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PowerSync Service Analyzer Reference Manual

February 8, 2010

Sifos Technologies page

The Detection resistance and capacitance ranges in the Detection subsystem are 9 K

-39 K

Ohms, and nominally 0, 5, 7,

and 11

F respectively. Newer “Type 2” or “Type 3” PSE Test Blades add capacitance values of 47, 52, 54, and 58

F to

aid with legacy PD emulation needs. The AC MPS signature consists of 24 K

in parallel with 0.1

F that becomes

visible above 11 volts – the same level where Detection Signature passives are removed and become invisible. Because of
the 11 volt activation floor, the effective DC resistance of the AC MPS signature is significantly greater than 24 K

until

the port voltage significantly exceeds 11V. This means that neither the Detection Signature nor the AC MPS signature
will produce any measurable error to Classification Signature loads created by the Active Load module.

There are 2 forward-biased diodes that the signal must pass through before entering the Detection and MPS passives
circuitry. These model typical PD bridge characteristics and are commensurate with recommended circuitry as described in
the 802.3 PoE standard.

2.3.2. Triggers

The PowerSync Analyzer has extensive triggering capabilities, which are divided into 2 categories:

internal (or waveform)

and

external (or event)

. The instrument also has the ability to perform non-triggered measurements. The triggering types

are depicted in Figures 2.7 and 2.8. Also depicted in
Figure 2.7 are trigger applications including the DC
meters, time-interval measurement, and load current
transient, each of which can be initiated with those
triggers.

Internal (or waveform) triggering is derived from the
common mode voltage levels received from the PSE
under test. For most measurements, this triggering is
based upon the trigger levels and directions (rising or
falling) set for

Trigger 1

. A second trigger,

Trigger 2

used exclusively for terminating time interval
measurements. Trigger 2 offers identical
programmability as Trigger 1 (levels and edge polarities).

External (or Event) triggering is also used to initiate measurements or actions, and is initiated by either a user command, an

action that is programmed to send out an external trigger, or
through an external event that appears on the trigger bus.
The trigger bus is a trigger signal connection that is shared by
all ports within a system, and by the Trig Out BNC connector
on each PowerSync Analyzer. Figure 2.8 shows the sources
used to generate External (or event) triggers on the left, and
shows the external bus configuration on the right.

Any External trigger
in the system will
appear on this bus, and
will trigger any port
which is waiting for an

external trigger event.   This enables cross-triggering across ports and triggering via
externally generated signals.  It also enables the user to use the trigger output for
other purposes, such as monitoring data throughput during PSE powering or load
transients.

The BNC trigger connector on the Chassis Controller front panel can be configured
as an output or an input.  As an output, it directly mirrors the External trigger bus.
Output triggers will appear as a 3.3V, 10 mSec pulse.  When set as an input, it can
drive the external trigger bus inside the PSA chassis. This enables triggering across
multiple instruments, which may be desirable when testing equipment with more than 24 ports.