Connecting The Analog Input Pins - Real Time Devices AD1200 User Manual

Connecting the Analog Input Pins
Connect the high side of the analog input to one of the analog input channels, AINI through AIN16, and
connect the low side o an ANALOG GND (pins 18 and 2A-22 onP2). Figure 2-2 shows how rhese connections are
made.
NOTE: It is good practice to connect all unused channels to ground, as shown in the following diagrams.
Failure to do so may affect the accuracy of your results.
I 200
I ' O C O N N E C T O R
P 2
I
I
Fig.2-2 - Analog Input Connections
Connecting the Trigger In and Trigger Out Pins, Cascading Boards
The 1200 board has an external trigger input (P2-39) and output (Y243) so that conversions can be started
based on external events, or so that two or more boards can be cascaded and run synchronously in a "master/slave"
configuration. By cascading two (or more) boards as shown in Figure 2-3, they can be triggered to start an A/D
conversion at the same time (sampling uncertainty is less ttran 50 nanoseconds). When you cascade boards, be sure
to set each board for a different base address (see Chapter l), or system contention will result.
NOTE: When cascading boards, the sampling uncertainty is less than 50 nanoseconds. If this level of uncer-
tainty is too geat for your application, you can connect the trigger signal to the rigger input of each board. In this
configuration, the boards are not cascaded, but rather driven by the same trigger pulse at the same time, and the
sampling uncertainty is reduced to less than 5 nanoseconds.
If you apply an external trigger to the board's nigger in pin, note that a jumper should be instaued on ET on p7
(see Chapter 1). The board is triggered on the positive edge of the pulse and the pulse duration should be at least 100
nanoseconds.
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24