- Accepts a 4-20mA analog process
input and provides a high speed, time proportional AC
- Permits a PLC, PC, DCS or other
control system to supply a TPO without any software programming or intensive
CPU calculations of variable on time vs off time.
- Output cycle time ("ON" time +
"OFF" time) = approximately 0.5 second at 50%. Output resolution is one half of
one sinewave (8.3 msec for 60 hz applications).
For example, when the POWER-IO unit
is used to control an electric heater, band heater, heat sealing bar, etc:
4mA = 0% = heater is off
12mA = 50%
= heater is ON for 250 msec, OFF for 250 msec, ON for 250
16mA = 75% = heater is ON for 375 msec, Off for
125 msec, ON for 375 msec...
20mA = 100% = heater is ON
Note: Rapid pulsing of the heaters provides the most precise temperature
control, PLUS it dramatically increases the life of the heaters due to a
reduction in the thermal stress of expansion and contraction. Since the
contactor is switching at the zero crossing mark of a sinewave, there is no
electrical noise that might interfere with nearby electronics. Also, since the
calculated ON or OFF time period is measured in half sine waves, the contactor
will automatically adjust the total cycle time in order to maintain the best
ratio of ON/OFF to match your control input.