Burleigh WAVEMETER JR WA-2500 User manual

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WA-2500 WAVEMETERJR
Ò
OPERATING MANUAL
Operating Manual (Rev. E)
04659-M-00
Copyright © Burleigh Instruments, Inc. 1997
All Rights Reserved
Wavemeter is a registered trademark of Burleigh Instruments Inc.
Burleigh Instruments, Inc.
Burleigh Park
P.O. Box E
Fishers, NY 14453-0755
Tel: [phone]
Fax: [phone]
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i
TABLE OF CONTENTS
1. INTRODUCTION....................................................................................................... 1-1
1.1 APPLICATIONS ............................................................................................................... 1-1
1.2 THEORY OF OPERATION .............................................................................................. 1-1
2. INITIAL INSPECTION............................................................................................... 2-1
2.1 VISUAL INSPECTION ..................................................................................................... 2-1
2.2 OPERATIONAL INSPECTION......................................................................................... 2-1
3. OPERATING INSTRUCTIONS ................................................................................. 3-1
3.1 INITIAL SET UP ...............................................................................................................3-1
3.2 BEAM RECEIVER MOUNTING ....................................................................................... 3-1
3.3 BEAM RECEIVER ALIGNMENT...................................................................................... 3-2
3.4 BAR-GRAPH INTENSITY METER .................................................................................. 3-4
3.5 UNITS SELECTION ......................................................................................................... 3-4
3.6 AVERAGE MODE ............................................................................................................ 3-4
3.7 CALIBRATION FUNCTION.............................................................................................. 3-5
3.8 MONITOR, TRIGGER AND WINDOW OUTPUTS ......................................................... 3-5
3.9 AUTO-RESOLUTION FEATURE..................................................................................... 3-6
3.10 RS-232 INTERFACE........................................................................................................ 3-8
3.11 INTERFEROMETER ALIGNMENT.................................................................................. 3-9
3.12 DETECTOR INTERCHANGE .......................................................................................... 3-13
3.13 100 VAC Operation .......................................................................................................... 3-14
3.14 Operation with Mode-locked and Other Low Coherence Lasers ..................................... 3-15
4. MAINTENANCE AND SERVICE............................................................................... 4-1
4.1 Error Messages................................................................................................................ 4-1
4.2 TROUBLESHOOTING ..................................................................................................... 4-2
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ii
4.3 Changing the Line Voltage ............................................................................................... 4-3
4.4 Changing the Fuse........................................................................................................... 4-3
5. ACCESSORIES ........................................................................................................ 5-1
5.1 Recommended Mounts.................................................................................................... 5-1
5.2 Optional Components ...................................................................................................... 5-2
6. SPECIFICATIONS .................................................................................................... 6-1
7. WARRANTY ............................................................................................................. 7-1
APPENDIX A. SAMPLE PROGRAM ...................................................................................... A-1
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Wavemeterjr Operating Manual 1. Introduction
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 1-1
Burleigh Park, Fishers, NY 14453
1. INTRODUCTION
1.1 APPLICATIONS
The WA-2500 Wavemeterjr is an instrument for wavelength measurement of CW
laser sources that combines accuracy with ease of use. The accuracy is ±1 part in
10,000 over the full wavelength range.
The primary application for Model WA-2500 is measurement of the wavelength or
the frequency of tunable lasers that operate from 400 to 1800 nanometers,
particularly dye lasers, Ti:Sapphire lasers and diode lasers. Two detectors are
provided to cover this range with high sensitivity. The VIS detector is used for
lasers operating from 400 to 1100 nanometers, and the IR detector for lasers that
operate from 600 to 1800 nanometers.
1.2 THEORY OF OPERATION
Laser light enters the Wavemeterjr through a fiber optic cable. Lasers that emit a
collimated beam can be easily coupled into the fiber by a beam receiver consisting of
an Input Beam Coupler (BC-1) and an FC connector terminated 3 meter patch cord
(PC-F). The beam receiver can be mounted in a simple optical mount that provides
rotation about 2 axes. The efficiency of coupling laser light into the fiber is
optimized by small angular adjustments of the beam receiver in qand f. The
opposite end of the fiber optic cable connects at the rear panel of the Wavemeterjr
and injects the light into the chassis.
