Laser-Doppler-Instrument LDI
User Manual
JENOPTIK Group.
Dear User
You are advised to read this manual carefully before you start using the Laser Doppler
Instrument (LDI). This is necessary to ensure that you will be able to utilise all the
capabilities which your new instrument offers. This technology is subject to further
development.
Note:
No part of this User Manual may be reproduced in any way (by print, photocopying,
microfilm or any other technique) without prior written approval by JENOPTIK Laser, Optik,
Systeme GmbH, nor may it be processed, duplicated or disseminated with the help of
electronic systems.
Appropriate care was used in preparing this document.
Editorial deadline:
Documentation number:
May 1999
012704-99-03-0699
JENOPTIK Laser, Optik, Systeme GmbH
2
Jena, 30.05.1999
Laser - Doppler - Instrument LDI
User Manual
Table of Contents
1.
2.
3.
4.
4.1.
4.2.
4.3.
5.
5.1.
5.2.
6.
7.
8.
9.
10.
10.1.
10.2.
11.
12.
13.
13.1.
13.2.
13.3.
13.4.
14.
Safety Instructions
Application of LDI
Principle
Product Description
Instrument set-up
Functioning of LDI
Interfaces
Initial Start-up
Installation and adjusting
Starting measurement and calibration
Optional Versions
Technical Specifications
Standard Delivered Configuration and Accessories
Instrument Error Reports
Cleaning and Technical Safety Checks
Cleaning
Technical safety checks
Customer Service
EC Conformity Declaration
Enclosures
Enclosure 1: Calibration certificate
Enclosure 2: Speed analysis
Enclosure 3: Counter setting
Enclosure 4: LDI-watch setting
Telefax
27
3
4
5
6
7
7
8
9
11
11
13
14
16
17
18
19
19
19
20
21
22
22
23
24
26
1. Safety Instructions
Safety and operating instructions must be read carefully and followed in practical usage. The
specified operating conditions must be observed when working with this instrument. Noncompliance with these instructions or improper usage may cause physical injury to the user
or cause damage to the instrument.
Caution:
There is danger of eye or skin injuries.
The optical measurement head emits laser radiation (laser class 3B according to EN 60
825/1: 1994). The LDI may only be operated with its shielding (protective cover, absorber)
properly installed. This is necessary to protect from laser radiation and uncontrolled
spreading of such radiation (laser class 3B according to EN 60 825/1: 1994).
An absorber is located behind the material being tested to protect from laser radiation in the
event of sudden material failure (for example web or cable rupture).
Do not remove any mechanical shields, nor look into the measuring head during LDI
operation, nor direct the measuring head onto any part of the human body!
This will result in eye or skin injuries!
Shielding parts may not be removed by anyone other than authorised personnel performing
installation or calibration work on the LDI.
Caution:
The use of control or adjustment tools or operating procedures others than those
specified herein may lead to hazardous radiation exposure!
Caution:
There is danger of electrical shock!
Repair work on the LDI must not be done by anyone but duly instructed service personnel,
since life-threatening voltages are created inside the instrument.
The same applies for calibration and counter setting. The LDI is to be opened only by
trained personnel.
Caution:
There is danger of destroying the LDI!
There is danger of eye or skin injury!
The laser cassette of the basic LDI unit and the optical measuring head are linked via
shielded glass fibres. This connection must not be removed.
Do not loosen any strain-relief screws to avoid breaking the glass fibres which
will inevitably lead to the destruction of the LDI!
As a consequence, laser radiation may spread in an uncontrolled manner and
cause eye or skin injury!
4
2. Application of the LDI
Manufacturing plants with conveyor lines transporting tape, ribbon or web material are
becoming more and more productive. This is achieved by increasing the advance speed,
which, in turn, calls for new measurement techniques.
The classical methods of mechanical measurements involve metrological errors that are
caused by slippage. Also they impact the surface to be measured. Non-contact measurement
provides a true alternative. The most frequently used measuring technique that avoids any
surface contact is based on the laser Doppler principle. Laser Doppler units can measure the
sample speed v and derived measures such as length L, material acceleration a and
periodical material speed changes v.
Most commercially available Laser Doppler units provide a multitude of functions and
parameters designed for flexible use. This keeps the operating cost high and requires the
user to have special technical knowledge.
The new LDI (Laser Doppler Instrument) from JENOPTIK Laser, Optik, Systeme GmbH is a
compact, rugged, easy-to-operate tool which allows non-contact longitudinal measurement
on solid moving surfaces. It measures exactly, even with motion reversal, at „zero“ speed,
and during acceleration phases.
