Molectron EPM2000 User manual

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EPM2000/EPM2000e
Dual-Channel
Joulemeter/Power Meter

EPM2000/EPM2000e
Dual-Channel
Joulemeter/Power Meter
Reference Guide

EPM2000/2000e Reference Guide
September 2001
Published by
Molectron Detector, Incorporated
7470 SW Bridgeport Road
Portland, OR 97224
Phone: [phone] or 503.620.9069
Fax: [phone]
www.molectron.com
© 2001 by Molectron Detector, Inc. All rights reserved.
No portion of this publication may be reproduced or transmitted in whole or in part in any form or by any means without
permission of the publisher.
Document Number: QD-19.17

Features & Description ........................................................................................... 1
Welcome ..................................................................................................................................... 1
Overview ............................................................................................................................... 1
Safety Information .................................................................................................................. 2
ManualInformation ................................................................................................................. 3
Features ..................................................................................................................................... 3
Interface ................................................................................................................................. 3
Units and Ranges .................................................................................................................... 3
Compatible Probes ................................................................................................................. 4
Understanding the EPM2000 Internal Trigger .......................................................................... 4
Understanding the EPM2000 External Trigger Circuit .............................................................. 6
Understanding the EPM2000 Speedup Feature ....................................................................... 7
Description ................................................................................................................................. 8
Rear Panel .............................................................................................................................. 8
Front Panel ............................................................................................................................. 10
Operation .................................................................................................................. 15
Tutorial ....................................................................................................................................... 15
Thermopile ............................................................................................................................. 15
Pyroelectric ............................................................................................................................ 17
Modes ........................................................................................................................................ 18
Normal Mode ........................................................................................................................ 18
Auto Mode ............................................................................................................................ 18
Average Mode ....................................................................................................................... 19
Statistics Mode ....................................................................................................................... 19
Ratio Mode ............................................................................................................................ 20
Instrument Settings ................................................................................................................... 20
Audible Beeper ...................................................................................................................... 20
Average Batch Size ................................................................................................................. 21
Display Backlight .................................................................................................................... 21
Display Speedup .................................................................................................................... 21
Factory Defaults ..................................................................................................................... 21
IEEE-488 Address ................................................................................................................. 22
IEEE-488 Enable/Disable ....................................................................................................... 22
Line Frequency ....................................................................................................................... 22
Long Risetime Mode .............................................................................................................. 23
PowerMax Enable/Disable ...................................................................................................... 23
Responsivity (Pyroelectric) ...................................................................................................... 24
Responsivity (Thermopile) ....................................................................................................... 24
TABLE OF CONTENTS

RS-232 Baud Rate ................................................................................................................. 25
RS-232 Enable/Disable .......................................................................................................... 25
RS-232 Parity ........................................................................................................................ 25
RS-232 Stop Bits ................................................................................................................... 26
Setup Store & Recall .............................................................................................................. 26
Statistics Batch Restart Mode ................................................................................................. 26
Statistics Batch Size ................................................................................................................ 27
Trigger Holdoff ....................................................................................................................... 27
Trigger Level .......................................................................................................................... 28
Trigger Source ........................................................................................................................ 28
Wavelength Compensation ...................................................................................................... 29
Programming ............................................................................................................ 31
Connection Methods ................................................................................................................. 31
Commands .................................................................................................................................. 31
Audible Beeper ...................................................................................................................... 32
Average Batch Size ................................................................................................................. 32
Backlight ................................................................................................................................32
Buffer Contents ...................................................................................................................... 33
Communications Error ............................................................................................................ 33
Display Current Reading ......................................................................................................... 33
Identification ........................................................................................................................... 34
IEEE-488 Address ................................................................................................................. 34
Instrument Setup Store/Recall ................................................................................................. 34
Line Frequency ....................................................................................................................... 35
Long Risetime Mode .............................................................................................................. 35
Operating Mode ..................................................................................................................... 35
Output Buffer ......................................................................................................................... 36
Output Continuous .................................................................................................................. 36
Output Depth ......................................................................................................................... 36
Output Dump ......................................................................................................................... 37
Output Format ........................................................................................................................ 37
Probe Type ............................................................................................................................ 40
Range, Current ....................................................................................................................... 40
Range, Maximum/Minimum ..................................................................................................... 41
Reset ...................................................................................................................................... 41
Responsivity ........................................................................................................................... 41
RS-232 Baud Rate ................................................................................................................. 42
RS-232 Parity ........................................................................................................................ 42
RS-232 Stop Bits ................................................................................................................... 42
Self-Test ................................................................................................................................. 43
Speedup ................................................................................................................................. 43
Statistics Batch Size ................................................................................................................ 43
Statistics Restart Mode ........................................................................................................... 44

