Watlow MICRODIN - Manual (Page 47)

Bumpless Transfer
When the sensor opens (fails), the MicroDIN switches from automatic to manual
operation.
When transferring from automatic to manual operation, the control output, or
outputs, remain stable — a bumpless, or smooth, transition.
If the Input Error Action parameter is set to 0, bumpless transfer, and the
process has stabilized at a power level less than 75% ( ± 5%) for a two-minute
period prior to the sensor break, then the MicroDIN switches to manual
operation at the last automatic power level. If these conditions are not met, the
output goes to 0% power (output disabled).
If the Input Error Action parameter is set to Fixed Manual Output, the
MicroDIN switches to manual operation at the Fixed Manual Output percent
power value.
Manual operation provides open-loop control of the outputs from a range of
-100% to 100% output. The MicroDIN allows a negative output value only when
Output 1 is set to cool.
Automatic operation provides closed-loop on/off or PID control. When the
operator transfers from a closed loop to an open loop, the MicroDIN sets the
power level to the setting of the Input Error Action parameter. If Input Error
Action is set to 0, bumpless transfer, the controller retains the power level from
the closed-loop control. When the MicroDIN returns to closed-loop control, it
restores the previous set point process value.
Figure 4.15 — Bumpless Transfer
Wa t l o w M i c r o D I N 4 . 1 5
Features
Time
Temperature
Power
100%
Tie
Break
2 min. Locks in
Output
Power
0%
Set Point Actual Temperature
Output Power
≤
75% power