We have TZN4S temperature controller which controls the temperature of heat sealer.
Problem with the controller is while running process value deeps in from the set value and after sometime it resettles like if you set the set value is 100 process value deeps into 92 and after 15-20 it becomes 100 while the machine is on. sensor attached with is a thermocouple. What is the reason for it?
1) the controller is not tuned aggressively enough to correct the temperature error or
2) the load exceeds the heat capacity until the load lightens or stops.
You didn't tell how the load changes while the sealer operates or whether the sealer can hold its own (supply sufficient heat) at some point in the operation or whether getting back to setpoint only occurs while 'idling' at no load.