Statistics Send ........................................................................................................................ 44
Statistics Start ......................................................................................................................... 44
Timestamp .............................................................................................................................. 45
Trigger Holdoff ....................................................................................................................... 45
Trigger Level .......................................................................................................................... 46
Trigger Source ........................................................................................................................ 46
Units ...................................................................................................................................... 46
Wavelength Compensation ...................................................................................................... 47
Zero ....................................................................................................................................... 47
Missing Data ............................................................................................................................. 48
FIFO Full Condition ............................................................................................................... 48
Communications Buffer Overrun ............................................................................................. 48
Programming Example .............................................................................................................. 49
EPM2000e-specific Features and Functions ............................................................................ 50
Taking Exposure Measurements .............................................................................................. 50
Exposure Mode ...................................................................................................................... 50
Exposure Mode-specific Computer Interface Commands ........................................................ 51
Maintenance, Service, & Calibration .................................................................... 53
Troubleshooting ......................................................................................................................... 53
Fuse Replacement ..................................................................................................................... 56
Instrument Calibration and Service .......................................................................................... 57
Specifications ............................................................................................................ 59
Electrical/Mechanical ................................................................................................................ 59
Display ................................................................................................................................... 59
Ranges ................................................................................................................................... 59
Resolution .............................................................................................................................. 59
Maximum Rep Rate ................................................................................................................ 59
Linearity ................................................................................................................................. 59
A/D Digital Resolution ............................................................................................................ 60
Input Impedance ..................................................................................................................... 60
Noise Equivalent Voltage (NEV) ............................................................................................. 60
Analog Output ........................................................................................................................ 60
External Trigger Input .............................................................................................................. 60
ElectronicAccuracy ................................................................................................................ 60
System Accuracy .................................................................................................................... 60
Maximum Pyroelectric Pulse Width ......................................................................................... 60
Internal Trigger ....................................................................................................................... 61
RS-232 Baud Rates ...............................................................................................................61
Power Requirements ............................................................................................................... 61
Dimensions ............................................................................................................................. 61
Weight .................................................................................................................................... 61
Firmware Revisions ................................................................................................................... 61

Factory Defaults ........................................................................................................................ 62
Warranted Characteristics ........................................................................................................ 62
Power .................................................................................................................................... 62
Atmospherics (Temperature) ................................................................................................... 62
Atmospherics (Relative Humidity) ........................................................................................... 62
Atmospherics (Altitude) .......................................................................................................... 63
Dynamics (Random Vibration) ................................................................................................ 63
Emissions ............................................................................................................................... 63
Susceptibility .......................................................................................................................... 63
Appendix - Declaration of Conformity ................................................................... 65
Index...........................................................................................................................67

Features & Description
EPM2000/EPM2000e Reference Guide 1
FEATURES & DESCRIPTION
WELCOME
OVERVIEW
Thank you for purchasing an EPM2000/EPM2000e (referred to as “EPM2000” in this reference
guide). The EPM2000 is a dual-channel AC powered, laboratory meter that can measure both pulsed
and CW lasers: energy, power, voltage, and (pulsed only) frequency. The EPM2000 is compatible
with all of Molectron Detector, Inc.’s pyroelectric, silicon, and PowerMax®thermopile probes.
The EPM2000 is fast, accurate, and easy to use. It features:
• two large, custom four-digit LCD’s
• selectable operating modes
• multifunction
• peak reading with automatic baseline drift compensation
• results displayed in selected units
• analog outputs
• adjustable internal triggers
• external trigger inputs
• an RS-232 communication port
• an IEEE-488 communication port

