Currently I am working on an interesting project that I would like to share. It is the design of complete instrumentation and electronics for a sensor characterization chamber. Let me first explain what a sensor characterization chamber is. In our Sensor hub many MEMS engineer design various types of low power low cost sensors to be implemented on the field. In order to plot the proper characteristics of these sensor one needs a characterization chamber. It can also be used to calibrate the response of a sensor to a much higher standard coming from ultra precise standardized sensor. It also helps to plot how the sensor behaves by simulating various environment like high humidity, high temperature presence of other gas which mixes with the targeted gas and contaminates the data. Let me share a block diagram of the various instruments used for the characterization chamber.
Most of the block diagram is self explanatory. The main controller controls the environment inside the chamber. User can use per-programed settings or even can use custom settings while using the chamber with their sensors. The fan controller is used for expelling the gases once the process is finished and the pump controller is used to increase or decrease the internal chamber pressure. The gas input controller lets the user to control the flow and amount of gas into the chamber. For collecting data from the sensor a low noise proper analog interface is used. Which then converts the analog value into a high resolution 16bit digital count. There is provision for storing the data or displaying it to a computer which gives various other functionality. The biasing power requirement for MEMS sensor can be difficult different designs require different voltage some needs constant current whereas some needs both. So a software controlled voltage and current source is dedicated for this purpose. The power module provides appropriate power to different sections.
From designing point of view I have broken the system into 5 independent PCBs.
- Power Module board.
- Main chamber controller board
- Sensor power, Sensor interface, DAC and PC interface all in one board.
- Gas input controller.
- Fan and vacuum pump controller.
I will start with the Fan and vacuum pump controller.
