BMA400 Right way to calibrating it

[mladen_miljic]

I have two questions. In short:

1. Assuming the sensor is used on elevators and moves up and down, how often shell we calibrate it?

2. Once I have the offset, can I save it on the BMA400, so I get calibrated values right away, or do I have to process the offset in my application (like, adding/ substracting the offset each time I read the acceleration values)?

Long:

On Question 1: From the design guide:

1. Place your sensor (the system with the sensor inside) on a well-defined surface, for example, a horizontal table. The expected sensor output for the x/y-axis should be 0 mg.
2. Set the sensor to the lowest g-range (2G)
3. Measure the sensor output to ensure the sensor is fully at rest, without vibrations, inclinations, big temperature changes or strong VDD fluctuations. It is advisable to take several values and generate the average over the values (e.g. 1000 values).
4. Consider the resolution of BMA400, and save the offset in LSB or mg.
5. The offset subtracted from the future accelerometer sensor data.

How to understand 4: Where to save it?
How to understand 5: Means, I have to substract in application implementation?

On Question 2: From the design guide: "..it is preferable to calibrate the accelerometer after assembling the device into the device housing. Therefore, it is recommended to calibrate the sensor after assembling the device into the device housing."

It does not say if once is ok or it shall be repeated.

Appreciate your help very much.

[BSTRobin]

Hello mladen_miljic,

During calibration, it is necessary to ensure the sensor is fully at rest.

You can save the offset in the application(like Flash memory) and subtract it every time the application uses it;

Yes, it is recommended to calibrate the sensor after assembling the device into the device housing.

[mladen_miljic]

Thanks a lot Robin.

1. Do you think I need to calibrate the sensor frequently, or is one time calibration enough?

2. So, I understand, the Chip itself does not support offset handling, so I have to take care about it completely,.

Best,

Mladen

[BSTRobin]

Hello mladen_miljic,

1. Normally, calibration only needed to be done one time.
2. The usual method of use is: save the offset in the application(like Flash memory) and subtract it every time the application uses it.