Newport 1830-C Instruction Manual
1830-C
Optical Power Meter
I
NSTRUCTION
M
ANUAL
1830-C Optical Power Meter
Warranty
Warranty
Newport Corporation warrants this product to be free from defects in material and workmanship for a period of 1 year from the 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 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.
Statement of Calibration
This instrument has been inspected and tested in accordance with specifications published by Newport Corporation.
The accuracy and calibration of this instrument and photodetector (where
applicable) is traceable to the National Institute for Standards and Technology through equipment which is calibrated at planned intervals by comparison to the certified standards maintained at Newport Corporation.
© 1994 Newport Corporation
P/N 20372-01, Rev. H
IN-07941 (07-00)
ii
ii
EC DECLARATION OF CONFORMITY
Model 1830-C
We declare that the accompanying product, identified with the
" " mark, meets the intent of the Electromagnetic Compatibility
Directive, 89/336/EEC and Low Voltage Directive 73/23/EEC.
Compliance was demonstrated to the following specifications:
EN50081-1 EMISSIONS:
Radiated and conducted emissions per EN55011, Group 1,
Class A
EN50082-1 IMMUNITY:
Electrostatic Discharge per IEC 1000-4-2, severity level 3
Radiated Emission Immunity per IEC 1000-4-3, severity level 2
Fast Burst Transients per IEC 1000-4-4, severity level 3
Surge Immunity per IEC 1000 4-5, severity level 3
IEC SAFETY:
Safety requirements for electrical equipment specified in
IEC 1010-1.
Alain Danielo Jeff Cannon
VP European Operations General Manager-Precision Systems
Zone Industrielle 1791 Deere Avenue
45340 Beaune-la-Rolande, France Irvine, CA USA
iii
Table of Contents
Warranty ................................................................................................................ ii
EC Declaration of Conformity .............................................................................iii
List of Figures ...................................................................................................... vii
List of Tables ....................................................................................................... vii
Safety Symbols and Terms ................................................................................ viii
Definitions ............................................................................................................. ix
Specifications......................................................................................................... x
Section 1 — General Information
1.1 System Overview ...................................................................................... 1
1.2 Scope of this Manual ................................................................................ 2
1.3 Unpacking and Inspection ....................................................................... 2
1.4 Preparation for Use .................................................................................. 2
Section 2 — Initial Setup
2.1 Introduction .............................................................................................. 3
2.2 Setting the Line Voltage Selector Switch ............................................... 3
2.3 Detector Connection and Setup ............................................................. 4
2.4 Configuring the Computer Interface ...................................................... 4
2.5 Power Up / Auto-Calibration ................................................................... 5
Section 3 — System Operation
3.1 Introduction .............................................................................................. 6
3.2 Digital Display ........................................................................................... 6
3.3 Front Panel Key Functions ...................................................................... 8
3.3.1 LOCAL (R/S) Local Mode & Run / Stop ......................................... 9
3.3.2 ZERO Offset Subtraction .................................................... 9
3.3.3 UNITS Display Units ............................................................. 9
3.3.4 STOREF Store Reference Value ........................................... 10
3.3.5 AVG Numerical Averaging ............................................. 10
3.3.6 λ䉱 Wavelength Increment .......................................... 10
3.3.7 λ䉲 Wavelength Decrement ......................................... 11
3.3.8 Power ....................................................................... 11
3.3.9 ATTN Optical Attenuator ................................................. 11
3.3.10 BKLT Backlight .................................................................. 11
3.3.11 BEEP Audible Beeper ....................................................... 11
3.3.12 AUTO Automatic Gain Ranging ........................................ 11
3.3.13 RANGE䉱 Manual Range Up ................................................... 12
3.3.14 RANGE䉲 Manual Range Down .............................................. 12
3.4 Default Meter Configuration.................................................................. 12
iv
Section 4 — Performing Measurements
4.1 Introduction ............................................................................................ 13
4.2 Photodetector Considerations ............................................................. 13
4.2.1 Detector Calibration and Accuracy............................................ 13
4.2.2 Quantum Detector Temperature Effects ................................... 14
4.2.3 Ambient and Stray Light .............................................................. 14
4.3 Setting the Wavelength .......................................................................... 15
4.4 Setting the Attenuator Mode ................................................................. 15
4.5 Performing Basic Measurements.......................................................... 16
4.5.1 Power Measurements .................................................................. 16
4.5.2 Logarithmic Measurements (dB and dBm) ............................... 16
4.5.2.1 Logarithmic Measurements Using Reference Powers (dB) . 17
4.5.2.2 Logarithmic Measurements Using 1 mW Reference (dBm) . 17
4.5.3 Relative Measurements ............................................................... 18
4.6 Common Measurement Errors ............................................................. 19
Section 5 — Computer Interfacing
