Three-Axis’ Heat Loss Anemometer Comprising Thick-Film Segmented Thermistors

NTC thick-film segmented thermistors were used as anemometer sensing devices. They were screen printed of thick-film thermistor paste based on modified NiMn2O4 fine powder, organic vehicle, and glass frit. Their electrical properties, such as resistance vs. temperature R(T) and thermistor exponential factor B were obtained using measurements in the climatic test chamber. A uniaxial anemometer was formed using a thick-film segmented thermistor, which was placed in the hole drilled in rectangular piece of thermally insulating material. The uniaxial anemometer was used for the optimization of operating point of segmented thermistors as self-heating/wind sensing devices. The dc supply voltage was correlated with the air temperature sub-ranges (RCV). The power save mode such as 30s self-heating/5 min pause was used to measure the thermistor response on stable wind blow. The three-axis' anemometer was formed using five sensor devices placed in five holes drilled in the cubical piece of thermally insulating material: three thermistor sensors measure wind speed on the x, y, z - axes, the fourth sensor Pt 1000 measures the air temperature T, while the fifth sensor (capacitive type) measures humidity H. The obtained sensitivity and inaccuracy were compared with respective ones of other anemometers

Electronic Properties of BZT Nano-Ceramic Grades at Low Frequency Region

Barium zirconium titanate ceramics were prepared using solid state reactions of BaCO3, TiO2 and ZrO2 at elevated temperatures. The prepared BZT was mechanically activated in the planetary ball mill from 0-120 min to achieve different powder grades from micro- to nanosized particles. After the powder characterization by XRD and SEM the samples were pressed in disc shape and sintered at 1100 and 1200 °C in the air. The sintered samples were characterized by SEM. After that the silver epoxy electrodes were deposited on sintered disc samples. The disc samples capacitance and resistivity were measured in the low frequency region from 1 Hz to 200 kHz using a low frequency impedance analyzer. Sintering temperatures and powder grades were used as parameters. Finally, specific resistance ρ, dielectric permittivity (ε' + jε") and tgδ were obtained from the impedance measurements. The trends in electronic properties were analyzed: the relaxation effect of the space charge (inter-granular electric charges) vs. sintering temperature and ceramic grades. These show that mechanical activation has a significant effect on electrical properties, resulting in generally improved overall performance

Application of thick film segmented thermistors for measurement and analysis of ground top layer temperature profile

A new sensor for measuring ground top layer temperature profile was formed as a row of 40 thermistor segments connected in series, with which the change of temperature in the soil is mesaured and placed on 550 mm depth. The temperature sensor is multiple protected of humidity, calibrated on room temperature and placed vertically in the hole drilled on the lawn. The main electrical properties of the new sensor based on NTC thick film segmented thermistors are given in brief. The ground top layer temperature profile measurements were done in 40 points at 7am and 2 pm each day from the beginning of November 2017 to the end of February 2018.At the same time and in the same period of time the air temperature were measured and recorded. The results of measurements of ground top layer temperatureT(t,z) were given in daily and monthly diagrams as a function of time t and ground deepness d on z-axis. The correlation between ground top layer temperature profile and air temperature was analyzed: changes of ground temperature gradient and effect of precipitations on ground temperature profile. The results obtained enable study of temperature regime of ground top layer.Novi senzor temperaturnog profila gornjeg sloja zemlje, formiran je kao niz od 40 termistorskih segmenata redno vezanih, kojim se meri promena temperature, u zemlji do dubine d=550 mm. Temperaturni senzor je višestruko zaštićen od vlage, kalibrisan na sobnoj temperaturi i postavljen u vertikalno izbušenu rupu na travnjaku. Osnovne električne karakteristike novog senzora na bazi NTC debeloslojnih segmentiranih termistora date su ukratko. Merenje temperaturnog profila gornjeg sloja zemlje u 40 tačaka vršeno je u 7 i u 14 časova od početka novembra 2017. do kraja februara 2018. godine. U tom periodu u istim terminima merena je i temperatura vazduha. Rezultati merenja temperature gornjeg sloja zemlje T(t,z) prikazani su dijagramima sa dnevnim i mesečnim pregledom kao funkcija vremena t i dubine zemlje d po z-osi. Analizirana je korelacija između temperature gornjeg sloja zemlje i vazduha: promena gradijenta temperature tla i uticaj padavina na temperaturni profil. Dobijeni rezultati omogućavaju dalje proučavanje temperaturnog režima gornjeg sloja zemlje

