7.10 Digital Inputs and Outputs
The YUAA supports several types of digital (discrete) inputs and outputs, as enabled by configuration including: Digital input
modes of NAMUR, Externally Wetted, Internally Wetted, and Digital Outputs through using mA outputs and interposing
relays. Terminal voltages for the YUAA must remain between 0 and 20 V for correct discrete input operation. To use inputs
of higher than 20 V, such as for 24 V discrete inputs, the user must use a series resistor which would be part of the open wire
detection. With the use of two resistors in parallel and series with the switch contact, external wetting voltages of up to 30 V
are allowed.
7.10.1 NAMUR Style Sensor Inputs
The NAMUR sensor is connected between IO+ and IO-. NAMUR style implies that the sensor is designed in accordance with
IEC60947-5-6 Control circuit devices and switching elements –DC Interface for proximity sensors and switching amplifiers
(NAMUR).
The NAMUR load 1K resistor is located on the IO- side of the connection. This prevents the use of a shared return wire for
multiple sensors as done on RTD devices – each sensor shall be wired separately to its channel’s two terminals.
194 GEH-6855_Vol_II GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
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