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AD1200 Reference
PC cards using them far ahead of any competition. The ADS574
has a conversion time of 25 microseconds and the ADS774 a
conversion time of 8 microseconds.
The AD converter takes an analog input voltage and
represents it as a 12 bit digital value. The analogue input signal
may be produced by vibration, pressure or temperature sensors
but as long as it is within +/-10 Volts the AD1200 series of
cards can convert the voltage to a 12 bit digital value. Low level
input signals can be amplified by a factor of 2, 4, 8, 10, 100 or
1000 to give 12 bit resolution from full scale signals as small as
2.5 millivolts.
The A/D system can be jumper set for 8 differential or 16
single ended input channels. It can be configured for unipolar,
positive only, inputs or bipolar, negative and positive, inputs.
The A/D conversion may be performed under programmed i/o,
interrupt driven input or via DMA, direct memory access, with
successive conversions being initiated either by the users
program, via the pacer clock or synchronised to external user
supplied signals.
Input Channel Selection.
_____________________ _
Whilst the AD1200 card has up to 16 input channels it has
only 1 A/D converter. The AD1200 series are configurable for
either 16 channels of Single Ended input, 16 channels of Pseudo
Differential Input or 8 channels of Differential Input. There is
only ONE A/D converter on the board and an analogue
multiplexer is used to route one of these 8 or 16 input channels
through the programmable gain amplifier to the A/D converter.
The analogue multiplexer is programmable, ie the input channel
is selected by the users software. Thus up to 16 voltage sources
can be permanently applied to the AD1200 series and the actual
channel to be converted be determined by the program the user
runs on the PC. The input channel is selected by writing to the
A/D Gain Channel Register, ADGCR, register 1.
When a new channel is selected the settling time to within
0.01% is 3.5 microseconds.
Page 10
Introduction
Chapter 1
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