Numerator

tor

1 1 2 MHz

Tuning

Oscillator 1 1

-to-

Counter 1

to

gg

Reference

1

99

Oscillator

Divider Divider

760851

Fig.3.

Simplified

block

diagram

of

Tracking

Filter

Type

1623

alysis

of

machinery

containing

gear

wheels

and

shafts

rotating

at

differ-

ent

speeds a

relatively

simple

mat-

ter.

The

multiplication

ratio

is se-

lected and

clearly

indicated

by

two

pairs

of

tens

and

units

knobs on

the

front

panel.

Noise

Filter

A special

low-pass

filter

is

built

into

the

tracking

input

circuitry

in

or-

der

to

attenuate

high

frequency

rip-

ple

which

could

cause

false

trigger-

ing

at

low

frequencies

. If

the

noise

filter

is

switched

in,

it

automatically

becomes

inoperative

for

tuning

sig-

nal

frequencies

above

200Hz

.

This

filter

is

particularly

applicable

for

fil-

tering

out

the

1 kHz

synchronization

signal

when

the

1

623

is used

in

conjunction

with

the

Frequency

Re-

sponse

Test

Unit

Type

441

6 and

the

Test

Records

OR

2009

and

OR

2010

.

Principle of Operation

Reference

is

made

to

the

simpli-

fied

block

diagram

shown

in Fig.3 .

The

tuning

signal

is

converted

by

the

Schmitt

trigger

.

into

a

uniform

pulse

form

with

a period

time

equal

to

the

period

of

the

original

input

waveform

.

This

period

time

is

mea-

sured

by

counting

the

number

of

pe-

riods

of

oscillation

of

a 2

MHz

oscil-

lator

between

each

trigger

pulse,

and

this

number

is

then

shifted

into

the

memory

. The

tracking

frequency

multiplier

function

is achieved

by

di-

viding

the

pulse

rate

and/

or

by

di-

viding

the

oscillator

rate (in

effect

multiplying

the

pulse

rate) by

the

fi-

gure

selected

on

the

denominator

and

numerator

knobs,

respectively

.

From

the

memory,

logic

circuits

digitally

control

the

tuning

of

the

main

filter

according

to

the

calcu-

lated

period

time

. The

filter

range

is

one

decade

of

frequency,

but

range

changing

is

automatic

until

the

fre-

quency

limits

are reached,

after

which

the

out-of-range

"frequency"

lamp

lights.

The

filter

is

tuned

over

each

decade

with

a

hyperbolic

sweep

consisting

of

175

discrete

steps

. The

step

width

varies be-

tween

0,8%

and

2%

of

the

tuned

frequency

as

shown

in

Fig.4.

Due

to

the

stepwise

method

of

tuning

the

filter,

the

1623

is

not

suitable

for

use

where

phase

accurate sig-

nals

are

required.

The

memory

also

controls

the

fre-

quency

display

logic

where

the

cal-

culated

period

time

is converted

to

frequency

for

the

digital

display

. So

that

the

specified

filter

gain

accu-

racy is

not

significantly

altered, it is

recommended

that

the

frequency

tuning

is

not

swept

faster

than

indi-

cated

in

Fig.5.

This

chart

is based

on

the

filter

settling

time

. The

exam-

ple

shows

a

sweep

from

10

Hz

to

50

Hz

with

the

1

2%

bandwidth

fil-

ter

which

requires

a

minimum

sweep

time

of

5

s-

1 s = 4 s.

With

a

logarithmic

sweep,

the

sweep

rate

(determined

by

the

lowest

fre-

quency,

10Hz)

will

be 5 decades

per

minute.

The

sweep

rate

could

be

progressively

increased

with

in-

creasing

frequency

to

25

decades-

/

min

at

50

Hz

.

Recorder

Synchronization

signals

are pro-

vided

for

controlling

one of

the

axes

of

a

recorder

in accordance

with

the

tuned

frequency,

so

that

vibration

le-

vel

versus

frequency

or

r.

p.m

. plots

can be

made

.

