Robotics: Sensors: Pressure Sensors
Robotics: Sensors: Environment Sensors: Pressure and Sound
Contents |
Overview
The ability to measure pressure within the subject of robotics is very useful.
Because the density of the atmosphere changes with altitude. If the pressure is known then the altitude can then be established. If the robot contains fluids at pressure it is benefitial from the view of fault finding for the machine to know what the pressure is at key parts in the system. Pressure sensors can also be installed to a compressed air tank to measure how much gas is left.
Measuring Pressure
Analogue Methods
A Bourdon gauge uses a coiled tube which as it expands due to pressure increase causes a rotation of an arm connected to the tube. This is not particularly useful however in Robotics. This is of course unless you design a way to get a voltage to vary with respect to needle displacement.
Electric Methods
- Resistive (Strain Gauge) - As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor. Foil strain gauges are for quite large deformations and are not very precise over small differences. So depending on the change in pressure and the amount of pressure.
- Capacitive - The deflection of the piston is often one half of a capacitor, so that when the piston moves, the capacitance of the device changes. This is a common way (with proper calibrations) to get a very precise, electronic reading from a manometer, and this configuration is called a capacitive manometer vacuume gauge.
- Piezoelectric/Piezoresistive - For measurements of small strain, semiconductor strain gauges, so called piezoresistors, are often preferred over foil gauges. A semiconductor gauge usually has a larger gauge factor than a foil gauge. Semiconductor gauges tend to be more expensive, more sensitive to temperature changes, and are more fragile than foil gauges.
