3-24
MASTERFLEX
®
Digital Pump Drive Operating Manual
Cole-Parmer
Section 3
Operation
The Tachometer output on this drive is an “open collector” type output
and cannot be wired in the same manner as relay outputs. An open
collector output is not isolated and must be configured differently than a
relay output. When the open collector output is active, the output is
effectively switched to earth ground and if improperly terminated could
result in damage to the drive and/or external equipment.
Recommendation
When connecting to open collector outputs, the output should be
connected to a current limiting resistor and then to a positive supply
source which is less than 28V DC. Typically this would be connected to a
24V PLC input (see Figure 3-11).
NOTE: when using the 24V supply on the interface connector, current
draw must be limited to 150 mA
.
NOTE: DO NOT connect 120V supply lines to open collector outputs!
Figure 3-11.
Terminating Open Collector Output to a PLC.
Open Collector Output
+24V
To PLC
Output
10k
