Newport 835 User Manual

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Model 835
Laser Pico -Watt Digital Power Meter

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Warranty

Newport Corporation warrants this product to be free from defects in
material and workmanship for a period of 1 year from date of shipment. If
found to be defective during the warranty period, the product will either be
repaired or replaced at Newport’s option.

To exercise this warranty, write or call your local Newport office or
representative, or contact Newport headquarters in Irvine, California. You
will be given prompt assistance and return instructions. Send the
instrument, transportation prepaid, to the indicated service facility.
Repairs will be made and the instrument returned, transportation prepaid.
Repaired products are warranted for the balance of the original warranty
period, or at least 90 days.

Limitation of Warranty

This warranty does not apply to defects resulting from modification or
misuse of any product or part. This warranty also does not apply to fuses,
batteries, or damage from battery leakage.

This warranty is in lieu of all other warranties, expressed or implied,
including any implied warranty of merchantability or fitness for a particular
use. Newport Corporation shall not be liable for any indirect, special, or
consequential damages.

©1987, Newport Corporation
Irvine, California U.S.A.

First Printing (April 15, 1987)
Copyrighted by Newport Corporation, Irvine, CA. All rights reserved. No

part of this manual may be reproduced or copied without the prior written
approval of Newport Corporation.

This manual has been provided for information only and product
specifications are subject to change without notice. Any changes will be
reflected in future printings.

P/N 13767-01, Rev. F3
IN-01872 (7-94)

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ii

About This Manual

This owner’s manual contains all of the necessary information for the
proper operation and maintenance of the Newport Corporation 835 Laser
Pico-Watt Digital Power Meter.

The manual has been divided into the following sections:

Section 1 provides general information about this instrument
Section 2 discusses the operation of the Model 835
Section 3 explains performance verification procedures
Section 4 discusses the Therory of Operation of the Model 835
Section 5 suggests maintenance procedures
Section 6 describes service suggestions and procedures.

See Section 1.1 for an expanded description of these topics and related
references.

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Table of Contents

Warranty................................................................................................................. ii

About This Manual ............................................................................................... iii

List of Illustrations .............................................................................................. vii

List of Tables........................................................................................................ vii

Safety Precautions............................................................................................... vii

Features ............................................................................................................... viii

Specifications ........................................................................................................ ix

Section 1 - General Information

1.1 Introduction..................................................................................................1

1.2 Getting Started .............................................................................................1

1.3 Unpacking and Inspection ..........................................................................3

1.4 Specifications ...............................................................................................3

1.5 Warranty Information ................................................................................. 3

1.6 Manual Addenda ..........................................................................................3

1.7 Safety Symbols and Terms .........................................................................4

1.8 Optional Accessories and Services .......................................................... 4

Section 2 - Operation

2.1 Introduction..................................................................................................5

2.2 Preparation for Use .................................................................................... 5

2.2.1 Line Power............................................................................................5

2.2.2 Battery Pack Power .............................................................................6

2.2.3 Battery Charging ................................................................................ 6

2.3 Tilt Stand ...................................................................................................... 6

2.4 Model 835 Familiarization ...........................................................................7

2.4.1 Digital Display ......................................................................................7

2.4.2 Bar Display ...........................................................................................8

2.4.3 Front Panel Controls ...........................................................................8

2.4.4 Input Connector ................................................................................. 9

2.4.5 Analog Output Connectors ................................................................9

2.5 Error Messages.............................................................................................9

2.6 Environmental Conditions ........................................................................10

2.7 Basic Measurements................................................................................. 10

2.7.1 Power-Up ............................................................................................11

2.7.2 Zero Check .........................................................................................11

2.7.3 Setting Wavelength ...........................................................................12

2.7.4 Setting Attenuator Status .................................................................13

2.7.5 Power Measurements .......................................................................13

2.7.6 Time Constant .................................................................................. 13

2.7.7 Null (REL) Measurements ................................................................13

2.7.8 Ratio Measurements .........................................................................14

2.7.9 Logarithmic Modes (dBm and dB) ..................................................15

2.7.10 Bar Display Zoom and Offset .......................................................... 17

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2.7.11 Storing the Wavelength and Attenuator Status for Power-Up .....18

2.7.12 Inverting Analog Output ...................................................................18

2.7.13 IEEE Interface Option ........................................................................19

2.8 Measurement Considerations ..................................................................19

2.8.1 Detector Calibration and Accuracy ................................................19

2.8.2 Temperature Effects .........................................................................20

2.8.3 Ambient and Stray Light...................................................................20

2.8.4 Wavelength Response of Detector and Attenuator ......................21

2.8.5 Detector Uniformity ..........................................................................22

2.8.6 Detector Saturation...........................................................................22

2.8.7 Attenuator Characteristics ............................................................. 23

2.8.8 Reflections and Interference Effects ...............................................23

2.8.9 Grounding Considerations .............................................................. 23

2.8.10 Changing Detectors...........................................................................23

Section 3 - Perfomance Verification

3.1 Introduction................................................................................................24

3.2 Environmental Conditions ........................................................................24

3.3 Recommended Test Equipment .............................................................. 24

3.4 Initial Conditions ........................................................................................25

3.5 Verification Procedure ............................................................................. 25

Section 4 - Theory of Operation

4.1 Introduction................................................................................................27

4.2 Overall Functional Description ................................................................27

4.3 Photodetector ............................................................................................27

4.4 Electronic Display Functional Description .............................................27

4.4.1 Input Amplifier.................................................................................. 28

4.4.2 Microcomputer and PROM ............................................................. 28

4.4.3 Power Supply .................................................................................... 28

4.4.4 Model 835-BAT Rechargeable Battery Option ...............................28

Section 5 - Maintenance

5.1 Introduction................................................................................................29

5.2 Top Cover Removal/Installation ............................................................. 29

5.3 Battery Pack (Model 835-BAT) Installation ............................................ 29

5.4 Special Handling of Static Sensitive Devices ......................................... 30

5.5 Detector/Attenuator Recalibration or Replacement ............................30

5.5.1 PROM Replacement Procedure ...................................................... 31

5.6 IEEE-488 (Model 835-IEEE) Interface Installation .................................. 31

5.7 Troubleshooting and Self Diagnostic Program ..................................... 31

Section 6 - Service

6.1 Introduction................................................................................................32

6.2 Factory Service...........................................................................................32

6.3 Component Location Drawings................................................................33

6.4 Service Form ...............................................................................................35

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List of Illustrations

2-1 Line Frequency Jumper .............................................................................. 5

2-2 Model 835 Front Panel ................................................................................ 7

2-3 Feedback Picoammeter and Signal Conditioning Circuit......................18

2-4 Wavelength Response of Silicon Detector and Attenuator ................. 21

2-5 Detector Saturation .................................................................................. 22

3-1 Interconnection of Current Source and Model 835 ...............................25

4-1 Simplified Block Diagram ..........................................................................27

6-1 Exploded View of Model 835 ....................................................................33

6-2 Mother Board Component Location Drawing ....................................... 34

List of Tables

2-1 Error Messages.............................................................................................9

2-2 Range, and Overload Conditions ............................................................ 10

3-1 Recommended Current Calibration Equipment ................................... 24

3-2 Calibration Check Table........................................................................... 25

Safety Precautions

The following safety precautions should be observed before operating the
Model 835.

This instrument is intended for use by qualified personnel who recognize
shock hazards and are familiar with safety precautions required to avoid
possible injury. Read the manual carefully before operating the instrument.

Exercise extreme caution when a shock hazard is present at the detector
input. The American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 30V RMS or 42.4V peak are

present. A good safety practice is to expect that a hazardous voltage is

present in any unknown circuit before measuring.

Do not exceed 30V RMS between the detector input connector and earth
ground.

Inspect detector leads for possible wear, cracks, or breaks before each use.
If any defects are found, replace with detector cable with one that has the
same measure of safety as the ones supplied with the instrument.

Do not connect any conducting detector housing to anything that may have
a voltage higher than 30V.

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Model 835

Laser Pico-Watt Digital Power Meter

Features:

• 4-1/2 Digit digital and 50 segment analog backlit LCD displays

• Digital wavelength response compensation

• Autoranging from 2 nW to 2 mW full scale, up to 2W with attenuator

• Linear and Log (dBm and dB) modes

• Ref Mode displays power ratio relative to stored power reference

• Choice of individually calibrated Silicon and Germanium detectors

• Analog Ouput

Options:

• Model 835-BAT Rechargeable Battery Pack

• Model 835-IEEE IEEE-488 Computer Interface

• Model 818-FA Fiber Connector Adaptor with FP3-CA series Snap-In
Fiber Connectors

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Model 835 Specifications

Electrical Accuracy Analog

18°C-28°C (1 Year) Rise Time

2

Range

Resolution

2 nW 0.1 pW 0.4 + 0.2 60 msec

20 nW 1 pW 0.4 + 0.05 60 msec

200 nW 10 pW 0.2 + 0.05 6 msec

2 mW 100 pW 0.15+ 0.05 3 msec

20 mW 1 nW 0.1 + 0.05 3 msec

200 mW 10 nW 0.1 + 0.05 1 msec

2 mW 100 nW 0.1 + 0.05 1 msec

Notes:

1. When properly zeroed. Detector response between 0.1 and 1 A/W (typical for detector
w/o attenuator)

2. Divide range and resolution by order of magnitude of detector response for detector
responsive less than 0.1 A/W. For example, if detector response is 0.002 A/W, divide
range and resolution specifications by 0.001/0.1 = 0.01.

Ranging: Manual or autoranging.

2

±(%rdg + %full scale)

1

(10%-90%)

Autoranging Time: Average 250 msec per range.
Settling Time at Display: Less than 1 second to within 2 counts on

fixed range.

Conversion Period: 170 msec.
Temperature Coefficient : +(0.1 x applicable accuracy specification)

(0°-18°C & 28°-50°C) per °C.

Maximum Common

Mode Voltage: 30V rms, DC to 60 Hz sine wave.

Analog Output

Output Voltage: Inverted direct amplification of the input

current. −10

3

to 108 V/A gain depending on

range selected.

