Obrad S. Aleksic

Comparative characteristics of thick-film integrated LC filters

The paper describes the design, fabrication and test of integrated LC filters in thick film technology. The range of filters was electrically characterized using a HP 8566B network analyzer. We present a scalable analytical model for thick film integrated LC filters that is suitable for design and circuit simulations. We also provide simple expressions for evaluating the optimum conductor thicknesses.

Resistivity Versus Geometry Relation In Bulk - Sintered And Thick Film MnCoFe - Oxide Thermistors

A relation between the electrical resistivity and geometry in bulk (pressed and sintered) and thick film NTC thermistors was determined. A powder mixture consisting of MnO, CoO and Fe2O3 called NTC-3K3 (EI Ferrites) was used for the realization of classical NTC disc shape thermistors sintered at 1200°C /30 min. After that, a thick film NTC thermistor paste was composed using the same powder (0.9 μm particle size on average), 4% of Bi2O3 and an organic vehicle (NTC-3K3-95 /2 EI Iritel). Different thick film thermistor geometry’s were printed of NTC paste on alumina and sintered at 850°C/10 min. PdAg paste was printed on both sintered-bulk and thick film thermistors. Their resistivity vs. geometry was compared. NTC coefficient B was determined on NTC - R (T) curves as B=4200 K. The range of the resistivity values obtained varied for planar shapes from 100 Ω to 10 MΩ, and for classical disc types from 2–200 kΩ

Micro‐flow sensor for water using NTC thick film segmented thermistors

Purpose – The purpose of this paper is to apply negative thermal coefficient (NTC) thick film segmented thermistors (TFSTs) in a micro‐flow sensor for water.Design/methodology/approach – A TFST is printed using NTC paste based on nickel manganite. The resistance of this thermistor is measured in a climatic chamber and the resulting curves are calibrated. A micro‐flow sensor is designed using a self‐heated segmented thermistor. The sensing principle is based on heat loss depending on the water flow intensity through the capillary. Water flow calibration is performed. The sensor sensitivity, inertia, and stability are analyzed.Findings – The micro‐flow sensor exhibits good stability, suitable sensitivity, and inertia for integral measurements of water flow.Practical implications – Advantages of a micro‐flow sensor using a TFST include low energy consumption, simple measuring procedure, and passive electronics.Originality/value – This paper describes initial work on a micro‐flow sensor for water using TFSTs.

A thick film NTC thermistor air flow sensor

Two planar NTC thick film thermistors were placed in a rectangular air guide with a large cross section area and connected to opposite branches of a Wheatstone bridge to form air flow sensor. Thick film sensors used in measurements were printed on alumina using of thermistor paste NTC 3K3 - 95/2 in EI Iritel. NTC thermistor paste was composed of submicronic powder (mixture of Mn, Co and Fe oxides), 4% B/sub 2/O/sub 3/ and an organic vehicle. The most suitable planar NTC thermistor geometry for an air sensor was segmented type with an optimized surface value of 75/spl times/12/spl times/0.5 mm. It was used to cover part of an open air gauge and conduct a heat from flowing air. The resistivity difference obtained on the thermistors was compared with the volume velocity of air laminar flow at room ambient temperature and humidity.

Analysis of Effects of Dielectric and Material Characteristics on the Performance of Thick Film Thermistors Using Commercial Software Tools

In this paper an alternative approach to analysis of NTC thermistors based on the use of commercial electromagnetic simulator tool is presented. Structure analyzed was a thick film segmented NTC thermistor. Influence of the material characteristics of thermistor paste used on the overall thermistor performance was analyzed and simulated. Obtained simulation results were compared with experimental results and validity of the adopted approach was verified

Segmented thermistors printed by NTC nanometric paste and applied in volume air-flow sensors

An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation, NTC thick-film characterization, realization and optimization of new planar thermistor geometries to custom design thermistors and their application for temperature and volume airflow sensors was recently determined. The aim was to make custom designed segmented NTC thermistors printed and sintered on alumina. Two types of volume airflow sensors were formed: indirectly heated and self-heated. A pair of segmented thermistors was placed in an air guide and connected to differential branches of the Wheatstone bridge. A heater was placed in the middle between the thermistors for the indirectly heated type, while for the self-heated type the same thermistors were self-heated by a constant current source. First the thermistor responses vs. the airflow (calibration curves) were measured, and then thermistor responses in time (inertia) to fast airflow changes from the minimum to the maxi

Thick film symmetrical EMI LC cells

Thick film symmetrical LC cells with two pairs of terminations were printed on alumina using PdAg paste and crossover dielectric. Planar inductors such as meander, spiral, bispiral, and solenoid in plane were distributed over planar capacitors such as sandwich, interdigitated and segmented. Attenu‐ation and Smith charts of symmetrical EMI LC cells were measured on network analyzer in the range of 1 MHz to 3 GHz. Two or three main LC cells were joined in series to sum attenuation. The obtained results were compared mutually, at first, and than with the cubic (chip) EMI LC filters. The obtained EMI noise suppression was similar, but the filter band of thick film LC cells was much wider.

A Thermal Sensor for Water Using Self-Heated NTC Thick-Film Segmented Thermistors

A simple thermal (heat loss) sensor system was designed in a small plastic tube housing using a negative thermal coefficient (NTC) thick-film thermistor as a self-heating sensor. The voltage power supply [range constant voltage (RCV)-range constant voltage] uses the measured input water temperature to select the applied voltage in steps (up and down) in order to enable operation of the sensor at optimal sensitivity for different water temperatures. The input water temperature was measured using a “cold” NTC thick-film segmented thermistor. The measured calibration curves were modeled. Additional calculated curves were interpolated between the experimental curves in fine steps to cover each temperature of input water and can be used for determining the water volume flow rate or water velocity. The realized prototype flow meter inertia, stability, repeatability, and tolerance were measured and analyzed. The proposed intelligent RCV thermal flow meter system will include a smart power supply with range-constant-voltages (auto-range), a simple acquisition card and custom designed flow meter software.

EM Simulator Analysis of Optimal Performance Thick-Film Segmented Thermistors versus Material Characteristics Selection

In this paper, an alternative approach to the analysis of thick-film segmented negative temperature coefficient thermistors based on the use of a commercial electromagnetic simulator tool is presented. The influence of the geometrical parameters and material characteristics of the used thermistor paste on the overall thermistor performance was analyzed and simulated. A physical model for the segmented thermistors is given in brief, together with experimental data. The diffusion of electrode metal into the thermistor layer was analyzed, simulated, and estimated. Obtained simulation results were compared with experimental results, and the validity of the adopted approach was verified.

Design and Simulation of Thick Film Thermistors Using Commercial Simulation Tools

Methods for predicting and analyzing the behavior of NTC thermistors have remained the same and they typically include accurate measurements of resistance and temperature, followed by curve-fitting methodologies for determining the relationship of temperature to resistance for similar thermistor devices. In this paper, new approach based on using commercial software tools was applied on the thick film segmented thermistor models. Obtained simulation results were compared with experimental results and validity of the adopted approach verified. Realized segmented thermistors were made of a low temperature NTC thick film paste NTC 3K3 95/2 with nanometer particle powder printed on alumina