Holtgreven GSE-375 - Manual (Page 43)

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A CTIVATION M ETHODS (G ENERAL )
Setpoint activation for Fill, Batch, Discharge, and Both can be initiated in one of two ways: Tare or
Auto. Check-weigh operations have no start function. Independent setpoint operations are limited
to Above or Below activation. The Model 370 and Model 375 setpoint option board may be
connected in-series with a larger automated control system or a manually activated switching
device. A foot switch, a two-hand safety station, or other permissive-start devices may be used
for safety or system compatibility.
Activation Method Description
Tare Operation [TARE] activates the setpoint. It waits for a no-motion condition, then tares scale to net zero.
The appropriate setpoint is then activated.
Remote Key The [REMOTE KEY] closure does not exist on the Model 370/375. Do not use
this choice.
Auto-Start Automatically activates the setpoint. It waits for a no-motion condition, then adds
the target to the current displayed weight to achieve a relative cutoff value.
Pre-Acts (General)
Pre-Acts are control actions prior to reaching a desired target value. Necessary to prevent over-
filling due to product flow rate, relay and valve response time and product suspension, Pre-Acts
and other system variables affect how much more product reaches the weighing device after the
Model 370/375 has deactivated a setpoint.
Pre-act 1
Used in dual-speed applications, pre-act 1 specifies when the 370/375 should switch from fast-fill
to slow-fill, allowing the system to perform the bulk of a filling operation as quickly as possible
before switching to a more manageable dribble mode for final cutoff. When using a single-speed
device, set pre-act 1 to 0.
Pre-act 2
Specifies the weight where the final cutoff should occur, enabling the 370/375 to compensate for
a dispensing control's closure time and account for free-fall material. Free-fall is the amount of
product that has passed the point of the dispensing control yet not yet reached the weighing
device.
Pre-act values are entered in terms of the amount of product that would over-fill or 'how early' to
close the control device. For instance, after repeated tests, a system consistently over-fills by .5
lbs. This is the value that should be entered as the pre-act. The 370/375 would then deactivate
the setpoint .5 lbs. less than the desired final target value.
Parameter Setting Actual Cutoff Value Comments
Target = 400 lbs. Desired final weight.
Pre-Act 1 = 28 400 – 28 = 372 Switch to slow feed at 372 lbs.
Pre-Act 2 = .5 400 – 0.5 = 399.5 Final fill valve closes at 399.5 lbs.
Learn Feature (General)
The Model 370/375 can 'learn' optimal pre-act values. When enabled, the learn feature will
automatically adjust the final cutoff value based on an analysis of the five previous fills, helping
achieve a final target by compensating for product viscosity, changes in plant air pressures, sticky
valves, etc. For each cycle, the prior five final weights are analyzed and a new pre-act value is
calculated.
Pause Feature (General)
The Model 370/375 can pause setpoint operations. This is useful as a safety device, for mid-cycle
operator breaks, mechanical adjustments, etc.