Current sensing configuration
UM1955
8/28
DocID028405 Rev 1
2.4
Software and measurements
The output voltage of the instrumentation amplifier is connected to pin A2 of the Arduino
UNO R3 connector. The X-CUBE-ANALOG1 software, available on www.st.com, allows
users to measure this voltage.
Note that with this predefined configuration, it is possible to measure up to 2.08 A. If a
higher current is drawn through the application, the operational amplifier will be saturated
and thus its output voltage will not reflect the real current.
The following table shows the correspondence between measured current, output voltage
and LSB on ADC.
Table 1. Output parameter values for current sensing configuration
Current (A)
Output voltage of
operational amplifier
Voltage after divider
bridge (at A4 node)
Number of LSBs with
12-bit ADC
0.1
240 mV
159 mV
197
0.2
480 mV
317 mV
394
0.5
1.20 V
793 mV
985
1.0
2.40 V
1.586 V
1969
1.5
3.60 V
2.380 V
2954
2.0
4.80 V
3.173 V
3938
