Photoacoustic detection system with differential amplifier for determing target species presence and triggering fault
A photoacoustic detection system includes a detector that has a chamber, a pulsed light source, piezoelectric tuning forks, and a photosensor. The chamber has an inlet and an outlet for flow of an analyte. The pulsed light source is adjacent the chamber and is operable to emit a light beam along a path through the chamber. The tuning forks are arranged along the path, and each of the tuning forks is operable to emit first sensor signals. The photosensor is arranged along the path and is operable to emit second sensor signals. A controller is connected to receive the first and second sensor signals. The controller is configured to determine whether a target species is present in the analyte based on the first sensor signals and determine whether the target species is present in the analyte based on the second sensor signals.
1. A photoacoustic detection system comprising:
a detector including,
a chamber having an inlet and an outlet for flow of an analyte,
a pulsed light source adjacent the chamber, the pulsed light source, when operated, emitting a light beam along a path through the chamber,
a plurality of piezoelectric tuning forks arranged along the path, each of the piezoelectric tuning forks operable to emit first sensor signals,
a photosensor arranged along the path and operable to emit second sensor signals; and
a controller connected to receive the first and second sensor signals, the controller configured to:
(a) determine whether a target species is present in the analyte based on the first sensor signals, and
(b) determine whether the target species is present in the analyte based on the second sensor signals,
the controller including a differential amplifier connected to receive the first sensor signals of each of the first and second piezoelectric tuning forks, the differential amplifier subtracting the first sensor signals of the second piezoelectric tuning fork from the first sensor signals of the first piezoelectric tuning fork, wherein the first sensor signals of the second piezoelectric tuning fork are out of phase with the first sensor signals of the first piezoelectric tuning fork, to produce differentiated sensor signals, wherein the controller makes the determination in (a) based on the differentiated sensor signals, and the controller is further configured to trigger a fault based on comparison of the determinations in (a) and (b), wherein the fault is triggered if there is a negative presence determination in (a) and a positive presence determination from (b) and the fault is triggered if there is a positive presence determination in (a) and a negative presence determination from (b).
2. The system as recited in claim 1 , wherein the controller is further configured to identify that a determination that the target species is present in the analyte based on the first sensor signals is a false positive when there is a determination that the target species is not present in the analyte based on the second sensor signals.
3. The system as recited in claim 2 , wherein the controller is configured to trigger a notification in response to the false positive.
4. The system as recited in claim 1 , further comprising a beam splitter in the path, the beam splitter operable to divide the light beam into first and second secondary light beams along respective first and second branch paths.
5. The system as recited in claim 4 , further comprising a surface plasmon resonance sensor arranged along the first branch path, the surface plasmon resonance sensor operable to emit third sensor signals.
6. The system as recited in claim 5 , wherein the controller is further configured to identify that a determination that the target species is present in the analyte based on the first sensor signals is a false positive when there is a determination that the target species is not present in the analyte based on the third sensor signals.
7. The system as recited in claim 6 , wherein the controller is configured to distinguish a chemical identity of the target species based on a distinct signature across the first, second, and third sensor signals.
8. The system as recited in claim 6 , wherein the controller is configured to trigger a notification in response to the false positive.
9. The system as recited in claim 1 , wherein the plurality of piezoelectric tuning forks includes first and second piezoelectric tuning forks, the first piezoelectric tuning fork arranged on a first side of the path and the second piezoelectric tuning fork arranged on a second, opposite side of the path across from the first piezoelectric tuning fork.
10. The system as recited in claim 1 , wherein the controller is configured to identify whether the plurality of piezoelectric tuning forks are faulty based on the differentiated sensor signals.