Pulse Instruments
System 4 Manual
Version 1.6
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23
6.8 pH = 11.77 mA = 0 spm
14 pH = 20 mA = maximum spm (360 strokes)
The ORP works using the same principle, but is set up in the opposite direction. Its set point in
the system, for example, is 670 mV. The ORP pump analog input range would then be from 4
mA to 14.72 mA (670 mV); then the pump speed range would be from its maximum speed at 4
mA input to 0 spm at 14.72 mA input. The ORP pump would then pump at its maximum speed at
0mV ORP, and slow down as the ORP level gets closer to 670 mV, finally stopping when the
level gets above 670 mV. With this setup, the user will be able to control the pumps
proportionally.
ORP range: 0 to 1000 mV = 4 to 20 mA scale
Reference: (20-4 mA) / (1000-0 mV) x (ORP setpoint value) + 4 mA = mA setting of the setpoint
Example 670 mV: (16 mA) / (1000 mV) x (670 mV) + 4 mA = 14.72 mA
0 mV = 4 mA = maximum spm (360 strokes)
670 mV = 14.72 mA = 0 spm