Features & Description
EPM2000/EPM2000e Reference Guide
2
SAFETY INFORMATION
Review this safety information carefully to avoid injury and prevent damage to this instrument or any
instrument connected to it. There are no user serviceable parts in the EPM2000. For Service, please
see Maintenance, Service, & Calibration.
This reference guide uses two terms to describe hazardous conditions: Caution and Warning.
Warning indicates serious injury or death may occur.
Caution indicates possible damage to equipment.
Use only the power cord specified for the instrument. The grounding conductor
of the cord must be connected to earth ground.
Do not operate the instrument if its panels are removed or any of the interior
circuitry is exposed.
Do not operate the instrument in wet or damp conditions or in an explosive
atmosphere.
Do not operate the instrument from a power source which applies more than the
voltage specified.
Do not apply a voltage outside the specified range to any of the terminals.
Use only the fuse type and rating specified for the instrument .
Provide proper ventilation to the instrument, particularly near the ventilation
slots in the back.
Do not operate the instrument with suspected failures. Refer damaged units to
qualified Molectron service personnel.

Features & Description
EPM2000/EPM2000e Reference Guide 3
MANUAL INFORMATION
This reference guide may be read sequentially, but should be stored near the EPM2000 and used as a
reference.
There are five basic components of this reference guide:
•Features & Description An introduction to the EPM2000 and its features and controls
•Operation A tutorial and complete description of the EPM2000’s functions
•Programming A list of commands and examples of communicating with the EPM2000 via
remote
•Maintenance, Service, & Calibration A list of frequently asked questions, and information
regarding calibration and service
•Specifications The standards and limits of the EPM2000
FEATURES
INTERFACE
The EPM2000 features a standard RS-232 9-pin connector on the back panel. This can connect to
any similar RS-232 port of a host PC.
IEEE-488 (or GPIB) interface is standard on every instrument. Use this port for the following
advantages:
• Higher transfer rates than the RS-232
• Can be added to an already existing instrument chain
• Can be used with other IEEE-488 instruments on the same host computer
UNITS AND RANGES
The EPM2000 can measure:
•Energy 1 pJ to 10 J in 28 ranges (depending on the probe type)
•Power 1 mW to 10 KW in 15 ranges
•Rep Rate 0.1 pps to 1000 pps
•Volts 2 mV to 30 V (for pyroelectric/silicon probes)
•Volts 200 µV to 1 V (for thermopile probes)
For more details, see Specifications.

Features & Description
EPM2000/EPM2000e Reference Guide
4
COMPATIBLE PROBES
The EPM2000 functions with any of Molectron's pyroelectric/Joulemeter probes with names of the
form Jx(for example: J25, J3, J4).
All PowerMax thermopile probes will function with the EPM2000. Connect thermopile probes that
terminate with a BNC connector to the EPM2000 with the PM-BNC adapter (available separately).
UNDERSTANDING THE EPM2000 INTERNAL TRIGGER
For greatest accuracy and repeatability, each channel of the EPM2000 must trigger reliably for each
laser pulse.
The EPM2000 should be triggered externally, via one of the Trigger In connectors, for best results.
This is particularly true in a noisy environment. The EPM2000 can be set to synchronize with either
the positive or negative transition of this external signal.
Without a reliable external trigger, set the EPM2000 to extract an artificial trigger from the incoming
signal. This is Internal Triggering.
To successfully extract an internally generated trigger, set the EPM2000 to a range such that the
incoming signal is at least 5% of the full scale. Set the trigger level for at least 2% above the noise
level and at least 2% below the peak height.
For example, with a peak height of 300 mJ, set the EPM2000 to a range of 3 J. A peak will occur at
10% of full scale, well above the 5% level. The trigger level should not be set higher than 8%. If the
noise level is 5% of full scale (approximately 150 mJ) then the trigger level should be set no lower
than 7%.
In Figure 1, the EPM2000's internal trigger threshold has been set to 8% (dashed line). Pulse D will
definitely not generate a reliable trigger. Pulse C may generate a trigger, but not reliably. Pulses A
and B will definitely generate reliable triggers.

