Pulsafeeder Pulsar DLCM - Manual (Page 62)

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At the 100% Adjustment (maximum value on the x-axis), the DLCM is operating at 100% stroke
length and 100% motor speed. This results in a 100% flow output. As the Adjustment is decreased to
50% for example, the motor speed is adjusted to 50% (motor speed has 'Priority') and the stroke length
remains at 100%. As we continue to decrease the Adjustment value, the DLCM continues to decrease
motor speed until it reaches its minimum End Point value (10%). At the 10% adjustment, the DLCM's
motor speed will be 10% and the stroke length will be 100%. As the Adjustment is set below 10%, the
motor speed setting will remain at its minimum End Point value of 10% and the stroke length will be
adjusted. Thus, as the Adjustment is reduced to 5%, the DLCM will keep the motor speed at it’s
minimum End Point value of 10% and adjust the Stroke Length to 50% (0.10 * 0.50 = 0.05). Finally,
when the DLCM is at its minimum Adjustment value (i.e., 0%), the motor speed will be at its minimum
End Point value of 10% and the Stroke Length will be at its minimum End Point value of 0% (0.10 *
0.00 = 0.00). When increasing the adjustment value, the same rule system is followed in the opposite
order. Thus, stroke length is increased until it reaches its maximum End Point, then speed is increased
until it reaches its maximum End Point.
Looking at this graph, you will notice that 90% of the pump's flow output is covered by motor speed
while 10% is covered by stroke length. The End Point and Priority settings allow you to change
characteristics such as this. For example, if you set the 'Priority' value to Stroke Length, then 100% of
the pump's flow is covered by stroke length (when the stroke length has a 0% Minimum End point, the
motor speed will also be set to its Minimum End Point as the Adjustment value will be 0%).
When controlling from a single analog input (1-CHANNEL), the above stated rule applies. When
controlling from two analog inputs (2-CHANNEL), the End Point values are enforced, but the
Priority is not.
During Pump Flow Calibration and Zero Calibration, the selected End Points may be violated.
You can fix the operating point of Stroke Length or Motor Speed by setting the Minimum and
Maximum End Point values equal (e.g., you can fix the stroke length at 50% by setting the
Minimum End Point to 50% and the Maximum End Point to 50%).
7.2.8.1 End Point Example
A PULSAR pump is purchased with the DLCM option. Due to anticipated future capacity growth, the
pump is twice as large as currently required. The process will require the pump to typically operate
between 5% and 35% flow. In addition, it is critical that the pump not operate above the 50% flow
output. The pump will be controlled by a single analog signal.
There are a number of ways to assure that the pump does not exceed the 50% flow output. For
example, the 4-20mA input calibration could be ratioed 50% to limit the output. But, this technique
would not prevent someone from walking up to the pump and manually adjusting it above 50%. A
better way is to adjust the End Point values. Using the default End Point and Priority values, the
DLCM will typically operate the motor speed from 50% to 10% and the stroke length from 100% to
0%. Unfortunately, this means that in the 5% to 25% anticipated flow range, the DLCM will transition
between stroke length and motor speed control (at the 10% flow point).