A method for calibrating an ultrasonic sensor including a transducer, a reflector spaced a known distance from the transducer, and a memory. A water bath is heated to approximately fifty centigrade and the ultrasonic sensor is at least partially submerged in the water bath. When submerged, an ultrasonic wave is transmitted through a portion of the water bath from the transducer. The ultrasonic wave is transmitted toward the reflector and a reflected ultrasonic wave is received back at the transducer. A time of flight of the ultrasonic wave is measured. A calibration coefficient is determined based on the time of flight of the ultrasonic wave and an expected time of flight of the ultrasonic wave. The calibration coefficient is loaded into the memory of the ultrasonic sensor.

Various embodiments include a method for monitoring the tank content of a storage tank comprising: metering a fluid from the tank into the exhaust gas tract, wherein the fluid has a concentration with respect to a reducing agent; acquiring a current concentration value for the reducing agent; calculating a change in concentration of the reducing agent on the basis of the current concentration value in comparison with a stored concentration value; determining a current operating state of the vehicle to identify an operating state in which refueling cannot be carried out; and carrying out a plausibility check of the calculated change in concentration if the calculated change in concentration exceeds a predetermined threshold value and the operating state is identified. The plausibility check includes acquiring the current tank filling level of the fluid.

An improved fire detector test device and methods for conducting field sensitivity and functionality testing of a fire detector in-situ are provided. The test device can include ambient condition or stimulus generating devices, and a programmable processor, wherein the programmable processor can identify information about a detector under test, wherein the programmable processor can obtain a configuration file based on the identified information about the detector under test, wherein the configuration file can identify a combination, level, or rate of a plurality of stimuli that cause an alarm in the detector under test, and wherein the programmable processor can execute the configuration file to cause the ambient condition or stimulus generating devices to generate and emit the plurality of stimuli in the combination and at the level and the rate identified in the configuration file.

A method of detecting one or more blocked sampling holes in a pipe of an aspirated smoke detector system. The method includes ascertaining the base flow of fluid through a particle detector using a flow sensor; monitoring subsequent flow through the particle detector; comparing the subsequent flow with the base flow; and indicating a fault if the difference between the base flow and the subsequent flow exceeds a predetermined threshold.

A photoacoustic detection system (20) includes a detector (22) that has a chamber (24), a pulsed light source (26), piezoelectric tuning forks (28), and a photosensor (30). 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 (38) 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.

A photoacoustic detection system (20) includes a detector (22) that has a chamber (24), a pulsed light source (26), piezoelectric tuning forks (28), and a photosensor (30). 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 (38) 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.

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.

Various embodiments include a method for monitoring the tank content of a storage tank comprising: metering a fluid from the tank into the exhaust gas tract, wherein the fluid has a concentration with respect to a reducing agent; acquiring a current concentration value for the reducing agent; calculating a change in concentration of the reducing agent on the basis of the current concentration value in comparison with a stored concentration value; determining a current operating state of the vehicle to identify an operating state in which refueling cannot be carried out; and carrying out a plausibility check of the calculated change in concentration if the calculated change in concentration exceeds a predetermined threshold value and the operating state is identified. The plausibility check includes acquiring the current tank filling level of the fluid.

A method including providing an acoustic resonator having an absorption element with a surface portion, providing a sample fluid or a fluid mixture containing the sample fluid with at least one absorption fluid or particles such that the acoustic resonator is filled with the same, the surface portion of the absorption element being in contact with the sample fluid. Irradiating the surface portion of the absorption element with a first electromagnetic radiation such that the absorption element at least partly absorbs the first electromagnetic radiation in the region of the surface portion, or irradiating the fluid mixture with a first electromagnetic radiation such that the absorption fluid or the absorption particles at least partly absorb(s) the first electromagnetic radiation, and so, by way of the absorption, pressure energy is generated in the sample fluid or the fluid mixture, with the first electromagnetic radiation being amplitude modulated or frequency modulated with a modulation frequency. Measuring an acoustic response signal from the acoustic resonator. Determining at least one amplitude or phase of the acoustic response signal.

A particulate matter sensor assembly including a resistance sensor and a resonance sensor. Each one of the resistance sensor and the resonance sensor is configured to measure particulate matter present in engine exhaust.