Features & Description
EPM2000/EPM2000e Reference Guide 5
Figure 1: Pulses which will or will not trigger the EPM2000 Internal trigger.
The ranges differ by powers of ten. A full-scale signal on one range may not trigger on the next
higher range unless the trigger level is set to less than 10%. For example, a near full-scale signal of
280 mJ on the 300 mJ range is less than 10% of full scale on the next higher range (2 J) and would
not trigger the reading, so adjust the trigger level to less than 8% for reliable triggering.
The trigger is synchronous with the leading edge of the pulse, but the actual peak is determined
algorithmically by sampling the input signal near the trigger. From the trigger point forward, the
algorithm searches for peaks and from the trigger point back, it searches for a baseline.
The EPM2000 can be programmed to ignore triggers for a specified time after a valid trigger. This
prevents “false” triggers in pulse tails from accidentally starting a new sample (see Figure 2). This
amount of delay time is called the Trigger Holdoff (see Operation -- Settings -- Trigger Holdoff).
The EPM2000 is set at the factory with a 0 ms trigger holdoff.
5%
10%
15%
Trigger
Level
Possible
False
Trigger
1 ms 2 ms
Figure 2: How a false trigger could occur.

Features & Description
EPM2000/EPM2000e Reference Guide
6
UNDERSTANDING THE EPM2000 EXTERNAL TRIGGER CIRCUIT
The Circuit
Each External Trigger of the EPM2000 is a 100 W resistor in series with an optical coupler. The
coupler is protected by an additional diode (see Figure 3). A rising edge at the Trigger In BNC
forward biases the optocoupler diode and triggers the channel. If the EPM2000 channel is set for
EXT NEG trigger, then the same sequence is initiated by a falling clock edge.
Figure 3: The external trigger circuit for the EPM2000.
The EPM2000 searches for a peak as soon as it receives the trigger signal. It compares successive
A/D conversions, defining a peak as the first value followed by a lesser value, as shown in Figure 4.
This allows the EPM2000 to read very long pulses with well-behaved rise characteristics.
Figure 4: Determining a peak.
Trigger the EPM2000 as close to the pulse as possible. If the EPM2000 is triggered too early, it will
detect fluctuations in the noise preceding the pulse and derive a false peak.

Features & Description
EPM2000/EPM2000e Reference Guide 7
Triggering
Typical instrumentation triggers the EPM2000 reliably. If the triggering instrument cannot source
enough current, boost the current supply externally using a trigger circuit such as shown in Figure 5.
Figure 5: Method to boost source current of triggering device.
UNDERSTANDING THE EPM2000 SPEEDUP FEATURE
For most applications, it's important to determine laser power quickly and accurately. However, some
probes, such as the PM5K, which can measure power as high as 7500 Watts, have a long response
time. The EPM2000 solves this problem by using probe information and an internal algorithm, called
the Speedup feature, to quickly estimate the final power value.
For long response time probes, the Speedup feature significantly reduces the amount of time required
for an estimated value.
While the Speedup feature is useful for a stable laser output, it is not well suited for constantly
changing or unstable laser outputs, as it tends to amplify noise. The most accurate way to measure
power, particularly for unstable laser outputs, is to deactivate the Speedup feature.
The fastest and most accurate results can be achieved when the Speedup feature is in Selective
mode. In Selective mode, the EPM2000 determines when the Speedup algorithm should be used.
Whenever the actual measurement and the estimated measurement differ by more than 5%, the
Speedup data will be displayed, but when the actual measurement falls within 1% of the estimated
measurement, the EPM2000 displays the actual measurement. For most probes, using the Selective
mode is very effective, taking advantage of the Speedup feature when needed and relying on the
EPM2000's raw accuracy otherwise.

