Tecfluid CP420P - Manual (Page 4)

4
2.2.2 Pulse input
The connection is made in the terminal block marked as PULSE. Details for this
connection are in the point 8.5 of this manual.
Due to the presence of a filter to avoid the effects of contact bounce, the maximum pulse
frequency for the COVOL input is 130 Hz.
The minimum input frequency is 0.06 Hz
1 M
2 2
1 1
+3.3V
NOTE: The input terminals are not isolated from the 4-20 mA loop. An electrical
connection between the 4-20 mA loop and the inputs must NEVER be made. In the event
of supplying various transmitters with the same power supply one must make sure that
the inputs isolated each other.
Series COVOL input
If the Pulse input is configured for series Covol (jumpers in position 2-3), a potential free
contact can be connected between terminals 1 & 2. Terminal 1 is connected to the
common of the instrument.
This input has a 1 MΩ pull-up resistor connected to terminal 2 and to the 3.3 V power
supply. The input has a hysteresis with the switching points situated at about 1 V & 2.1 V.
If an open collector transistor is to be used as the switching element instead of a COVOL,
then the aforementioned parameters must be taken into account.