5.1 Introduction ............................................................................................ 20
5.2 Computer Interface Terminology ......................................................... 20
5.3 Entering Remote Computer Interface Mode ....................................... 21
5.4 RS-232C Communication........................................................................ 22
5.4.1 Setting the Baud Rate .................................................................. 23
5.4.2 RS-232C Command Termination ................................................. 23
5.4.3 General Guidelines for Using the RS-232C Port ........................ 24
5.5 GPIB Communication ............................................................................. 24
5.5.1 Setting the GPIB Address ............................................................ 24
5.5.2 GPIB Command Termination ...................................................... 25
5.5.3 General Guidelines for Using the GPIB Port ............................. 26
5.5.4 Procedure for Reading Only New Measurements .................... 26
v
Section 6 — Remote Command Set
6.1 Summary of Command/Query Set ........................................................ 27
6.2 Detailed Description of Commands and Queries ............................... 29
An Attenuator on/off ................................................................ 29
A? Attenuator query................................................................. 29
Bn Beeper on/off ........................................................................ 30
B? Beeper query ....................................................................... 30
C Clear Status Byte Register .................................................. 30
D? Data query............................................................................ 31
En Echo mode on/off—( RS-232C interface only) .................. 31
E? Echo mode query ................................................................ 31
Fn Filter ( same as averaging ) Slow, Medium, Fast .............. 32
F? Filter (same as averaging) status query .......................... 32
Gn Go on/off (Run/Stop signal acquistition) .......................... 33
G? Go query ............................................................................... 33
Kn Keypad / Display Backlight on/off ..................................... 34
K? Keypad / Display Backlight intensity level query ............ 34
Ln Local-lockout on/off ............................................................. 35
L? Local-lockout query ............................................................ 35
Mn Service Request Enable Register (mask) .......................... 36
M? Service Request Enable Register query ............................ 37
O Auto-Calibration ................................................................... 37
Q? Status Byte Register query ................................................. 38
Rn Range setting ........................................................................ 39
R? Range query .......................................................................... 40
S Store reference ..................................................................... 40
Un Units....................................................................................... 41
U? Units query ........................................................................... 41
Wnnnn Set wavelength to nnnn ....................................................... 42
W? Wavelength query ................................................................ 42
Zn Zero on/off ............................................................................ 43
Z? Zero function query ............................................................. 43
Section 7 — Troubleshooting and Maintenance
7.1 Troubleshooting Guide .......................................................................... 44
7.2 Cleaning Procedure ................................................................................ 45
7.3 Re-Calibration Schedule ........................................................................ 45
Section 8 — Factory Service
8.1 Introduction ............................................................................................ 46
8.2 Obtaining Service ................................................................................... 46
Appendices
A Status Reporting System ....................................................................... 49
B Sample Programs .................................................................................... 52
B.1 Example Program for RS-232C Communication ....................... 52
B.2 Example Program for IEEE 488 Communication ...................... 55
C Simplified 1830-C Functional Block Diagram....................................... 58
vi
List of Figures
1. 1830-C Power Meter and Compatible Detectors................................... 1
2. Line Voltage Selector Switch................................................................... 3
3. Connecting a Detector with its Calibration Module............................. 4
4. Calibration Module Connector Port ....................................................... 4
5. The 1830-C Liquid Crystal Display ......................................................... 6
6. Front Panel Key Pad ................................................................................. 8
7. RS-232C Cable Connections................................................................... 22
8. RS-232C Baud Rate Selector Switches.................................................. 23
9. GPIB Address Selector Switches .......................................................... 25
10. The 1830-C’s Status Reporting System for the GPIB Bus ................... 49
11. Simplified Functional Block Diagram ................................................... 58
List of Tables
1. Measurement Modes ................................................................................ x
2. 1830-C Display Annunciators/Messages ................................................ 7
3. 1830-C Key Functions and Associated Remote Commands ................ 8
4. 1830-C Default Power-up Conditions.................................................... 12
5. Common Measurement Errors ............................................................. 19
6. Symptom/Fault Troubleshooting Guide .............................................. 45
vii
Safety Symbols and Terms
The following safety terms are used 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.
