ZiLOG Z80-AIO Hardware User Manual page 17

Operation by making a "pseudo differential" connection.
involves sensing the ground at the signal source rather than
To use this method, all input Signals must be
on the sanie ground System at their source.
been removed and JPl is installed.
3.5.4 Input System Low Level Operation
When it is desired to operate the input systein
instrumentation amplifier at other than unity gain for low
is all that is required.
resistor R9 form this resistance.
setting resistor can be calculated from the following
formula:
Stable (10 ppm/deg C) wire-wound resistors should be used.
Increasing the amplifier gain also increases its settling
time. As a result, the System delay timer must be extended
by increasing the value of R15 and the optional parallel
resistor R14. Delays and values of R15 versus Gain are shown
in Table 3.5.4.1.
Amplifier Gain
l
10
100
1000
TABLE 3.5.4.1. Delay Time vs. Amplifier Gain.
3.5.5 Input System Application
The data acquisition System, incorporated into the AIO or
and the Start of data conversion.
be increased by the addition of an external resistor and
This procedure is described in the low level
Operation section.
R8 and the optional parallel
The value of the gain
20K
R =
G - l
Delay Time (us)
20
30
40
100
This
R15 (+20%)
19K