A high signal-to-noise ratio is achieved by narrow-band frequency filtering, so even weakly
scattering surfaces are measured reliably. State-of-the-art optical technologies, using such
features as laser diodes, integrated optical chips and glass fibre connection between the
basic LDI unit and the measuring head, guarantee highly reliable operation of the LDI and
make it particularly suitable for on-line operation in harsh industry environments.
The LDI is designed for length and speed measurement on moving material samples.
Because of its on-line measurement capability, the measured speed values vN can be used to
present a graph or, after a FFT-analysis a spectral course. Periodical speed changes in
production lines can thus be detected and preventive measures against be taken.
The LDI is designed to cover the following applications:
 measuring the length where material is cut to length
 measuring the length where markers are applied on surfaces
 controlling production process for cable, ribbon or web material
 spectral presentation of the speed course (FFT-analysis).
Measurements can be done for cable, ribbon or web materials such as:
 paper or cardboard
 cables or wire
 textiles or leather
 film or foil
 other materials.
3. Principle
The LDI uses the cross-beam principle (differential Doppler method) in reflection with a frequency shift fSh between the two transmission beams S1 and S2.
The fringe model provides a simple explanation for the generation of the Doppler frequency
of light scattered on moving samples. If two coherent sub beams S1, S2 with a wavelength of
 are superimposed onto each other under an angle of 2 at the measurement location, they
form a pattern of interference fringes with the fringe distance of d (Fig.1):
5
d=sin2).
(1)
As particles of the sample surface move through this line pattern, they scatter light every
time they pass a bright zone. A detector detects modulated light with the frequency fD
(Doppler frequency). The particle speed v can be calculated from this Doppler frequency fD:
v=fDsin2)=fDd.
(2)
v
v
S1
d
2
Interference
pattern
S2
Fig.1: Interference pattern in the measurement region
One length increment I0 is counted after a /2 phase shift of the Doppler signal relative to a
reference signal. One increment I0 corresponds to a moved sample length of d/4. The
smallest length increment is about 4 µm.
In the case of „zero“ speed (v=0), there is no frequency information in a stationary fringe
pattern, and signal processing is not possible. Also no forward/backward recognition can be
done because the generated Doppler frequency fD has no sign to distinguish forward and
backward motion.
Laser Doppler units, suitable for the measurement of small speeds (including standstill) and
in reverse-travel motion, must generate a frequency shift fSh between the two transmitted
laser beams S1, S2. This frequency shift generates a moving line pattern on the sample. It is
characterised by the line speed vi:
vi=dfShift
(3)
The resulting speed is the sum (forward) or difference (backward) of this line speed vi and
the sample speed v.
Currently laser Doppler set-ups use Bragg cells to generate this frequency shift. In the LDI, a
new principle is employed:
beam splitting and phase modulation accomplished with an Integrated Optical Chip (IOC).
This principle allows the construction of an all-fibre-version. The light from the laser source
to the measuring head is permanently guided in optical fibres. Use of the IOC essentially
simplifies the optical assembly and allows the construction of a compact and rugged unit
with high long term stability. Thermal, electromagnetic and mechanical stresses have no
influence on measuring accuracy.
6
4. Product Description
4.1. Instrument set-up
LC
9
1
8
CC
PS
7
8888,88
2
3
4
10
5
11
Fig.2: Front side of basic LDI unit ,
schemat ic view
6
v
15
12
16
14
13
2
Fig.33: Back side of basic LDI unit ,
schemat ic view
17
22
18
19
20
21
The LDI consists of basic unit containing the laser cassette (LC), counter cassette (CC) and
power supply (PS), and the measuring head (13). These two components are permanently
connected via a screened conductor tube (12) with both transmitting and receiving fibres.
Caution! The screened tube is mechanically connected to the laser cassette and
the measuring head. Do not loosen the strain-relief screws to avoid breaking of
the glass fibres!
This may lead to uncontrolled spreading of laser radiation and eye or skin injury!