Output Resistance: 1000Ω.

Front Panel Switches

Power: On and Off.
Range ▼: Selects manual range and decreases the

range.

Range ▲: Selects manual range and increases the

range.
Auto: Selects manual or autoranging.
Time Constant: Changes the effective time constant

between slow, medium and fast. Does not

affect analog output.

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Null: Stores or clears the dark or ambient light

level photodetector current. Subsequent
power readings are computed after
subtracting this current from photodetector
current.

Log/Lin: Switches between linear and logarithmic

display modes.

Ref: Stores or clears reference level. Enter or

exit ratio or dB display modes.

λ Cal ▼ ▲ : While held, increments (decrements) the

λ Cal Save: Store the power-up wavelength and

Attenuator: When on, includes attenuator transmission

Bar Graph: 50 segment display of value in digital

Zoom Ρ: Increases bar graph sensitivity.
Zoom Θ: Decreases bar graph sensitivity.
Offset: Offsets the zero of the bar segment display

Zero Check: Used to adjust zero on lowest range.

wavelength by 10nm steps. Detector /
attenuator serial number display.

attenuator status.

factor in detector response used to compute
optical power.

display with user selectable full scale ranges
of ±5, 25, 50, 125, 250, 500, 1250, 2500, 5000,

12500, 25000 counts and offset control.

to the value displayed on the digital display.

IEEE-488 Bus Implementation (Option 835–IEEE)

Multiline Commands: DCL, SDC, GET, GTL, UNT, UNL, SPE, SPD.
Uniline Commands: IFC, REN, EOI, SRQ, ATN.
Interface Functions: SH1, AH1, T5, TE0, L4, LE0, SR1, RL1, PP0,

DC1, DT1, C0, E1.

Programmable Parameters: Zero Check, Current Range, Null, Reference

Level On/Off, Wavelength, Attenuator On/
Off, Log (dBm, dB), Trigger, EOI, SRQ, Status,
Output Format, Terminator.

Readable Parameters: Power, Power Range, Wavelength, Status

Word, Probe/Attenuator Serial Number.

General

Displays: 4-1/2 digit backlit LCD, 0.5 “ height, polarity,

range, wavelength and status indication. 50
segment Analog Display with zero offset and

selectable full scale ranges of ±5, 25, 50, 125,
250, 500, 1250, 2500, 5000, 12500, 25000

counts.

Overange Indication: “OL” or “-OL” displayed.

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Connectors:

Input: BNC.
Analog Output: Banana Jacks

Operating Environment: 0-50°C, less than 70% R.H. up to 35°C;

linearly derate 3% R.H./°C up to 50°C.
Storage Environment: −25°C to +60°C.

Power: 105-125V or 210-250V (switch selected), 90-

110V available, 50-60Hz, 12VA. Optional 5

hour battery pack, Model 835-BAT.
Dimensions: 216 mm wide x 89 mm high x 267 mm deep

(8.5" x 3.5" x 10.5").
Net Weight: 2.1 kg (4.7 lbs.)

Accessories Available

Model 835-BAT: Rechargeable Battery Pack
Model 835-IEEE: IEEE-488 Interface
Model 818-SL: Large Area Silicon Photodetector
Model 818-ST: Beam Sampling Silicon Photodetector
Model 818-IR: Germanium Infrared Photodetector
Model 818-UV: Silicon Ultraviolet Photodetector
Model 818-SCAL: Detector Calibration Service
Model 818-RCAL: Detector Recalibration Service

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Section 1

General Information

Introduction

1.1

This instruction manual contains the necessary information for operating
and maintaining the Model 835 Series Laser Pico-Watt Digital Power Meter
and the Model 835-BAT Rechargeable Battery Pack. This information is
divided into the following sections:

1. Section 1 contains general information and provides guidelines for
using this manual. Important safety information is also presented
here.

2. Section 2 contains detailed operating information for the Model 835
Series Power Meters.

3. Section 3 contains the information needed to verify the electronic
accuracy of the Model 835. Performance verification can be done
upon the receipt of the unit or whenever the accuracy is in question.

4. For the more technically oriented user, information on theory of
operation and maintenance is contained in Sections 4 and 5.

5. Section 6 contains information on factory service and component
location drawings.

NOTE

The Model 835-IEEE IEEE-488 computer interface and all
photodetectors come supplied with separate instruction manuals.

Getting Started

1.2

Perform the following steps in sequence to quickly and safely become
familiar with the basic operation of the Model 835.

1. Verify that the Model 835 was not damaged in transit, as explained in
paragraph 1.3.

2. Carefully read sections on Safety Precautions, General Information,
and Operation. Understand and observe the warnings found in these
sections.

3. Referring to paragraph 2.2.1 (Line Power) set the line voltage switch
and line frequency (if necessary) and plug the power cord into a
properly grounded outlet. If the optional battery pack is installed the
charge circuitry will be activated.

4. Become familiar with the controls and displays of the Model 835 as
follows:

A. Turn on the Model 835 by pressing in the red ON/OFF pushbutton.

F60 or F50 will be briefly displayed, followed by the detector or
attenuator serial number. F60 indicates that the unit is configured
to operate at a 60 Hz line frequency. F50 indicates that the unit is
configured for 50 Hz. Do NOT connect any detector yet.

B. The ATTENUATOR annunciator may be on. Press the ATTEN

button several times. The ATTENUATOR annunciator will turn on
and off. While in Attenuator mode, the display readings are
compensated for the optical characteristics of the attenuator. End
with the ATTENUATOR annunciator off.

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C. The meter will be in autoranging mode on power up. The AUTO

annunciator will be displayed. To put the meter into manual
ranging mode, press the AUTO pushbutton. The AUTO
annunciator will turn off. Press RANGE ▲ to set a less sensitive
range or RANGE ▼ to set a more sensitive range. Press AUTO
again to return to autoranging. The wavelength of photodetector
responsivity data used for power calculation will be displayed in
the upper right of the digital display. followed by the nm
annunciator.

D. Press the ZERO CHECK pushbutton and note that the ZERO

CHECK annunciator turns on. Press again to turn off.

E. The Null (REL) mode can be used in the linear measurement

(watt) mode or the logarithm mode. The stored Null current level
will be subtracted from all subsequent measurements. Press the
NULL pushbutton and note that the REL (for relative) annunciator
turns on. Press again to turn off.

F. Select logarithm mode (for decibel readings) by pressing the LOG/

LIN button. The dBm annunciator will turn on. Press again to take
the Model 835 out of the decibel mode.

G. The REF (reference) button stores the reference level to be used

to calculate dB (relative) or to make ratio measurements. Press
the REF button and note that the watt (W) annunciator turns off to
indicate that the reading is a ratio. The OL (overload) annunciator
may turn on indicating that the reference level is too small or the
signal too large to give a meaningful ratio. Press the LOG/LIN
button to put the instrument in logarithmic mode, then press the
REF button. The dB annunciator will light. Press again to clear the
reference level and take the instrument out of REF mode.

H. Photodetectors have response characteristics which depend upon

the wavelength of the light incident upon them. Press the λ CAL
▲ (wavelength up) and hold in until the wavelength annunciator
turns off. The word PROBE will light, and the main display will
show the detector serial number. Press the ATTEN button and the
display will show the attenuator serial number, the ATTENUATOR
annunciator will light, and the PROBE annunciator will turn off.
Press the λ CAL ▼ (wavelength down) button and hold until the
attenuator serial number is again displayed. Press the ATTEN
button again to turn the attenuator calibration factor off.

I. The λ CAL SAVE button stores the wavelength and attenuator

status as power-up conditions. See paragraph 2.7.11.

J. The TIME CONST button controls the effective time constant of

the displayed readings. Press and hold the TIME CONST button.
The TIME CONSTANT annunciator on the lower display will
change in a repeating SLOW, MED, FAST sequence.

K. The group of buttons below the bar segment display control the

zero and resolution of the bar segment display. The OFFSET
button sets the zero of the bar display to the digital reading when
the OFFSET button is pressed. Press the analog display OFFSET
button. The OFFSET annunciator in the lower display should light.
Press again to reset the bar display zero. The ZOOM buttons
control the resolution and range of the bar display. The numbers
at the end of the bar display indicate the range. Depress and hold
the ZOOM out <button until the number at the ends of the bar

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segment display is 25000. Momentarily depress the ZOOM in Ρ
button. The number at the end of the display will change to 12500.
Press and hold until that number is 5. Depress and hold the
ZOOM out Θ until the full scale range of the bar graph is +25000
counts.

NOTE

In this manual the term “counts” refers to an increment of one in
the least significant digit of the digital display. For example, if the
digital display read 1.9453 mW, 1 count is 0.0001 mW. If the display
reads –23.45 dB, 1 count is 0.01 dB.

Connect the detector in normal room lights and familiarize yourself with
the operation of the instrument following the steps above as a guide.

When you are comfortable with the controls of the Model 835, go on and
make the desired measurements using Section 2, Operation as a guide.

Unpacking and

1.3

Inspection

Specifications

1.4

Warranty Information

1.5

The Model 835 Laser Pico-Watt Autoranging Power Meter was carefully
inspected mechanically, electrically, and optically, before shipment. Upon
receiving the Model 835, check for any obvious signs of physical damage
that might have occurred during shipment. Report the damage to the
shipping agent immediately. Retain the original packing materials in case
reshipment becomes necessary. The following items are included with
every Model 835 order:

• Model 835 Laser Pico-Watt Autoranging Power Meter

• Photodetector (some models include stand)

• Photodetector Manual and Calibration Certificate

• Model 835 Instruction Manual

• Additional Accessories and Options as included

Detailed Model 835 specifications may be found immediately preceding the
table of contents of this manual.

Warranty information may be found on the inside front cover of this
manual. Should it be necessary to exercise the warranty, contact your
Newport representative or the factory to determine the correct course of
action. Newport Corporation maintains offices in the United States and
worldwide. Information concerning the application, operation, or service of
your instrument may be directed to any of these locations. Check the back
cover of this manual for offices and their addresses.

