Number of Conversions

0

200

400

600

800

1000

Conversion Time: 140 s

m

Conversion Time: 1.1ms

Conversion Time: 8.244ms

INA231

SBOS644 – FEBRUARY 2013

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Averaging and Conversion Time Considerations

The INA231 has programmable conversion times for both the shunt voltage and bus voltage measurements. The

conversion times for these measurements can be selected from as fast as 140

μs to as long as 8.244 ms. The

conversion time settings, along with the programmable averaging mode, allow the INA231 to be configured to

optimize the available timing requirements in a given application. For example, if a system requires that data be

read every 5 ms, the INA231 can be configured with the conversion times set to 588

μs and the averaging mode

set to 4. This configuration results in the data updating approximately every 4.7 ms. The INA231 can also be

configured with a different conversion time setting for the shunt and bus voltage measurements. This type of

approach is common in applications where the bus voltage tends to be relatively stable. This situation allows for

the time spent measuring the bus voltage to be reduced relative to the shunt voltage measurement. The shunt

voltage conversion time can be set to 4.156 ms with the bus voltage conversion time set to 588

μs, and the

averaging mode set to 1. This configuration also results in data updating approximately every 4.7 ms.

There are trade-offs associated with the conversion time settings and the averaging mode used. The averaging

feature can significantly improve the measurement accuracy by effectively filtering the signal. This approach

allows the INA231 to reduce noise in the measurement that may be caused by noise coupling into the signal. A

greater number of averages enables the INA231 to be more effective in reducing the noise component of the

measurement.

The conversion times selected can also have an impact on the measurement accuracy; this effect can be seen in

Figure 21. Multiple conversion times are shown to illustrate the impact of noise on the measurement. In order to

achieve the highest accuracy measurement possible, use a combination of the longest allowable conversion

times and highest number of averages, based on the timing requirements of the system.

Figure 21. Noise vs Conversion Time

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