Air Pressure Sensor
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In Stock   AIRPRES    Air Pressure Sensor    $29.00       

The Air Pressure Sensor lets your robot know how much pressure is in it's pneumatic system.

The Lego Pneumatic system uses air pressure in cylinders to create movement.  The amount of force generated by an air piston is proportional to the air pressure, and the size of the cylinder.  The Techno-stuff air pressure sensor lets your RCX measure the air pressure, and therefore know how much force is being applied to the piston.  This sensor measures air pressure in the range of 0 to 200 KiloPascals.  (0-29 Pounds per square inch)

Air cylinders are reversable.  You can apply force to the piston to create air pressure.  You can then measure the air pressure, and know how much force is applied to the cylinder.  This technique can be used to build a scale to measure weight.

         Air Pressure Sensor.

Pressure sensor with Lego air pump       Simple Test.

You program the Air Pressure Sensor just like the Lego light sensor.  Use the Light Sensor block in the Mindstorms program environment to cause program branches. A sinple example of programming is shown in the picture below.

Air pressure sensor program in Lego RIS 1.0

The sensor is factory calibrated for easy reading in metric units.  When read as a light sensor, the RCX value multiplied by two gives the pressure in KiloPascals.  This means each unit on the RCX represent 2 Kp.  A value of 100 on the RCX represents 200 Kp.  If you prefer to work in English units (PSI) and do not require extreme accuracy, a simple conversion is one RCX unit equals 0.3 PSI.  This estimate will by high by about 3.4 percent.  For more accurate conversion, use the formulas below.

One PSI = 6895  Pascals  (Newton/meter2)
One  KiloPascal = 0.145 Pound per Square Inch

When this sensor is used with NXT and the conversion cable, it must be read as a light* sensor set to raw mode. Air pressure in KiloPascals is calculated by the formula 200(1-(x-342)/666) where x is the raw value from the NXT. To get the air pressure in PSI use the formula 29(1-(x-342)/666).