Manual Addenda

1.6

Information concerning improvements or changes to the instrument which
occur after the printing of this manual will be found on the addendum sheet
included with this manual. Be sure to review these changes before
attempting to operate or service the instrument.

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Safety Symbols

1.7

and Terms

The following safety symbols and terms are used in this manual or found on
the Model 835.

The symbol ! on the instrument indicates that the user should refer to
the operating instructions in this manual.

The WARNING heading in this manual explains dangers that could result in
personal injury or death.

The CAUTION heading in this manual explains hazards that could damage
the instrument.

Optional Accessories

1.8

and Services

The following accessories can be used with the Model 835.
Model 818-SL Silicon Photosensor — A 1 cm

packaged to facilitate mounting and accept fiber adapters. Useful spectral
range 400-1100 nm. Includes detachable attenuator.

Model 818-UV Silicon Photodiode — A 1 cm2 aperture silicon photodiode
packaged to facilitate mounting and accept fiber adapters. Useful spectral
range 250-1100 nm. Includes detachable attenuator.

Model 818-ST Silicon photosensor — A handheld silicon photosensor in a
very thin package especially useful for measuring power in hard to reach
places. Includes sliding OD-3 attenuator.

Model 818-IR — A 3 mm diameter Germanium photosensor with a post
mountable housing capable of accepting filters and fiber adapters. Useful
spectral range 800-1800 nm. Includes detachable attenuator.

Model 883 Series Attenuators — Replacement attenuators for use with the
Model 818-SL, 818-UV, or 818-IR photosensor.

Model 835-BAT Rechargeable Battery Pack — Provides a minimum of 5
hours operation from full charge, recharges within 10 hours and is field
installable.

Model 835-IEEE Computer Interface — IEEE-488 standard interface option
provides isolated data output and instrument control. Switch-selectable
talk only or addressable modes. Mounts within and is powered by the
Model 835.

2

aperture silicon photodiode

Calibration - Newport maintains a National Institute of Standards and
Technology (NIST) traceable spectrophotometric calibration facility.
Photodetectors are recalibrated on a fee for service basis. In addition,
special calibration services can be arranged. Contact Newport for details.

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4

Section 2

Operation

Introduction

2.1

Preparation for use

2.2

This section contains the information needed to prepare and operate the
Model 835 as a power meter. Bench operation consists of using the Model
835 to perform basic optical power measurements. Using the instrument to
compensate for dark current and ambient light, as well as making ratio and
logarithmic (dBm, dB) measurements, is also covered. The capabilities of
the Model 835 can be enhanced with the addition of then Model 835-IEEE
interface. IEEE-488 computer interface operation is covered in the Model
835-IEEE Instruction Manual.

2.2.1 Line Power

The Model 835 is provided with a three-wire line cord which mates with
third wire grounded receptacles. Connect the instrument to AC line power
as follows:

1. Set the LINE VOLTAGE switch on the back of the instrument to
correspond to line voltage available. Ranges are 105-125V or 210-250V
50/60Hz AC. If the Model 835 is ordered with the 90-100V operation
option, a label on the back panel will indicate that the meter is
configured for 100V operation.

CAUTION

Connect only to the line voltage selected. Application of incorrect
voltage can damage the instrument.

2. If 50 Hz operation is desired, open the top cover of the instrument
(see paragraph 5.2), and connect the line frequency jumper as shown
below. Units are normally shipped configured for 60 Hz operation as
indicated by the F60 display immediately after power-up.

50 Hz

VIEW FROM REAR

Figure 2-1 50/60 Hz Selection Jumper

3. Plug the power cord into a properly grounded outlet.

60 Hz

WARNING

Ground the instrument through a properly grounded receptacle
before operation. Failure to ground the instrument can result in
severe injury or death in the event of short circuit or malfunction.

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NOTE

Although the Model 835 is specified at 50 Hz and 60 Hz, the
instrument may be operated at 400 Hz and 440 Hz. Add 10 counts
to instrument specifications under this condition.

2.2.2 Battery Pack Power

The Model 835 may also be operated from rechargeable sealed nickel­cadmium batteries contained in the optional Model 835-BAT Rechargeable
Battery Pack. A fully charged battery pack will operate the Model 835 for
five hours. The BAT annunciator will turn on when the battery charge is
insufficient to maintain accurate readings. Refer to Section 5, paragraph

5.3 for installation procedures.

2.2.3 Battery Charging

After the Model 835-BAT Battery pack is installed in the Model 835 it can be
charged and recharged as follows:

1. Connect the instrument to line power as described in paragraph 1.2.

2. With the power switch off, the battery charge circuitry is

automatically energized to charge the battery at the maximum rate.
When the battery pack is first installed, or if it is completely
discharged, allow it to charge for ten hours.

2.3

Tilt Stand

NOTE

For maximum battery efficiency only charge the battery pack after
it has become discharged and only charge until it is fully charged
(10 hours). Continuous charging over long periods of time will not
damage the batteries, but useful life will gradually decrease. This
loss is not permanent and may be restored by cycling the battery
pack through several complete charge/discharge cycles. The
battery pack is capable of 500 to 1000 charge/discharge cycles
before replacement is needed.

Do not make measurements with the BAT annunciator on as the
readings may be erroneous.

3. When the Model 835 is in use on line power, the battery charger
maintains a trickle charge on the battery pack.

The Model 835 is equipped with a tilt bail which makes it possible to elevate
the instrument to a convienent viewing position. To elevate the instrument
pull the bail on the bottom of instrument out until it locks in position.

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Model 835

2.4

Familiarization

The following paragraphs and Figure 2-2 provides a brief description of the
display, front panel controls and connectors.

ATTENUATOR

AUTO

RMT LLO
ZERO CHECK

■

Optical Power Meter ■

125000 0 125000

–

On

Off

TIME CONSTANT
SLOW MED FAST

OFFSET

2.4.1 Digital Display

The Model 835 has a 4-1/2 digit backlit liquid crystal display (LCD). The
minus sign is displayed. The plus sign is implied by the absence of the
minus sign. The following annunciators are displayed on the LCD.

BAT — Low battery indicator for the Model 835-BAT.

Zoom

BAT

nW
µW
mW

PROBE CAL

dBm REL

Model 835

nm

DISPLAY MODE

Null

+

Offset

Figure 2-2 Model 835 Front Panel

RANGE

Log

λ CAL

Auto

Ref

/

Lin

Save

Time

Const. Attn.

Zero

Check

Detector

Zero

nW, mW, mW, or W — Nanowatts, microwatts, milliwatts, or watts display
range selected.

dBm, dB — Decibels relative to 1 mW (dBm) or decibels relative to user set
level (dB) selected.

When neither watts or decibels displayed — Value displayed is a linear
ratio referenced to user set power.

RMT (Remote) — Model 835 being controlled over the IEEE-488 bus (Model
835-IEEE installed).

AUTO — Autorange selected.
REL —Null selected.
ZERO CHECK — Zero Check selected.
nm — Follows wavelength used to determine detector responsivity used to

compute optical power from detector photocurrent. If NOT displayed,
detector or attenuator serial number is displayed.

ATTENUATOR — Indicates attenuator selected. When in serial number
display mode, indicates that attenuator serial number is displayed.

PROBE — Indicates detector serial number is displayed.
CAL — Model 835 in current calibration mode. This is normally a factory

procedure.

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2.4.2 Bar Display

The lower LCD display is a 50 segment bar with variable resolution. The
zero of the analog display is at the center of the bar, and is marked 0.

Numbers at ends of the bar — Above each end of the bar numbers are
displayed which indicate the full scale range of the bar segment. Full scale

is ±5, 25, 125, 250, 500, 1250, 2500, 5000, 12500 or 25000 counts.
OFFSET — Indicates that the zero of the bar graph has been offset from the

digital display zero.

TIME CONSTANT (SLOW, MED, or FAST) — Indicates instrument response
time constant selected.

2.4.3 Front Panel Controls

ON/OFF — Pressing this button turns the Model 835 on. Releasing (out) this

pushbutton turns the instrument off.

ZERO CHECK and ZERO — This pushbutton and trimpot are used to zero
the instrument‘s internal effects.

ATTEN — This button is used indicate that the attenuator is used with the
detector. Press again to indicate that the attenuator is not used.

Range Buttons

▼▲ — Pressing either of these buttons sets the instrument to manual range.
When ▲ is pressed, the full scale range of the instrument is increased.
When ▼ is pressed, the range is decreased. Ranges set are current ranges

and are ±2 nA to ±2 mA full scale. Full scale power ranges will depend upon
the detector responsivity and are wavelength dependent.

AUTO — Pressing the AUTO button when the instrument is in manual
ranging sets the instrument to autoranging. When the instrument is already

in autoranging, the instrument is set to manual ranging without changing the
range.

TIME CONST — Pressing this button changes the effective time constant
between slow, medium, and fast.

NULL — Press this button to store the dark or ambient light level
photodetector current. Subsequent measurements will be displayed with

this current subtracted before conversion to optical power. The REL
annunciator will light when Null is on. Pressing this button again shuts Null
off.

LOG/LIN — Press this button to select the logarithmic display modes. The
displayed power is expressed as decibels relative to 1 milliwatt when the

dBm annunciator is lit, and as decibels relative to a user stored reference
level when the dB annunciator is lit.

REF (Reference) — Press to store reference power. In linear mode, the
display is the ratio of the power with respect to the stored reference power.

Power annunciator (W) turns off. In log mode, the display changes to dB
referenced to stored power.

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λ CAL:

▼▲Wavelength up/down — Changes the wavelength used in the
detector response calculation. Press momentarily to change by 10 nm.
Hold in to scan wavelengths. At ends of wavelength range, detector
serial number is displayed with the annunciator PROBE lit. If attenuator

is on, attenuator serial number is displayed with only the annunciator
ATTENUATOR lit.

SAVE — Press to save wavelength value and attenuator status as initial
conditions on next power up. Stor annunciator lights briefly, then

instrument continues to make measurements.

Bar Graph Display Controls:

The bar graph input is the digital display. Therefore, range changes
affect the bar graph display. To avoid unexpected range changes, use
manual ranging.

