3KP64 - 5.8
3000PLUS WITH 5D64 INSTRUCTION MANUAL V. SB.2
Daytronic Corporation
2211 Arbor Blvd. Dayton, OH 45439 • (800) 668-4745
Tel: (937) 293-2566 • Fax: (937) 293-2586 • www.daytronic.com
Expressed in the active engineering units, the absolute
value of either limit value should not be greater than the
3000PLUS instrument’s currently effective
Full Scale
Units (FSU)
value (discussed in Section 1.D).
RUN-TIME MODIFICATION OF LIMIT VALUES
As mentioned in Section 1.D, when the 3000PLUS
instrument’s
LIMITS SECURITY (LMS) is OFF, the local
operator is able to use the front-panel buttons to quick-
ly view and adjust the operating limit values
during nor-
mal run-time operation, without having to enter Setup
Mode
. This is the case even when limit monitoring is
currently disabled (see above).
As long as LMS = OFF, the 3000PLUS meter’s currently
effective LOW-LIMIT and HIGH-LIMIT setpoint values will
be added to the run-time display cycle controlled by the
button (as explained in Section 1.E).
When either limit is displayed, its numerical value may
be changed by means of the
and
buttons, as explained in Sections 3.A and 3.B (“Setup
Stage 5: Limits”). To finalize the limit alteration, you
must press
once more (NOT
Enter). This will step the display to
the HIGH LIMIT value (if LOW LIMIT is currently dis-
played) or to Channel 1 (if HIGH LIMIT is currently dis-
played).
SETTING LIMIT LATCH MODE
Limit monitoring may be in either LATCHING or NON-
LATCHING mode. In latching mode, when a high-limit
or low-limit violation is detected, that violation condition
will remain in effect—regardless of the subsequent
behavior of Channel 2—until the limits have been
“released,” as explained below. When limits are non-
latching, any detected limit violation condition will cease
to occur as soon as the Channel 2 reading leaves the
corresponding limit zone (or associated hysteresis
deadband).*
Like the limits enable status (above), the active latch
mode can be specified as part of the normal 3000PLUS
setup procedure. It can be changed on a strictly
run-
time
basis by selecting “ON” or “OFF” in the “LAT” field
in the Configurator’s “Live Output” window when
Channel 2 is being displayed (see Fig. 11). It may also
be specified at any time by issuing the “write” form of
the
LIMIT LATCH (LAT) command to the 3000PLUS.
SETTING LIMIT HYSTERESIS
The high and low limit hysteresis values let you define
the hysteresis windows (or “deadbands”) shown in Fig.
21, in order to prevent low-level signal noise from tog-
gling the limit relays on and off while the reading of
Channel 2 remains in the neighborhood of the corre-
sponding setpoint.
Expressed in the active engineering units, the
high hys-
teresis value is
subtracted from the present high limit
value to determine the
lower threshold of the high
deadband. Similarly, the
low hysteresis value is added
to the present low limit to determine the upper thresh-
old
of the low deadband.
In the example shown in Fig. 21, a “high violation” is trig-
gered when the Channel 2 reading enters the “Greater
Than” zone by exceeding the high limit value at time t
1
.
At time t
2
, Channel 2 falls back to the “OK” zone. If
there were no hysteresis band—and assuming that lim-
its are NONLATCHING—the high violation would cease
to occur at t
2
. In this case, however, the limit status con-
tinues to be evaluated as “high violation” until such time
as the reading becomes less than the lower threshold
of the high hysteresis band, which happens at time t
3
.
At this point, the limit status returns to “OK.”
Normally entered during 3000PLUS setup, the high/low
hysteresis values can be changed on a strictly
run-time
basis by entering desired values in the “HHY” and
“LHY” fields, respectively, in the Configurator’s
“Live
Output”
window when Channel 2 is being displayed
(see Fig. 11). They may also be specified at any time by
issuing the “write” forms of the
HIGH HYSTERESIS
(HHY)
and LOW HYSTERESIS (LHY) commands to the
3000PLUS.
Note that you cannot enter a negative hysteresis value,
or a number that is greater than the
difference between
the existing high and low limit values.
SETTING LIMIT RELAY POLARITY
The 3000PLUS meter lets you set the contact polarity of
the six limit relays to NORMALLY OPEN (“NO”) or NOR-
MALLY CLOSED (“NC”).
Like the limits enable status and latch mode (above),
the active relay polarity can be specified as part of the
normal 3000PLUS setup procedure. It can be changed
on a strictly
run-time basis by selecting the desired
state in the “POL” field in the Configurator’s
“Live Out-
put”
window when Channel 2 is being displayed (see
Fig. 11). It may also be specified at any time by issuing
the “write” form of the
POLARITY (POL) command to
the 3000PLUS.
5. OPERATING CONSIDERATIONS
* Latching also applies to the “BETWEEN” (“OK”) limit zone. That
is, when a limit violation occurs and latching is enabled, the
“OK” indicator will remain on and the “OK” relays will remain
activated until limits are released.
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