Current sensing configuration

UM1955

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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