Two

forms

of

synchro-

nization

signal

are provided: A

pulse

2,01,------

------

-~

1,

6+------::..-------,..--

--

----.,.,c...--1

'*-

0,8

c

0

:~

c

~

Cl

/

0,2.-""-

___

_...._

___

_.__

____

-::'

2 4 8 20

l------1

decade

of

frequency

•I

760850

Fig.4.

The

filter

is

tuned

through

each de-

cade

of

frequency

in

steps.

The

step

width

and

therefore

the

filter

defini-

tion

varies

between

0,8%

and

2%

of

the

tuned

frequency

as

shown

.

The

definition

of

the

frequency

display

va-

ries

between

0,2%

and 2%, as

traced

by

the

broken

line

3

output

representing

the

tuned

fre-

quency, on a

logarithmic

scale. This

is intended

for

controlling

the

posi-

tion

of

the

recording paper on

the

portable Level Recorder Types

2306

and

2309.

A

switch

on

the

rear

panel of

the

1

623

selects

either

for-

wards and backwards paper move-

ment

or

forwards

(increasing fre-

quency) paper

movement

only

.

Unless

the

Level Recorder Type

2306

is modified

the

recording

paper can

only

be fed in

the

for

-

ward

direction

.

Where

the

tuned

fre-

quency falls, for example due to a

reduction of

machine

r.p.

m.,

the

paper feed

will

stop. The paper feed

will

commence

only

if

that

fre-

quency (or r.p.m.) is reached and ex-

ceeded again.

Modification

Kits

for

the

Level Re-

corder Type

2306

to enable

it

to

run both backwards and

forwards

are: Kit No.

WB

0250

for

2306's

with

serial

No

.

lower

than

718

058.

Kit No.

WB

0329

for

2306's

with

serial No.

718

058

and

higher.

Two-Channel Level Recorder Type

2309

may be run in both

forward

and backward directions

under

con-

trol from

the

1

623.

The second

form

of

synchroniza-

tion signal provided is a

DC

ramp

voltage

which

is

logarithmically

pro-

portional to

the

filter

tuned

fre-

quency. This operates in both direc-

tions and is intended

for

controlling

one of

the

axes of

the

X-Y Recorder

Type

2308

.

Power

Supply

The

internal

power

supply con-

sists of six, 4

Ampere

-

hour

capacity

Nickel Cadmium rechargeable cells.

Their capacity is

sufficient

to cover

a

continuous

operating

time

of 8

hours. The separate battery

charger, Type

ZG

0113,

supplied

can recharge

the

cells

from

a com-

pletely discharged condition in

about

14

hours.

Alternatively, an external

DC

power supply of + 6 V

to

+ 15 V can

be used

to

power

the

instrument.

The external

power

supply and bat-

tery charger are connected

through

a socket on

the

rear panel of

the

1623.

4

0,25

J. I I I

Note: Valid

for

denominator settings D<10

for

D>10,

multiply

Time by

-RJ

I I I

and

multiply

Sweep

Rate

by

~--1-----l

250

500

Frequency (Hz)

760863

/ 1

Fig.5.

Chart

for

determining

the

recommended

maximum

logarithmic

frequency

sweep

rate

and

the

recommended

minimum

frequency

sweep

time

for

filtered

signal

inaccuracy

<-1

dB

(additional

to

specified

filter

gain

accuracy)

:If

CA.UttON

CH

ll.ltGE VOLTAGE

MOS

T ONLY

IE

APPUED

WHEN USING

RECHAIIGEAB

LE

BATTEIIIES

Fig.&. Rear panel

view

of

Tracking

Filter

Type

1623

Photoelectric Tachometer

Probe

MM

0012

Tracking Filter

Vibration Meter

Chart

Synchronisation

----l

I

L

__

_,.•..:.'

,.,

..

,.

.....

Level

Recorder 2306 or 2309

or

X-Y Recorder 2308

Filtered

Signal

Fig.7. Typical

instrument

set-

up

for

synchronous

vibration

analysis

760852

BRUEL & KJAER 1623 User manual

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