Watson-Marlow 720UN and 720SN User Manual
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19.4 Speed: analogue output
An analogue voltage output signal is available on
the Tacho output connector (J11), between the
V
terminal and the
0V
terminal. The voltage is directly
proportional to the pumphead rotation speed. 0V =
zero speed; 10V = maximum allowed speed.
19.5 Tachometer frequency output
A tachometer frequency output is available on the Tacho output connector (J11), be-
tween the
freq
terminal and the
0V
terminal. It provides a +5V square wave pulse,
maximum 0.5mA, the frequency of which is directly proportional to pumphead rota-
tion speed. It provides 2.133 Hz/rpm—128 pulses per pumphead revolution. The
pulse train from the pump can be used to calculate the speed of rotation or to deter-
mine the number of pumphead revolutions. This output has the required strength to
be effective up to 3m from the pump. Longer cable runs require signal amplification.