7
On the front side of the basic unit are located (see Fig.2):
(1):
(2):
(3):
(4):
LED:
LED:
LED:
LED:
(5):
LED:
(6):
(7):
(8):
(9):
(10):
(11):
Switch:
SMC-jack:
setting knob:
level indicator:
indicator:
output:
Laser diode for „ON“
RESET signal
Channel C: fail signal
Channel A: signal „clock“ or „sin“
(standard delivered with: „clock“)
Channel B: „up/down“ or „cos“
(standard delivered with: „up/down“)
RESET-switch and print command
Speed interface
to adjust signal level (optional)
Optical signal level
Counter reading (length in m)
Fibre output to measuring head
The optical measuring head (of Cr-Ni-steel) contains:
(12): Shielded tube with optical fibres
(13): Measuring probe
(14): Front lens
(15): Customised cover shield
(16): Customised absorber
Located on the back side of the basic unit (Fig.3) are:
(17): Fuse Compartment
(18): Power switch
(19): AC power port
(20): 9-position Sub-D jack for printer
(21): Interface
(22): Switch for manual or automatic control of signal level (optional)
4.2. LDI operation
The LDI measures covered length on solid surfaces by counting 4-phase transitions of the
detected Doppler signal with the Doppler frequency fD. There are four pre-selection switches
on the cassette which can be used for LDI calibration (counter values 163, 162, 161, 160).
Calibration is done by selecting the right number of increments I0=d/4 to accumulate for the
output of a standard length increment I (standard 1cm).
The monitoring, controlling and indicator elements on the LDI unit have the following
functions:
(1):
LED shows the function of the laser diode (LDI ready to start).
(2):
LED shows the RESET state
(3):
LED shows fail signal or signal level falls below minimum level. Measurement is
interrupted 0.3s after fail signal , the last measured value is indicated, measurement
continues after a valid signal is received again.
(4):
LED shows the operation of channel A, it lights after every outgoing length increment
I
(5):
LED shows the operation of channel B, it shines in the case of „up“ (forward motion)
(6):
RESET-switch and print command simultaneously, to bring the display to „zero“
(7):
Speed interface
(8):
Setting knob to adjust the correct signal level (in standard version, this knob
is ineffective) manually.
8
(9):
level
(10):
(20):
(21):
(22):
Indication of the optical signal level (exact level only with moving samples). If the
falls below a certain minimum, LED3 will light and measurement is interrupted.
Display of measured length (standard: m, resolution: cm)
Printer interface
Interface
Switch for manual or automatic control of signal level (optional). In standard outfit
version, the automatic mode operates and the setting knob 8 is disabled.
4.3. Standard interfaces
1. Interface 7: speed output
The SMC jack output 7 delivers an output signal proportional to motion speed. The user can
choose between the signal forms of digital frequency signal fD , voltage signal U or current
loop i, by plugging the SMC-plug into the „X“, „Y“ or „Z“ jack of the counter cassette (Fig.4).
Standard:
Optional:
Doppler frequency fD(t), plug into jack „X“ (fD)
0m/min=0MHz
1.000m/min=CMHz
50mV-peak on 50, pulse width: 50ns
Please take the constant C from the calibration certificate (enclosure 1).
Voltage U(t), plug in jack „Y“ (U)
0m/min=0V
1.000m/min=1V (optional 10V)
current loop i(t), plug in jack „Z“ (i)
0m/min=4mA
1.000m/min=20mA
pre-selection
sw itches
0
2
1
Y
U
3
Z
4f D
X
fD
E
F
G
A
B
C
D jumper
Fig.4: Counter cassette, schematic view
i
2. Interface 20: printer (aliasi printer)
The printer is plugged into interface 20 at the back of the basic unit (Fig.3). A PTB
certificated LDI version (PTB - Physical-Technical Federal Institution of Germany) with an
open interface must use an aliasi printer which records all measures results unmistakable.
On a RESET pulse, both manually (6) or remotely triggered (interface 21) the following file
will be printed:
system number:
running number:
date:
time (MEZ):
length:
xx
1 ...99.999
xx.yy.zz
xx.yy.zz
0 ...9.999,99 m
9
10
5V
(24V)
1k
(4,7k )
1
2
A
1k
(4,7k )
A: TTL
(SPS)
-A
output
B
The standard interface prints only the final length
value L (after RESET). The current length can not be
called up during measurement.
The time is set to MEZ. Conversion to MESZ does
not occur automatically. The re-setting of date and
time is described in enclosure 4.
Warning!
Danger of an electrical shock. The re-setting
of date and time must be done by instructed
service personnel.
3. Interface 21
Interface 21 is designed for the non-feedback
-B
transmission of the signal input and output of a
4
selected length measurement mode to and from an
external source. Connection is via a 9-position Sub-D
jack at the back of the basic LDI unit. The output
0V
signals are „length increments (clock)“, „motion
direction (up/down)“ and „signal loss“. The input signal is the external „RESET“.
