Datasheet

INA117
SBOS154A
7
MEASURING CURRENT
The INA117 can be used to measure a current by sensing the
voltage drop across a series resistor, R
S
. Figure 4 shows the
INA117 used to measure the supply currents of a device
under test. The circuit in Figure 5 measures the output
current of a power supply. If the power supply has a sense
connection, it can be connected to the output side of R
S
to
eliminate the voltage-drop error. Another common applica-
tion is current-to-voltage conversion, as shown in Figure 6.
FIGURE 4. Measuring Supply Currents of Device Under
Test.
380kΩ
380kΩ
380kΩ
21.1kΩ 20kΩ
47
2
3
815
V– V+
V
2
V
3
V
O
= V
3
– V
2
6
200Ω
10Ω
10Ω
If offset adjust is also required,
connect to offset circuit, Figure 2.
CMR
Adjust
FIGURE 3. CMR Trim Circuit.
FIGURE 5. Measuring Power Supply Output Current.
380kΩ
20kΩ
380kΩ
380kΩ
380kΩ380kΩ
380kΩ
21.1kΩ
47
2
3
815
6
R
S
R
C
*
C
I
DUT+
I
DUT–
21.1kΩ
20kΩ
47
2
3
815
V–
V+
6
R
S
V– V+
Device
Under
Test
–V
S
+V
S
*Not needed if R is less than 20 —see text.Ω
S
(+200V max)
(–200V max)
V
O
= R
S
I
DUT+
V
O
= R
S
I
DUT–
R
C
*
380kΩ 380kΩ
380kΩ
20kΩ21.1kΩ
47
2
3
815
6
R
S
R
C
*
I
L
V– V+
±200V max
Load
Power Supply
Out
Sense
*R
C
= R
S
not needed if R
S
is less than 20Ω—see text.
Optional Load
Sense Connection
(see text)
V
O
= I
L
R
S