A recent article in an EET Asia technology magazine discussed the advantages of linear position sensors based on variable inductance, as compared to those based on either magneto-strictive or potentiometer based sensors. The article was really a thinly veiled plug for variable inductance sensors (written by the company that makes them), and it chose to compare them to potentiometer based sensors, and traditional magnetostrictive sensors. Notably absent were the family of modern draw-wire sensors made by CPI that are having so much success in harsh duty applications.
LVDT Based, Draw-Wire Linear Position Sensors. Readers of this blog will find some of the advantages of inductive sensors stated in the article sound vaguely similar to the advantages of CPI SL-Series Draw wire sensors that have been discussed previously.
Finally for subsea applications, we note that a rating to 3000m and 3000psig may not provide the operating design margin required for many large scale hydraulics on the deep sea bed. It is in these applications that CPI sensors were born to live. The CPI SL-Series sensors have no dynamic seals, and no pressure vessels in a subsea deployment. Our sensors have been deployed at operational depths of 5000m and almost any hydraulic pressure. CPI Linear Position Sensors for Subsea Applications If you require robust operation on the sea floor at stroke lengths up to 10 meters, CPI sensors were designed for your application. Visit www.cpi-nj.com today. This content was originally published at https://www.cpi-nj.com/blog/draw-wire-vs-variable-inductance-position-sensors/. Traditional Linear Position Sensor technologies (ie. Magnetostrictive sensors) used in hydraulic cylinders have been limited in their ability to function in high temperature environments. One of the strongest applications for CPI SL series sensors are in these high temperature hydraulics applications, when you need to function reliably for long periods under an extended temperature range. These larger power hydraulics are commonly found in offshore oil & gas drilling, mining operations, steel mills or heavy outdoor equipment. What Temperature is Your Sensor Rated For? CPI Linear Position Sensors have been Qualified to operate up to 300F (150C). That is 50% more than highest rated temperature of so called “Extended Temperature” magnetostrictive sensors. What Causes High Temperatures in Hydraulic Position Sensors? Don’t forget that even in scenarios where ambient air does not reach stated limits, there are many factors that contribute to the effective operating temperature seen by the sensor.
How does extended temperature affect sensor operation? One of the primary effects of high temperatures is to create a loss of accuracy referred to as “sensor drift”. Depending on the tolerance needed by your application this can become an issue if your sensor is inherently vulnerable to this (magnetostrictive sensors). Often software can compensate for this drift but this increases the complexity of your control system. Another more series issue is component failure. Repeated exposure to high temperatures can greatly shorten the life of a sensor as measured by MTBF (Mean Time Before Failure). In general, MTBF is rated at 25C and drops in half for every 10C you go above the ambient rating. It is in this area that magnetostrictive sensors show one of their most glaring weaknesses for high endurance applications. Replacing these sensors typically requires complete shutdown of the equipment for an extended period and disassembly of the cylinder to fish out the “rod”. Field replacement depends on having a rod of the exact length available at the job site as every magnetostrictive sensor waveguide length must match the stroke length of the cylinder exactly for proper operation. 5 Ways the CPI SL series LVDT Based Linear Position Sensors Meet Extended Temperature Environments. The SL1500 – The Cadillac of high endurance position sensors. CPI position sensors were specifically designed for the ultra-durable segment of the market where hydraulics are asked to do their work reliably and accurately under the most difficult operating conditions on the planet. Because our technology is inherently different than the complicated physics and electronics of magnetostriction, we suffer none of these shortcomings and are ideal replacements for this technology wherever long stroke, high power, high temperature environments are found
This content was originally published at https://www.cpi-nj.com/blog/linear-position-sensors-for-high-temperature-environments/. |
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