Z-World eDisplay OP7200, Руководство пользователя

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User’s Manual 23
The input circuit of the OP7200 was designed to use the differential mode in a unique way
to support measuring voltages in an equal range above and below ground. This method
also requires you to move the 0
Ω
jumper (see Figure 10) on the header associated with
the A/D converter inputs (JP4, JP5, JP6, or JP7) from analog ground to the 2.048 V refer-
ence voltage. The input is connected to the even-numbered channel, and the odd-
numbered channel is tied to analog ground. Table 4 provides the bipolar voltage ranges for
this setup.
3.4.2 Analog Current Measurements
The A/D converter inputs can also be used with 4–20 mA
current sources by measuring the resulting analog volt-
age drop across a 100
Ω
1% precision resistor placed
between the analog input and analog ground as shown
in Figure 12.
The single-ended scale of 0–2.56 V with a gain of 8 is
used to get an A/D current conversion of 12.5 µA/tick.
Table 4. Bipolar Voltages
Min. Voltage
(V)
Max. Voltage
(V)
Amplifier
Gain
mV per Tick
-20.0 +20.0 1 10
-10.0 +10.0 2 5
-5.0 +5.0 4 2.5
-4.0 +4.0 5 2.0
-2.5 +2.5 8 1.25
-2.0 +2.0 10 1.00
-1.25 +1.25 16 0.625
-1.0 +1.0 20 0.500
Figure 12. Resistor for 4–20 mA
Current Sources
100 W
1%
AIN0–AIN7
AGND