An example method to perform optical measurements involves: emitting a first light beam via a first light source; performing first measurements by detecting the first light beam via a first optical sensor; emitting a second light beam via a second light source; performing second measurements by detecting the second light beam via a second optical sensor, the first and second measurements comprising variable components; performing third measurements by detecting a third light beam emitted from the second light source via a third optical sensor, the third measurements comprising a first steady state component representative of light intensities of the first and second light sources; and compensating a first light output of the first light beam and a second light output of the second light beam by controlling one or more currents to the first and second light sources based on the first steady state component of the third measurements.

An example method to perform optical measurements involves: emitting a first light beam via a first light source; performing first measurements by detecting the first light beam via a first optical sensor; emitting a second light beam via a second light source; performing second measurements by detecting the second light beam via a second optical sensor, the first and second measurements comprising variable components; performing third measurements by detecting a third light beam emitted from the second light source via a third optical sensor, the third measurements comprising a first steady state component representative of light intensities of the first and second light sources; and compensating a first light output of the first light beam and a second light output of the second light beam by controlling one or more currents to the first and second light sources based on the first steady state component of the third measurements.

The subject matter of this specification can be embodied in, among other things, a method of sensing that includes measuring an acoustic impedance of a fluid, measuring a first time of flight in a first direction through the fluid, measuring a second time of flight in a second direction through the fluid, determining a mass fluid flow rate based on the measured acoustic impedance, the measured first time of flight, and the measured second time of flight, and providing the determined mass fluid flow rate.

The subject matter of this specification can be embodied in, among other things, a method of sensing that includes measuring an acoustic impedance of a fluid, measuring a first time of flight in a first direction through the fluid, measuring a second time of flight in a second direction through the fluid, determining a mass fluid flow rate based on the measured acoustic impedance, the measured first time of flight, and the measured second time of flight, and providing the determined mass fluid flow rate.

An example optical measurement system includes: a first light source configured to emit a first light beam; a first optical sensor configured to output first measurements based on detecting the first light beam; a second light source configured to emit a second light beam; a second optical sensor configured to output second measurements based on detecting the second light beam, wherein the first measurements and the second measurements comprise variable components; a third optical sensor configured to output third measurements based on detecting the second light beam or a third light beam, wherein the third measurements comprise a first steady state component; and a compensation circuit configured to control a first light output of the first light beam and a second light output of the second light beam by controlling current to the first light source and the second light source based on the third measurements.

An example optical measurement system includes: a first light source configured to emit a first light beam; a first optical sensor configured to output first measurements based on detecting the first light beam; a second light source configured to emit a second light beam; a second optical sensor configured to output second measurements based on detecting the second light beam, wherein the first measurements and the second measurements comprise variable components; a third optical sensor configured to output third measurements based on detecting the second light beam or a third light beam, wherein the third measurements comprise a first steady state component; and a compensation circuit configured to control a first light output of the first light beam and a second light output of the second light beam by controlling current to the first light source and the second light source based on the third measurements.

There is provided a method of automatically controlling the mass flow rate of a gas through an orifice through which, in use, choked flow is arranged to occur. The method uses an electronic valve located downstream of a gas source, a piezoelectric oscillator in contact with the gas upstream of the orifice and downstream of the electronic valve and a temperature sensor. The method comprises: a) driving the piezoelectric crystal oscillator at a resonant frequency b) measuring the resonant frequency of the piezoelectric oscillator c) measuring the temperature of the gas; and d) controlling the electronic valve in response to the resonant frequency of the piezoelectric oscillator and the temperature of the gas in order to regulate the mass flow rate of gas through said orifice.

There is provided a method of automatically controlling the mass flow rate of a gas through an orifice through which, in use, choked flow is arranged to occur. The method uses an electronic valve located downstream of a gas source, a piezoelectric oscillator in contact with the gas upstream of the orifice and downstream of the electronic valve and a temperature sensor. The method comprises: a) driving the piezoelectric crystal oscillator at a resonant frequency b) measuring the resonant frequency of the piezoelectric oscillator c) measuring the temperature of the gas; and d) controlling the electronic valve in response to the resonant frequency of the piezoelectric oscillator and the temperature of the gas in order to regulate the mass flow rate of gas through said orifice.

An electronic utility gas meter using MEMS thermal mass flow sensor to measure gas custody transfer data in city gas metering application is disclosed in the present invention. The meter is designed to have its mechanical connectors identical to those of the current diaphragm gas meters while the insertion metrology unit guided channel is placed coaxially in the main flow channel inside the meter body with gas flow conditioning apparatus. The mechanical installation of the electronic utility gas meter then can be fully compatible with the current mechanical utility gas meters, which allows a seamless replacement. The electronic utility gas meter provides gas metrology that significantly improves the accuracy of the city gas metering, and provides additional benefits for data safety, enhanced gas chemical safety, billing alternatives and full data management either locally or remotely.

An electronic utility gas meter using MEMS thermal mass flow sensor to measure gas custody transfer data in city gas metering application is disclosed in the present invention. The meter is designed to have its mechanical connectors identical to those of the current diaphragm gas meters while the insertion metrology unit guided channel is placed coaxially in the main flow channel inside the meter body with gas flow conditioning apparatus. The mechanical installation of the electronic utility gas meter then can be fully compatible with the current mechanical utility gas meters, which allows a seamless replacement. The electronic utility gas meter provides gas metrology that significantly improves the accuracy of the city gas metering, and provides additional benefits for data safety, enhanced gas chemical safety, billing alternatives and full data management either locally or remotely.