| General > General Technical Chat |
| Reliability of accelerometers. |
| (1/1) |
| Psi:
I've been using an old NXP/Freescale MMA7660 accelerometer in a product for many many years and never had any problems with it. But the chip has been out of production for a while now and I've been running through my old stock which is now gone. It has come time to replace the accelerometer in the product with something new and I'm unsure how reliable the modern brands are. For this application I do need one that isn't going to lock-up randomly. Some drift/error is ok, but not a lockup. Anyone have any recommendations for good brands, or brands to stay away from? I see there are lots of MEMSIC accelerometers available, but I've never heard of that brand until now. And some ST ones are available too, but stock is limited. |
| jpanhalt:
I used the MEMSIC MXD2020, and it never locked up. It works on a different principle than cantilever or ball accelerometers. Sears also used the same device in its early, digital torpedo level. It is no longer available, but MEMSIC still produces comparable devices. MEMSIC has been around since 1999. https://www.memsic.com/thermal-accelerometer http://ww1.microchip.com/downloads/en/AppNotes/00996a.pdf |
| Psi:
Do I need to be careful about asking the PCBA house not to do any ultrasonic cleaning of the PCB with MEMS accelerometer? I've never worried about it in the past with the MMA7660 but I'm unsure how sensitive newer accelerometers are. |
| jpanhalt:
I cannot advise you on that. The device is quite robust, and I don't recall seeing any such precautions mentioned in its datasheets or application notes. It is my understanding that since there is no moving mechanical part it is safe to clean and even drop. That is one reason I chose it. If still in doubt, call Memsic. The sensing chamber is hermetically sealed with solder, and I was advised by one if Memsic's technical people that overheating while soldering can be a problem. We were discussing hand soldering specifically. I suspect reflow is less of a problem, but it might be worth checking whether there is any special precaution that needs to be taken. The Sears level appeared to be reflow soldered. Attached is a picture of the PCB from the Sears level. Device is silver colored upper left. |
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