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01 May 2003

HART interface monitor diagnostic opportunities

• Relay #1—Triggered by any or all of the diagnostic status bits defined as:
• Bit 1: Primary variable out of range
• Bit 2: Secondary variable out of range, such as with failed thermocouple reference junction compensation
• Bit 3: Primary variable analog output fixed—loop was in manual mode or no input change
• Bit 4: More status available—signals a change in any of up to 40 other available status bits
• Bit 5: Cold start after power interruption
• Bit 6: Configuration changed
• Bit 7: Field device malfunction
• Relay #2—Interface monitor fault alarm
• Relays #3 and #4—High/Low alarms
• Analog (4–20 mA) outputs