Inside the chassis of the Wavemeterjr is a compact scanning Michelson
interferometer. The incoming laser beam is split into two paths, with one path
length varied by a scan mechanism. The two paths are recombined, producing
interference fringes that are detected by a photodiode. Simultaneously, the
displacement of the scan mechanism is measured by a high resolution Moiré gauge.
The microprocessor computes the correct wavelength or frequency from these two
signals, and transmits this data to the front panel display and RS-232 port. The
units of measurement are selected by a push button on the front panel.
The Moiré gauge attached to the scan mechanism of the Michelson interferometer
must be calibrated against a red HeNe laser. This is accomplished by introducing a
HeNe laser beam into the beam receiver and depressing the CALIBRATION button
on the front panel. The calibration value is stored in non-volatile memory that is
unaffected by power interruption.
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Wavemeterjr Operating Manual 1. Introduction
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 1-2
Burleigh Park, Fishers, NY 14453
Figure 1.1. Wavemeterjr Layout.
Two modes exist for the measurement cycle. In the standard mode, the
measurement is performed and displayed every 200 milliseconds. When the
AVERAGE button is depressed, the data is accumulated for 10 sequential
measurements and the display is updated with the average value every 2 seconds.
The AVERAGE mode is particularly useful for lasers that possess some frequency
jitter.
The Wavemeterjr upper front panel includes a six digit LED display and a bar-
graph intensity meter. The intensity meter indicates the peak to peak intensity of
the interferometer fringe signal, and can be used to facilitate alignment of the beam
receiver with the input laser beam. A “LO SIG” or “HI SIG” message will also be
flashed on the display when a low or high input intensity condition exists.
Three BNC coaxial connectors on the rear panel allow you to diagnose the operation
of the instrument with an oscilloscope. These are labeled MONITOR, WINDOW,
and TRIGGER. Together, they enable the user to observe the fringe signals from
the Michelson interferometer in order to align the beam receiver, optimize the
alignment of the interferometer’s adjustable mirror, and analyze the characteristics
of the laser input.
The auto-resolution feature built into the Wavemeterjr circuitry allows the
instrument to measure the wavelength of lasers with linewidths as great as 3000
GHz, despite the associated low coherence length. The auto-resolution circuitry
automatically adjusts the measurement range to be consistent with the coherence
length, and the result is displayed with relevant precision.
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Wavemeterjr Operating Manual 2. Initial Inspection
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 2-1
Burleigh Park, Fishers, NY 14453
2. INITIAL INSPECTION
2.1 VISUAL INSPECTION
The Wavemeterjr has been packaged in a special carton designed to give maximum
protection during shipment. If the outside of the shipping carton is damaged, notify
your shipping department immediately. The shipping department may wish to
notify the carrier at this point.
If the shipping carton is undamaged externally, the instrument can be removed
from the carton. If any damage is evident visually or if any loose components can be
heard when the instrument is inverted, notify your shipping department and
Burleigh Instruments, Inc. It is advisable to save the special carton for future
storage or transportation.
2.2 OPERATIONAL INSPECTION
The purpose of this section is to provide a brief functional check of the Wavemeterjr.
Please perform the following procedure upon receiving the instrument. Complete
operating instructions and feature descriptions will be found in Section 3 of this
manual.
NOTE: Before plugging in the instrument check that the 115/230 VAC switch on the rear
panel is correctly set for the line voltage. Incorrect setting can cause permanent
damage to the instrument. For 100 VAC operation set the 115/230 VAC switch to
115 VAC and refer to Section 3.13 for the correct internal transformer
connections.
Place the Wavemeterjr on a firm horizontal surface (optical bench or lab table).
Attach the AC line cord. Turn on the power switch and listen for any unusual
noises. When the power switch is turned on or off, you should hear an audible click
caused by the solenoid lock that secures the interferometer scanning assembly
when power is off.