In addition, a NOTES heading gives information to the user that may be
beneficial in the use of this instrument.
GENERAL WARNINGS AND CAUTIONS
The following general warnings and cautions are applicable to this instrument:
This instrument is intended for use by qualified personnel who recog-
nize shock hazards or laser hazards and are familiar with safety
precautions required to avoid possible injury. Read the instruction
manual thoroughly before using, to become familiar with the
instrument’s operations and capabilities.
WARNING
WARNING
The American National Safety Institute (ANSI) states that a shock
hazard exists when probes or sensors are exposed to voltage levels
greater than 42VDC or 42V peak AC. Do not exceed 42V between any
portion of the Model 1830-C (or any attached detector or probe) and
earth ground or a shock hazard will result.
CAUTION
There are no user serviceable parts inside the Model 1830-C. Work
performed by persons not authorized by Newport may void the
warranty. For instructions on obtaining warranty repair or service
please refer to Section 8 of this manual.
viii
Definitions
A amps
ADC analog-to-digital converter
BNC standard coaxial connector type
degree C degrees Centigrade
Hz Hertz (cycles per second)
k kilo (103)
kHz kilohertz
kΩ kilo-ohms
µ micro (10
m milli (10-3)
mA milliamps
mV millivolts
n nano (10-9)
nA nanoamps
nm nanometers
RH relative humidity
S/N serial number
µA microamps
µs microseconds
V volts
W watts
--6
)
ix
Specifications
Dimensions: 3.7 x 7.5 x 9.0 in. (94 x 191 x 229 mm )
Weight: 5 lb ( 2.3 kg )
Enclosure: Metal case, painted
Connectors: Calibration Module: 8-Pin Sub Mini DIN
Analog Output: BNC
RS-232: 9 pin D-Sub
GPIB: 24 Conductor D
Power : 100-120, 220-240 VAC ±10%, 50/60 Hz
Absolute Maximum Line
Current Rating: 200 mA
Signal Ranges: Up to 8 decades (dependent on detector type)
Display: 4.5 digit, annunciated, backlit, wide angle view LCD
Display Update Rate: 75 ms
Auto-Ranging Time: 200 ms (typical)
GPIB Bus Transfer Time: 10 ms (typical)
Operating Environment: 0 to +40 degree C; < 70% RH noncondensing
Storage Environment: −20 to +60 degree C; < 90% RH noncondensing
Compatible Detectors: Low-Power (Semiconductor) Family
Signal Range
Full-Scale Current
1, 2
12345678
3
2 nA 20 nA 200 nA 2 µA 20 µA 200 µA 2 mA 5 mA
Gain 1000 M 100 M 10 M 1 M 100 k 10 k 1 k 100
Resolution 0.1 pA 1 pA 10 pA 100 pA 1 nA 10 nA 100 nA 1 µA
Analog Bandwidth 35 Hz 35 Hz 1.5 kHz 1.5 kHz 5 kHz 15 kHz 10 kHz 20 kHz
Full-Scale Accuracy
4
0.2 % 0.2 % 0.2 % 0.2 % 0.2 % 0.2 % 0.2 % 0.2 %
(Typical)
Full-Scale Accuracy
4
0.4 % 0.4 % 0.4 % 0.4 % 0.4 % 0.4 % 0.4 % 0.4 %
(Worst Case)
1
Listed signal ranges specify meter capability. Available signal ranges are detector dependent.
