Pulse Instruments
System 4 Manual
Version 1.6
Visit us Online at
www.pulseinstrument.com
22
6.4
Chemical Metering Pump Control
EZ Series
EW Series
EK Series
EH Series
6.4.1 Priming
Normally, the pump should self prime. In order to prime the pump, set the stroke length to 100%
and the frequency to 360 strokes per minute (SPM). If the pump is equipped with an air vent
valve, open the knob a half turn. Liquid should move up through the suction tubing and into the
pump head. When the liquid starts running through the vent side tubing, close the air vent knob
and continue with output adjustment (See pump manual for details).
If the pump has no air vent valve, disconnect the discharge tubing from the injection valve. When
liquid enters the discharge tubing at the pump head, stop the pump, then reconnect the discharge
tubing to the injection valve.
If the pump does not self prime, remove the check valve housing on the discharge and suction
sides to make sure cartridges and gaskets are in correct positions.
6.4.2 Proportional
Control
In order to proportionally control the metering pumps for acid and oxidation injection, the chemical
metering pumps must be connected to the ON/OFF control outputs and to the 4-20 mA signals
from the control panel.
The system panel is able to output ON/OFF control functions for metering pumps in order to inject
acid and chlorine (controlled by either ORP or chlorine). The 4-20 mA output signals span the pH
and ORP scales, 0 – 14 pH, and 0 – 1000 mV, respectively.
The set points to control the pumps are entered into the system and the pumps are set to run in
external analog-input mode. For example, the set point of the acid pump is entered into the
control system at 6.8 pH, which means the acid pump will turn ON above 6.8 pH and turn OFF
below 6.8 pH. At 6.8 pH, the control system is outputting 11.77 mA. Therefore, set the acid
pump analog input range to be from 11.77 mA to 20 mA and set its pumping speed to be from 0
stroke per minute (spm) to its maximum spm, respectively. With this setup, the pumping speed of
the acid pump will increase as the pH level gets higher than 6.8 pH and will slow down as it gets
close to 6.8 pH. Finally, the pump will turn OFF when the pH value gets below 6.8 pH.
pH range: 0 to 14 pH = 4 to 20 mA scale
Reference: (20-4 mA) / (14-0 pH) x (pH setpoint value) + 4 mA = mA setting of the setpoint
Example 6.8 pH: (16 mA) / (14 pH) x (6.8 pH) + 4 mA = 11.77 mA