3
B: TTL
(SPS)
Standard setting:
- smallest length increment: I=1cm,
- maximum output frequency: 40kHz (standard optocoupler)
The increment output I can also be chosen in other units, for example dm, mm or smaller
units. The output frequency of 40kHz limits the maximum sample speed transmitted by the
opto-coupler. The maximum sample speed of 2.400m/min can not be transmitted by
transmitting increments smaller than cm.
(Faster opto-coupler can be used optional)
Pin assignments of the 9-position Sub-D jack:
Outputs:
1: + channel A
2: - channel A
sin
3: + channel B
4: - channel B
cos
5: + channel C
6: - channel C
Input:
7: + RESET
8: -RESET
11
input:
output:
clk (cm), 0,1ms or
output:
up/down, static or
output:
failure signal level
RESET-signal
Fig.5: interface output
5V
(24V)
1k
(4,7k )
+RES
7
input
8
-RES
0V
Fig.6: interface input
12
Three output channels and one input channel are, electrically isolated, from the basic LDI
unit by optocouplers.. They are OC-stages (open collector) with protecting diode and can be
integrated directly into current loops of a PLC-control unit. Suitable resistors are necessary, if
the control unit has no current loops (Figs. 5, 6).
The length measurement mode can be changed by setting other jumpers in the counter
cassette (Fig.4).
Please note that changes of this type may only be performed by the manufacturer or duly
authorised personnel.
Standard version :
jumper A unplugged:
jumper B unplugged:
jumper C unplugged:
Jumper E, F plugged:
Optional: outputs as sin/cos
jumper A plugged:
jumper B plugged:
jumper C plugged:
jumper F, G plugged:
CH A: clock
CH A non negate
CH B non negate
RESET
CH B: up/down
CH A: sin
CH A negate
CH B negate
RESET negate
CH B: cos
5. Initial Start-up
Initial start-up may not be performed by anyone other than duly authorised personnel.
5.1. Installation and adjusting
Install the basic LDI unit at a maximum distance of 4m (fibre length) from the measurement
location. The customised holder with the measuring head 13 is installed over or beside the
sample to be measured (Fig.8). The distance L from the measuring head to the sample
surface is set to 250mm1mm by means of a standard (Fig.7).
Make sure the shielded tube is not bent beyond a minimum allowed radius of 25mm.
The measuring head must be aligned to the direction of the sample motion (Fig.7), to
achieve an accuracy of 0.1% for speed- and length measurements. The measuring head is
factory-mounted in a holder, so that the head angle  forms an angle of 00 to the plane C of
the attaching plate. This plate is mounted at the machinery in such a way, that plane C is
parallel to sample motion (=00) and the measuring head is at right angle to the sample
surface (=900).
Place LDI roughly in upright position (=900)
An angle error orreduces the measurement accuracy of the LDI (cos-error eq.4)



v/vL/L=cos()cos()
(4)
A misalignment of the angles  or  of 30 generates measurement errors of about 0.1%.
Because the LDI measures sample length in forward and backward directions, forward
sample motion must count length increments in „plus“-direction. Otherwise the measuring
head must be rotated with the clamp 1 and 2 by 1800.
To do this, the screws in the holder ground plate (G1, G2) must be removed (Fig.8) and
fixed in thread holes (G3, G4). An arrow „„ at the back of the measuring head shows the
sample motion direction „forward“ (main motion direction).
13
measuring head
250


=900 ( decreases only signal level)
=900 <30 (meas. error L/L<0,1% )
C

v
sample
=00 <30 (meas. error L/L<0,1% )
aligned to plane C of holder
Fig.7: Alignment of the measuring head
Re-adjustment of the head angle  may be done only in special cases. To re-adjust the
screws in the clamps 1 and 2 must be loosened. The measuring head in the holder is then
rotated so that the plane of the two transmission beams creates an angle of =00 with the
sample motion direction (Fig.7).
1. Adjustment with constant sample speed v0
An exact adjustment can be made, if the sample speed v0 is a constant. The angle 
is adjusted till the speed v=v0cos measured with the LDI (interface 7) gets a
maximum value (v=v0 if =00).
