- 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
12mA = 50% = heater is ON for 250 msec, OFF for
250 msec, ON for 1/4 second, OFF for 1/4
16mA = 75% = heater is ON for 375 msec,
OFF for 125 msec, ON for 375 msec...
84.375% = heater is ON for 422 msec, OFF for 88 msec, ON for 422
20mA = 100% = heater is ON
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.