2
Maximum measurable signal is detector dependent. See description of detector saturation message “SA” in Table 2.
3
Full scale current may vary due to the Auto-Calibration compensation of amplifier DC offsets.
4
After 60 minute warm-up, followed by execution of an Auto-Calibration. See Section 2.5 and Section 6.2 (“O” Command).
Analog Output
Full-Scale Voltage: 2V into 1MΩ
Full-Scale Accuracy: ±1%
Maximum AC Noise: Range 1: <4 mV
(open input) Ranges 2-8: <1 mV
p-p
p-p
x
Display Display
Calculation Unit Comment
I/R W ZERO Disabled
(I-Iz)/R W ZERO Enabled
101log
/IR
mW
dBm ZERO Disabled
(
101log
10 log
I
STOREF
10 log
II
STOREF Z
I
I
STOREF
II
−
Z
II
−
STOREF Z
−
Z
mW
I
−
II
/II R
)
Z
−
dBm ZERO Enabled
dB ZERO Disabled
dB ZERO Enabled
REL ZERO Disabled
REL ZERO Enabled
Where I = detector current
Iz= detector background current defined when the
ZERO key was pressed
R = responsivity of the detector (A/W)
I
STOREF
= referenced detector current defined when the
STOREF key was pressed
Table 1. Measurement Modes
xi
xii
Section 1
General Information
1.1 System Overview
The 1830-C Optical Power Meter is a ±20,000 count A/D resolution, autoranging picoammeter. Measurements are displayed on a large 4 1/2 digit
liquid crystal display (LCD) and can also be taken remotely via the RS-232C
port or the IEEE 488 GPIB bus. The 1830-C is designed to take continuous
wave optical power measurements and is compatible with all of Newport’s
Low-Power Semiconductor photodetectors. A family tree of the 1830-C
compatible detectors and accessories is shown in Figure 1 below.
FP3-FH1
818-FA2
818-UV/CM
818-SL/CM
818-IR/CM
818-FA3-SMA
818-FA3-ST
818-FA3-FC
818-F-SL
818-F-IR
■
Optical Power Meter ■
Model 1830-C
(LOCAL)
R/S
AVG
STOREF
UNITSZERO
BEEPBKLT
ATTN
AUTO
INPUT
RANGEλλRANGE
818-ST/CM
Figure 1. 1830-C Power Meter and Compatible Detectors
Detectors connect to the 1830-C through a calibration module, in which the
responsivities and other information unique to the detectors is stored.
Calibration modules are ordered with the detectors at the time of purchase
and are labeled with the detectors’ model number and serial number.
Detectors with calibration modules have a “/CM” appended to their model
number.
EXAMPLE: 818-SL (no calibration module)
818-SL/CM (with calibration module)
1
1.2 Scope of this Manual
1.3 Unpacking and Inspection
Please carefully read this instruction manual before using the 1830-C. Be
especially careful to observe the warnings and cautions throughout this
manual (see Safety Symbols and Terms). If any operating instructions are
not clear, contact Newport Corporation.
This instruction manual contains the necessary information for operation
and maintenance of the 1830-C, as well as information for troubleshooting
and obtaining service if necessary. This information is divided into the
following sections:
Section 1 General Information
Section 2 Initial Setup
Section 3 System Operation
Section 4 Performing Measurements
Section 5 Computer Interfacing
Section 6 Remote Command Set
Section 7 Troubleshooting and Maintenance
Section 8 Factory Service
1.4 Preparation for Use
All 1830-C meters are carefully assembled, tested and inspected before
shipment. Upon receiving this instrument, check for any obvious signs of
physical damage that might have occurred during shipment. Report any
such damage to the shipping agent immediately.
