The following product line is being discontinued. A recommended replacement is shown at:

4-20mA contactor

4-20mA activated, single phase, 25 or 40 amp, din rail contactor
  • Accepts a 4-20mA analog process input and provides a high speed, time proportional AC output (TPO)
  • 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 1/4 second, OFF for 1/4 second...
   16mA = 75% = heater is ON for 375 msec, OFF for 125 msec, ON for 375 msec...
   17.5mA = 84.375% = heater is ON for 422 msec, OFF for 88 msec, ON for 422 msec...
   20mA = 100% = heater is ON
Note: This 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.


  • Maximum Surge Survival™ technology -- triple layer, voltage surge protection
  • Green LED for input status
  • Thermally optimized heat sink permits edge-to-edge installations on a din rail
  • Built-in snubber circuit
  • Zero crossing activation -- low EMI, low noise to nearby electronics
  • Internal 50A thyristors for high inrush capability
  • 4000 volt isolation, 1400 blocking voltage
  • 1000 volt per microsecond immunity
  • Highest thermal efficiency -- less than 1.2 watts dissipated per amp switched.
  • UL, CSA, CE
  • Industry standard A1, A2, L1, T1 terminal numbers
  • High density design permits more amps per square inch
DDA solid state contactor
DDA solid state contactor

Part Number

DMA-6V25   25A, 660V max, 4-20 mA analog input activated Buy
DMA-6V40   40A, 660V max, 4-20 mA analog input activated Buy

DDA temperature curver


Part Number Line Voltage Range (VAC) Load Current Range (A RMS) Max Voltage Drop at 20mA
DMA-6V25 24-660 .10-25 6VDC
DMA-6V40 24-660 .10-40 6VDC
Off-State dv/dt 1000 v/µs
Isolation 4000 volts
I²T fuse 50A or less, for example: Bussman FWP-50A14F, FWP-40A14F, FWP-30A14F. Ferraz B093910, M330015, K330013
Turn-on time <8.3 ms at 60hz
Turn-off time <8.3 ms at 60hz
Terminals Will accept #24-#10 AWG wire. Torque: 7-9 inch lbs.
Multiple units Can one 4-20mA output from a PLC activate several units? Yes, determine the compliance of the 4-20mA such as 20 volts. Power-io has a 6 volt drop. So, you could activate 3 units when wired in series (not parallel). OR, your PLC may say 20mA into a 1K max load resistance. 20mA*1K = 20 volts compliance. OR, Ohm's law: 6V (drop) / .020 (mA) = 300 ohm per Power-io unit.
DDA size
Zoomed in product picture
Three, din rail solid state contactors and their labels
Schematic of the internal design
4-20 input contactor schematic