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Hey,

I am trying to understand the terms In-run Bias Stability, Bias repeatability, and Sensitivity Temperature Coefficient from the datasheet:

• I understand that the Bias repeatability is the error of the output of the sensor that appears when you turn it on with an input of the sensor 0°/sec. Or is it the error for a long term behaviour and is defined over a long time like 1 year?
• Are these terms: In-Run Bias Stability, Angular Random Walk, Output Noise, and Rate Noise Density; different ways to define the noise of the sensor? Or is the In-Run Bias Stability a different source of noise in the sensor?
• How the parameter Sensitivity Temperature Coefficient affect the sensor? Does it affect only the output in volts some way like the following formula? Where "a" is the sensitivity temperature coefficient.

Edgard

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• Hi Edgard,

I just wanted to add a note on the questions you had about the noise metrics relating to gyro specs. One of the standard measurement techniques for gyroscopes is the measure the offset over a long period of time (hours to days, depending on the relative amplitudes and frequency content of your noise and drift terms), and then analyze it using the Allan variance technique (Allan variance - Wikipedia ). This will allow you to determine various noise contributions based on the slopes of different sections of the resulting plot (such as Angle Random Walk, which should be proportional to your white noise or noise floor as measured in a PSD, and Bias Stability, which will tell you at what point your 1/f noise contribution means continuing to average will not help you resolve your angle any further). For a rate gyroscope, Allan variance plots are interpreted like this:

Rate Noise Density is measured as the RMS of the offset in LSBs, divided by the gyro scale factor to convert to °/s, and normalized by the bandwidth.

As to your question about the sensitivity temperature coefficient, this is a measure of how the scale factor of the gyro changes over temperature, as the offset can change with temperature with both a DC term and a term proportional to your rotation rate. Ie,

Offset (T) [°/s] = (Offset (T0)(1 + Offset_TempCo) [LSBs])/(Sensitivity(T0)(1 + Sensitivity_TempCo) [LSBs/°/s]

Cheers!

• Hi Edgard,

I just wanted to add a note on the questions you had about the noise metrics relating to gyro specs. One of the standard measurement techniques for gyroscopes is the measure the offset over a long period of time (hours to days, depending on the relative amplitudes and frequency content of your noise and drift terms), and then analyze it using the Allan variance technique (Allan variance - Wikipedia ). This will allow you to determine various noise contributions based on the slopes of different sections of the resulting plot (such as Angle Random Walk, which should be proportional to your white noise or noise floor as measured in a PSD, and Bias Stability, which will tell you at what point your 1/f noise contribution means continuing to average will not help you resolve your angle any further). For a rate gyroscope, Allan variance plots are interpreted like this:

Rate Noise Density is measured as the RMS of the offset in LSBs, divided by the gyro scale factor to convert to °/s, and normalized by the bandwidth.

As to your question about the sensitivity temperature coefficient, this is a measure of how the scale factor of the gyro changes over temperature, as the offset can change with temperature with both a DC term and a term proportional to your rotation rate. Ie,

Offset (T) [°/s] = (Offset (T0)(1 + Offset_TempCo) [LSBs])/(Sensitivity(T0)(1 + Sensitivity_TempCo) [LSBs/°/s]

Cheers!

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