Watson-Marlow 520Du - Manual (Page 64)

Watson-Marlow 520DuN IP66/NEMA 4X User Manual 64
22.2 Scaling: analogue input 2
It is possible to scale the speed of the pump remotely by one of these methods: a
voltage analogue signal within the range 0-10V; or a current analogue signal within
the range 4-20mA; or a remote potentiometer.
The analogue scaling signal must be applied to pin 22 of the lower D-connector. 0V
to pin 20. The speed of the pump as set by Analogue 1 is scaled in proportion to the
signal from Analogue 2 according to the formula y=as, where a is the speed set by
Analogue 1, s is the scaling set by Analogue 2 (0V or 4mA = 0, increasing linearly
to 10V or 20mA = 1), and y is the scaled rotation speed. If Analogue 2 has been set
for an inverted response, the reverse is true. See 18.2 Analogue in the Setup menu.
4-20mA circuit impedance: 250 Ω
For voltage mode, 0-10V, a stable, reliable voltage source can be used with a DC
voltmeter. Circuit impedance: 22k
Ω
Inverting the response is set up in software. Do not invert the polarity of the pins.
A remote potentiometer with a nominal value of between 1k and 2k with a minimum
of 0.25W should be wired as shown. When using a remote potentiometer, do not
apply a voltage or current control input signal at the same time. The speed control
signal will require calibration relative to the minimum and maximum settings of the
potentiometer. This is done in software - see 18.1 Trim in the Setup section.
When using a remote potentiometer, it is important to set the analogue input to volt-
age in the Setup menu. Otherwise the reference voltage supply from pin 21 will be
overloaded and will not provide a full 10V.