AD8-16 ISA Eight Bit A/D Converter

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  • 16 Single-ended or 8 differential analog inputs
  • Eight-bit resolution
  • Over 16,000 conversions per second
  • Programmable scan rate and voltage ranges
  • Two 8-bit analog outputs
  • Three programmable counter/timers
  • Eight digital inputs
  • Eight digital outputs
  • +5V output, 1 amp, fused
  • Designed, made, supported, and manufactured in the USA
Last updated on November 2, 2023, 6:28 pm


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Model AD8-16 (alternate part number ADA-8) is an economical, multiplexed, eight-bit Analog-to-Digital Converter (A/D) and Counter-Timer card for ISA-bus computers. It accepts up to eight differential or 16 single-ended analog inputs (jumper configured). AD8-16 requires a full-size expansion slot. All connections are made through a standard 50-pin connector. Base I/O address selection is via dip switch.

Analog inputs are multiplexed, amplified, held by a sample and hold amplifier, and then digitized by an eight-bit A/D converter. Amplifier gain is selected by software and can differ from channel to channel.

Full scale voltage ranges are ±128 mV, ±5V, 0-255mV, and 0-10V. When operating in the bipolar ranges, the digital output is available in 2’s complement or offset binary format. The end-of-conversion signal can be used to interrupt the computer when configured by jumper. You can select from IRQ levels 2-7. The interrupt request is automatically cancelled when the A/D data are read.

There are two 8-bit Digital-to-Analog converters on this card. These D/A’s output ranges are -10V to +10V and are intended to drive 10 kilohm or greater load. Maximum output current is 5 mA.

Model AD8-16 also accepts up to eight TTL-level or switch inputs. High inputs may be from 2.5 to 24 VDC or an “open.” All digital inputs are pulled up to 5 VDC by 1 kilohm resistors on the card. Low inputs should not exceed 0.8 VDC.

This card also provides eight discrete digital outputs. Each output can sink up to 24 mA with zener diode protection at 5.6 VDC. At system turn-on or reset the digital outputs are tri-stated and remain so until the computer writes to them. For interface to your application program, there are also two highly useful capabilities: Digital Output Read which allows a bit-by-bit readback of the current digital output byte and Command Readback which provides readback of the Control Register.

Model AD8-16 also contains an 8254 timer-counter consisting of three 16-bit counters. These counters may be loaded and read by software. You have complete ability to configure gates, clocks, and outputs either at the I/O connector or via jumpers on the card. A clock at 1/2, 1/4, 1/8 or 1/16 the computer clock rate is available for counter operation. Also, the color oscillator frequency can be used. Alternatively, an external clock may be applied via the I/O connector.




Drivers and Downloads

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

Information about our Free Software packages:

ACCES is proud to provide a full suite of software support with every Data Acquisition product. We are committed to supporting the most popular operating systems and platforms for our customers. Currently we are actively supporting XP -> 10, both 32 & 64 bit, including “Server 2008,” “Embedded,” and “Compact” flavors for all plug-and-play products including PCI, PCI Express, USB, and more. Many products continue to ship with support for additional operating systems such as DOS, Windows 95, 98, Me, NT4, and 2000.


Among the software we deliver with our products are sample programs in a wide variety of programming languages. These samples are used to demonstrate the software interfaces to our products — and many can be used as-is in your production environments, or to test functionality of the devices out-of-the-box. We’re currently actively supporting sample programs in Microsoft Visual C#, Visual Basic, Delphi, and Visual C/C++, with many devices including samples in Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and many demonstration VIs for our devices.


Drivers for various operating systems are also provided, including active support for Windows XP -> 10 — all in both 32-bit and 64-bit flavors, and including consumer, server, and embedded varieties — as well as the 2.6 and newer Linux kernels and recent OSX / macOS versions. Many products continue to ship with driver support for Windows 95, 98, Me, NT4, and Windows 2000, but support for these operating systems is considered deprecated.

Setup Programs and Utilites

Our Data Acquisition devices also include a graphical setup utility that walks you through the process of configuring any option jumpers or switches on the device, as well as explaining a little about the various connectors present.

Many devices also include utility programs – little tools to make your use of the device easier, such as EWriter, a program that allows you to read and write data in the user-accessible EEPROM locations on all our USB data acquisitition products; or WinRISC, a “Really Incredibly Simple Communications” terminal program that lets you get started instantly with serial devices.