Zoom Θ, Ρ — Changes the resolution of the bar graph. Ρ increases
segment resolution and decreases bar graph range. Θ decreases
segment resolution and increases bar graph range. Full scale bar graph

range can be ±5, 25, 50, 125, 250, 500, 1250, 2500, 5000, 12500, 25000
counts corresponding to individual segment resolution of 0.2, 1, 2, 5, 10,

20, 50, 100, 250, 500, and 1000 counts on the digital display.

OFFSET — Press this button to offset zero of bar segment display to the
value presently displayed on the digital display. Press again to clear

offset.

2.4.4 Input Connector

The input connector is a standard BNC type with a floating outer shell.

2.4.5 Analog Output Connectors

A voltage level that is proportional to the incoming current can be
monitored using the analog output banana jacks located on the rear panel.
Note that range changes, even on autoranging, will change the constant of
proportionality (gain) of the output signal. Range changes which are not
apparent on the front panel display may occur if the instrument is in
autorange mode.

Error Messages

2.5

Display Message Comments

0000 RAM Error Model 835 locks up. See Section 5 for troubleshooting information
cErr Calibration Error Model 835 locks up, but operation can be restored by pressing any one of

(NVRAM Failure) the momentary pushbuttons. If restored, calibration is invalid as indicated

Table 2-1 lists the error messages associated with basic front panel
operation. Note that the instrument has a number of other messages that
are discussed in the appropriate sections of this manual.

Table 2-1 Error Messages

by flashing “CAL” annunciator. Readings are still approximately correct.
See Section 5 for troubleshooting information.

OL Overrange 1. Overrange input applied to the Model 835.

2. Ratio is too large

-OL Overrange Logarithm of negative power

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Environmental

2.6

Conditions

All measurements should be made at ambient temperature within the range
0°C to 50°C, and with a relative humidity of 0% to 70% up to 35°C. For
instruments operating above 35°C derate humidity specification 3% per °C
up to 50°C. If the instrument has been subjected to extremes of
temperature, allow sufficient time for internal temperatures to reach
environmental conditions. Typically, it takes one hour to stabilize a unit
that is 10°C (18°F) out of specified temperature range.

The photodetector temperature should be at or below the calibration
temperature.

NOTE

The photodetectors supplied with this instrument have
characteristics which are temperature dependent. Dark noise and
detector responsivity change with temperature. See the appropriate
detector manual.

Basic Measurements

2.7

Basic measurement techniques for using the Model 835 to measure DC
optical power are covered in the following paragraphs. Also included is the
operation of the bar graph display, making measurements in decibels (dBm
and dB), and using the Null and Reference functions. A summary of range
and overload conditions of the instrument is given in Table 2-2. Instrument
drift will depend upon the detector used. In general, absolute accuracy is
limited by the accuracy of the detector calibration and environmental
factors affecting the detector. See the appropriate detector manual for this
information.

Table 2-2 Range Electrical Accuracy and Overload Conditions

Accuracy

Power Maximum Current ±(%Rdg +%Full Scale)

Range

1

Reading

1,2

Range

1

18°C – 28°C

3

2 nW 1.9999 nW 2 nA 0.4 + 0.2

20 nW 19.999 nW 20 nA 0.4 + 0.05

200 nW 199.99 nW 200 nA 0.2 + 0.05

2 µW 1.9999 µW2 µA 0.15+ 0.05

20 µW 19.999 µW 20 µA 0.1 + 0.05

200 µW 199.99 µW 200 µA 0.1 + 0.05

2 mW 1.9999 mW 2 mA 0.1 + 0.05

Notes:

1. Assuming detector response in the range 0.1 to 1.0 Amp/Watt. For
detector response smaller than 0.1 Amp/Watt, divide power range and
maximum reading by the ratio of the order of magnitude of the detector
response to 0.1. For example, if the detector response is 0.03 Amp/Watt,
divide power range and maximum reading by 0.01/0.1 = 0.1, so the ranges
will be from 20 nW to 20 mW.

2. Power above the maximum will result in “OL” display.

3. Electrical accuracy depends on current range. Detector calibration
accuracy usually limits reading accuracy.

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WARNING

Before opening or operating the Model 835, observe the safety
precautions found preceding Section 1. Failure to observe these
and other safety precautions found in this manual could result in
severe injury or death.

WARNING

Do not exceed 30V RMS between input low and power line ground
or a shock hazard will result. Also, current inputs that exceed 3 mA
may be erroneously displayed as an on-scale reading.

2.7.1 Power-Up
NOTE

The software revision of the Model 835 can be displayed upon
power-up by running the diagnostic program. See Section 5,
paragraph 5.7, for more information.

Turn on the Model 835 by pressing the ON/OFF switch. The following will
occur automatically:

1. Reset — F60 or F50 will be briefly displayed before displaying the
detector serial number. F60 (F50) indicates that the unit is configured

for 60 Hz (50Hz).

2. RAM Test — If this test fails the Model 835 will lock up with F60 or
F50 displayed.

3. NVRAM test — This test determines if the instrument analog
electronics, not the detector response calibration, are properly read
from the NVRAM. If this test fails the display will show the error

message cErr.

4. Serial number display — The detector serial number will be briefly
displayed. If the attenuator is on, the attenuator serial number will be

displayed with the annunciator ATTENUATOR lit. Verify that the
detector and attenuator attached to the instrument has the same

serial number as the number displayed to ensure calibration
accuracy.

5. Begin measurement — The instrument will use the wavelength and
attenuator status values last stored with the λ CAL SAVE button.

Autoranging will be on.

Refer to Table 2-1 for more information pertaining to error messages.

CAUTION

During power up and power down, using AC line or battery pack,
a current surge (5mA, 5V maximum) can appear at the INPUT of the
Model 835. Protect the photodetector by making circuit
connections only after turning on the Model 835. Disconnect the
photodetector before turning off the Model 835.

2.7.2 Zero Check

The instrument should be properly zeroed (after one hour warm-up) before
making any current measurements. Upon pressing ZERO CHECK, the
instrument will automatically enter the current display mode. Set manual
range mode, and range to the most sensitive range (2 nA full scale).

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Display will read .xxxx nW. To check or adjust zero, proceed as follows:

1. Write down instrument settings to restore after finishing checking the
zero. Null, Log, and Ref will automatically be turned off by pressing
ZERO CHECK.

2. Press the ZERO CHECK button.

3. Adjust the zero level trimpot via the access hole on the front panel for
a zero indication on the digital display.

4. Press the ZERO CHECK button again to turn off.

5. Restore instrument settings as desired to continue measurement.

2.7.3 Setting the Wavelength

In order to obtain accurate optical power measurements, it is necessary to
set the instrument calibration wavelength to the wavelength of the light
incident upon the photodetector. The instrument calibration wavelength is
indicated in nanometers in the upper right hand of the digital LCD display
and is followed by the annunciator nm. Upon power-up, the wavelength will

be set to the value last stored by pressing the λ CAL SAVE button. To
change the wavelength:

1. Determine the wavelength of the light being measured to the nearest
10 nm. If the source is broadband, use a value near the center
wavelength of the light, or the wavelength of greatest intensity.

2. If the wavelength is greater than the value displayed, depress the λ
CAL ▲ button, and hold until the desired wavelength is reached.

3. If the wavelength is lower than the value displayed, depress the λ
CAL ▼ button, and hold until the desired wavelength is reached.

Notes:

1. Momentarily depressing the λ CAL ▼ or ▲ buttons will increase or
decrease the calibration wavelength by 10 nm. Wavelength will

continue to change as long as the wavelength button is held in.

2. Different detectors are sensitive over different wavelength ranges.
See the appropriate detector manual and calibration data to
determine the range of wavelengths for which the detector connected
to the instruments can be used. The calibration constants stored in
the instrument span only the wavelength range appropriate for the
detector, and can be determined by following Note 3 below.

3. Depressing and holding either the λ CAL ▼ or ▲ buttons until the
wavelength range of the detector is exceeded will cause the detector

serial number and the PROBE annunciator to be displayed on the
main digital display, and the wavelength annunciator to turn off. If
ATTENUATOR is on, the attenuator serial number will be displayed
instead, and the PROBE annunciator will be off.

4. To stop the serial number display, press λ CAL ▲. If the instrument
remains in serial number display mode, press λ CAL ▼. Use the λ

CAL ▼ or ▲ buttons to set the desired calibration wavelength as
above.

5. If the instrument calibration wavelength cannot be set to within 5 nm
of the desired value, then the detector/PROM combination being used
is not appropriate for this measurement. See Section 5 for Detector/
PROM replacement.

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2.7.4 Setting Attenuator Status

Some Newport photodetectors are provided with calibrated attenuators.
The calibration constants for an attenuator and detector combination are
stored in the Model 835. To measure optical powers above the saturation
limit of the photodetector (see appropriate photodetector manual), use an
attenuator. When the attenuator is selected the following occurs:

1. The ATTENUATOR annunciator is displayed.

2. The wavelength calibration constants are computed including the
effects of the attenuator.

If the attenuator is subsequently removed, the ATTEN button should be
pressed to turn the attenuator off. Subsequently, all displayed values will
be computed using wavelength calibration constants computed for the
detector without the attenuator.

NOTE

The transmission characteristic of each attenuator is slightly different,
therefore the user must be careful to use ONLY the attenuator and detector
pair with the same serial numbers as the particular Model 835 PROM is
calibrated for.

2.7.5 Power Measurements

1. Zero the instrument as described in paragraph 2.7.2

2. Select autoranging or manually range to a desired range for the
expected power level.

3. Connect the detector to the INPUT connector on the front panel. A
summary of range, and input overload information is given in Table 2-

2. Detector calibration accuracy and drift information is supplied
with the detector.

4. Read the optical power on the digital display. Overrange is indicated
by an OL message.

2.7.6 Time Constant

Three time constants are available for operating the Model 835: slow,
medium, and fast. To select the desired time constant:

1. Press the TIME CONST button until the TIME CONSTANT annunciator
on the lower LCD indicates that the desired time constant is set.

