1. The program selects the two closest readings of the three inputs (-20 to +80 degC), averages these values, and saves the answer in memory 4 (Mem4). See the flow chart below.
2. The 4 to 20mA output follow the value in Mem4 (-20 to +80 degC).
3. Both relays 1 and 2 will switch on if:
• If the two selected readings deviate more than 1 deg C (Con_a 'Dev').
• If Mem4 is below an alarm value -10 deg C (Con_b 'Alarm').
• The relays have zero dead-band but have a 10 second on delay (fail condition must occur continuously for 10 seconds) and a 5 second off delay (after the fail condition the good condition must occur continuously for 5 seconds).
4. The ACCESS module trim menu adjusts:
   • Relay on delay (0 to 2300 seconds).
   • Relay off delay (0 to 2300 seconds).
     Note the time delays for relay 1 and relay 2 are set independently.
   • The 'Dev' level, this is the maximum allowed variation between the two closest temperatures.
   • The 'Alarm' level, this is compared to the average of the two closest temperatures to produce an alarm.

UAP1066a.usc