Features & Description
EPM2000/EPM2000e Reference Guide
8
5 W
10 W
15 W
Measured
Power
Probe Output
5 s 10 s
Speedup Reading
Figure 6: The Speedup feature estimating a 15 Watt power reading.
DESCRIPTION
REAR PANEL
Figure 7: EPM2000 Rear Panel.

Features & Description
EPM2000/EPM2000e Reference Guide 9
Smart Probe Connectors
These connections are for all of Molectron’s PowerMax probes, as well as specially powered
Joulemeter probes.
Pulse In Connectors
Pulse In connects pyroelectric laser energy probes and are internally terminated with 1MΩ
impedance. Probes with 50 Ω impedance (such as J3, J3S, and J4 probes) must use a 50 Ω feed-
through terminator, available through Molectron Detector, Inc., or equivalent to Pomona P/N 4119.
Analog Out Connectors
These connections provide an output voltage into loads ≥600 W that is proportional to the input pulse
amplitude, scaled to the full scale of the display. The output range is 0 to Vmax VDC, where Vmax is
defined in Figure 8. Rload is the impedance of the monitoring device (oscilloscope, A/D converter,
etc.). The outputs update three times per second. Note that, although in some instances the
EPM2000’s display will exceed the selected range, under no circumstances will the output value
exceed Vmax.
Figure 8: Conversion formula for Analog Out levels.
Trigger In Connectors
These inputs accept synchronized pulses from the laser. They are electrically isolated from the
EPM2000 and consist of a 100 Ω resistor in series with an optoisolator. They can be set from the
front panel or via remote to trigger on the rising or falling edge of the input signal. They only trigger
pyroelectric/silicon measurements.
RS-232 Interface
The EPM2000 acts as a DTE (Data Terminal Equipment) device through this 9-pin RS-232
connector. It mates with a standard 9-pin straight-through serial cable to a typical IBM-AT
compatible PC, or other DCE (Data Communications Equipment) device. Hardware handshaking is
implemented.
Pin Assignment
1 DCD (not used in the EPM2000)
2 RXD
3 TXD
4 DTR
5 GND
6 DSR
7 RTS
8 CTS
9 RI (not used in the EPM2000)
Table 1: RS-232 pin assignments.

Features & Description
EPM2000/EPM2000e Reference Guide
10
AC In Connector
Connect only to the factory supplied, polarized AC cord. The EPM2000 will function at AC voltages
from 90 to 264 VAC at frequencies between 50 Hz and 60 Hz.
Fuseholder
Replace this fuse with only a 240 VAC 1 Amp fast-blow fuse. A convenient replacement fuse is
stored in the holder. See Maintenance, Service, & Calibration for replacement instructions.
Power Switch
Press the symbol for ON and the symbol for OFF.
IEEE-488 Connector
This connector mates with a standard IEEE-488 cable.
FRONT PANEL
Figure 9: EPM2000 Front Panel.
Channel B Controls
Channel B Controls operate the same as channel A Controls. Indicators appear for channel B
functions appear on the channel B LCD.

Features & Description
EPM2000/EPM2000e Reference Guide 11
Ratio Keys
Use these keys to set the EPM2000 into Ratio Mode. One of the two channels must have a trigger
source set to SLAVE.
This key displays the ratio of A/B on the channel A.
This key displays the ratio of B/A on channel B.
System Keys
These three keys navigate through the EPM2000’s configuration menus.
This key permits modification of the EPM2000’s communication parameters (such as baud
rate, I/O port, etc.) by offering access to the communications parameters menu. It is also the
“0” key for the Numeric Entry Keys.
This key permits modification of the EPM2000’s system parameters (such as Display
Speedup and Backlight) by offering access to the system parameters menu. It also acts as
the decimal point key for the Numeric Entry Keys.
Pressing this key during configuration menus or while entering a number on the numeric
keypad will accept the currently displayed value or number.
Numeric Entry Keys
Use this keypad for data entry, such as detector responsivity or setup information such as statistics
batch size.