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Small diameter submersible level sensor for borehole measurement
22nd July 2007
 For level measurement of fresh-water boreholes with diameter restrictions of less than 1 inch the choice of hydrostatic level sensors becomes much more limited since most are typically 1 - 1.5 inches in diameter.
If you are also planning to measure shallow water levels the low water head pressure introduces another problem, since small diameter pressure sensor diaphragms are less sensitive at low pressures and this has an impact on the output signal and ultimate level measurement accuracy. So which sensing technology is going to provide the most sensitivity with the smallest diameter? Silicon pressure sensors which incorporate a semiconductor strain gauge have very small surface areas making them ideal for use inside small diameter pressure sensors. Piezo-resistive silicon strain gauges also offer very high sensitivity to changes in pressure compared to other strain gauge technologies which makes a big difference to pressure sensor performance particularly at lower pressure ranges. The LMP305 borehole level sensor is 19mm in diameter and includes a silicon sensor element packaged in an oil filled capsule with a thin isolation diaphragm. The level ranges available for the LMP-305 borehole level sensor begin with 1 mWG and finish with a 250 mWG. A measurement accuracy of 0.175% full scale best straight line which includes non-linearity, hysteresis & repeatability is specified as standard for the LMP 305 bore-hole level sensor and this can be improved to 0.125% FS if necessary. The LMP305 small diameter submersible level sensor has a 316 grade stainless steel sensor housing with a 316L stainless steel isolation diaphragm. The electrical interface is IP68 rated for long immersion in water and the cable which has a vent tube running through it to provide the gauge pressure reference is available in a PVC, PUR or FEP outer jacket material. The LMP 305 borehole level sensor is powered by 12-36Vdc and it outputs a 4-20mA loop signal for transmitting over long distances between boreholes and telemetry stations.
Related Products LMP305 product page with pdf downloads and product options Submersible sensors for measuring hydrostatic pressure Small diameter loggers for monitoring groundwater level Liquid level measurement instrumentation
Associated Topics Preventing damage to submersible pressure sensors due to moisture ingress Measuring water depth with a non-vented absolute pressure sensor When to use a submersible pressure sensor Selecting level sensors for different media
Resources Conversion table for mH2O level units Conversion factors for meters of water column Look up a technical term used to specify pressure sensors
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