User Manual

RedLab 1208LS User's Guide Functional Details
19
-3V
-11V
-7V
+/-7V
8V Differential
-11V
-7V
-3V
3V
CHLO
CHHI
Measured Signal
Figure 8. Differential voltage example: common mode voltage of -7 V
Since the analog inputs are restricted to a −10 V to +20 V signal swing with respect to ground, all ranges except
±20V can realize a linear output for any differential signal with zero common mode voltage and full scale signal
inputs. The ±20 V range is the exception. You cannot put −20 V on CHHI and 0 V on CHLO since this violates
the input range criteria.
The table below shows some possible inputs and the expected results.
Table 3-1. Sample inputs and differential results
CHHI CHLO Result
-20 V 0 V Invalid
-15 V +5 V Invalid
-10 V 0 V -10 V
-10 V +10 V -20 V
0 V +10 V -10 V
0 V +20 V -20 V
+10 V -10 V +20 V
+10 V 0 V +10 V
+15 V -5 V +20 V
+20 V 0 +20 V
For more information on analog signal connections
For more information on single-ended and differential inputs, refer to the Guide to Signal Connections (this
document is available on our RedLab CD (root directory))
Digital I/O terminals (Port A0 to A7, and Port B0 to B7)
You can connect up to 16 digital I/O lines to the screw terminal containing pins 21 to 40 (Port A0 to Port A7,
and Port B0 to Port B7.) Refer to the pinout diagrams on page 16 for the location of these pins. You can
configure each digital port for either input or output.
When you configure the digital bits for input, you can use the digital I/O terminals to detect the state of any
TTL level input. Refer to the switch shown in Figure9 and the schematic shown in Figure 10. If the switch is set
to the +5 V input, Port A0 reads TRUE (1). If you move the switch to GND, Port A0 reads FALSE.