Ransburg RCS 2 Ratio Control System - Manual (Page 79)

APPENDIX N: IMPROVING THE ACCURACY OF
THE RCS-2 (Continued)
flow at some fixed value in the middle of the range
of flows expected. That is, if the range of flow rates
of the pump during normal operation is expected
to be from 100 cc’s/min to 500 cc’s/min, set the
target flow rate to 300 cc’s/min. Flow material for a
significant amount of time (we suggest a minimum
of 2 minutes) into a beaker and measure the vol-
ume. It is highly recommended that the material
be weighed as opposed to measured for increased
accuracy. 1 If the flow rate multiplied by the time
results in more material than was actually obtained
in the flow test, than the Pump Size programmed
in the Configure Channel screen is too large. Try
reducing the value by the same percentage that
the volume exceeded the expected volume and
try the test again. If the actual volume of material
obtained was greater than the calculated value, try
increasing the Pump Size value by that percentage
and try the test again. Repeat this several times
until acceptable volumes result.
Example:
Pump Size = 5.5 cc’s/rev
Programmed flow rate = 300 cc’s/min
Flow time = 3 minutes
Calculated volume = 3 minutes x 300 cc’s/min =
900 cc’s
Actual volume collected = 887 cc’s
887 cc’s 900 cc’s
5.5 cc/rev x New PS
Therefore, New PS = 900 x 5.5 = 5.58 cc/rev
887
Put 5.58 cc’s/rev in for the Pump Size on the
Configure Channel screen, push Send to RCS-2
and retest.
Pump Pulses per Liter and Totalization:
On the Configure Channel screen of the user-in-
terface software there is a value named Pump
Pulses per Liter. All of the RCS-2 flow rate and
volume displays are based on this value. The motor
amplifier sends 500 pulses per revolution back to
the RCS-2 channel card no matter what RPM it
is running at. Therefore, it is easy to calculate a
volume of material per pulse or a number of pulses
per volume (in this case, per liter). However, by
adjusting the Pump Size value (as shown above)
the pulses per liter value will also be affected and
should be adjusted. There are two ways this can be
accomplished: Mathematically or experimentally.
Mathematically: Simply divide 500,000 (1000 cc’s/
liter x 500 pulses/rev) by the new pump size. In
the case above, 500000/5.58 = 89605 pulses/liter.
Experimentally: Zero the volume on one of the
totalizer values on the Flow Totals screen of the
RCS-2 then flow a random volume of material into
a beaker and measure the actual volume. (Once
again, it is highly recommended that the volume
be determined by weight as opposed to trying to
measure it based on the fluid level in the beaker. 1 )
Compare the actual volume with the volume re-
corded on the RCS-2 Totalization screen. If the
actual volume obtained was greater than what was
displayed on the totalization screen, then the Pump
Pulses per Liter value is too small. If the actual
volume obtained was less than that displayed
on the totalization screen, the Pump Pulses per
Liter is too large. Modify the value up or down as
required by the percentage they differ and retest.
RCS-2 User Manual - Appendix
76 LN-9407-00.2
Ransburg