2.7.7 Null (REL) Measurements

When NULL (relative) is selected with an on-scale reading on the display,
the following occurs:

1. The REL annunciator is displayed.

2. The next current reading is stored.

3. The stored current is then algebraically subtracted from all
subsequent current readings before the optical power computation.

The primary purpose of NULL is to allow the user to take accurate readings
even when significant amounts of dark current or ambient light are present.
The conversion factor from current to optical power depends upon the

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wavelength of light. For this reason, the current and NOT the optical power
is stored and subtracted from subsequent current readings prior to
conversion to optical power.

A Null current offset can be established for the linear measurement mode
or the decibel measurement mode, and is effective for both modes.
Changing modes or wavelengths will not affect a Null level, however, if
NULL is pressed again, the Null current offset will be cleared and cannot be
recalled.

It is important to note that the use of Null in manual range mode may
reduce the dynamic range of the measurements by that current level. For

instance, assume that the Null current offset is +1.5 µA and the Model 835 is
manually set to the 2 µW full scale range. Also, assume that the detector

response is 0.5 amp/watt. The maximum positive displayed reading that
could be displayed before overranging would be 1.9999 µW. The displayed

power is then (1.9999−1.5)/0.5 = 0.9998 µW . Thus, the dynamic range of
measurement is −1.9999 µW to +0.9998 µW compared to the normal −1.9999
µW to +1.9999 µW with the same detector response. The dynamic range of

the measurement has been reduced by 1 µW (0.5 µA). The effects on
dynamic range can be reduced by selecting a higher range or using
autorange. The large dynamic range of the Model 835 allows measurements
to be made with null current offsets of 90% or more of full scale which are
still accurate and precise.

2.7.8 Ratio Measurements

When the ratio mode is selected by pressing the REF button in linear mode
with an on-scale reading on the display the following occurs:

1. The power annunciator (nW, µW, mW, or W) is turned off.

2. The next power reading is stored.

3. The stored reading is then algebraically divided into all subsequent
readings and displayed.

See paragraph 2.7.9 for the action when REF is pressed in Log mode.
Changing modes to Log after pressing REF will clear the REF level.

The method used is calculate the ratio is shown below:

RATIO = ((I - Id)/Response)/Stored Power

where

I = Photodetector current

Id = Stored Null current (see paragraph 2.7.7)

Response = Response in amps/watt of the detector, or detector and

attenuator, at the wavelength currently displayed in the
LCD

Stored Power = Displayed power value stored when REF button was

pressed.

Note that this method of computation allows accurate optical power ratio
measurements to be made with the reference and measurement
wavelengths to be different.

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2.7.9 Logarithmic Modes (dBm and dB)

The Model 835 can make logarithm measurements referenced to a 1 mW
power level or to other power levels with the use of the REF feature.

The basic procedure for using the Log mode is to select autorange and
press the LOG button (dBm annunciator comes on). To get out of Log
mode, press the LOG button again. The dBm annunciator will turn off, and
one of the watt annunciators will turn on.

Because the logarithm of a negative number is undefined, -OL is displayed if
the logarithm of a negative number is attempted.

NOTE

Log measurements should always be made on the lowest possible
range (without overranging). Readings on high ranges will not
allow optimum calculations of the logarithm. When in doubt, use
autorange.

1. Log measurements with a 1 mW Reference (dBm): The Log
measurement mode displays the absolute value of 10 times the
logarithm (base 10) of the input current referenced to 1 mW. The
following equation illustrates this relationship:

dBm reading = 10 Log (Net Applied Power/ 1 mW)

= 10 Log (((I-Id) /Response)/1 mW)

Using this reference power, the dBm reading span is from –100.0 to

+33.00 dBm (0.1 pW to 2 W).

The following examples compute the expected Log readings for various

power levels applied to the Model 835.

A. 1 nW (0.5 nA with detector response of 0.5 A/W)

Power = (0.5 nA/ 0.5 A/W) = 1 nW
Log reading = 10 Log (1 nW/1mW)
Log reading = -60.00 dBm

B. 1 W (1 mA with detector and attenuator response of .001 A/W)

Power = (1 mA / 0.001 A/W) = 1000 mW = 1 W
Log reading = 10 Log (1000 mW/ 1 mW)

Log reading = +30.00 dBm

C. 0.5 mW ( 0.5 mA - 0.25 mA stored null current offset and detector

response of 0.5 A/W)
Power = ((0.5 - 0.25 mA)/0.5 A/W) = 0.5 µW

Log reading = 10 Log (0.5 mW/ 1 mW)
Log reading = -33.01 dBm

To make dBm measurements (relative to 1 mW optical power) without

Null current offset, proceed as follows:

A. Zero the instrument, if required, as described in paragraph 2.7.2.
B. Select AUTO range on the Model 835
C. Connect the source to the Model 835

D. Press the LOG/LIN button

E. Take the dBm reading from the display.

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To make dBm measurements (relative to 1 mW optical power) with Null

current offset, proceed as follows:

A. Follow steps A to C above
B. Block the optical signal to the detector (for example, block the

laser beam)

C. Press the NULL button. Display should read approximately zero,

but will fluctuate depending upon the variations in the amount of
light irradiating the detector as well as with detector dark current
fluctuations.

D. Illuminate the detector with the optical signal to be measured.

E. Press the LOG/LIN button
F. Take the dBm reading from the display

Note : When using Log mode with Null current offset, the signal after
the subtraction of the stored Null offset may be negative. In this case,
–OL will be displayed since the logarithm of a negative number is not
defined. This will be automatically cleared when the signal becomes
positive.

2. Log measurements using other reference powers (dB):
Decibel (dB) measurements, referenced to other optical power levels,

can be read directly from the display of the Model 835 by utilizing the
Ref feature.

To make dB measurements referenced to another power level, proceed

as follows:

A. Follow either sequence (A-D or A-F) above.
B. After pressing the LOG/LIN button, illuminate the detector with

the reference signal.

C. Press REF to select reference mode. The following will occur:

1. The dB annunciator is displayed.

2. The next power reading (in dBm) is stored.

3. The stored reading (in dBm) is then algebraically subtracted
from all subsequent readings (in dBm) and displayed.

D. The Model 835 is now set up to make decibel (dB) measurements

referenced to the stored power level. Simply input the power to
be measured and take the reading from the display.

Decibel readings may be positive or negative. OL will be
displayed if the input current exceeds 2 mA, or if the optical
power exceeds the maximum power for the detector or detector
attenuator combination (in autoranging), or the range selected (in

manual ranging). –OL will be displayed if the input current is less
than the stored Null current offset.

Example:

1. Signal = 2 mW
Press LOG/LIN

Display = +3.01 dBm
Press REF.

Display = +0.00 dB
Signal = 0.5 mW

Display = −6.02 dB

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2.7.10 Bar Display Zoom and Offset

The Model 835 includes a 50 segment bar display with zoom and offset
controls to provide a qualitative method to observe changes in the signal
level. The bar display functions like an analog meter with variable range
and zero offset. The display is driven by the digital display value, and
works in both logarithmic and linear modes. The zoom control allows the
user to set the resolution of the display, while offset allows the user to
offset the bar display and digital display zeros.

NOTE

When using the bar graph display, setting the instrument to
manual ranging is often a convenient method to avoid unexpected
jumps in the bar display due to range changes.

OFFSET: When offset is selected, the following occurs:

1. The bar segment display OFFSET annunciator is displayed.

2. The value of the digital display is stored.

3. The value used to drive the bar display segments is obtained by
subtracting the stored value from all subsequent digital display
readings.

Offset may be turned off by pressing the OFFSET button again.
ZOOM : The ZOOM Θ and Ρ buttons control the range and resolution of the

bar segment display. Full scale range of the display is selectable from ±5,
25, 50, 125, 250, 500, 1250, 2500, 5000, 12500, or 25000 “counts”. See Figure

2-2 for a drawing of the analog display. The range is displayed at either end
of the bar. See the Note following section 1.2 paragraph K for an
explanation of the term “count.”

At the ends of the bar segment displays, two arrows are used to indicate
underflow and overflow. The Underflow Arrow Θ will turn on if either of
two conditions is met:

1. The digital display value is too small to show within the range of the
analog display. To display an underflowed signal, press ZOOM Θ to
increase the range of the bar segment display, or press OFFSET once
or twice to reset the bar segment display zero to the digital display
value.

2. -OL is displayed in the digital display.

The Overflow Arrow Ρ will turn on if either of two conditions is met:

1. The digital display value is too large to show within the range of the
analog display. To display an overflowed signal, press ZOOM Θ to
increase the range of the bar segment display, or press OFFSET once
or twice to reset the bar segment display zero to the digitial display
value.

2. OL is displayed in the digital display.

The MED time constant is designed specifically to be used in conjunction

with the bar display.

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17

2.7.11 Storing the Wavelength and Attenuator Status for

–
+

R

S

R

FB

C

FB

C

S

910Ω

100Ω

ANALOG
OUTPUT

TO A/D
CONVERTER

I

in

Power-Up

When λ CAL SAVE is pressed, the following occurs:

1. The current wavelength is stored in non-volatile memory.

2. The attenuator status is stored. If the ATTENUATOR annunciator is
on, Attenuator On is stored. If the annunciator is off, Attenuator Off is
stored.

3. The Stor annunciator lights briefly.

4. The instrument returns to normal operation

The stored values are recalled whenever the Model 835 is powered-up.

2.7.12 Inverting Analog Output

Two banana jacks, accessible from the rear panel, permit monitoring or
recording of the output from the current -to-voltage converter within the
Model 835. Since the Model 835 is based on a feedback ammeter, as shown
in Figure 2-3, the input current is forced through the feedback resistor and
an inverted output voltage is developed by the operational amplifier. The
feedback (range) resistors are selected such that voltage for an on-scale

reading on the 2 nA range will be between zero and ±200mV. The output
voltage for the rest of the ranges will be betwen zero and ±2V. Here, range

refers to the full-scale current range.

Figure 2-3 Feedback Picoammeter and Input Signal Conditioning Circuit

The analog output is direct current-to-voltage conversion of the
input current. It is NOT directly related to the digital display,

NOTE

and hence is NOT dependent upon the wavelength, attenuator
status, or the mode of the instrument (dB, Reference, etc.) or time

constant.

