Zilogic Systems ZIO User Manual page 17

ZIO, Motherboard User Manual
To better understand the operation of the circuit, the circuit is shown with the internal pull-up
resistor on the Sensor signal, in the following diagram.
Using superposition, the voltage at Sensor 0 is given by the following formula.
Voltage at Sensor 0 = 1.5V + V
As V decreases from 3V to -3V, the voltage at the Sensor 0 decreases linearly from 3V to 0V, and
i
the raw value from 0xFFFF to 0.
V (V)
i
3
0
-3
Voltage measurement, -15V to +15V.
in the range -15V to +15V. The input voltages and the corresponding raw values is shown in the
table below.
V (V)
i
15
0
-15
4.3. Non-resistive Sensors
Transistor Buffer.
parameter being measured. Such sensors cannot be directly connected to the Sensor N signal,
due the signal being pulled-up to 3V using a 10K resistor. A transistor buffer can be used to
overcome this problem. The transistor isolates the sensor from the pull-up. A transistor buffer
circuit is shown below.
/ 2
i
Voltage at Sensor 0 (V)
3
1.5
0
The following circuit can be used to measure voltages
Voltage at Sensor 0 (V)
3.0
1.5
0.0
Non-resistive sensors usually generate a voltage signal that varies with the
Zilogic Systems
Rev. 2.0
Raw Value
0xFFFF
0x7FFF
0
Raw Value
0xFFFF
0x7FFF
0
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