Mass flow meters/controllers and methods having improved accuracy

A method to perform optical measurements, the method comprising:

• emitting a first light beam via a first light source comprising a first light emitting diode;
• performing first measurements by detecting the first light beam via a first optical sensor;
• emitting a second light beam via a second light source comprising a second light emitting diode, wherein the first light emitting diode and the second light emitting diode are coupled in series and have a same excitation current;
• performing second measurements by detecting the second light beam via a second optical sensor, wherein the first measurements and the second measurements comprise variable components;
• performing third measurements by detecting a third light beam emitted from the second light source via a third optical sensor, wherein the third measurements comprise a first steady state component representative of light intensities of the second light source;
• performing fourth measurements by detecting a fourth light beam emitted from the first light source via a fourth optical sensor, wherein the fourth measurements comprise a second steady state component representative of light intensities of the first light source;
• filtering the first and second steady state components via a filter circuit;
• and
• controlling, via a compensation circuit, the excitation current to the first light source and the second light source based on the filtered first and second steady state components.

A method to perform optical measurements, the method comprising:

• 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, wherein the first measurements and the second measurements comprise variable components;
• performing third measurements by detecting a third light beam emitted from the second light source via a third optical sensor, wherein the third measurements comprise a first steady state component representative of light intensities of the second light source;
• performing fourth measurements by detecting a fourth light beam emitted from the first light source via a fourth optical sensor, wherein the fourth measurements comprise a second steady state component representative of light intensities of the first light source;
• filtering the first and second steady state components via a filter circuit;
• and
• controlling, via a compensation circuit, the one or more currents to the first light source and the second light source based on the filtered first and second steady state components,
• wherein the controlling the one or more currents to the first light output of the first light beam and the second light output of the second light beam comprises controlling the first light source and the second light source to output a substantially constant output over a range of temperatures of the first light source and the second light source.

A method to perform optical measurements, the method comprising:

• 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, wherein the first measurements and the second measurements comprise variable components;
• emitting a third light beam via a third light source;
• performing third measurements by detecting the third light beam via a third optical sensor, wherein the third measurements comprise a first steady state component representative of light intensities of the first light source and the second light source;
• controlling, via a compensation circuit, 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 light source and the second light source based on the first steady state component of the third measurements.