With power on, two of the UNITS lights should illuminate and the numerical
display should light all 8’s and decimal points for one second followed by a count
down beginning at 10. After a few seconds the countdown should be interrupted by
a display that alternates between “LO SIG” and “_ _ _ _ _ _” until a laser input is
introduced. If the countdown continues to zero, turn off the unit, wait 10 seconds,
and try again. Consult the troubleshooting section of this manual if the countdown
to zero operation persists.
To test the UNITS display, press the UNITS button on the lower front panel. Two
lights should illuminate, and the UNITS display should change in sequence —
nm/vac, cm-1/vac, nm/air, cm-1/air - each time you press the button.
Press the AVERAGE button. It should illuminate and remain locked in place until
you press the button again.
Press the CALIBRATE button. The display should read “CAL” for approximately
two seconds followed by the word “FAIL”. This is correct, given that there is no
calibration laser input.
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Wavemeterjr Operating Manual 2. Initial Inspection
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 2-2
Burleigh Park, Fishers, NY 14453
Observe the two DETECTOR indicators on the rear panel. The VIS indicator
illuminates when the detector is configured for visible wavelength (400-1100 nm)
operation. The IR indicator illuminates when the detector is configured for a
wavelength range from 600 to 1800 nm.
Once you have completed all of these checks successfully, refer to Section 3 of this
manual for further operating instructions.
Figure 2.1. WA-2500 Front Panel.
Figure 2.2. WA-2500 Rear Panel.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-1
Burleigh Park, Fishers, NY 14453
3. OPERATING INSTRUCTIONS
3.1 INITIAL SET UP
Position the Wavemeterjr on a firm horizontal surface. It is important that this
surface be horizontal and stable to ensure proper operation of the internal
interferometer scanning mechanism. The upper front panel is swivel mounted to
accommodate a wide range of viewing angles. Tilt the upper front panel to a
comfortable viewing angle.
NOTE: Check that the 115/230 VAC on the rear panel is correctly set and attach the AC
line cord. If the initial operational check has not been performed, refer to Section
2.2 of this manual. For 100 VAC operation, refer to Section 3.13.
3.2 BEAM RECEIVER MOUNTING
The optional beam receiver accessory consists of an optical coupling head (BC-1)
attached to a 3 meter FC connector terminated patch cord (PC-F) which provides the
input beam for the instrument.
CAUTION: The fiber optic cable and internal components of the coupling head are made of
glass and must be handled with care. Do not drop, bend sharply, stretch, or
otherwise stress the cable particularly in the vicinity of the connector. Permanent
damage to the cable can result. Do not drop the coupling head.
Optical power incident on the beam receiver should not exceed 100 milliwatts over
the entire operating range of 400 to 1800 nm. For beams smaller than the input
aperture of 2.5 mm, the maximum allowable power must be adjusted downward to
avoid exceeding safe power densities. Optical powers in excess of these limits
may cause irreparable damage to the assembly.
To install the beam receiver, first remove the dust covers from the fiber optic input
on the rear panel of the Wavemeterjr, the BC-1 optical coupling head and both ends
of the FC connector terminated patch cord. Store these dust covers for future use.
Connect the2 fiber optic cable to the FC connector on the rear panel of the
instrument and to the BC-1 optical coupling head. There is a “keyed” position for the
connector. Rotate this into position before tightening the knurled lock ring.
Figure 3.1. Beam Receiver.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-2
Burleigh Park, Fishers, NY 14453
NOTE: Handle this assembly with care. Avoid contact with exposed optical surfaces. Do
not apply stress to the fiber optic cable. The knurled lock ring requires only
modest torque to correctly secure the connector.
The beam receiver may be mounted in most q, fadjustable optical mounts designed
for a 25.4 millimeter diameter optic. Several models of suitable mounts from a
variety of manufacturers are listed in Section 5.1.
NOTE: The beam receiver is also available with a mounting diameter of 30 mm (BC-3).
Consult your Burleigh representative for more information.
Optical mounts with X-Y as well as q, fadjustments may be convenient in some
laboratory configurations. However, basic q, fadjustments are usually sufficient.
