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Isolated Digital Input Card


The IDI-48AC fully-loaded with all options
  • Individually-isolated digital inputs for up to three 16-bit groups
  • Polarity-protected input voltage amplitudes to 28V and 60V
  • 60Vrms Isolation, Channel-to-Channel and Channel-to-Host PC
  • On-card shields prevent accidental contact with user voltages
  • Some models can generate interrupts when input bits change state.
  • Output connectors via on-card ribbon-cable headers
  • Lower cost per point than externally-racked solid-state relay modules

IDI-xx Series cards provide individual-input optical isolation and accept as many as 48 parallel, differential digital inputs at voltages up to 60 VDC. Protection circuits are included in case of accidental polarity reversal of input connections. These cards provide a much lower cost per point than externally-mounted, optically-isolated, solid-state modules or PLC's. Input connections are via ribbon-cable headers on the cards and a tie-down bar is included to provide strain relief for those cables. IDI-Series cards are especially useful in applications where high common mode external voltages are present as found in factory automation, energy management, security systems, and process monitoring applications. In addition to protecting your computer from accidental contact with high external voltages, this isolation eliminates troublesome ground loops.

If your installation will be in an electrically noisy area, then you may want to consider using a protective jacket on the ribbon cables. We optionally offer "Zippertubing" shielded protective jackets. (These are referred to as ZTR-xx on our price list.) The jacket uses 10-mil. high temperature PVC material laminated to a 1-mil. shield of aluminum foil/polyester and groundable through a tinned copper braid.

48-Bit, 32-Bit, and 16-Bit versions are available. The latter two models are de-populated versions of the 48-bit card. Further, letters are appended to the model numbers to signify options included in the card. (See table)

Model Number of Bits Maximum Input Voltage Change of State Interrupt Capability
IDI-16A 16 28 V No
IDI-16AC 16 28 V Yes
IDI-16B 16 60 V No
IDI-16BC 16 60 V Yes
IDI-32A 32 28 V No
IDI-32AC 32 28 V Yes
IDI-32B 32 60 V No
IDI-32BC 32 60 V Yes
IDI-48A 48 28 V No
IDI-48AC 48 28 V Yes
IDI-48B 48 60 V No
IDI-48BC 48 60 V Yes


Optional change-of-state detection capability provides means to automatically interrupt the host computer in real time. When activated, latched interrupt requests can be generated when one or more bits change state. That interrupt, in turn, can be used by your application program to poll the inputs, then signal an alarm, and/or initiate scan of other I/O points that have not been previously activated. This can greatly simplify your application program and eliminate need for the application program to continuously poll inputs. Interrupts IRQ 2 through 7, 10-12, and 14-15 can be selected by jumper installation on the card. An on-board microcontroller on "C"-version cards provides capability for a variety of modes of operation as follows:

  • Channels 0-15 active only.
  • Channels 16-31 active.
  • Channels 32-47 active.
  • Change-of-state interrupt active on channels 0-15.
  • Change-of-state interrupt active on channels 16-31.
  • Change-of-state interrupt active on channels 32-47.
  • Periodic scan of all active input channels.

That last operation mode can occur concurrently with Change-of-State operations. It makes use of an on-board crystal oscillator and a microcontroller and provides means to verify proper system operation, on a timed basis. This is useful in situations where there has not been any bit state changes for an extended period of time and you wish to confirm that the system is still operating properly.


Digital Inputs

  • Logic 0: Open or 1.5VDC maximum
  • Logic 1: 28V Models: 3.5V min. at 0.6 mA, 28V max. at 13 mA
    60V Models: 2.4V min. at 2.0 mA, 60V max. at 2.3 mA.
  • Frequency Response:
    • 28V Models: Up to 5 KHz
    • 60V Models: Up to 10 KHz
  • Isolation: 60 Vrms channel-to-channel and channel-to-computer.
    (Note: Alternate wires in the ribbon cables are not connected at the card, thus providing bit- to-bit isolation higher than that normally provided by ribbon cables.)


  • Operating Temperature: 0 to 60 degree C.
  • Storage Temperature: -20 to 100 degree C.
  • Humidity: 0% to 90% non-condensing.
  • Size: 13.310 inches. Install in a full-size slot.

Power Requirements

  • 5 VDC at 300 mA typical for fully populated 48 bit card

Regulatory Compliance

  • This product is in full compliance with CE requirements.

Part NumberPrice(USD)
View / Download Manual (in .pdf format)
Acquisition Control Communications Engineering / Systems
USA Office

Address: 1480 Gulf Road, Suite 837,
PO Box 1364
Point Roberts, WA 98281

Western Canada - Vancouver BC

Tel:1.800.663.6001 or 1.604.925.6150
Address: 2454 Haywood Ave
West Vancouver, BC V7V 1Y1

Eastern Canada - Markham, Ontario

Tel:1.800.465.0164 or 1.905.513.7027