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Watson-Marlow 620DuN and 620Du User Manual 70
23.3 Speed: analogue output
An analogue output signal is available as a 0V-10V signal on pin 2 of the lower D-
connector. Ground to pin 15. The voltage is fixed and directly proportional to the
pumphead rotation speed. 0V = zero speed; 10V = maximum speed.
An analogue output signal is available as a 4-20mA signal on pin 12 of the lower D-
connector, requiring a 250Ω resister in series. Ground to pin 20. The current is fixed
and directly proportional to the pumphead rotation speed. 4mA = zero speed; 20mA
= maximum speed.
23.4 Tachometer frequency output
A tachometer frequency output is available on pin 1 of the lower D-connector.
Ground to pin 14. It provides a +5V square wave pulse, maximum 0.5mA, the fre-
quency of which is directly proportional to pumphead rotation speed. It provides
5.578 Hz/rpm - 334 pulses per output shaft revolution. The pulse train from the
pump can be used to calculate the speed of rotation or to determine 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.