When selecting a mount, please note that there must be a ‘clearance hole’ which is
slightly larger than the coupling head’s main body diameter (0.990”). If such a
mount is unavailable, you can mount the coupling head facing in a direction opposite
to that shown.
Install the beam receiver coupling head in the optical mount. You may have to
separate the BC-1 coupling head from the fiber optic cable to insert it in some styles
of optical mount. To detach the fiber optic connector, loosen the knurled lock ring.
Handle the beam receiver assembly with care.
3.3 BEAM RECEIVER ALIGNMENT
The beam receiver head has a 25.4 mm diameter target disk with a 2.5 mm aperture.
A lens centered behind the aperture efficiently couples a collimated laser beam into
the optical fiber when the axis is properly aligned to the laser beam axis.
Alignment is simplified by two reflections from inside the beam receiver. Accurate
alignment into the fiber can be achieved by centering these reflected spots about the
incoming beam, as shown in Figure 3.2.
Figure 3.2. Beam Receiver Alignment.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-3
Burleigh Park, Fishers, NY 14453
The laser beam should be centered on the input aperture. This is typically
accomplished with upstream optics, such as a beamsplitter, that directs a small
portion of the laser beam toward the beam receiver. Adjust the face of the beam
receiver to be orthogonal to the laser beam using the angular adjustments of the
optical mount.
Two back reflections from inside the beam receiver should be visible near the laser
output aperture. They can also be seen by placing a white card (with a hole in the
center) in the beam as shown in Figure 3.2. Adjust the optical mount until the point
halfway between the two spots is centered on the laser beam. There should now be
enough light coupled into the fiber optic cable to maximize the throughput by
observing the bar-graph intensity meter on the upper front panel.
The input intensity bar-graph meter should be illuminating a number of segments
proportional to the amount of optical intensity incident on the beam receiver.
Optimize the alignment to illuminate approximately 5 to 8 segments of the bar-
graph meter.
If the LED display indicates “LO SIG”, verify that the laser power incident at the
beam receiver exceeds the specified input power in a 2.5 mm collimated beam. If the
intensity bar-graph meter is fully lit, slightly misalign the optical mount so that
approximately 5 to 8 of the 10 segments of the bar-graph are on. At this point the
Wavemeterjr will display the wavelength or frequency of the laser.
If there is sufficient intensity in the incident laser beam, but insufficient intensity to
observe the back reflections, try one of the following procedures:
WARNING: Although the FC connector emits an output beam with a wide divergence angle,
optical power densities from a visible or non-visible laser viewed at any distance
can still cause irreparable eye damage. Never look along or even close to the axis
of the FC connector when laser light is present at either end of the assembly.
Never look directly at the output of the FC connector receptacle at the back end of
the coupling head when the FC cable is disconnected. Handle the beam receiver
safely; laser light will transmit over great distances.
1. Remove the FC connector from the rear panel of the Wavemeterjr and
observe the transmitted intensity against a suitable viewing screen before
reconnecting the fiber optic cable to the instrument.
2. Observe the actual fringe signal from the internal Michelson interferometer
by connecting an oscilloscope to the MONITOR output on the Wavemeterjr
rear panel. The oscilloscope sweep should be synchronized with the scan of
the interferometer using the TRIGGER output from the Wavemeterjr.
Utilizing the extra sensitivity of the oscilloscope, it is possible to detect very
low intensity input signals as a starting point for optimizing the alignment
of the beam receiver. Refer to Section 3.8 of this manual for a description of
the oscilloscope pattern from the MONITOR output. If no fringe signal can
be detected on the oscilloscope, refer to Section 3.11 for details regarding
alignment of the Michelson interferometer.
3. If the initial alignment to an infrared laser is difficult due to the absence of
infrared viewing equipment, the beam receiver can be aligned with a HeNe
tracer beam that is set up to be collinear with the infrared beam. The
co-linearity of the two beams can be established by a pair of apertures and a
photodetector that is sensitive at the wavelength of the infrared laser. Once
the Wavemeterjr is aligned with the HeNe tracer beam, it should be possible
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-4
Burleigh Park, Fishers, NY 14453
to observe a weak signal from the infrared beam on the bar-graph intensity
meter or the MONITOR output.
