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Overview
•
DAS-8/AO
— same as DAS-8/PGA with two 12-bit analog outputs
and onboard pacer clock for sample timing.
The DAS-8 Series features an 8-channel, 12-bit successive approximation
A/D converter with sample and hold. The full scale input of each channel
is fixed at ±5V on the DAS-8and DAS-8LT and software-programmable
on the DAS-8PGA and DAS-8/AO. The A/D conversion time is typically
25
µ
s (35
µ
s max.). Using the DriverLINX software supplied with the
board, throughputs of up to 4ksamples per second are attainable.
An onboard 82C54 programmable counter-timer provides periodic
interrupts for the A/D sample timing. In the DAS-8, this timer obtains its
input clock directly from the computer’s ISA bus clock (usually 4.77, 6,
or 8 MHz). The DAS-8/LT, DAS-8PGA, and DAS-8/AO have an onboard
1 MHz crystal. Two additional counters on the 82C54 are available for
event counting, pulse and waveform generation, frequency, period, and
pulse width measurements.
The 7 bits of TTL digital I/O consist of one 4-bit output port and one 3-bit
input port. In addition, a pre10.00V (±0.1V) reference voltage
output is derived from the A/D converter reference. This output can
source/sink 2mA.
A jumper-selectable external interrupt input selects any of the interrupt
levels (2 through 7) and allows interrupt routines to provide background
data acquisition or interrupt-driven control. The interrupt input can be
externally connected to the counter/timer or other trigger source.
The two 12-bit analog output channels of the DAS-8/AO are
independently switch-selectable to full-scale output ranges of ±10V, ±5 V,
±2.5V, 0 to +10V, 0 to +5V, or 4 to 20mA. Simultaneous update of both
channels is supported in DriverLINX.
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