The analog output is protected up to 20V RMS and during an input current
overload the analog output is clamped to a maximum voltage swing of

approximately ±4V. Although protected up to 20V to prevent instrument
damage, a voltage applied to the analog output could cause an erroneous

display, rather that the OL message.

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Since the output of the current-to-voltage converter is bipolar, the inverting
analog output can also be used to measure low frequency AC power which
falls within the specified analog rise time. The inverting analog output
resistance is 1.01 kΩ; 910Ω in series with the signal leads and 100Ω in
series with the ground lead.

Typical Analog Output Accuracy:

Nonlinearity: < 0.1% full scale
Gain Accuracy : ±1%

Output Resistance : ±5%

2.7.13 IEEE Interface Option

The Model 835-IEEE Interface Option is available for the Model 835. The
interface allows computerized data acquisition and control of the Model

835. Detailed operating instructions for the IEEE interface are found in the
Model 835-IEEE Interface Instruction Manual supplied with the interface or
available from Newport Corporation.

Measurement

2.8

Considerations

This section describes effects of detector and attenuator characteristics,
optical and electrical considerations, environmental conditions, and
changing detectors. The accuracy of the Model 835 is generally limited by
the accuracy of the detector calibration. Making accurate measurements of
optical power is dependent upon controlling the environmental conditions,
specifically temperature and illumination conditions, and understanding
the factors that affect power measurement.

2.8.1 Detector Calibration and Accuracy

Newport Corporation calibrates its photodetectors using secondary
standards directly traceable to the United States National Bureau of
Standards. At the present time, not all wavelengths are covered by optical
power standards at the power levels appropriate to the photodiode based
sensors. Since the details and accuracy of the calibration procedure vary
with each photodetector model, a more detailed description of the
calibration restrictions is supplied with each individually calibrated
photodetector. Some Newport photodetectors are supplied with typical
response curves and have not been individually calibrated.

In general, detector calibration accuracy is ±3% to 10% in absolute terms,
and varies with wavelength. Each detector will have some variations in the

response over different sections of the surface. This is caused by
variations in the semiconductor material. Therefore, for the most
reproducible measurements, light should illuminate the detector as
uniformly as possible.

CAUTION

AVOID FOCUSING onto the detector surface. Inaccurate readings
and possible detector damage may result.

Individual detectors change with time, especially in the ultraviolet and
should be returned for recalibration at 1 year intervals to assure confidence
in the accuracy of the measurement. For the most reproducible
measurements, the same detector should always be used for measurements
which are to be directly comparable.

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2.8.2 Temperature Effects

Photodiode characteristics are significantly affected by temperature.
Typically, at longer wavelengths, detectors increase in sensitivity at longer
wavelengths with increasing temperature. However, the detector/amplifier
combination noise increases exponentially with temperature. With silicon
photodetectors, this is generally on the order of a few picoamps at
temperatures near room temperature. With uncooled germanium
detectors, however, this drift is typically 1,000 to 10,000 times larger, on the
order of a few nanoamps. These drifts can be nulled by covering the
detector and pressing NULL. However, since the current drift changes with
time, the Null should be set just prior to any measurements.

If the detector temperature is constant, sensitivity changes are significantly
reduced. In addition, if detectors are cooled, noise will decrease. For the
most accurate measurements, particularly with germanium detectors, the
user should cool the detector to approximately 0°C, and to control the

temperature of the detector to approximately ±1°C.
Since different detectors differ significantly in their characteristics, consult

the appropriate detector manual for information about the details of the
detector you are using.

2.8.3 Ambient and Stray Light

Ambient and stray light striking the detector will be measured by the Model
835, and should be considered when making careful measurements.
Ambient light can be distinguished from dark current by turning off or
blocking the source and covering the detector face with opaque material,
such as a piece of black rubber or metal. Using a hand to cover the
detector surface is not advised because the human hand emits a significant
amount of infrared radiation, and is at a temperature significantly different
from ambient. Particular care should be taken with infrared sensing
detectors. With the detector properly covered, take a reading on the power
meter. This is the dark current. Press NULL to offset the dark current. Next,
remove the material which is covering the detector face and take another
reading. This reading is the ambient light level. To make measurements
with this background eliminated, press NULL twice. The meter should read
approximately zero. Turn the source on and make measurements which
are now corrected for dark currents and ambient light.

NOTE

Changes in ambient light levels can occur from such factors as
turning room lights on or off, or by moving people or equipment.
To check if the variations in ambient light are affecting the
measurements, set the Model 835 on MANUAL ranging on the range
which will be used for taking actual measurements. Press NULL
twice to null dark currents and ambient light. Monitor the display
for some time. If the display changes by more than the fluctuations
in dark current, then special care in shielding the detector from
ambient light is required.

The effects of ambient and stray light can be minimized by using the Model
818-FA Fiber Adapter Holder with the appropriate FP3-CA series fiber
adapter when measurements of power in fiber optics are being made. If
free space beam measurements are desired, using the Model 883 Attenuator
will reduce stray light, and often improve the ratio of signal to ambient.

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Wavelength specific filters, such as optical cutoff, bandpass, or spike filters
can also be used if the signal wavelength spectrum permits. Other
techniques to reduce stray light include using apertures, placing the
detector in a box or other housing to shield the surface from light which is
not coming from the source, and turning off room and other lights.

2.8.4 Wavelength Response of Detector and Attenuator

All photodiode detectors have a response which varies with the wavelength
of light which is incident upon the detector. The response is measured in
amps/watt, and is typically between 0.1 and 0.6 amps/watt. A typical
response curve for the Model 818-SL silicon detector is shown in Figure 2–4.

0

10

-1

10

10

10

w/o 883 Attenuator

-2

-3

818-UV
818-IR
818-SL

-4

10

Absolute Spectral Data (Amp/Watt)

-5

10

200 400 600 800 1000 1200 1400 1600 1800

w/ 883 Attenuator

Wavelength (nm)

Figure 2-4 Wavelength Response of 818 Series Detectors (upper curves)

and Detectors with Attenuator (lower curves)

The Model 835 Laser Pico-Watt Digital Power Meter measures the
photodetector current, and converts the signal to an optical power by
dividing the current by the response of the detector. The detector
response as a function of wavelength is stored in a table in the Model 835,
and the appropriate value is chosen using the wavelength set by the user. If
the spectral source is broader than 10 nm, a choice must be made as to
which wavelength will give the best reading. Usually this wavelength will
be near the center of the optical spectrum of the source. In the central
portion of the detector spectral response curve, the response varies slowly
as a function of wavelength. However, near the minimum and maximum
wavelengths where the detectors are sensitive, the fractional detector
response can change by 1% per nanometer. In addition, attenuators also
have a spectral response which is typically different from the detector
response. Newport Corporation detectors are supplied with information
showing detector response characteristics. Please see the information
included with the detector used with the Model 835.

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2.8.5 Detector Uniformity

The response of the detectors vary slightly over the detector surface. This
is a result of small non-uniformities in the semiconductor composition and
fabrication process. Typical non-uniformities are a few percent peak to
peak for different 1 mm2 areas on the detector surface. To reduce the
effects of detector non-uniformity on measurement accuracy, illuminate as
much of the detector surface as possible with the optical signal.

CAUTION

Focusing light on the detector surface increases the sensitivity of
the measurement to variations in the detector response, and can
lead to detector saturation and possible detector damage.

Although care is taken to select detectors with good unformity of the
detector response over the surface, the calibration data supplied with
detectors is for full surface illumination.

2.8.6 Detector Saturation

For small optical powers, the current generated by the photodiode is
proportional to the optical signal incident upon the detector. For larger
optical powers, saturation begins to occur, and the photodetector current
is lower than would be expected if the output remained proportional to the
signal. A typical saturation curve for a silicon photodiode is shown in
Figure 2-5.

(Typ. at 720 nm. 25°C)

-6

10

10

-4

-2

10

0

10

OUTPUT CURRENT (A)

10

10

10

10

10

-10

10

-12

10

0

-2

-4

-6

-8

-12 10-10

10

-8

10

OPTICAL POWER (W)

Figure 2-5 Typical Silicon Photodetector Saturation Characteristics

Note that the saturation is “soft”, i.e. the detector output does NOT
suddenly stop increasing, but the rate of increase slows. For Gaussian and
other signals with spatially varying intensities, local saturation may occur.
The onset of saturation is not always obvious, and can lead to inaccurate
measurements. Approximate saturation levels are given in the detector
manuals. To see if a detector is saturating, reduce the optical power by a
known amount, for example, by a factor of 1000 and verify that the reading
is as expected. Calibrated attenuators supplied by Newport can be used for
this purpose. If the reading is not as expected, apply an attenuator of
known attenuation to reduce the optical power. The Model 835 Power
Meter can be used to measure the transmission of the attenuator. Reduce

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22

the signal to a level small enough to avoid detector saturation, then place
the attenuator in the beam path, and take another reading. The ratio of the
two readings is the transmission of the attenuator.

NOTE

The detector saturation current for each kind of detector is read by
the microprocessor upon power-up. If the saturation current level
is exceeded, an “OL” condition will be displayed on the readout.

2.8.7 Attenuator Characteristics

Optical attenuator characteristics also affect measurement accuracy. Most
optical attenuators are sensitive to the angle of illumination, i.e. the angle at
which light is incident upon them. For absorbing filters, the attenuation
increases if the angle of incidence is not normal. Attenuators also have a
transmission which depends upon wavelength. This wavelength
dependence is measured and included in the calibration table stored in the
Model 835 and is used to calculate the detector response when
ATTENUATOR is lit on the LCD display. See Figure 2-4 for typical attenuator
characteristics for each detector.

2.8.8 Reflections and Interference Effects

The photodetector surface and window material reflect light. The amount
of light reflected depends upon the angle of incidence and the polarization
of the light. Reflected light does NOT get absorbed by the detector, and
hence, is not included in the detector signal. The detector calibration
includes the loss due to reflection for incoherent light normally incident
upon the detector as sold by Newport Corporation. Use of the detector at
non-normal angles of incidence will affect the reading.