3.4 BAR-GRAPH INTENSITY METER
The bar-graph intensity meter on the upper front panel of the Wavemeterjr is a
valuable aid for optimizing the input intensity to the instrument. It indicates the
peak-to-peak amplitude of the fringe signal detected by the internal Michelson
interferometer. The bar-graph intensity is sampled from the fringe signal (as
observed from the MONITOR output) at the beginning of the TRIGGER period. If
the Michelson interferometer is properly aligned this fringe signal and the bar-graph
meter will increase and decrease with input laser intensity.
NOTE: If the Michelson interferometer is out of alignment, no signal will be indicated on
the bar-graph meter even when the input intensity is very high. In this case an
“ALI Er” message will appear on the display to warn against introducing too much
intensity. Never illuminate the beam coupler head with intensity above 100
milliwatts as described in Section 3.2.
The bar-graph meter has a non-linear response. The sensitivity is greatest at low
intensities for detecting weak input beams but becomes less sensitive for greater
dynamic range as the intensity increases. It is factory set so that 1 or 2 segments are
lit at the threshold where the Wavemeterjr starts to read. Below this level the
display will flash the message “LO SIG”. All segments are illuminated at
approximately 10 times the threshold input power, and the display will flash the
message “HI SIG” when the range of the bar-graph is exceeded. For optimal
operation, the input intensity level should be adjusted to illuminate approximately
5 to 8 segments on the 10 segment bar-graph meter to allow for variations in the
laser power.
3.5 UNITS SELECTION
You can select any one of four display units for the Wavemeterjr readout. To change
the display units selection, press the UNITS button on the lower front panel until
the desired selection appears on the upper front panel.
VACUUM WAVELENGTH in nanometers (nm/vac)
VACUUM FREQUENCY in wavenumbers (cm-1/vac)
AIR WAVELENGTH in nanometers (nm/air)
AIR FREQUENCY in wavenumbers (cm-1/air)
The units selection is stored in non-volatile memory so that it is not changed when
power to the Wavemeterjr is interrupted.
3.6 AVERAGE MODE
The Wavemeterjr normally completes and displays a new measurement every
200 milliseconds (5 times per second). In the Average Mode, 10 measurements are
taken in succession and averaged to generate each new display value. The display
updates approximately every 2 seconds.
To activate the Average Mode, press the AVERAGE button on the lower front panel.
The button lights when it is in the “on” position. Press the button again to return to
normal operation.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-5
Burleigh Park, Fishers, NY 14453
3.7 CALIBRATION FUNCTION
The scan of the Michelson interferometer inside the Wavemeterjr must be calibrated
against an external HeNe laser. This is done at the factory and the initial calibration
constant is stored in non-volatile memory. The calibration can be checked at any
time by measuring the wavelength of any red HeNe laser.
HeNe Vacuum Wavelength = 632.99 nanometers
If calibration is necessary, press the CALIBRATE button on the lower front panel
while there is a red HeNe laser beam input. The upper front panel will display the
message “CAL” for approximately 2 seconds during the calibration measurement
and then return to display the correct HeNe wavelength or frequency, depending on
the units selected.
If the CALIBRATE button is depressed without a red HeNe laser input, the
Wavemeterjr will display the message “CAL” followed by “FAIL” and return to the
previously displayed data without altering the stored calibration constant.
Consequently, the possibility of accidentally losing the calibration value is low. The
only exception to this calibration protection feature involves the presence of laser
light within approximately ±0.5% of the HeNe wavelength.
3.8 MONITOR, TRIGGER AND WINDOW OUTPUTS
Three BNC coaxial connectors on the rear panel allow you to check the Wavemeterjr
operation with an oscilloscope. They are designated as TRIGGER, WINDOW, and
MONITOR. The MONITOR output is the detector signal generated by the laser
interference fringes from the Michelson interferometer. This is an analog signal with
a peak-to-peak value that represents the intensity of the interference fringes.