NOTE
Retain the original packing materials in case reshipment becomes necessary.
The 1830-C should have some basic operations performed before measurements are made. These include:
Setting the Line Voltage Selector Switch ( Section 2.2)
Detector Connection and Setup ( Section 2.3)
2
Section 2
LINE SELECT
230V
115 V
100–120V 50–60 Hz, 0.25A, SLO- BLO, 250V
220–240V 50–60 Hz, 0.25A, SLO- BLO, 250V
FUSE
Initial Setup
2.1 Introduction
This section contains information on how to configure the 1830-C to your
local line voltage and how to connect the detector and calibration module
to the meter. It also includes a short discussion about the remote interface
and the 1830-C’s power-up and auto-calibration.
2.2 Setting the Line Voltage Selector Switch
The 1830-C can be configured to operate with line voltages of 100-120 VAC
and 220-240 VAC, and line frequencies between 50-60 Hz. Before turning the
meter on, configure it to the local voltage by setting the voltage selection
switches on the 1830-C back panel to match the nominal local voltage. See
Figure 2. Plug the AC line power cord to the rear of the 1830-C and then
connect the cord to AC power.
Figure 2. Line Voltage Selection Switch
WARNING
This product is equipped with a 3 wire grounding type plug. Any
interruption of the grounding connection can create an electric shock
hazard. If you are unable to insert the plug into your wall plug receptacle, contact your electrician to perform the necessary alterations to
assure that the green (green-yellow) wire is attached to earth ground.
3
2.3 Detector Connection and Setup
Connect the detector to its calibration module as shown in Figure 3. The
detector’s model and serial numbers must match the model and serial
numbers found on the calibration module. Insert the calibration module,
with its groove facing left, into the connector port on the front panel of the
1830-C, as shown in Figure 4. An alignment pin assures the proper orientation of the calibration module.
Detector Cable BNC Calibration Module
Figure 3. Connecting a Detector with its Calibration Module
Plug calibration
module into this port.
INPUT
Always power off the meter before removing or inserting the calibration
module.
2.4 Configuring the Computer Interface
The RS-232C baud rate and the IEEE 488 GPIB address must be properly set
via the back panel system switches if either interface is to be used. Please
refer to Section 6 for detailed instructions.
Figure 4. Calibration Module Connector Port
NOTE
4
2.5 Power Up / Auto Calibration
Turn on the 1830-C by depressing the red power switch, located in the lower
left-hand corner of the front panel, until it clicks and remains in its depressed
position. At power-up, the 1830-C will perform the following sequence:
1) Momentarily display all the segments on the display
2) Display the software version number
3) Perform an Auto-Calibration, designated by displaying CAL on the
4) Display the serial number of the detector/calibration module
5) Display the wavelength to which the meter is set (If no calibration
The auto-calibration process involves measuring amplifier offset voltages
which arise from aging and temperature effects. These offsets are then
appropriately corrected for during normal operation. The 1830-C will
automatically disconnect the input signal from the amplifier during the
auto-calibration mode. To achieve stable readings at the specified accuracy, auto-calibration should be executed after a minimum 60 minute warmup period. This can be done either by resetting the 1830-C with the RESET
button on the back of the meter, or by sending the auto-calibration remote
command, O.
display
(If no calibration module is installed, the meter will display 000 as the
serial number.)
module is installed, the meter will display 0257nm as the wavelength.)
NOTE
The 1830-C must be powered-up with the calibration module connected to
the meter in order for the calibration data to be downloaded into the 1830-C.
Always power off the meter before removing or inserting the calibration
module.
5
Section 3
System Operation
3.1 Introduction
3.2 Digital Display
This section contains the information needed to operate the 1830-C power
meter, via the front panel key pad. The meanings of the display annunciators and the operation of all keys are discussed later in this section.
The 1830-C has a large 4-1/2 digit, back-lit liquid crystal display (LCD)
which can be seen at large angles of view. Figure 5 illustrates the layout of
the 1830-C’s display. Table 2, on the following page, explains the meaning of
the various annunciators and messages on the display.
