Datasheet

Gain Error (%) = 100 (100 Gain Error Factor)- ´
10,000
(9 R + 10,000´
S
)
20,000
(17 R + 20,000´
S
)
5000
(9 R + 5000´
S
)
10,000
(13 R + 10,000´
S
)
1000
R + 1000
S
Gain Error Factor =
(1250 ´
INT
R )
(1250
S
´ ´ ´R ) + (1250 R ) + (R R )
INT S INT
INA210, INA211
INA212, INA213
INA214
www.ti.com SBOS437E –MAY 2008–REVISED JUNE 2013
The amount of variance in the differential voltage present at the device input relative to the voltage developed at
the shunt resistor is based both on the external series resistance value as well as the internal input resistors, R3
and R4 (or R
INT
as shown in Figure 24). The reduction of the shunt voltage reaching the device input pins
appears as a gain error when comparing the output voltage relative to the voltage across the shunt resistor. A
factor can be calculated to determine the amount of gain error that is introduced by the addition of external series
resistance. The equation used to calculate the expected deviation from the shunt voltage to what is seen at the
device input pins is given in Equation 1:
where:
R
INT
is the internal input resistor (R3 and R4), and
R
S
is the external series resistance. (1)
With the adjustment factor equation including the device internal input resistance, this factor varies with each
gain version, as shown in Table 1. Each individual device gain error factor is shown in Table 2.
Table 1. Input Resistance
PRODUCT GAIN R
INT
(kΩ)
INA210 200 5
INA211 500 2
INA212 1000 1
INA213 50 20
INA214 100 10
Table 2. Device Gain Error Factor
PRODUCT SIMPLIFIED GAIN ERROR FACTOR
INA210
INA211
INA212
INA213
INA214
The gain error that can be expected from the addition of the external series resistors can then be calculated
based on Equation 2:
(2)
For example, using an INA212 and the corresponding gain error equation from Table 2, a series resistance of
10Ω results in a gain error factor of 0.982. The corresponding gain error is then calculated using Equation 2,
resulting in a gain error of approximately 1.77% solely because of the external 10Ω series resistors. Using an
INA213 with the same 10Ω series resistor results in a gain error factor of 0.991 and a gain error of 0.84% again
solely because of these external resistors.
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