2.8.9 Grounding Considerations

Input LO (outer ring of the connector) should not be connected to a
potential at the source that exceeds 30V RMS from ground. The Model 835
will function properly if the detector is completely floating, i.e. not
connected to any ground. However, with some detectors, the noise
immunity will improve if the detector housing is connected to earth ground.

NOTE

The extremely high sensitivity Model 835 electronics are capable
of detecting changes in the capacitance of the cable to ground or
cable movement. When very low power measurements are being
made, care should be taken to avoid moving the cable and to
ground the outer shield of the cable if possible.

2.8.10 Changing Detectors

The Model 835 uses a programmable read only memory (PROM) to store
the calibration data for each detector. Newport individually calibrates each
detector, and programs the PROM with the individual calibration data.
Different detector models have very different spectral response
characteristics. To ensure the most accurate measurements, the PROM
should also be changed according to the instructions in Section 5 whenever
a new or recalibrated detector is used.

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23

Section 3

Performance Verification

Introduction

3.1

Environmental

3.2

Conditions

Recommended Test

3.3

Equipment

This section contains information to verify that the Model 835 electrical
performance is within the specified accuracy. Model 835 specifications may
be found at the front of this manual. Unfortunately, optical power
standards are not generally available. To verify detector calibration,
contact Newport Corporation. Ideally, performance verification should be
performed when the instrument is first received to verify that no damage or
change in calibration has occurred during shipment. The verification
procedure may also be performed whenever instrument accuracy is
suspect or following calibration. If performance on any of these ranges is
outside specified limits, contact Newport Corporation

NOTE

If the instrument does not meet specifications and it is still under
warranty (less than 12 months since date of shipment), contact
your local Newport Corporation representative or the factory to
determine the action to be taken.

All measurements should be made with ambient temperature surrounding
the display box between 18°C and 28°C (65° to 82° F) with a relative
humidity less than 70%.

Equipment for verifying the performance of the Model 835 is listed in Table
3-1. Alternative equipment may be used as long as the equipment accuracy
is at least as good as the specifications listed in Table 3-1. Interconnection
of the test equipment is shown in Figure 3-1.

Table 3-1 Recommended Current Calibration Equipment

Description Specification Mfr. Model

Current Source 1.900 nA to 1.900 mA Keithley 220

Required Accuracy:

< 02 nA ± 0.4%
< 20 nA ± 0.2%

> 20 nA ± 0.1%

Recommended Cables and Connectors:
(A) 3 ft. (1m) TwinAx Connector Trompeter PL75-29

(B) TwinAx Cable Trompeter TWC 124-1A
(C) BNC Connector for TwinAx Newport 13713-01

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24

+

–

Guard

BNC
Detector
Input

Initial Conditions

3.4

Verification

3.5

Procedure

Current Source

Twinax to

BNC adapter

Model 835Precision

Figure 3-1 Interconnection of Current Source and Model 835

Before performing the verification procedures, make sure the Model 835
meets the following conditions:

1. If the instrument has been subject to temperatures below 18°C (65°F)
or above 28°C (82°F), allow sufficient time for the instrument to reach
temperatures within the range. Generally, it takes one hour to
stabilize an instrument that is 10°C (18°F) outside of this range.

2. Turn on the Model 835 and allow it to warm up one hour. The
instrument may be operated from either line power or battery pack
power, as long as the battery pack has been fully charged as
described in paragraph 2.2.3.

The following paragraphs give the basic verfication procedure for checking
accuracy.

To properly check the accuracy of the Model 835, a precision current
source is necessary. The precise currents required are obtained by using a
precisely settable current source such as the Keithley Instruments Model
220 connected to the Model 835 as shown in Figure 3-1.

Proceed as follows to check the accuracy of the Model 835:

NOTE

Record the following measurements and calculations in Table 3-2.
Use pencil so that the table can be re-used.

Table 3-2 Calibration Check Table

Actual

835 Desired Required Allowable Reading

Range Reading Current Readings 18°C – 28°C

2 nW 1.9000 nW _________ _________ 1.8808 + 1.9192

20 nW 19.000 nW _________ _________ 18.857 + 19.143

200 nW 190.00 nW _________ _________ 188.95 + 191.05

2 µW 1.9000 µW _________ _________ 1.8932 + 1.9068

20 µW 19.000 µW _________ _________ 18.962 + 19.038

200 µW 190.00 µW _________ _________ 189.62 + 190.38

2 mW 1.9000 mW _________ _________ 1.8962 + 1.9038

Detector Response __________ A/W at _________ nm
The required current is obtained by multiplying the desired reading by the

detector response at the wavelength set. For example, if the Model 835 is set
for 850 nm, and the detector response at 850 nm is 0.55 A/W, the current setting
on the 2 nW range is:

1.9000 nW x 0.555 A/W = 1.0450 nA

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1. Set the Model 835 to a wavelength for which the detector response for
which the PROM is programmed is accurately known. This
information is given in the detector data sheets supplied with the
detector. If the response is known for more than one wavelength,
choose the wavelength for which the response is a maximum. Write
the detector response in the space provided on the Table 3–2.

2. Calculate and record the current source settings required for each
range as follows:

Current Source Setting I = Reading X Response

3. Disconnect any inputs to the Model 835.

4. Depress ZERO CHECK and select the 2nA (most sensitive) range by
pressing and holding RANGE until the most sensitive range is set.

5. With an open input, adjust the ZERO pot for .0000 ±1 count on the
display.

6. With the current source power off, connect a Keithley Instruments
Model 220 or equivalent precision current source to the input of the
Model 835.

7. Set the Model 835 to the least sensitive range by pressing and holding
RANGE ▲.

8. Using Table 3-2 as a guide, set the appropriate output current to the
calculated setting and check the least sensitive range.

9. Repeat for all other ranges by changing the current source current
and pressing RANGE ▼ momentarily once for each range.

10. Change the polarity of the current source, and repeat steps
7 through 9.

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26

Section 4

Theory of Operation

Introduction

4.1

Overall Function

4.2

Photodetector

4.3

Electronic Display

4.4

Functional
Description

This section contains a brief overall functional description of the Model

835. Information pertaining to the Model 835-BAT Battery Pack option is
also included. Component layout drawings (useful for changing the PROM)
are located at the end of this instruction manual.

The Model 835 Power Meter system includes a photodetector and an
electronic display. Each part is described in turn.

The photodetector is a sensor which is connected to the electronic display
through a cable with standard BNC connector. The photodetector is a
semiconductor photodiode which generates current proportional to the
total amount of light incident upon the detector. The photodetector is
operated without bias to reduce dark currents and shot noise. The current
is then measured by the electronic display, and converted into optical
power as described in section 4.4.

Photodetector response characteristics depend upon many factors which
are described in section 2.8 and in the appropriate photodetector
calibration manual.

Basically, the Model 835 is a 4-1/2 digit, ±20,000 count autoranging
picoammeter with seven DC current ranges and a photodetector. A
simplified block diagram of the Model 835 is shown in Figure 4-1. The heart
of the Model 835 is a current to voltage converter followed by an A/D
converter that translates the conditioned analog input signals into a form
useable by the microcomputer.

CURRENT TO

VOLTAGE CONVERTER

2mA RANGE

2nA - 200µA RANGES

– 2V

REFERENCE

RANGE CONTROL

MUX

MUX
CONTROL

MICROCOMPUTER

AMP

x1

x10

x1, x10

A/D OUTPUT

LCD DISPLAYS

PHOTODIODE

DETECTOR

RANGE

RESISTORS

INPUT

AMP

Figure 4-1 Simplified Functional Block Diagram.

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A/D

A/D CONTROL

DISPLAY
DRIVER

INVERTING
ANALOG
OUTPUT

RANGE/
FEATURE
SWITCHES

4.4.1 Input Amplifier

The input buffer amplifier provides the necessary isolation between the
input signal and the A/D converter. The amplifier is a non-inverting, low

noise, high impedance circuit with ×1 gain for the 20nA-2mA ranges and ×10
gain for the 2nA range. The amplifier gain is controlled by the

microprocessor. See Figure 2-3 for a functional diagram of the feedback
picoammeter input amplifier circuit.

4.4.2 Microcomputer and PROM

The microcomputer performs the necessary calculations to convert from
current to optical power using the detector response data stored in the
programmable read-only memory (PROM). In addition, the microcomputer
performs the mathematical operations neccessary to implement the
features of the Model 835 such as Null, Reference (ratio), and Log (dBm,
dB), and to drive the analog bar display.

The microcomputer centers around the 146805E2 CMOS microprocessor. It
is an 8 bit processor. Software for the MPU is stored in U113 (PROM).
Temporary storage is provided by a RAM which is used to store calibration
constants on power-up and as RAM for the microprocessors in-house
functions. A third memory, the non-volatile RAM (NVRAM) is used to store
the current calibration constants and the power-up wavelength and
attenuator status.

4.4.3 Power Supply

WARNING

Before opening or operating the Model 835, observe the safety
precautions found preceding Section 1. Failure to observe these
and other safety precautions found in this manual could result in
severe injury or death.

The LINE FUSE is internally accessible. S101 is the Power ON/OFF switch,
and S102 selects 115V or 230V operations by placing the transformer
primary windings in parallel or series.

The power transformer has two secondary windings, one for the Model 835
and the other for the IEEE option (Model 835–IEEE). A bridge rectifier
functions as a fullwave rectifier for both the plus and minus supplies.

4.4.4 Model 835-BAT Rechargeable Battery Option

Maximum battery charging rate is achieved when the instrument is
connected to line power and the ON/OFF switch is off. Fullwave rectified
voltage is applied to charge the batteries. A transistor acts as a current
sink if the charging current rises above 150mA. The batteries are of the
quick recharge type and will charge in 8 to 10 hours. With the instrument
turned on the batteries will trickle charge at approximately 40mA.

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28

Section 5

Maintenance

Introduction

5.1

Top Cover

5.2

This section contains the installation, photodetector calibration and service
information for the Model 835 and 835-BAT Battery Pack.

