Digital temperature compensation of a thermistor flowmeter

Katz, I.; Shaughnessy, Edward J.

doi:10.1088/0022-3735/20/5/021

“…Current meters of this type measure flow rate through the process of heat dissipation from a heated thermistor bead (LABARBERA & VOCEL, 1976), which also makes them sensitive to changes in the temperature of the surrounding water. The problem of temperature sensitivity can be overcome through the calculation of a temperatureindependent power dissipation coefficient K (mW/"C) (KATZ & SHAUGHNESSY, 1987). which takes into consideration the temperature of the sensor bead and the ambient temperature.…”

Section: Micro-current Meter Temperature Probe and Data Logger Designmentioning

confidence: 99%

Short‐Term and Small‐Scale Variation in Food Availability to Natural Oyster Populations: Food, Flow and Flux

Wilson-Ormond

¹

,

Powell

²

,

Ray

³

1997

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Food resources and water flow speeds vary on short-temporal and small-spatial scales important to feeding in natural populations of oysters (Crassosfrea uirginica). To better describe food availability to the oyster population, micro-current meters were used to measure flow 1-3 cm above the bottom and frequent water sampling was used to determine the quantity and composition of the,seston on Confederate Reef, Galveston Bay, Texas. The quantity and quality of food varied on time scales at least as short as 3 h and throughout the water column. Seston was high in detrital carbon, nitrogen poor, and had a high fraction of inorganic particles. The quantity of food at the bed was not predictable from samples taken near the surface. Water flow speeds were also highly variable. Whereas rapid flow speeds were measured, flow speed tended to cluster about a narrower range of slower speeds resulting in the mean speed being much higher than the median. Fluxes of food calculated from the quantity of food and water flow speeds were low and highly variable. Under most conditions, water flow speed was more important than food quantity in determining flux. Rapid flow rates could overcome low food quantity to result in relatively high fluxes, whereas slow flow resulted in small fluxes even if food was abundant. Changes in water flow rate associated with tidal changes and changes in speed are probably the primary agents controlling food availability on a daily basis. Decreased wind speed at night normally reduced flux in the early morning hours, for example. These results stress the importance of measuring food quantity and water flow speed on spatial and temporal scales important to oyster feeding. Model simulations of oyster populations at varying densities, flow rates and clump heights across the range of measured values show that flow rate is insufficient during most hours of the day and days of the year to prevent oysters from locally reducing food supply by their filtering efforts. Thus flow rate probably limits population density and adult size on Confederate Reef. ProblemThe food available to natural populations of suspension-feeding bivalves is dependent on the amount of food present in the water column and the characteristics of the water flow delivering food to the population. If the quantity of food is low, or the rate of water flow is slow, food limitation may occur resulting in decreased U. S.

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“…A constant-temperature hot-thermistor anemometer can tolerate wider range of temperature and airflow rate changes but has a slower response time than a hot-wire anemometer. Most constant-temperature anemometers use the idea of temperature compensation as presented in [15][16][17][18] to overcome temperature changes in their surroundings. With temperature compensation, the feedback control circuit of the anemometer maintains a constant differential temperature between a heated probe and a reference probe.…”

Section: Constant-temperature Hot-thermistor Anemometermentioning

confidence: 99%

Adaptive Measurement Control of a Thermal Flow Sensor

Yiu¹

2021

Preprint

0

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In the present work, an adaptive gain switching control strategy and a digital temperature compensation technique are integrated with a hot-thermistor anemometer to achieve sensor speed and accuracy improvement. The limitation of the Wheatstone bridge technique for temperature thermistors is compensated to achieve accuracy improvement. The feedback control gains are adapted to the particular range of airflow rates to achieve faster response. Simulation results have confirmed the response speed and accuracy improvement with the proposed digital sensor system. The proposed design has been implemented, and experiments have been conducted. Compared to an original thermal flow sensor with analog circuit, the measurement speed is significantly improved at low airflow rates with adaptive feedback control gains implemented in the prototype digital sensor system. The developed digital sensor system possesses desirable features such as a direct interface to the computer through a serial port, easy change of operational parameters and sensor configurations, and energy conservation, as well as simpler control design with the use of Pulse Width Modulation (PWM) to control the probe heater power.

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“…The basic principles assume that heat losses by conduction and radiation are assumed to be negligible compared to the heat transported by the gas through forced convection [19,20]. Hence the mass flow of the gas is proportional to the electrical power needed to hold a constant differential temperature between a heated probe and a reference probe [15][16][17][18][19][20].…”

Section: Constant-temperature Hot-wire Anemometer Reviewmentioning

confidence: 99%

“…As stated in the November 1989 issue of the Process Industries Canada [24], the trend of flow metering is going digital. Examples of academic papers on digital flow meters are [17] in 1986 and [16] in 1994. Many companies also advertise performance of their digital flow meters yet details of their instruments are kept as trade secrets.…”

Section: Recent Technologies On Flow Metersmentioning

confidence: 99%

Adaptive Measurement Control of a Thermal Flow Sensor

Yiu¹

2021

Preprint

0

View full text Add to dashboard Cite

In the present work, an adaptive gain switching control strategy and a digital temperature compensation technique are integrated with a hot-thermistor anemometer to achieve sensor speed and accuracy improvement. The limitation of the Wheatstone bridge technique for temperature thermistors is compensated to achieve accuracy improvement. The feedback control gains are adapted to the particular range of airflow rates to achieve faster response. Simulation results have confirmed the response speed and accuracy improvement with the proposed digital sensor system. The proposed design has been implemented, and experiments have been conducted. Compared to an original thermal flow sensor with analog circuit, the measurement speed is significantly improved at low airflow rates with adaptive feedback control gains implemented in the prototype digital sensor system. The developed digital sensor system possesses desirable features such as a direct interface to the computer through a serial port, easy change of operational parameters and sensor configurations, and energy conservation, as well as simpler control design with the use of Pulse Width Modulation (PWM) to control the probe heater power.

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Digital temperature compensation of a thermistor flowmeter

Cited by 6 publications

References 4 publications

Short‐Term and Small‐Scale Variation in Food Availability to Natural Oyster Populations: Food, Flow and Flux

Short‐Term and Small‐Scale Variation in Food Availability to Natural Oyster Populations: Food, Flow and Flux

Adaptive Measurement Control of a Thermal Flow Sensor

Adaptive Measurement Control of a Thermal Flow Sensor

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