Figure 5. The 1830-C Liquid Crystal Display
6
Annunciator/Message Comment
SN This annunciator denotes serial number and is displayed at turn-on when
the detector’s serial number is displayed.
dBm This annunciator specifies that either dB or dBm measurements are being
displayed.
REL This annunciator specifies that relative measurements are being displayed.
k µ m Only one of the characters of this annunciator will light at any time to specify
engineering prefixes of kilo, micro, nano, or milli. The “m” in this annunciator
serves as both “m” and “n”.
W This annunciator specifies that measurements in units of watts are being
displayed.
nm This annunciator indicates nanometer whenever the wavelength is displayed.
ATTN The responsivity in use includes the effect of the detector’s OD3 attenuator.
AUTO Automatic signal ranging is activated.
ZERO Background signal subtraction (zeroing) is activated.
HOLD No new readings will be displayed, nor be available on the remote interface bus.
REM The meter has received a command/query either through the IEEE 488 or
the RS-232C bus.
LLO The meter has been set to local-lockout from the remote interface bus and
will not respond to any front panel keys.
AVG: S M F Either Slow, Medium, or Fast numerical averaging for the displayed
measurement is activated.
OL This message indicates that the input signal level exceeds the capability of
the present signal range. Either use auto-ranging or increment the signal
range until the OL message goes away.
SA This message indicates that the input signal level exceeds the specified
saturation current of the detector being used with the meter. This level is
detector dependent.
CAL This message indicates that the meter is currently performing an auto-
calibration. The auto-calibration process involves measuring amplifier offset
voltages. See Section 2.5 for more details.
Table 2. 1830-C Display Annunciators/Messages
7
3.3 Front Panel Key Functions
The front panel key pad of the 1830-C, Figure 6, provides access to all the
basic measurement functions. Table 3 and Sections 3.3.1 through 3.3.14 list
and describe in detail each key function. For power-up default conditions,
please see Table 4 at the end of this section.
(LOCAL)
R/S
ZERO
ATTN
UNITS
BKLT
STOREF
BEEP
AVG
AUTO
RANGE RANGE
λλ
Figure 6. Front Panel Key Pad
Keypad Remote Command Description
(LOCAL) L0 Enables local mode.
R/S G0, G1 Run/Stop signal acquisition.
ZERO Z0, Z1 Zero the display by subtracting the present reading from all
subsequent readings.
UNITS U1-U4 Cycles between the four available measurement units (Watt, dB,
dBm, Relative).
STOREF S Stores last measurement for future dB or relative measure-
ments.
AVG F1-F3 Cycles between Slow, Medium, or Fast numerical averaging of
readings that are within a certain percentage of each other.
λ 䉱 Wnnnn Increments the calibration wavelength in use.
λ 䉲 Wnnnn Decrements the calibration wavelength in use.
None Turns the meter on/off.
ATTN A0, A1 Sets the responsivity value for either:
BKLT K0, K1, K2 Cycles the display backlight brightness between Off, Medium,
BEEP B0, B1 Turns the variable frequency beeper on/off.
AUTO R0, R1-R8 Turns the automatic signal ranging on/off.
RANGE 䉱 Rx Increments the signal range and disables the automatic signal
RANGE 䉲 Rx Decrements the signal range and disables the automatic signal
Table 3. 1830-C Key Functions and Associated Remote Commands
1) detector alone, or
2) detector and OD3 optical attenuator.
or High.
ranging.
ranging.
8
3.3.1
(LOCAL)
R/S
Local Mode
Run / Stop
This key serves two purposes:
1) When the meter receives a command through either the RS-232C or the
IEEE 488 GPIB interface, the meter is automatically put into remote
mode and the REM annunciator is displayed. Now all front panel keys
are disabled except this (LOCAL) key which, when pressed, puts the
meter back into the local mode. The meter can also be put in the local
mode by sending the remote command, L0.
