Installation
Outputs
39
5
5.7 Outputs
5.7.1 Relay
The relay output is used as an alarm for failsafe conditions or as a setpoint relay. The relay output can be used to
indicate an alarm state or to control external actions. The relay functionality can either be set to:
•
NO (normally open), NC (normally closed)
•
PO (permanently open), PC (permanently closed)
by the appropriate ASCII command. The relay PO and PC state can be used to detect wiring problems between
the sensor and the process environment.
The alarm output can be controlled by the target object temperature or the internal case temperature of the sensor.
In case of an alarm, the output switches the potential free contacts from a solid-state relay. The maximum load for
this output is 48 V / 300 mA.
If a spike voltage exceeding the absolute maximum rated value is generated between the output terminals, insert
a clamping diode in parallel to the inductive load as shown in the following circuit diagram to limit the spike voltage.
Figure 5-11: Spike Voltage Limitation for the Alarm Relay
5.7.1.1 Setpoint
The setpoint function is a temperature alarm mechanism defining a maximum supervising value for the measured
temperature. If the setpoint value is exceeded, an alarm state will be signaled by the relay output.
A zero entry as setpoint value deactivates the alarm functionality (alarm mode off). To activate the alarm
functionality, set the setpoint entry to a value between the lowest and the highest measurable target temperature.
5.7.1.2 Deadband
Deadband is a zone of flexibility around the setpoint. The alarm does not go abnormal until the temperature
exceeds the setpoint value by the number of set deadband degrees. Thereafter, it does not go normal until the
temperature is below the setpoint by the number of set deadband degrees. The deadband is factory preset to
± 2° (C or F). Adjusting the deadband entry is accomplished through the control panel or ASCII command.
Relay (G)
≤ 48 V
Process
Sensor
Relay (H)
