For a part of my P.h. Degree I'm evaluating the propagation of measurement errors of MEMS, using from now an ADXL335 as experimental reference (using Z axis), in the reconstruction of speed and displacement by double integration, more precisely, evaluating the movement of a hydraulic cylinder.
Checking the datasheet I have doubts about some errors definition. Checking figures 5 and 17 of “Typical performance characteristics; N > 1000 for all typical performance plots, unless otherwise noted.” Shall I understand that it’s referred to repetitibility, i.e. a multiple measures of a single “typical” device or a sample of different devices, single typical measure? From my point of view it’s the first case but I need to be sure.
On the other hand, is any data available about hysteresis of measurement? More precisely, does sensitivity variation data exist between positive and negative acceleration measures?
Thank you on advance for any response. It will be very helpful for my research.
Thank you for your interest. N > 1000 typically means that this has been observed on more than 1000 units. Out of curiosity, for the stated purpose, could you help us understand your selection of the ADXL335? The ADXL355 would seem to offer significant performance advantages. Just want to make sure we can focus our research/support on what matters for you.
Thank you for your fast response. The selected accelerometer is due to its bandwidth, measuring range and availability from previous research, in order to get comparable data, also. Your kind recomendation will be considered in the future.
May I consider that data of repetibility and histeresys is not available?
I am not sure I would assume that just yet. Can you help me understand what you mean by hysteresis?
I'm talking about the defined in the point 8. Hysteresis of the following link:
I'm also interested in Repeatability (also known as precision): "Repeatability is defined as the range of actual positions the system takes while being repeatedly commanded to the same location under identical conditions. Some linear measurement systems differentiate between unidirectional and bidirectional repeatability, which defines if the target has been approached from only one direction or from both." This last sentence could make sense in accelerometers, as 0 g offset repetitively/bias, for example.
The first hypothesis are that the main deviation in first and second integration could come from this two measurements error, even when they are very small. On the other hand, It's suspected that instead of hysteresis, Dynamic Linearity (section 10 of the link above) could be an alternative cause.
You can see that we need to evaluate in detail the measuring performance.
Thank you on advance.
Thank you! I did already understand what “hysteresis” means, but I am always glad to read new material. My question was more about confirming that you were looking for hysteresis in the bias. Hysteresis can apply to a number of parameters, but bias is the most common. I am going to be out of the office for a few days, but I will see what I can find for you when I get back. I suspect that we are going to be limited to what is already offered in the data sheet, but it won’t be difficult for me to look through what we have, to see if there is anything useful, when I get back.
As a sidenote, repeatability is already defined in the ADXL355 datasheet, as this product was targeted more towards and applications that value this particular behavior. That specification normally encompasses a lot of different considerations (including hysteresis), which may not be available for the product that you have selected.