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ISA Bus 12-Bit 8-Input Programmable-Gain A/D Converter and Counter/Timer Card


  • Eight single-ended or differential analog inputs
  • 12-bit resolution
  • Nine software programmable voltage ranges
  • Programmable scan rate
  • Foreground/background operation
  • Three 16-bit counter/timers for event counting, pulse and waveform generation, and frequency measurement.
  • Seven bits of digital I/O
  • Can assert interrupts
  • Designed, made, supported, and manufactured in the USA
The AD12-8G is an eight-channel, 12-bit, analog/digital card for use in IBM Personal Computers. It is a 3/4 length card that can be installed in expansion slots of ISA-bus computers. All connections are made through a standard 37-pin D type connector that projects through the rear of the computer.


The input analog channels are individually switch selectable for either differential or single-ended input signals. A choice of nine software-selectable voltage ranges are available and the card can withstand ±30 VDC overload and transients of several hundred volts. The A/D converter is a successive-approximation type with solid-state input analog multiplexer and sample and hold amplifier. A/D conversion time is typically 25 microseconds.


This card also contains a type 8254 counter/timer chip which has three 16-bit counters. These counters can be used as an A/D pacer clock and/or can be used to measure pulse width, count events, measure or generate frequencies, etc. An on-board 1 MHz crystal controlled clock is hard-wired to one counter input and the clock inputs to the other two counters are available at the I/O connector. All the gate inputs and counter outputs are accessible at the I/O connector.


AD12-8G also can accept three bits of digital input and can provide four bits of digital output both in standard TTL/CMOS logic levels. One of these outputs, for example, can be used to initiate an interrupt upon end of A/D conversion. Jumper positions on the card provide means to assert interrupts on your choice of levels 2 through 7.

Available Reference Manuals

Available Software Downloads

Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.


Analog Inputs

  • Number of Channels: Eight differential or single- ended, individually DIP switch selectable for S.E. or Diff.
  • Voltage Range: Programmable, ±5V (default), ±10V, ±0.5V, ±0.05V, ±0.01V, 0-10V, 0-1V, 0-0.1V, 0-0.02V.
  • Overvoltage Protection: ±30 VDC.
  • Input Impedance: 10 Megohm or 125 nA at 25°C.
  • Common Mode Rejection Ratio: 90 db when gain = 1; 125 db when gain = 100.
  • Multiplexer/Sample and Hold Settle Time: When gain = 1 : 30 µSec; When gain = 100 : 95 µSec
  • Overall Accuracy: ±0.05% of full scale.
  • Linearity: ±1 LSB.
  • Resolution: 12 bit binary.
  • A/D Trigger Source: Software selectable, external trigger, programmable timer, or program command.
  • Conversion Time: 35 µSec max., 25 µSec typical.
  • Temperature Coefficient: ±10 µV per °C zero stability. ±25 µV per °C gain stability.

Digital I/O

  • Logic Low: 0 to 0.8V at -0.4 mA max.
  • Logic High: 2.4 to 5V at 20 µA max.
  • Logic Low: 0 to 0.5V at 8 mA sink.
  • Logic High: 2.4 to 5V at 0.4 mA source.

Counter Timer

  • Type: 8254 type programmable interval timer, three 16-bit counters.
  • Drive Capability: 5 LSTTL loads (2.5 mA at 0.80 VDC).
  • Input Load (Gate and Clock): ±10 µA, TTL/CMOS compatible.
  • Input Clock Frequency: 10 MHz max.
  • Active Count Edge: Negative edge.
  • Clock Pulse Width: 30 nSec high / 50 nSec low min.


  • Level: Jumper selectable, levels 2-7.
  • Enable/Disable: Via software. (INTE bit of Control Register. Service routines should acknowledge and re-enable interrupts.)
  • Source: External, positive edge triggered.


  • Operating Temperature Range: 0° to 60°C.
  • Storage Temperature Range: -40° to +100°C.
  • Humidity: 0 to 95% RH, non-condensing.

Power Required

  • +5 VDC at 180 mA max.
  • +12 VDC at 500 mA max.


  • 9.0 inches long. (229mm)
  • Requires full-size slot.

Regulatory Compliance

  • This product is in full compliance with CE requirements.

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