2) When the meter is in the local mode, pressing this key will toggle
between run/stop acquisition modes. The HOLD annunciator is displayed when the meter is in the stop acquisition mode.
3.3.2
ZERO
Offset Subtraction
This key turns the offset subtraction on and off. When turned on, the ZERO
annunciator is displayed and the last measurement is saved as Pz and
subtracted from all subsequent measurements P. This causes subsequent
measurement calculations shown on the display and available on the
remote interface to use the value ( P− Pz) instead of P.
Offset subtraction allows one to remove the effects of ambient DC signals,
by zeroing the display before making a measurement. A second ZERO key
press turns off the ZERO annunciator and stops offset subtraction.
3.3.3
UNITS
Display Units
Measurements can be displayed in units of watts W, decibels dB or dBm,
and relative REL. Pressing the UNITS key repeatedly cycles the display
through these four units.
The W mode is a straightforward measurement which converts the current
from the detector into a power reading via the responsivity of the detector
at the set wavelength.
The dB mode uses the relationship dB = 10 * log( P / P
most recent measurement and P
is the reference measurement. At power-
ref
), where P is the
ref
up the reference for the dB mode is a level equivalent to 1mW. This can be
changed by pressing STOREF, which makes the most recent measurement
the new P
.
ref
The dBm mode uses the relationship dBm = 10 * log( P / 1mW ), where P is
the most recent measurement.
The REL mode uses the relationship ( P / P
measurement and P
is the reference measurement. At power-up the
ref
), where P is the most recent
ref
reference for the REL mode is a level equivalent to 1mW. This can be
changed by pressing STOREF, which makes the most recent measurement
the new P
.
ref
When the engineering prefixes n, µ, m and k are displayed in the REL
mode, they multiply the reading on the display by their appropriate
weights. For example, a display of 1.8300µ
REL
means ( P/ P
) * 10−6.
ref
9
3.3.4
STOREF
Store Reference Value
Pressing STOREF causes the most recent measurement P to be stored as P
ref
for subsequent use in relative measurement calculations. When the units
are dB and STOREF has been pressed, the displayed value is the function
10 * log( P/P
displayed value is the ratio P/P
P
is always a power reading stored in the units of Watts. Pressing STOREF
ref
causes a new P
3.3.5
). When the units are REL and STOREF has been pressed, the
ref
to overwrite the existing P
ref
AVG
Numerical Averaging
.
ref
value.
ref
Pressing AVG causes the numerical averaging feature to cycle through
slow S, medium M, and fast F modes. The slow mode takes the last 16
measurements that are within ±9 counts of the oldest measurement and
averages them for the displayed reading. The medium mode averages the
last 4 measurements, and the fast mode does no averaging.
The averaging buffer is a sliding buffer that always maintains 16 or 4
measurements, depending on the mode. Initially the buffer is completely
filled with the same measurement, and thereafter subsequent measurements replace the older measurements in the buffer. If, at any time, a single
measurement is acquired that is not within ±9 counts of the oldest measurement, the averaging algorithm starts over, not retaining any of the
previous measurements.
3.3.6
λ
Wavelength Increment
Pressing this key once causes the wavelength to be displayed. If the key is
pressed again or held down, the wavelength will increment or scroll,
respectively.
The detector calibration module contains responsivity data at discrete
wavelengths for its associated detector. By entering the wavelength which
is being measured, the correct responsivity value is used by the 1830-C in
calculating the measured power. When a wavelength falls between two
calibration points, linear interpolation is used to approximate the true
responsivity value.
Upon the initial power-up on a new calibration module, the meter defaults
to the shortest wavelength available for that specific detector. Whenever
the calibration wavelength is changed, this new wavelength is written to the
PROM in the calibration module and is used as the default wavelength at
subsequent power-ups.
NOTE:
If the detector and calibration module are changed to a different set, the
power meter must be powered-up again to allow for the downloading of
the new calibration data into the power meter. Always remember to
power off the meter before removing or inserting the calibration module.
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