2. Adjustment with non constant sample speed v1
14
If the sample moves with varying speed v1 an adjustment to the speed minimum
(measured with the LDI) can be done. The angle  is so adjusted, that the speed
measurement v=v1cos shows a minimum value (v=0 if 900). After fixing the
measuring head in the clamp holder, the clamps 1 and 2 (including the measuring
head) are unfixed from the ground plate, rotated by 900 and fastened again on the
ground plate.
Warning!
Provide laser safety! Do not look into the measuring head. Watch the laser radiation with
enclosed IR-detection card!
The customised absorber 16 must be mounted after alignment of the measuring head.
5.2. Starting measurement and calibration
part of machinery
ground plate
G3
G1
scramp 1
measuring
head
scramp 2
G4
G2
Connect LDI to AC power point (120V, 100W,
60Hz) and turn on power with switch 18 at the
back of the basic LDI unit.
The display undergoes an internal test routine:
displayed value „8888.88“.
LED1 will light steadily as soon as the instrument
has reached its operating temperature (after
about three minutes). The LDI is ready to start.
Prior to each length measurement, the LDI must
be zeroed with a RESET signal which may be
triggered manually via RESET (switch 6) or by
supplying an external RESET to the 9-pin Sub-D
connector 21. The display shows: „0000.00“ m.
The sample must lie in the measurement location
of the LDI. After defined length motion, the
measured length can be read on the display 10 or
processed via interface 21. A manual or external
RESET pulse sets the display back to „0000,00“. If
a printer is connected to the interface 20, the data
length will be printed after the RESET pulse.

v
Fig.8: Customised LDI-mounting
sample
Delivery of the LDI includes with automatic control of the signal level. The signal level is
matched automatically to different materials. Switch 22 and control knob 8 are disabled in
this operation mode.
For special applications, particularly for transparent or weakly scattering materials, the
manual signal level control may be advantageous (see 6.12. optional LDI versions).
The instrument is factory-calibrated. A calibration certificate is included. The calibration data
and assure traceability of the measured results to a glass scale calibrated by PTB
Braunschweig/Berlin and a two-dimensional calibration standard.
Re-calibration or changes in the counter setting means an intervention in the signal
processing system. Calculation errors or false setting of the pre-selection switches result in
15
measurement errors. The calibration or the adjustment of other length increments is
described in enclosure 3.
Warranty claims will be null and void if the customer changes the counter setting. The
warranty may be restored after a re-calibration by manufacturer personnel.
6. Optional LDI-Versions
1. RS232 interface (unidirectional)
The printer interface 20 must be connected to an alias printer if the customer uses
the open interface 21 and the length measurement must be calibrated.
We recommend a second unidirectional interface RS 232, parallel to the printer
interface 20, for data processing in a PC. So the data acquisition of the length data
L can occur direct to the PCB data are for the signal processing in a connected PC
2 Non-volatile static RAM for data storage
Instead of an alibi printer a non-volatile static RAM (512K x 8) in the basic LDI unit
also can be used for data storage. The RAM can store 20.000 records at least (LDI
number, product number, running number, date, time and measured length) before
the first record is overwritten.
A RS485 (RS232) interface realises the bidirectional data transfer between LDI and
PC. Data of the sample (product number, running number) make the surching of
special data in the RAM easier. The PC takes the current length L(t) after calling
from the LDI. Also after calling the records of the RAM are searched for special
criterions (product number, running number) and displayed on the PC.
3. Operating voltage 24V
The LDI can also be powered with 24V.
4. Other laser wavelength 
We recommend using a laser diode with the wavelength of 910nm, especially, for
photosensitive materials.
5. Increased measurement accuracy
The stability of the laser wavelength  is increased, if a laser diode with internal
optical isolator is used. So length measurements under constant measurement
conditions (material, distance L, speed, acceleration) are highly reproducible. The
measurement error is less than 0.02%.
6. 19“-plug-in unit
The basic LDI unit can be provided as a 19“-plug-in unit for the installation in a
rack.
7. Other fibre length
The fibre length can be increased from 4m to 10m, to bridge a longer distance
between measuring head and basic LDI unit.
8. Scanning routine
The standard signal processing routine can not follow Doppler frequency changes if
speed jumps or accelerations higher than 40m/s2 occur. As a consequence, the
signal frequency fS is no more in the bandwidth of the signal filter and the
measurement is interrupted.
16
This effect also occurs if at the start of the measurement the measuring head is
directed to a moving object with a speed v>400m/min. The LDI can not follow this
speed jump from „zero“ speed to v>400m/min.
The whole frequency range (speed range) is scanned by using the optional scanning
routine. The measurement is started or goes on, after the frequency (speed) is
matched.
