Bus Configuration for I/O Modules (RAD-ISM-900-EN-BD-BUS only)
2476_en_I
PHOENIX CONTACT
5-25
AC/DC Coupling
Set the jumper to AC Coupling if the pulse voltage will never drop below 3.6 V with respect
to the transceiver's power supply negative. This would apply where there is a DC bias
voltage added to the pulse input voltage, and the DC bias exceeds 3.6 V, such as in a
ground loop condition. All other applications, including an AC sine wave input, should be set
to DC Coupling.
Low/High Input Impedance
The low impedance setting has an input impedance of 1 k
and the high setting has an
impedance of 90 k
. High impedance should be used with magnetic transducers to prevent
the current draw from dropping the voltage below the 100 mV AC peak-to-peak minimum.
The low impedance setting should be used with digital and relay interfaces because the
additional current draw will prevent electrical noise from causing false pulse counts.
Counter/Frequency Operating Mode
The pulse input values can be stored in the PLC register in two formats; either a count of the
number of pulses or a frequency value. The frequency setting will take the average number
of pulses every second.
Low/High Speed Operation
The low speed pulse setting is restricted to a maximum input frequency of 2 Hz with a
minimum pulse width of 70 ms. The high speed setting is designed for pulse frequencies up
to 32 kHz and requires a 10 µs minimum pulse width. Use the low speed setting for
mechanical pulse generating devices such as relays and the high speed setting for all other
applications. The low speed setting prevents contact bounce from being recorded as
pulses.
Single Ended/Differential Input
If the pulse signal is expected to be of negative polarity with respect to ground, set the
module to a different input. If the signal is to remain positive at all times, set it to single
ended.
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