Watson-Marlow Qdos30 Universal - Manual (Page 40)

Watson-Marlow qdos30 Universal and Universal+ Pump User Manual 40
The 4-20mA profile is a linear relationship where y=mx+c the scaling factor alters the
gradient m. The speed limit function in control settings will also scale the analogue
signal. The difference between scaling factor and speed limit is that the speed limit
is a global variable applied in all modes. The speed limit cannot exceed the high flow
rate set point (B). The speed limit function takes precedence over the scaling factor,
i.e. if the 4-20mA profile is 0% flow at 4mA to 100% flow at 20mA and a speed limit
of 100rpm is applied, followed by a scaling factor of 0.5, then the output will be 40%.
If a scaling factor of 2 is applied in the same scenario then the output will be 100rpm
or 80%, as the speed limit takes precedence over the scaling factor.
If you are using manual scaling it is recommended to not use speed limit to avoid
confusion