It takes an extremely durable design to make reliable measurements in extreme conditions. Extreme environment position/displacement sensors perform where most sensors cannot survive.
Guest piece by: Will Meenan, Kaman Precision Products / Measuring.
These sensors are designed to operate in the following environmental conditions:
Extreme environment sensors are necessary for applications that require high accuracy, high reliability, and structural integrity in adverse conditions.
Sensor options for extreme conditions
When it comes to difficult environments, two primary sensor technologies are used to measure position or displacement: capacitive and inductive. Each technology has distinct advantages and disadvantages, which are described below.
Specialised sensor applications
For many years, extreme environment sensors have been utilised for position and displacement measurements in difficult environmental conditions where most sensors will not survive. Typical applications include:
Sensors designed to withstand extreme conditions
Extreme environment sensors which are capable of making both static and dynamic measurements are required for measurements in adverse conditions.
For example, Kaman manufactures a range of extreme environment inductive displacement sensors designed for continuous operation at temperatures up to 638°C (1,000°F) or down to -196°C (-320°F). The sensor probes can withstand pressures to 340 bar (5,000 psi) and are of totally inorganic construction for use in high radiation environments without degradation. The outer housing is resistant to a wide variety of chemicals.
A complete measuring channel consists of:
The sensor probe materials of construction were carefully selected to survive these extreme environments. The mineral insulated cable is manufactured to precise specifications and is used to transmit the probe signal to a more benign environment where the signal conditioning electronics can be located. Cable lengths (both mineral insulated and flexible) can be customised to fit each application. Calibration parameters (target material, temperatures, measuring range) can also customised.
The sensor system uses thermal compensation techniques that minimise thermal shift of the output signal over the wide temperature spans. Specially designed calibration equipment is required to negate effects of thermal expansion and contraction of the calibration test set up. The result is a linear, accurate measurement of displacement over a wide range of environmental conditions. Sensor housings are rigid and not affected by pressure variations within design parameters.
New testing and monitoring applications on the rise
With the overall industry trend toward additional product performance testing and monitoring, demand for sensors to operate in extreme conditions is increasing. Extreme environment sensors are measuring position and displacement in new and increasingly difficult applications.