Analysis and optimization of a thermal sensor system for measuring water flow

A simple thermal sensor system was designed for measuring water flow in the water mains using the heat loss principle with a NTC thick film segmented thermistor as a self-heating sensor. Thick film segmented thermistors were screen printed on alumina substrate. NTC thermistor paste was formed of very fine Cu0.2Ni0.5Zn1.0Mn1.3O4 powder obtained by a combined mechanical activation/thermal treatment process, an organic vehicle and glass frit. The thermal sensor system was analyzed in the static and dynamic regime. A range constant voltage power supply was defined in the range 9-19 V for input water temperatures of 30-2 degrees C, maintaining a supply voltage in steps of 2 V for a change in 5 degrees C of input water temperature. This enables optimal operating power, i.e. heat generation on the self-heating thermistor. Measured calibration curves for different input water temperatures and input water flow rates were modeled, enabling interpolation of additional calculated curves to cover a wide range of input water temperatures

Heat Loss Flowmeter for Water Based on Thick Film Thermistors in Power Save Regime

Novel heat loss flowmeter for water consists of the small plastic housing and two NTC thick film segmented thermistors with reduced dimensions placed along the main axis. The segmented thermistors were printed using the modified nickel-manganese paste and sintered in air at 850 degrees C / 10 min in the conveyor furnace. The first thermistor Th-1 is cold and measures input water temperature and the second thermistor Th-2 is self-heated at constant voltage and measures water flow rate. A short switch mode operating cycle for the self-heating thermistor was introduced: 30s of self-heating from the initial state and after that 90s of natural cooling to the initial state. The self heating DC current in 30th second I-30 is recognized as the flowmeter response on stable water flow Q, while input water temperature T-w was used as a parameter. The flowmeter temperature range was divided in a few sub-ranges and adaptive DC voltage power supply (RCV) was introduced for each sub-range. The flowmeter measuring range and inaccuracy were compared with respective ones of other flowmeters

A Ground Temperature Profile Sensor Based on NTC Thick Film Segmented Thermistors: Main Properties and Applications

A new ground temperature profile sensor comprising of a row of thermistors enables a large number of equidistantly arranged measuring points. The row of thermistors was formed using a group of negative temperature coefficient thick film segmented thermistors connected in series. After that calibration of the DC thermistor resistance R was performed at room temperature and the sensor was placed in a hole drilled on the lawn. DC resistances R of the row of thermistors were measured versus depth z as a parameter and converted to actual temperature T(z) in the ground using the Steinhart-Hart equation. The temperature profile of the ground depending on deepness z and time t as a function T(t, z) was measured on different days during one year in the early morning and in the afternoon. The temperature at the ground surface was compared with the temperature of the deepest sensor point in the ground. Thermal diffusivity D of the ground was determined using measured data T(t, z) in the periods of steady ground temperatures. The new ground temperature profile sensor was realized to investigate the correlation between air and ground temperature, observation of ground temperature profile changes and heat exchange (heat transfer, diffusion, gradient, and heat flow direction) through the ground top layer and finally humidity estimation versus deepness

Application of thick film segmented thermistors for measurement and analysis of ground top layer temperature profile

A new sensor for measuring ground top layer temperature profile was formed as a row of 40 thermistor segments connected in series, with which the change of temperature in the soil is mesaured and placed on 550 mm depth. The temperature sensor is multiple protected of humidity, calibrated on room temperature and placed vertically in the hole drilled on the lawn. The main electrical properties of the new sensor based on NTC thick film segmented thermistors are given in brief. The ground top layer temperature profile measurements were done in 40 points at 7am and 2 pm each day from the beginning of November 2017 to the end of February 2018.At the same time and in the same period of time the air temperature were measured and recorded. The results of measurements of ground top layer temperatureT(t,z) were given in daily and monthly diagrams as a function of time t and ground deepness d on z-axis. The correlation between ground top layer temperature profile and air temperature was analyzed: changes of ground temperature gradient and effect of precipitations on ground temperature profile. The results obtained enable study of temperature regime of ground top layer

Electronic Properties of BZT Nano-Ceramic Grades at Low Frequency Region

BZT ceramics was prepared by using fine powder mixture of BaCO3, TiO2 and ZrO2 in the respective molar ratio to form Ba(Zr0.10Ti0.90)O3 via solid state reaction at elevated temperature. The prepared BZT was milled in the planetary ball mill from 0-120 min to achieve different powder grades from micron to nano-sized particles. After the powder characterization by XRD and SEM the samples were pressed in disc shape and sintered at different temperatures from 1100-1350°C in the air. The sintered samples were characterized by SEM and their density and average grain size was determined and presented vs. sintering temperature and powder grades (milling time). After that the silver epoxy electrodes were deposited on sintered disc samples. The disc samples capacity and resistivity were measured at low frequency region from 1 Hz to 200 kHz using low frequency impedance analyzer. The sintering temperatures and powder grades were used as parameters. Finally the specific resistance ρ, dielectric constant (ε' + jε") and tgδ where determined from the impedance measurements. The behavior of electronic properties where analyzed e.g. the relaxation effect of the space charge (inter-granular electric charges) vs. sintering temperature and ceramic grades. The results obtained were compared with best literature data for the losses in BZT ceramics at low frequencies