A digital fiber-optic liquid level sensor

In this paper, a CMOS liquid level to frequency converter with calibration circuits for detecting liquid level of intravenous drip is newly proposed. A calibration technique is proposed in the work. Another innovation is that the outputs of the proposed chip are directly digitized, they could be easily sent over a wide range of transmission media, such as PSN, radio, optical, IR, ultrasonic, and etc. Before performing the proposed calibration circuits, the maximum linear error is 46.44%. After calibration, the maximum linear error is reduced to 2.04%.The liquid level range is 32 steps, and the corresponding output frequency range is 3.14 to 58.14 kHz. The chip area is 2 1.96 mm 2 . The proposed chip is suitable for devices of measuring liquid level, such as device of detecting liquid level of intravenous drip.

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“…(8) Before calibration, the maximum linear error of output frequency is 46.44%. After calibration, the maximum linear error is down to 2.04%.…”

Section: Circuit Descriptions and Simulation Resultsmentioning

confidence: 99%

A CMOS liquid level to frequency converter with calibration circuits for detecting liquid level of intravenous drip

Chiang

Tsai

2014

2014 IEEE International Conference on Mechatronics and Automation

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“…Having in mind that liquid surface tilts less than the half value of the beam divergence, α, do not influenc the sensor response and that the sensor head with the big lens is less sensitive to these effects. Anyway, in mobile tanks with great tilts and ripples it is mandatory to use other type of liquid level sensors as those reported in [3,8,9], although they must be placed inside the liquid so wetting of the sensor can alter its performance and their range is limited to the sensor dimensions.…”

Section: Discussionmentioning

confidence: 99%

“…The FDM technique developed in this work along with the use of passive components to combine all the receiving fibers allows to simplify the electronics at the reception. In the level sensor reported in [9] a wavelength multiplexing technique (WDM) is proposed. In doing so, optical filter are necessary to address each sensor with a specifi wavelength.…”

Section: Discussionmentioning

confidence: 99%

“…Optical fiber have been used in the sensor heads for measuring very short distances, in the micrometer range with a high precision, using fiber-opti long period gratings as in [3], for measuring tens * + + of centimeters employing: continuous flui sensing fiber [4][5][6], or intrusive large arrays of individual fluid-sensit ve transducers [7]. Another works on liquid level sensors reported intrusive digital transducers with a range of several meters using fiber with clad and unclad zones [8] or liquid-coupling waveguides [9], microbending optical-fibe sensors with hysteresis for indirectly measuring up to 2.5 m [10] and transducers for point measurements in control level devices [11][12][13]. A remote sensor head based on optical fiber for long distances, non-intrusive and without hysteresis is presented in [14] but using different lenses for transmitter and receiver fiber and the level in the vessel is measured as a function of the time required for a laser signal to be transmitted from the sensor, reflecte off the liquid surface and returned to the receiver lens located in the sensor.…”

Section: Introductionmentioning

confidence: 99%

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Multi-sensor system using plastic optical fibers for intrinsically safe level measurements

Vázquez

Gonzalo

Vargas

et al. 2004

Sensors and Actuators A: Physical

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A system for measuring liquid level in multiple tanks using optical fibe technology has been developed. Oil fiel service industry or any sector requiring liquid level measurements in flammabl atmospheres can be benefite from this intrinsically safe technology. The device used a single lens for the emitting and receiving fibe and it is based on amplitude variations as a function of the liquid distance and not in time of fligh or phase detection. Being the firs fiber-opti liquid level sensor with those characteristics for long ranges (>200 cm). A simple model to describe their behavior has been derived and tested on two prototypes. A Monte-Carlo method is used to fi the experimental data and obtain the model parameters. High accuracy between experimental data and fitte curve is obtained. The prototypes have a good linearity, better than 1.5% FS (full scale). Sensor heads are made of plastic optical fiber (POF) that are easy to handle, fl xible and economical. They are excited by 650 nm lasers, housed in ST-connectors to obtain compact and rough prototypes. Optical multiplexing is used to increase the measuring safety area. Frequency division multiplexing is used to address each sensor head. A discussion about the influenc of tilts and aberrations is also included.

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“…The issue with electrical liquid level sensor is their limitation to detect if the liquid is conductive, potentially explosive or erosive. Other problems include high cost, slow response, heavy weight and potential excessive liquid fuel in tanks [1][2][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Fiber optic liquid level sensor system for aerospace applications

2014

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Detection of the liquid level in fuel tank becomes a critical element for the safety and efficiency in aerospace operations. Two liquid level sensing techniques are presented in this paper. The first technique is based on optical fiber Long Period Gratings (LPG). In this system, the full length of a specially fabricated fiber is the body of the probe because the length of the sensing fiber that is submerged in the liquid can be detected by the interrogation system. The second system based on Total Internal Reflection (TIR) uses optical fibers to guide light to and from an array of point probes. These probes are specially fabricated, miniature optical components which reflects a substantial amount of light back into the lead fiber when the probe is gas but almost no light when it is in liquid. A detailed theoretical study by computer simulation was carried out on these two techniques in order to determine which technique was more suitable for experimental investigation. The study revealed that although the first technique may provide more potential benefits in terms of weight and easy installation; a number of technical challenges make it not suitable for a short term solution. The second, probe array based technique, on the other hand, is more mature technically. The rest of the research program was therefore focused on the experimental investigation of the probe array detection technique and the test results are presented in this paper.

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A digital fiber-optic liquid level sensor

Cited by 25 publications

References 4 publications

A CMOS liquid level to frequency converter with calibration circuits for detecting liquid level of intravenous drip

A CMOS liquid level to frequency converter with calibration circuits for detecting liquid level of intravenous drip

Multi-sensor system using plastic optical fibers for intrinsically safe level measurements

Fiber optic liquid level sensor system for aerospace applications

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