The TRIGGER output is a TTL signal that is high (+ 5 v) for that portion of the
interferometer scan during which a measurement can be made. It initiates the
measurement cycle and should be used to trigger the oscilloscope when observing
the MONITOR and WINDOW signals. The TRIGGER interval is factory set to be
approximately 30 milliseconds.
The WINDOW output is a TTL signal that is high (+ 5 v) for that portion of the
interferometer scan during which the measurement is actually made. The WINDOW
signal starts at the same time as the TRIGGER signal and terminates as soon as the
fringe signal amplitude falls below an adequate level.
Examples of the MONITOR, TRIGGER and WINDOW signals for various types of
laser inputs are shown in Figure 3.3. For highly monochromatic lasers depicted in
the upper spectrum, the TRIGGER and WINDOW signals will be identical because
there is no decrease in the fringe amplitude until the end of the scan. For lasers that
are spectrally broad, including multi-line lasers, the measurement will be
terminated as soon as the fringe envelope falls below 500 millivolts peak-to-peak.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-6
Burleigh Park, Fishers, NY 14453
Figure 3.3. Monitor, Trigger and Window Outputs for Different Spectra.
3.9 AUTO-RESOLUTION FEATURE
The Wavemeterjr displays the wavelength or frequency to the specified accuracy of
±1 part in 10,000 for lasers with linewidths less that 150 GHz (5 cm-1). Lasers with
greater linewidths exhibit reduced coherence lengths, which in turn reduces the
number of useful fringes generated in the Michelson interferometer.
The Auto-Resolution feature automatically adjusts the precision of the wavelength
or frequency display for lasers with linewidths greater that 150 GHz. The length of
the WINDOW defines the number of useful fringes actually counted by the
Wavemeterjr. The Auto-Resolution circuitry computes the appropriate readout based
on the accuracy implicit in the number of fringes that can be counted. Insignificant
digits are eliminated and replaced by a “_” character on the display.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-7
Burleigh Park, Fishers, NY 14453
For example, the wavelength 654.32 nm will be displayed as 654.3_ nm for a
linewidth between 150 and 1500 GHz, while a display of 654. _ _ nm will result from
a laser with a linewidth between 1500 and 3000 GHz. If the linewidth exceeds
3000 GHz, the display will present the message “COH Er” indicating that the
coherence length is insufficient for wavelength measurement.
To establish the correspondence between linewidths in wavelength units and
frequency units, use the graph in Figure 3.4 for the particular laser wavelength of
interest. Interpolate for wavelengths in between those that are plotted. For example,
a 654.32 nm dye laser with a wavelength linewidth of 0.5 nm has a frequency
linewidth equal to 12 wavenumbers according to the graph and would be displayed
with 4 digit resolution as 654.3_ nm.
Figure 3.4. Auto-Resolution Conversion Chart.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-8
Burleigh Park, Fishers, NY 14453
3.10 RS-232 INTERFACE
The Wavemeterjr features an RS-232 port (often referred to as a serial or
asynchronous communications port) for connecting to peripherals such as printers or
terminals. The RS-232 port can also be used to transfer data to a personal computer.
Measurement values and error messages transmitted to the port comply with the
RS-232-C Serial Communications EIA Standard.
Pin Wire Label Description
(O = Output, I = Input)
1 Brown GRND Protected Ground
2 Blue NC Not Used
3 Yellow TXD Transmit Data (O)
4 Green DTR Data Terminal Rdy (O)
5 Red RXD Receive Data (I)
6 Black CTS Clear to Send (I)
7 Orange SGRND Signal Ground
8 White NC Not Used
Pin #
1
Figure 3.5. RS-232 Receptacle.
The Wavemeterjr RS-232 output is configured as 2400 Baud, 8 data bits, 2 stop bits
and no parity. Flow control is handled via software (XON/XOFF) or hardware
(CTS/RTS) handshaking. The maximum line length is 22 characters followed by a
carriage return/line feed (CR/LF) character pair indicating the end of each line of
data.
