Keithley / MetraByte DAS-8 Analog-to-Digital Converter

The Keithley/MetraByte DAS-8 is a 12-bit successive approximation analog-to-digital converter for data acquisition on ISA bus PCs. It has eight configurable analog input channels, fixed ±5V range, and 25 µs typical conversion time, delivering up to 4 kS/s sampling rates. The board integrates an Intel 82C54 programmable counter-timer with three internal 16-bit counters for event counting, pulse generation, and timing measurements. Seven bits of TTL digital I/O - comprising a 4-bit output port and 3-bit input port - enable direct hardware interfacing. A precision +10.00V (±0.1V) reference voltage output is derived from the ADC reference and available on the rear D-type connector. The DAS-8 operates from the ISA bus clock (4.77 to 8 MHz) and supports hardware interrupts on levels 2–7. Base address defaults to 768 decimal (0x300 hex) but is user-reconfigurable via DIP switches.

Technical Specifications

Analog Input Channels: 8

ADC Resolution: 12-bit

Conversion Method: Successive approximation with sample and hold

Input Range: ±5V (fixed)

Conversion Time: 25 µs typical, 35 µs maximum

Maximum Sampling Rate: 4 kS/s

Counter/Timer: Intel 82C54 with three 16-bit counters

Clock Source: ISA bus clock (4.77 MHz, 6 MHz, or 8 MHz)

Digital I/O: 7-bit TTL (4-bit output, 3-bit input)

Reference Voltage Output: +10.00V (±0.1V)

Interrupts: Hardware interrupts, levels 2–7

Base Address: 768 decimal (0x300 hex), DIP-switch configurable

Key Features

Single-ended or differential analog input configuration

Programmable interval timer supports event counting, frequency measurement, and waveform generation

TTL digital I/O for direct sensor and control interfacing

Precision reference voltage available to external circuitry

ISA bus integration for legacy PC systems

Typical Applications Data logging, industrial process monitoring, real-time signal acquisition, event timing and counting, and periodic sampling with software control via DriverLINX or compatible data acquisition packages.

Compatibility & Integration The DAS-8 operates under MS-DOS and supports VIEWDAC, EASYEST LX, EASYEST AG, ASYST (version 2.10 or greater), DriverLINX, and Daqarta for DOS software environments.