Features & Description
EPM1000 User’s Guide
8
Compatible Probes
The EPM1000 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 EPM1000.
Connect thermopile probes that terminate with a BNC connector to the
EPM1000 with the PM-BNC adapter (available separately).
Understanding the
EPM1000 Internal
Trigger
For greatest accuracy and repeatability, the EPM1000 must trigger
reliably for each laser pulse.
The EPM1000 should be triggered externally, via the Trigger In connec-
tor, for best results. This is particularly true in a noisy environment. The
EPM1000 can be set to synchronize with either the positive or negative
transition of this external signal.
Without a reliable external trigger, set the EPM1000 to extract an artifi-
cial trigger from the incoming signal. This is called Internal Triggering.
To successfully extract an internally generated trigger, set the EPM1000
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 EPM1000 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 EPM1000's internal trigger threshold has been set to 8%
(dashed line). Pulse A will definitely not generate a reliable trigger.
Pulse B may generate a trigger, but not reliably. Pulses C and D will
definitely generate reliable triggers.
5%
10%
15%
Trigger
Level
A
D
C
B
Definitely will not trigger
May trigger, but not reliable
Definitely will trigger
Figure 1: Pulses which will or will not trigger as valid
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