Watson-Marlow 720DuN User Manual
65
22.3 Speed: analogue input
It is possible to control the speed of the pump remotely by
one of these methods: a voltage analogue signal within the
ranges 0-10V or 1-5V; or a current analogue signal within
the range 4-20mA; or a remote potentiometer using the
10V
supply at J7.
The analogue process signal must be applied to the
i/p
ter-
minal of the Analogue 1 connector (J5). Ground to the
0V
terminal of the same connector. The pump will provide an
increasing flow rate for a rising control signal (non-inverted
response) or an increasing flow rate for a falling control sig-
nal (inverted response). See 18.2
Analogue
.
4-20mA circuit impedance: 250
Ω
.
For voltage modes, 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 termi-
nals.
A remote potentiometer with
anominal value of between 1k and
2k with a minimum of 0.25W
should be wired between the
terminals of the Rem-pot connec-
tor (J7) and the
i/p
terminal of
the Analogue 1 connector (J5).
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 the Rem-pot
connector will be overloaded and will not provide a full 5V or 10V.