WARNING

The procedures described in this section are for use only by
qualified service personnel. Do not perform these procedures
unless qualified to do so. Many of the steps covered in the section
may expose the individual to potentially lethal voltages that could
result in personal injury or death if normal safety precautions are
not observed.

The top cover of the Model 835 must be removed in order to move the
calibration jumper, service the unit, change the line frequency, change the
PROM, or to install the Model 835-BAT battery pack and/or the Model 835­IEEE computer interface. Proceed as follows:

WARNING

Service by qualified personnel only. Disconnect the line cord and
all other sources and cables before removing the top cover.

1. Turn off the power, disconnect the line cord and remove all test leads
from the terminals of the Model 835.

2. Remove the 4-40 hex-head screws (4 each) from the top of the case.

Battery Pack

5.3

(Model 835-BAT)
Installation

3. Lift off the top cover, and separate from the unit.

4. To reinstall the top cover, reverse the above procedure.

Refer to Figure 6-1 and perform the following procedure to install the
battery pack:

WARNING

Service by qualified personnel only. Disconnect line cord and
remove all test leads from terminals of the Model 835.

1. Remove the top cover as explained in paragraph 5.2.

2. Remove the four screws securing the shield to the mother board.

3. Position the battery board on the metal shield and secure it to the
shield using two supplied screws. The screws are fed through the
shield into the battery board fasteners.

4. Place the battery pack in the bracket and position it on the shield as
shown. Feed the two screws through the shield into the bracket and
tighten.

CAUTION

Do not allow the battery leads to short together or damage to the
batteries may occur.

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5. Carefully place the shield (with battery pack) back into the Model 835
and replace the four screws securing it.

6. Connect the ribbon cable from the battery board to the male
connector (marked BAT) on the mother board. Take care to ensure
that the plug is centered on the pins, and that it is not shifted to one
side.

CAUTION

Make a close visual inspection to ensure that the connector is
properly mated or damage to the instrument may result.

7. Connect the red battery lead to the +RED terminal pin on the battery
board. Connect the black battery lead to the –BLK terminal pin on

the battery board.

8. Reinstall the top cover as explained in paragraph 5.2

9. Charge the battery pack per instructions in paragraph 2.2.1.

Special Handling of

5.4

Static Sensitive
Devices

Detector and

5.5

Attenuator
Recalibration or
Replacement

Some of the electronic circuits used in the Model 835 contain are CMOS
devices designed to operate at very high impedance levels for low power
consumption. As a result, any normal static discharge that builds up on
your body or clothing may be sufficient to destroy these devices if they are
not handled properly. In particular, the programmable read-only memory
(PROM) used to store the detector response characteristics should be
handled using the following precautions to avoid damaging them:

1. The PROM should be transported and handled only in containers
specially designed to prevent static build-up. Typically, PROMs will
be received in static-protective containers until ready for installation.

2. Remove PROMs from their protective containers only at a properly
grounded work station. Also ground yourself with a suitable
wriststrap.

3. Handle the PROM only by the body; do not touch the pins.

4. PC boards must be grounded to the bench while inserting PROMs.

Calibration data for individual detectors are stored in a programmable
read-only memory (PROM) on the mother board of the Model 835. The
Model 835 may be used with detectors or attenuators other than the
detector/attenuator supplied with the unit. However, the PROM which
contains the calibration data should be replaced with one calibrated for the
detector/attenuator combination being used.

When a detector/attenuator is recalibrated, a new PROM with the new
calibration data will be sent with the detector if the PROM is properly
ordered with the recalibration.

Paragraph 5.5.1 gives the procedure for removing the PROM and replacing
it with another.

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5.5.1 PROM Replacement Procedure

CAUTION

It is important to follow the handling procedures in paragraph 5.4
to avoid damaging the PROM.

WARNING

Before opening or operating the Model 835, observe the safety
precautions found preceding Section 1. Failure to observe these
and other safety precautions found in this manual could result in
severe injury or death.

To replace a PROM in the Model 835, follow the procedure below:

1. Remove the top cover as described in paragraph 5.2

2. Using a PROM puller, remove chip U113 from its socket. See figure 6-2
for the position of U113. It is located on the main circuit board on the
right hand side as viewed from the front of the instrument. It can be
identified by the label applied to the top of the top of the chip.

3. Place the removed PROM in a piece of conductive foam to avoid
damage from possible static discharges. Keep this PROM for later use
if the detector is replaced and may be used again in the future.

4. Remove the new PROM from its protective packaging, and insert into
the socket for U113, taking care to orient the small indentation in the
PROM the same way as shown in Figure 6-3.

IEEE-488

5.6

(Model 835-IEEE)
Interface Installation

Troubleshooting and

5.7

Self-Diagnostic
Program

5. Make a careful visual inspection of the PROM and check to be sure
that all pins are in the proper positions in the socket, and that none
have been bent.

6. Replace the top cover as described in paragraph 5.2

The Model 835 should now be ready for functional use with the new PROM.
Plug in the instrument, and press ▼ CAL ▲ until the serial number is
displayed as described in paragraph 2.7.3, Note 3. Verify that both the
detector and attenuator serial numbers match the serial numbers for the
detector and attenuator used. The Model 835 is now ready for general use.

Installation of the Model 835-IEEE computer interface is described in detail
in the instruction manual for the Model 835-IEEE.

A self-diagnostic program is contained in the Model 835 firmware. The self­diagnostic program can be used to learn the software revision and to aid in
the isolation of defective components of the Model 835.

To enter the self-diagnostic program, power-up the Model 835 while holding
in the AUTO button. The following will occur:

1. All LCD digits and annunciators will turn on.

2. The software revision level will be displayed (i.e. A1).

3. The Model 835 will go into troubleshooting test mode.

To exit self-diagnostic mode, turn the power off then on.

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31

Section 6

Service

Introduction

6.1

Factory Service

6.2

This section contains information about servicing the Model 835 and
accessories, and component location drawings. The Model 835 is designed
to be serviced by replacing PC boards. This method eliminates the need for
the user to return the entire unit to the factory for repair. In some
instances, however, field repair may be more appropriate. Contact
Newport Corporation or your Newport representative for assistance.

To obtain information concerning factory service, contact the factory or
your Newport representative. Please have the following information
available:

1. Instrument Model Number

2. Instrument Serial Number

3. Detector Serial Number and, if available, calibration date.

4. Attenuator Serial Number and, if available, calibration date.

5. Description of problem

When returning the instrument to Newport, please complete the service
form which follows this section and return it with the instrument or circuit
boards.

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

32

Component Location

6.3

Drawings

Figure 6-1. Exploded View of Model 835

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

33

Figure 6-2. Mother Board, Component Layout

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

34

Service Form

6.4

Newport Corporation

U.S.A. Office: 714/863-3144
FAX: [phone]

Name _____________________________________________________________________________________ RETURN AUTHORIZATION # ____________________________

Company _______________________________________________________________________________ (Please obtain prior to return of item)

Address _________________________________________________________________________________

Country _________________________________________________________________________________ Date _______________________________________________________________

P.O. Number __________________________________________________________________________ Phone Number ________________________________________________

Item(s) Being Returned:

Model # ________________________________________________________ Serial # __________________________________________________________________________________________

Description: _________________________________________________________________________________________________________________________________________________________

Reason for return of goods (please list any specific problems) ______________________________________________________________________________

____________________________________________________________________________________________________________________________________________________________________________

Please complete the below, as appropriate.

List all control settings and describe problem: ______________________________________________________________________________________________________

____________________________________________________________________________________________________________________________________________________________________________

____________________________________________________________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________ (Attach additional sheets as necessary).

Show a block diagram of your measurement system including all instruments connected (whether power is turned
on or not). Describe signal source. If source is a laser, describe ouput mode, peak power, pulse width, repetition
rate and energy density.

Where is the measurement being performed?

(factory, controlled laboratory, out-of-doors, etc.) ________________________________________________________________________________________________
What power line voltage is used? ____________________________________________ Variation? __________________________________________________________
Frequency? ___________________________________________________ Ambient Temperature? ________________________________________________________________
Variation? ______________________________________ °F. Rel. Humidity? ________________________________ Other? _________________________________________

Any additional information. (If special modifications have been made by the user, please describe below).

____________________________________________________________________________________________________________________________________________________________________________

____________________________________________________________________________________________________________________________________________________________________________

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

35

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

36

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

37

R

E

G

I

S

T

Certificate No.: FM 27207

M

R

I

F

D

E

E

R

Newport Corporation, Irvine,
California, has been certified
compliant with ISO 9002 by the
British Standards Institution.

Corporate Headquarters

Newport Corporation
P.O. Box 19607
1791 Deere Avenue
Irvine, CA 92713- 9607
Telephone: [phone]
Facsimile: 714-253 -1680

Belgium

Telephone: [phone]
Facsimile: 016-402227

Canada

Telephone: [phone]
Facsimile: 905-567-0392

France

Telephone: [phone]
Facsimile: 1-60 91 68 69

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com

Germany

Telephone: [phone]
Facsimile: 06151-15450

Italy

Telephone: [phone]
Facsimile: 02-923-2448

Japan

Telephone: [phone]
Facsimile: 03-5379-0155

38

Klinger Systems Center

Telephone: [phone]
Facsimile: 516-745-6812

Netherlands

Telephone: [phone]
Facsimile: 03402-50577

Printed in the USA on recycled paper

Switzerland

Telephone: [phone]
Facsimile: 01-740-2503

United Kingdom

Telephone: [phone]
Facsimile: 0635-521348

Artisan Technology Group is your source for quality

new and certied-used/pre-owned equipment

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DELIVERY

• TENS OF THOUSANDS OF
IN-STOCK ITEMS

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RENTALS

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SERVICE CENTER REPAIRS

Experienced engineers and technicians on staff
at our full-service, in-house repair center

Instra

Remotely inspect equipment before purchasing with
our interactive website at www.instraview.com

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SM

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View

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We also offer credit for buy-backs and trade-ins

www.artisantg.com/WeBuyEquipment

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