If the user halts the data transmission for more than 10 lines of readings or 30 lines
of error messages, the transmission buffer will clear itself and wait for a CTS or an
XON before filling again. This is to prevent the transmission of old data in the event
that the user indefinitely suspends data transmission. A “232 Er” message will
appear periodically on the display warning of a data transmission problem. When
transmission resumes, a “Transmission Break” message will be transmitted before
new data appears, indicating there has been a gap in data transmission.
The WAVEMETERjr is a “talk only” device that supports the Xon/Xoff handshake
protocol. Data transmission can be halted (Xoff) by sending a “^S” character (13
Hexadecimal) to the “Receive Data” (RXD:pin#5) line. Data transmission can be
restarted (Xon) by sending a "^Q”character (11 Hexadecimal) to RXD.
An alternative method to control data transmission is provided through the “Clear
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-9
Burleigh Park, Fishers, NY 14453
To Send” (CTS:pin#6) line. The CTS line is pulled high (+12V) to produce a “true” by
default, enabling data transmission in the absence of a user supplied signal to CTS.
If the CTS line is made “false,” data transmission will cease until CTS is made “true”
again.
If the data transmission is halted by the user for more than 10 lines of readings or
30 lines of error messages, the transmission buffer will clear itself and wait for a
true level on the CTS line or an Xon command on the RXD line before filling again.
This is to prevent the transmission of old data in the event that the user indefinitely
suspends data transmission. A “232 Er” message will appear periodically on the
display warning of a data transmission problem. When transmission resumes after
such a buffer clearing a “Transmission Break” message will be transmitted before
new data appears, indicating there has been a gap in data transmission.
Data from the WAVEMETERjr is transmitted at 2400 Baud on the “Transmit Data”
(TXD:pin#3) line. The data transmission format is a single start bit followed by an 8-
bit ASCII character; starting with the least significant bit (LSB) and ending with the
most significant bit (MSB). This 8-bit ASCII character is followed by 2 stop bits for a
total of 11 bits, no parity. The maximum line length is 22 characters followed by
carriage return/line feed (CR/LF) characters indicating the end of each line of data.
NOTE: Appendix A contains a sample program for communicating with the Wavemeterjr
via RS-232.
3.11 INTERFEROMETER ALIGNMENT
Figure 1.1 shows the physical layout of the internal Michelson interferometer. Only
one end mirror is adjustable and it can be aligned using a small flat blade
screwdriver through two access holes in the rear panel.
Normally, major interferometer alignment should not be necessary. However, slight
adjustments to the ALIGNMENT screws may be useful to optimize the sensitivity of
the Wavemeterjr for low intensity laser sources.
If major realignment of the Michelson interferometer is required, refer to Figure 3.6
and use the following procedure:
1. Turn off the Wavemeterjr and disconnect the AC line cord.
2. Remove the top cover of the chassis. It is secured by 2 black screws in each
side. Carefully detach the ribbon cable connector on the main circuit board
that provides power to the display panel.
3. Remove the silver dust cover from the interferometer, which is secured by
one top screw.
4. Disconnect the 6-conductor ribbon cable from the Detector Board and remove
the single mounting screw that secures the board. Carefully lift the board
from the black plastic guide at its base.
5. Align the beam receiver with a HeNe laser and observe the laser beam that
would normally hit the detector by placing a white card just beyond where
the detector mounts, as shown in Figure 3.6.
6. Adjust the end mirror alignment until the spots observed on the white card
are superimposed. Interference fringes will be evident when the spots are
superimposed. Adjust the alignment until only one broad fringe exists.
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Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-10
Burleigh Park, Fishers, NY 14453
7. Replace the detector board dust cover, chassis cover and AC line cord.
8. Turn on the Wavemeterjr and fine adjust the end mirror alignment to
maximize the intensity level on the bar-graph meter or the MONITOR
output.
NOTE: If you have difficulty obtaining enough signal to activate the bar-graph meter,
connect an oscilloscope to the MONITOR and TRIGGER outputs for greater
sensitivity in detecting the fringe signal.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

Wavemeterjr Operating Manual 3. Operating Instructions
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 3-11
Burleigh Park, Fishers, NY 14453
Figure 3.6. Wavemeterjr Exploded View.
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