What is it?

This is a air pressure prototyping and development board. Using a wheatstone bridge air pressure sensor, MPS3117-006GC, and instrumentation amplifier, INA129, with gain resistor giving it the ability to measures these wide range of pressures. Output is a analogue voltage can range from 0 - 15V as determined by the sensor, but designed for use with 0 - 5V range in mind specifically for an Arduino.

A range of pressure ranges is available to cater for different project types. This range makes it suitable for either a pneumatic system that has a relatively high pressure of 40kpa, human interface of 20kpa or for a inflow kiel probe for air speed of 5kpa. A reference voltage pin available to move the zero pressure making it possible to measure negative pressures, otherwise connecting the reference to ground will give only positive readings.

Uses

Two examples of how it can be used are below and were areas that that this board could be used.

Pneumatically actuated robotic hand from Hack-a-Day Typically the use of this board in this context has the air pressure range from ambient to 40kPa, the sensor can go beyond this range without immediate damage, but the output becomes non-linear. This means that the 0ohm resistor can/should be added to ground the reference pin on the instrumentation amplifier. It is advisable that capacitors to be added to the Vin and Output pins to reduce noise, but is not necessary for prototyping a solution.

Converting the voltage to pressure using the 2.2kohm resistor is Vo = Vin(1.635*P)

For use with a kiel probe dynamic pressure can be measured and then total pressure can be derived for air velocity. Attaching a 56ohm gain resistor gives a range up to 2kPa, suitable for measuring the total pressure of air flow of about 60m/s. Using the formula for total pressure P_total=P_static+0.5rhov^2, rho = air density, v = velocity (search basicairdata for a nice explanation).

Converting the voltage to pressure using the 56ohm resistor is Vo = Vin(0.294*P)

Why did you make it?

I have projects that require air pressure sensors and have some extra boards to populate.

What makes it special?

This board brings in the sensor and amplifier for convenient prototyping. The sensor board is designed for adaptable use in a variety of systems as described above. By changing the gain resistor the sensor a different range an output sensitive to a range of pressure is possible. Then by setting the reference voltage negative gauge pressure is possible.