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mx270a

Posted 1/6/2018 22:21 (#6485098)
Subject: Inside a Trimble AutoSense (Pics)

Cedar Rapids, Iowa

I acquired a broken AutoSense and finally decided to open it up to see whats inside. It was a challenge to get open. The case is made from two pieces of aluminum with an o-ring to make a waterproof seal. Once that was open I discovered the whole thing has been 'potted' in a black epoxy. Potting a circuit board is somewhat common in the electronics world for several reasons. Common reasons for potting a board are: to protect the board from being physically damaged, waterproofing, or to obscure the design so it is much harder to reverse-engineer. However, in this case I suspect it is mainly to make a very solid connection between the gyro and the case. Eliminating any possible vibration or movement is necessary for a high accuracy gyro.

The top of the gyro sensor was visible, the name on the top is Silicon Sensing Systems. That company specializes in MEMS gyros. I had once heard that the AutoPilot/AutoSense used a Ring Laser Gyro, but I guess that's not the case. This appears to be either the CRS03 or CRS43 MEMS gyro. Cost of that one part alone is $125-260 depending on accuracy.
https://www.siliconsensing.com/products/gyroscopes/crs03/

I then cut the case around the connector so that I could get the whole black epoxy brick out of the aluminum. Luckily the epoxy was not adhered to the aluminum, so it separated relatively easily. This revealed a circuit board. There are 4 pins on one side for the connection out of the case, and three pins on the other side that go to the gyro. It looks like this board simply translates the analog gyro signal to a digital signal to go to the NAV2.