9. Narrow band frequency filter
If LDI measurements with provide a too small signal to noise ratio (SNR), for
example in the case of optical fibres or weakly scattering samples, the
measurement error can be considerable. A further reduction of the filter-bandwidth
generates an increased SNR and allows the exact measurement also on materials
with weak signals.
The reduction of the signal filter bandwidth also allows the measurement of slowly
moving samples with increased accuracy.
10. Connection of counters
If counters (Hengstler, Omron, Hübner, ...) are connected to the LDI-interface 21,
the following counter options can be applied:
- Length counting and closing of relay to decrease the sample speed, after a pre-set
counterstate (L0, L1) is matched.
- Using of counter options, for example interface (RS 232, RS 485) for data
transmission.
11. Analysis of sample speed
The sample speed course v(t) can be recorded (1024 data) by means of a DAQ-PCboard and presented on the PC. The 1024 data can also be processed by a FFTanalysis. So a spectral presentation of the sample speed can be carried out
(enclosure 2).
12. Manual signal level control
The manual signal level control is only recommended if sample tests in the
laboratory of the manufacturer are not successful.
Then, switch 22 is activated by the manufacturer. This manual signal level control
(switch 22 down) activates also the control knob 8.
The manual signal level control may be advantageous in the case of weakly
scattering materials. There are two switch positions after activation of switch 22:
- position 22: „ON“ (up)
function: automatic signal level control
the control knob 8 is out of work
- position 22: „OFF“ (down)
function: manual signal level control
the signal level is adjusted with the control knob 8, the level on the reading 9
must be adjusted during sample motion to 5 ...6. In this LDI operation state the
measurement can be manipulated (manual level state too small), so the PTB does
not allow this state.
17
7. Technical specifications dates
Displayable length:
Max. Motion speed :
Length resolution:
Measuring distance:
Measuring accuracy:
Radiation source:
Laser diode:
Mode
Wavelength:
Optical power:
Power on sample:
Beam diameter on
sample spot :
Divergence:
Laser class:
0...9999,99m
-2.400m/min...0...+2.400m/min (max. acceleration 40m/s2)
0.01m, optional 0.001m, 0.1m, ...
L=250mm8mm
0.1% L=250mm3mm
0.2% L=250mm8mm
HL 7851 G
continuous (stabilised with monitor diode)
790nm (stabilised in temperature and power)
40mW
2 x 3mW
cover
0.8mm
10mrad for both transmission beams
3 B according EN 60 825/1:1994 (if no customised shield cover
and absorber)
1 according EN 60 825/1:1994 (including customised shield
and absorber)
Operating temperature:
basic LDI unit:
measuring head:
Storage temperature:
Max. air humidity:
5 - 70
-200C - +700C
85% (at +250C)
Dimensions:
Weight:
basic unit:
measuring head:
Interface:
Interface printer:
interface speed:
Power supply:
50 - 450C
0
0
basic unit: (W x L x H)
260mm x 150mm x 310mm
measuring head:
=38mm L=240mm
Fibre between basic unit and measuring head:
4m
5.5kg
0.5kg
9-position Sub-D (open collector)
outputs:
clock, up/down (or sin/cos) pulse width: 0.1ms
fail signal
input:
RESET
RS232 connected to alibi printer
speed exit: frequency (standard)
optional: voltage or current loop
Fuse:
operating voltage: 220V...240V, power consumption: 100W
frequency 50Hz
optional 110V or 24V
2,0A (T)
Protecting grade:
basic unit: IP20
measuring head: IP53
18
8. Standard Delivered Configuration and Accessories
Included in LDI delivery:
LDI basic unit and measuring head
User Manual
Power plug
Optical wipe
IR-detection-card
Calibration certificate / test log
Accessories:
Holder for optical measuring head (custom-adapted)
Laser protection device (custom-adapted)
19
9. Instrument Error Reports
Installation errors
Error
Reason
Elimination
LDI does not count
signal level too small (<2)
measuring head misadjusted
signal level too small (<2)
switch 22 „Off“
(manual signal level control)
transmission beams interrupted
(check with IR-detection card),
material surface disrupted
signal level too small (<2)
material not suitable for
measurement with automatic
signal level control
transmission lens at measuring
head is dirty
adjust measuring head to sample
surface (see initial start-up)
switch 22 „ON“
(automatic signal level control)
LDI does not count
LDI does not count
LDI does not count
LDI does not count
LDI counts backward
0, 9999, 9998, ....
