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Design and implementation of an intrinsically safe liquid-level sensor using coaxial cable.

Jin B, Liu X, Bai Q, Wang D, Wang Y - Sensors (Basel) (2015)

Bottom Line: In this paper, an intrinsically safe liquid-level sensor system for flammable and explosive environments is designed and implemented.Additionally, the system is designed with characteristics of intrinsic safety by limiting the energy of the circuit to avoid or restrain the thermal effects and sparks.The test results demonstrate that over the measurement range of 1.0 m, the maximum nonlinearity error is 0.8% full-scale span (FSS), the maximum repeatability error is 0.5% FSS, and the maximum hysteresis error is reduced from 0.7% FSS to 0.5% FSS by applying software compensation algorithms.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Advanced Transducers and Intelligent Control Systems, Ministry of Education, Taiyuan University of Technology, No.79 Yingzexi Street, Taiyuan 030024, China. jbq_007@163.com.

ABSTRACT
Real-time detection of liquid level in complex environments has always been a knotty issue. In this paper, an intrinsically safe liquid-level sensor system for flammable and explosive environments is designed and implemented. The poly vinyl chloride (PVC) coaxial cable is chosen as the sensing element and the measuring mechanism is analyzed. Then, the capacitance-to-voltage conversion circuit is designed and the expected output signal is achieved by adopting parameter optimization. Furthermore, the experimental platform of the liquid-level sensor system is constructed, which involves the entire process of measuring, converting, filtering, processing, visualizing and communicating. Additionally, the system is designed with characteristics of intrinsic safety by limiting the energy of the circuit to avoid or restrain the thermal effects and sparks. Finally, the approach of the piecewise linearization is adopted in order to improve the measuring accuracy by matching the appropriate calibration points. The test results demonstrate that over the measurement range of 1.0 m, the maximum nonlinearity error is 0.8% full-scale span (FSS), the maximum repeatability error is 0.5% FSS, and the maximum hysteresis error is reduced from 0.7% FSS to 0.5% FSS by applying software compensation algorithms.

No MeSH data available.


(a) Experimental data of the hysteresis test, and (b) and enlarged view of the shaded area in (a).
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sensors-15-12613-f014: (a) Experimental data of the hysteresis test, and (b) and enlarged view of the shaded area in (a).

Mentions: The liquid level was measured in increasing mode and then in decreasing mode, respectively, in order to evaluate the hysteresis effect of our proposed sensor. The testing process was repeated five times in total. We calculated the average value of every tested point in two different modes and plotted them in Figure 14. It can be seen that there exists a slight difference at the same level. When in the decreasing mode, the measured liquid values are a little higher than those in the increasing mode. From Figure 14, the maximum hysteresis error is 0.7% FSS, or 0.7 cm, when the actual liquid level is 63 cm. The reason for this hysteresis is the “flow-back phenomenon”: when the liquid level decreased, the water flow-back film was attached on electrode plate causing the hysteresis error [22].


Design and implementation of an intrinsically safe liquid-level sensor using coaxial cable.

Jin B, Liu X, Bai Q, Wang D, Wang Y - Sensors (Basel) (2015)

(a) Experimental data of the hysteresis test, and (b) and enlarged view of the shaded area in (a).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507675&req=5

sensors-15-12613-f014: (a) Experimental data of the hysteresis test, and (b) and enlarged view of the shaded area in (a).
Mentions: The liquid level was measured in increasing mode and then in decreasing mode, respectively, in order to evaluate the hysteresis effect of our proposed sensor. The testing process was repeated five times in total. We calculated the average value of every tested point in two different modes and plotted them in Figure 14. It can be seen that there exists a slight difference at the same level. When in the decreasing mode, the measured liquid values are a little higher than those in the increasing mode. From Figure 14, the maximum hysteresis error is 0.7% FSS, or 0.7 cm, when the actual liquid level is 63 cm. The reason for this hysteresis is the “flow-back phenomenon”: when the liquid level decreased, the water flow-back film was attached on electrode plate causing the hysteresis error [22].

Bottom Line: In this paper, an intrinsically safe liquid-level sensor system for flammable and explosive environments is designed and implemented.Additionally, the system is designed with characteristics of intrinsic safety by limiting the energy of the circuit to avoid or restrain the thermal effects and sparks.The test results demonstrate that over the measurement range of 1.0 m, the maximum nonlinearity error is 0.8% full-scale span (FSS), the maximum repeatability error is 0.5% FSS, and the maximum hysteresis error is reduced from 0.7% FSS to 0.5% FSS by applying software compensation algorithms.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Advanced Transducers and Intelligent Control Systems, Ministry of Education, Taiyuan University of Technology, No.79 Yingzexi Street, Taiyuan 030024, China. jbq_007@163.com.

ABSTRACT
Real-time detection of liquid level in complex environments has always been a knotty issue. In this paper, an intrinsically safe liquid-level sensor system for flammable and explosive environments is designed and implemented. The poly vinyl chloride (PVC) coaxial cable is chosen as the sensing element and the measuring mechanism is analyzed. Then, the capacitance-to-voltage conversion circuit is designed and the expected output signal is achieved by adopting parameter optimization. Furthermore, the experimental platform of the liquid-level sensor system is constructed, which involves the entire process of measuring, converting, filtering, processing, visualizing and communicating. Additionally, the system is designed with characteristics of intrinsic safety by limiting the energy of the circuit to avoid or restrain the thermal effects and sparks. Finally, the approach of the piecewise linearization is adopted in order to improve the measuring accuracy by matching the appropriate calibration points. The test results demonstrate that over the measurement range of 1.0 m, the maximum nonlinearity error is 0.8% full-scale span (FSS), the maximum repeatability error is 0.5% FSS, and the maximum hysteresis error is reduced from 0.7% FSS to 0.5% FSS by applying software compensation algorithms.

No MeSH data available.