miniLAB 1008 User's Guide
Functional
Details
+4V
-4V
+4V
-4V
0V
CHLO
CHHI
+/-8V
8V Differential
Measured Signal
Figure 4-5. Differential voltage example: common mode voltage of 0 V
If you increase the common mode voltage to 11 V, the differential remains at ±8 V.
Although the [
common-mode v signal
] on each input now has a range of +7 V to
+15 V, both inputs still satisfy the -10 V to +20 V input requirement (see Figure 4-6).
+11V
+7V
+11V
+/-8V
+15V
8V Differential
CHLO
CHHI
Measured Signal
Figure 4-6. Differential voltage example: common mode voltage of 11 V
If you decrease the common-mode voltage to -7 V, the differential stays at ±8 V.
However, the solution now violates the input range condition of -10 V to +20 V. The
voltage on each analog input now swings from -3 V to -11 V. Voltages between -10 V
and -3 V are resolved, but those below -10 V are clipped (see Figure 4-7).
-3V
-11V
-7V
+/-7V
8V Differential
-11V
-7V
-3V
3V
CHLO
CHHI
Measured Signal
Figure 4-7. Differential voltage example: common mode voltage of -7 V
4-9