Measurement error
Measurement error
wrong installing of the measuring
head
no RESET (zero) before measuring
start
wrong adjustment of the
measuring head to the sample
motion
transmission beams must illuminate
sample surface
provide sample for material test at
manufacturer’s site,
test manual signal level control
clean the lens with enclosed optical
wipe (wet cleaning, use optical
cleaner)
rotate the holder with the measuring
head 1800
before measuring give a manual or
external RESET pulse (zero)
readjust angles  and  of the
measuring head
LDI errors:
Error
Reason
Elimination
Laser diode not
operating LED 1 off
Laser diode does not
operate after run-in
time
laser diode has not reached pre-set wait run-in time
temperature
laser diode, driver or thermostatic consult technical service
control module defective
Signal level: zero
IOC-modulation failure,
fibre breakage
20
consult technical service
10. Cleaning and Technical Safety Checks
10.1. Cleaning
The LDI requires no scheduled maintenance. Once aligned to the sample surface, it need not
be re-adjusted any more. Measurement can be performed even with the front lens
(transmitting lens) of the measuring head contaminated in part. Use optical wipe (supplied)
and standard means to clean the lens (water, glass cleaner, alcohol, etc.). Cleaning may be
performed by authorised personnel only.
To clean , shut the LDI down, disconnect from main supply, and remove shielding cover
(15). Clean as necessary. Replace the shielding cover before you turn on power again. This
is necessary to protect from laser radiation and uncontrolled spreading of laser radiation,
while also preventing improper instrument use.
Warning note according to EN 60 825-1: 1994:
Caution: The use of control and adjustment tools or operating procedures others
than those described in this Manual may lead to dangerous radiation exposure!
10.2. Technical safety checks
Following each new start-up procedure, service and repair work or longer down times, the
following technical safety checks are required:
1. Visual inspection  Are shielding cover (15) and absorber (16) screwed on
properly?
2. Visual inspection  Are laser cassette, shielded tube and measuring head
firmly connected with each other?
3. Check of normal function of protective ground wire
21
11. Customer Service
Please notify your local distributor or the manufacturer if your LDI develops a mal-function
or failure.
Defective instruments must be repaired at the manufacturer’s site.
Manufacturer:
JENOPTIK Laser, Optik, Systeme GmbH
Göschwitzer Straße 25
07745 Jena
Tel.: +49 3641 65 3028
Fax: +49 3641 65 3813
22
12. EC Conformity Declaration
(in accordance with EMC Directive 89/336/EEC, Appendix 1)
It is hereby declared by the undersigned officers duly authorised by the manufacturer that
the product specified hereafter:
Laser Doppler Instrument (LDI)
to which this declaration relates is in conformity with the applicable regulations/directives
and normative documentation listed below, existing in the form of the harmonised
standards:
EN 55 011, class B
EN 55082, part 2, together with IEC 801, parts 2 and 3
(industry sector)
Jena, on 20 December 1995
Dr. Erich Hacker
JENOPTIK Laser, Optik, Systeme GmbH
Ingolf Berger
Quality officer
23
13. Enclosures
13.1. Enclosure 1: Calibration certificate
LDI-250
Serial No:
Date:
opt. Head Distance:
Laser diode:
XXXX
03/02/1999
250mm
No:B 121
5.1mW
1,3V
3843
53:47
AA0080
6F76
0B25
1.1896M Hz
1.40110 -5m
Optical pow er output:
Operating temperature:
Number
Splitting ratio:
M odulator (IOC):
Detector:
Counter state (dm increment):
Counter state (cm increment):
Doppler frequency f D (1000m/min):
Constant C (v=Cf D):
error over head distance
rel. error [% ]
0,3
0,2
0,1
0
239
241
243
245
247
249
251
253
255
257
259
261
263
head distance [mm]
-0,1
-0,2
optimum distance
-0,3
rel. error [% ]
error over speed
0,3
0,2
0,1
speed [m/min]
0
0
2,4
8
24
80
-0,1
-0,2
-0,3
24
240
800
2400
13.2. Enclosure 2: Speed analysis
The presentation of the temporal or spectral course of a sample motion occurs by means of
the LDI-FFT (Speed Analyzer), shown by the example of a cable extrusion machine (Fig.9).
The simple graph v(t) at the speed of 125m/min does not resolve small speed variations.
Fig.9: Speed diagram v(t)
Small speed changes (for examplev=0,9m/min) are resolved, after the out-filtering the DCspeed-component and amplification of the remaining AC-speed-component.
