DM5210 analog input module 1-9 RTD Embedded Technologies, Inc.
8255
PORT A
( PA 0 - 7 )
V
G
PA
+5 V
PUL L - UP
PORT C
L OWE R
( PC0 - 3 )
V
G
CL
+5 V
PUL L - DOWN
1 0 K
1 0 K
PORT C
UP PE R
( PC4 - 7 )
V
G
CH
+ 5 V
Fig. 1-11 — Adding Pull-ups and Pull-downs to Digital I/O Lines
Gx, Resistor Configurable Gain
The 210/5210 has a resistor configurable gain circuitry, Gx, so that you can easily configure special gain settings
for a specific application. Note that when you use this feature, all of the input channels will operate only at your
custom gain setting. Gx is derived by adding resistors R1 and R2, trimpot TR3, and capacitor C21, all located in the
upper right area of the module. The resistors and trimpot combine to set the gain, as shown in the formula in Fig-
ure 1-12. Capacitor C21 is provided so that you can add low-pass filtering in the gain circuit. If your input signal is a
slowly changing one and you do not need to measure it at a higher rate, you may want to add a capacitor at C21 in
order to reduce the input frequency range and in turn reduce the noise on your input signal. The formula for setting
the frequency is given in the diagram. Figure 1-12 shows how the Gx circuitry is configured.
As shown in Figure 1-12, a solder short must be removed from the module to activate the Gx circuitry. This
short is located on the bottom side of the module under U11 (AD712 IC). Figure 1-13 shows the location of the
solder short.
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