Network manageable advanced gas sensor apparatus and method
Mechanical, electronic, algorithmic, and computer network facets are combined to create a highly integrated advanced gas sensor. A sensor is integrated into switchgear housings. These sensors integrated into high voltage switchgear products, deployed by electric utility end users in replacement and expansion cycles, function to detect and mitigate atmospheric pollution caused by leaking SF 6 . As its associated gas insulated tank is charged with 10 to 350 lbs. of SF 6 , each gas sensor monitors its local cache of gas, accurately sensing and computing fractional percentage losses (emissions) and gains (maintenance replacement) in SF 6 mass, storing data in onboard data logs, and communicating data when triggered by detection events or in response to remote requests over a hierarchical communications network, a process that continues without labor until a fractional leak is automatically detected and reported creating the opportunity for early leak mitigation.
1. A method for computing gas density comprising the steps of:
acquiring a raw temperature measurement from a temperature probe in connection with a gas;
converting said raw temperature measurement to an accurate temperature reading using pre-determined temperature calibration information;
acquiring a raw displacement measurement from a displacement sensor in connection with a moveable element responding to the pressure and to the temperature of said gas;
converting said raw displacement measurement to an accurate displacement measurement using pre-determined displacement calibration information;
determining a nominal pressure measurement corresponding to said accurate displacement measurement using pre-determined displacement to pressure transformation information;
converting said nominal pressure measurement to an accurate pressure reading using said accurate temperature reading in conjunction with pre-determined temperature to pressure compensation information, and
computing the density of said gas using said accurate temperature reading and said accurate pressure reading in conjunction with a gas law.
2. A method for computing gas density as claimed in claim 1 wherein said temperature probe is a thermistor.
3. A method for computing gas density as claimed in claim 1 wherein said displacement sensor is a reflective object sensor.
4. A method for computing gas density as claimed in claim 1 wherein said displacement sensor is a Hall effect sensor.
5. A method for computing gas density as claimed in claim 1 wherein said gas is sulfur hexafluoride.
6. A method for computing gas density as claimed in claim 1 where said gas law is a second or higher order polynomial function of said gas density and said polynomial function coefficients are a function of said accurate temperature reading.
7. A method for computing gas density as claimed in claim 1 further comprising the step of:
recording all measurements, readings, and calculations in a microcontroller memory including said raw temperature measurement, said accurate temperature reading, said raw displacement measurement, said nominal pressure measurement, said accurate pressure reading, and said gas density.
8. A method for computing gas density as claimed in claim 7 further comprising the steps of:
repeating said foregoing steps periodically thereby creating a stored time sequence of said measurements, readings, and gas density, and
utilizing said stored time sequence to determine a leakage of gas or an addition of gas.