Fig.10: AC-speed diagram
The spectral graph (FFT-analysis) shows the frequency components fN consisting in the
temporal course.
Fig.11: Spectral graph fN
25
13.3. Enclosure 3: Counter setting
Please inform the manufacturer before delivery, if you want other length units than the
standard unit I=1cm. The manufacturer will implement necessary changes in setting and
write a new calibration certificate.
The warranty claims to the measurement accuracy will be null and void if the
customer changes the counter setting
Warranty can be restored after re-calibration by the manufacturer.
New setting of pre-selection switches
Shut the LDI down and disconnect it from the power supply. Take the counter cassette (CC)
out of the basic LDI unit (remove the seal, unscrew the 2 cassette screws and remove
cassette from the basic unit). After loosening 6 screws, the counter cassette can be opened.
Four pre-selection switches, 3, 2, 1, 0 are located at the PCB (Fig.4). The LDI will be
calibrated by setting these switches.
Caution!
If the LDI is not correctly shut down and disconnected from the mains supply,
there is danger of an electrical shock because dangerous voltages are present in
the interior instrument space.
pre selection
X
switches
0
2
1
Y
U(t)
3
4fD(t)
fD(t)
E
F
G
A
B
C
D Jumper
Z
i(t)
Fig.11: Counter cassette
Every pre-selection switch can be adjusted in hexadecimal numbers from 0 ...8, A, ...F. This
corresponds to a decimal adjustment of 0 ...15 (A=10, F=15).
Fig.12: Pre-selection switch in laser cassette
26
Example of pre-selection switch state:
Pre-selection switch no.:
State:
3
2
1
0
163
162
161
160
Old switch state Z0hex :
0
B
3
E
Old counter state Z0dez :
0163
11162
3161
14160
=2878
To get new counter state Z1 the correction factor C must be calculated. It is the quotient of
actual length L1 and target length L0:
C=L1/L0
With an actual length of L1=101m and a target length of L0=101m, C is calculated as:
C=101/100=1,01
and the new counter state Z1 will be:
Z1dez=1,012878=2907
Conversion from decimal to hexadecimal numbers:
Pre-selection switch no:
3
2
1
0
New switch state:
0
B
5
B
New counter state:
0163
=2907
11162
5161
11160
The counter cassette must be inserted to the basic LDI unit and screwed on after calibration.
After connection to mains supply, the LDI is switched on. The user can start measurement
according to 5.2, realisation of operation state.
13.4. Enclosure 4: LDI-watch setting
LC
CC
PS
Fig.13: Position of input elements
input elements
27
A small key and two decimal code switches are accessible to the user after removing the
cover of the basic LDI unit (Fig.10).
Date and time can be adjusted with these three elements. A acoustical signal sounds, if the
key is pressed during the switch on operation for about 2s.
The adjustment of date and time occurs with two decimal code switches.
9
0
1
9
0
1
8
2
8
2
7
3
7
3
4
5
single place
6
4
6
5
decimal place
Fig.14: Setting of date and time
butt on
A small screwdriver is necessary for turning the code switches. The input must be done in
prescribed order.
An acoustic signal will sound, if the input is incorrect.
Sequence and correct input range:
1. day:
2. month:
3. year:
1 ...31
1 ...12
4. hour:
5. minute:
6. second:
0 ...23
0 ...59
0 ... 59
0 ... 99
A short button press will quit the actual input. The computer will represent the latest input
state at the printer.
The LDI passes to the operation standard state after the last input (second) is quit. After
quitting, fail inputs can not be corrected. The complete LDI watch setting must be closed
and started again.
The calculator will print the code switch state as system number (from 00 ... 99) in the
printer record.
The following indication will be printed in the year 2.000:
31.12.99. 23:59:59  01.01.00 00:00:00
28
14. Telefax
Please copy, complete and send this fax reply form to:
JENOPTIK LASER, OPTIK, SYSTEME GmbH
if you require our assistance.
Fax:
+49 3641 65 3813
Our reference: .........................
Your reference: ...................................
No. Of pages (incl. Cover): .......
Date: ..................................................
Message:
I require service support. Please give me a call.
I request information about new products in the field of:
.............................................................................................................
Do not forget to indicate your mailing address:
Surname, first name: .............................................................................
Company:
.............................................................................
Address:
.............................................................................
Phone:
.............................................................................
Fax:
.............................................................................
signature:
.............................................................................
29