User Guide - Eurotherm Ltda

nanodac RECORDER/CONTROLLER: USER GUIDEB2.6.11 Time ProportioningPID controllers somtimes use Time Proportioning to control the average power to the load. This is done byrepeatedly switching the output on for a period (T on ) and then off for a period (T off ). The total period (T on +T off ) is called the ‘cycle time’. During each cycle, the average power delivered to the load is:P Avg = P Heater x Duty cycle,where ‘P Heater ‘ is the actual transferred heater (or cooler) power and Duty cycle = T on /(T on + T off ), normallyrepresented as a percentage value.The PID controller calculates the Duty Cycle (the PID output control signal from 0 to 100%) and provides aMinimum on time between 100ms to 150 seconds.Figure B2.6.11 shows how T on , T off and cycle time vary with demand %.MilliecondsT on + T off = Cycle timeT onTminT offOutput demand (%)Figure B2.6.11 Time proportioning curves (Minimum on time = 625ms)Note: For this instrument, only ‘Min on time’ is configurableB2.7 DIAGNOSTICSSee section 4.6.7 for definitions of these parametersAppendix BPage 326HA030554Issue 7 Nov 12