“Register Level” Documentation

Besides all this software in all these languages and operating systems ACCES has a policy of open and transparent development: none of our lowest-level “register” interfaces are hidden from you — we document every register in every bus card, every command in every serial board, and every usb control transfer in every USB Data Acquisition board. These lowest-level interfaces allow you to develop for our products in ANY operating system or language, regardless of our actively supporting it or having a driver for it. We have customers actively developing in ADA, Android, Python, Java, MATLAB, Solaris, and more, just by referring to our complete low-level interface documentation! And we provide the full source code to all of our drivers, regardless of operating system, to give you an even bigger head start in your own development tasks.

No Fees or Royalties

All of this software is provided at no additional charge, and is licensed under any of a variety of flexible — and royalty free — options. Check out our software license explanation if you’d like more information.

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

  • No. of Channels: Eight differential or 16 single-ended inputs.
  • Voltage Ranges: Software selectable, ±128 mV or 0-255 mV w/1 mV resolution, ±5V or 0-10V w/39 mV resolution.
  • Overvoltage Protection: ±40 VDC, single channel.
  • Input Impedance: 10 Megohm
  • Accuracy: ±0.4% ±1 count.
  • Linearity: ±1 count.
  • Resolution: 8 bit binary.
  • Temperature Coefficient: Zero and gain stability each ±1 LSB over full operating temperature range.
  • Throughput: 16,600 conversions/second maximum.

Analog Outputs

  • No. of Channels: 2
  • Output Voltage Range: ±10 VDC.
  • Resolution: 8 bit binary.
  • Output Load: 5 mA maximum.
  • Accuracy: ±0.4% ±1 bit.

Digital Inputs

  • No. of Inputs: 8 TTL- and switch-compatible.
  • Inputs pulled up to +5 VDC by 1 Kilohm resistor.
  • Logic Low: 0 to 0.4 VDC.
  • Logic High: 2.4 to 24 VDC.

Digital Outputs

  • No. of Outputs: 8, TTL/DTL compatible. Outputs are tri-stated at power on and at reset. Zener diode protected at 5.6 VDC.
  • Logic Low: 0 to 0.4 VDC at 24 mA sink current
  • Logic High: 2.5 to 5.0 VDC at 10 mA source current.


  • Level: Jumper selectable, levels 2-7.
  • Enable/Disable: Interrupt generated by completion of A/D conversion. Interrupt cancelled when A/D data are read or when there is a computer write to base address plus 1 (reset interrupt request).


  • No. of Counters: Three independent, 16-bit, fully programmable.
  • Clock: Either internal derived from computer clock (or color oscillator frequency) divided by 1/2, 1/4, 1/8, or 1/16 or from external clock source.
  • Drive Capability: 5 LSTTL loads. (2.2 mA at 0.45 VDC).
  • Input Load (Gate and Clock): ±10 mA, TTL/CMOS compatible.
  • Input Clock Frequency:10 MHz max.
  • Active Count Edge:Negative edge.
  • Clock Pulse Width: 50 nSec high / 50 nSec low min.

Power Required

  • +5 VDC at 0.5 A.
    +12 VDC at 20 mA.
    -12 VDC at 20 mA.


  • Operating Temperature Range: 0° to 60°C.
  • Storage Temperature Range: -40° to +100°C.
  • Humidity: 5% to 90% RH, non-condensing.


  • 13.1 inches (333mm), plugs into a “long slot” in PC

Regulatory Compliance

  • This product is in full compliance with CE requirements.
  • MOQ’s may be required.
ModelDescriptionPrice (USD)

8 bit, 16 SE/8 Differential Input A/D ISA Card

CAB50F-6 50-pin ribbon cable with female header connectors, 6 feet long $30
STB-50 DIN-rail mountable screw terminal board with latches for 50-pin header $44
STA-50 50 screw terminal board for wiring and ribbon cable connectors for outputs to ACCES Cards. These cards are provided with stand-offs and easily install in a T-Box. $79
STA-112 112 screw terminal board for wiring and ribbon cable connectors for outputs to ACCES Cards. These cards are provided with stand-offs and easily install in a T-Box. $79
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Unlike the STA-xx line of screw terminal adapters, the terminals on these products have pin-names instead of numbers associated with them. $115
T-BOX Steel enclosure for STA-xx cards.  $49
CAB50-6 Ribbon cable with 50-pin female edge connector on one end and 50-pin female connector on the other end $30