Back to results
US 5,140,168 AGranted
Turbidimeter signal processing circuit using alternating light sources
AssigneeGreat Lakes Instruments, Inc.
InventorKarl L. King
Life of this patent
Estimating the term…
Abstract
A turbidimeter includes a housing having a cavity with an inlet through which a fluid flows. Two emitters are alternately driven by an alternating signal having a given frequency to transmit modulated light beams through the fluid. Two detectors produce signals representing the intensity of scattered and unscattered light within the fluid. Each of these detector signals is processed to measure the level of the signal component at the given frequency. Such processing includes filtering and phase demodulataing the detector signals to produce a signal indicative of the levels of the component signals at the given frequency. The turbidity is calculated from the signal levels measured as each emitter is excited.
Claims19
An apparatus for measuring turbidity of a material comprising:
- an emitter which when excited transmits a light beam through the material;
- means for exciting said emitter with an alternating signal having a given frequency;
- a first detector for producing a first detector signal representative of an intensity of light travelling in substantially in a straight line through the material from said emitter;
- a second detector for producing a second detector signal representative of an intensity of light from said emitter which is scattered within the material;
- a means for producing a first output signal corresponding to a magnitude of a component of the first detector signal at the given frequency;
- a means for producing a second output signal corresponding to a magnitude of a component of the second detector signal at the given frequency;
- and
- means for determining the turbidity of the fluid in response to the first and second output signals.
5 more elements
An apparatus for measuring turbidity of a material comprising:
- a first emitter which when excited transmits a first light beam into the material;
- a second emitter which when excited transmits a second light beam into the material, the second light beam being transverse to the first light beam;
- means for exciting said first and second emitters one at a time with an alternating signal having a given frequency;
- a first detector positioned to receive light traveling in a straight line through the material from said first emitter and producing a first detector signal indicating the intensity of light received by said first detector;
- a second detector positioned to receive light traveling in a straight line through the material from said second emitter and producing a second detector signal indicating the intensity of light received by said second detector;
- a means for producing a first output signal corresponding to a magnitude of a signal component of the first detector signal at the given frequency;
- a means for producing a second output signal corresponding to a magnitude of a component of the second detector signal at the given frequency;
- means for sampling the first and second output signals while the first emitter is being excited to produce a first pair of light intensity values and while the second emitter is being excited to produce a second pair of light intensity values;
- and
- processor means for deriving the turbidity of the fluid from the first and second pairs of light intensity values.
7 more elements
An apparatus for measuring turbidity of a fluid comprising:
- a body having a cavity through which the fluid can flow;
- a first emitter for transmitting a first light beam through the cavity when said first emitter is excited;
- a second emitter for transmitting a second light beam through the cavity when said second emitter is excited, the second light beam being substantially coplanar with and substantially orthogonal to the first light beam;
- means for exciting said first and second emitters one at a time with an alternating signal having a given frequency;
- a first detector positioned to receive light traveling in a straight line through the cavity from said first emitter and producing a first detector signal representative of received light intensity;
- a second detector positioned to receive light traveling in a straight line through the cavity from said second emitter and producing a second detector signal representative of received light intensity;
- a first signal channel comprising a first bandpass filter receiving the first detector signal and having a transmission band that includes the given frequency, a first variable gain amplifier having an input coupled to said first bandpass filter, and a first phase demodulator for detecting a component signal at the given frequency contained in a signal from said first variable gain amplifier and producing a first output signal indicative of the magnitude for that component signal;
- and
- a second signal channel comprising a second bandpass filter receiving the second detector signal and having a transmission band that includes the given frequency, a second variable gain amplifier having an input coupled to said second bandpass filter, and a second phase demodulator for detecting a component signal at the given frequency contained in a signal from said second variable gain amplifier and producing a second output signal indicative of the magnitude for that component signal;
- and
- processor means for deriving the turbidity of the fluid from the first and second output signals and controlling the gain of said first and second variable gain amplifiers.
8 more elements
Dependencies are inferred from the claim text.