Measurement Computing DAC488 v.1 - Manual (Page 7)

DAC488 User’s Manual DAC488 Overview 1
DAC488 Overview 1
Introduction…… 1
Accessories…… 2
Specifications…… 2
Digital I/O…… 2
Analog Output…… 3
IEEE 488…… 3
General…… 4
Introduction
The DAC488 is a multiple output Digital-to-Analog Converter (DAC) interface for the IEEE 488 bus. Each
port uses a 12-bit plus-sign D/A converter and is isolated from IEEE common and the other ports by up to
500 volts. Each port can be programmed for full-scale output of
±
1 volt,
±
5 volts and
±
10 volts. Voltage
values may be specified in volts or bits in increments of 1 part in 4096 plus-sign. The resolution of the
ranges is 250 µVolts, 1.25 mVolts and 2.5 mVolts respectively.
Four operational modes are available to allow each port to be controlled directly from the IEEE bus or in an
automatic manner. An internal 8,191 sample buffer is included which can be loaded with waveform
voltages. These voltages may then be output in sequence either on a periodic interval or in a triggered
fashion. The DAC488 sample buffer is automatically saved in Non-Volatile RAM (NV-RAM) as it is
loaded, allowing a once only configuration of the device for many applications. All configuration settings
may also be saved in Non-Volatile RAM for use as the permanent defaults.
Each of the ports can be triggered from three different sources: An external trigger, a trigger command, or a
Group Execute Trigger (
GET ) bus command. Since each port can be triggered independently, different
trigger sources may be selected for each port.
The interface also provides 8 TTL level digital inputs and 8 digital outputs. The digital outputs may be
internally configured as either TTL level or 100 mA outputs to allow interfacing with solenoids, relays or
other devices. An external trigger/SRQ input is also provided which can trigger the interface or generate an
SRQ on either a falling or rising edge of a TTL compatible signal. All digital signals as well as +5 Volts
and ground are accessible via a 20-pin card edge connector (Standard version) or a DB25 pin connector
(CE version) located on the rear panel.
Calibration may be done automatically by connecting the interface to a Keithley Model 199 DMM. No
mechanical adjustments are required. After calibration, a complete calibration report will be printed if the
interface is connected to an IEEE printer.
Throughout this manual, the term “DAC488” refers to either a DAC488/4 or a DAC488/2.