• Journal of the Korean Institute of Telematics and Electronics
• /
• v.20 no.1
• /
• pp.50-54
• /
• 1983

Contact resistance variation which may be called sliding noise in carbon film variable resistors whose resistance elements consists of linear resistivity distribution were measured with several kinds of sliders and were analyzed to reduce the contact resistance variation. About the measuring method, the standard method of measuring contact resistance variation specified by the variable Resistance Components Institute was adupted. By analyzing the experimental results, it has been shown that the primary cause of contact resistance variation is due to current constriction and small discharge sparks in the resistance film in the area close to the slide contact. Moreover, it has been found that the sliding noise would be reduced by increasing the number of contact points, sliding speed, and pressure, and by using some kinds of insulation oil on the contacting surface. High contact resistance variation is likely to occur in the area of high resistance variation in a logrithmic resistance taper.

• Journal of Sensor Science and Technology
• /
• v.16 no.4
• /
• pp.263-269
• /
• 2007

Although variable resistance displacement transducer is widely applied for its technical simplicity, electrical point contact limits measurement resolution (precision). The present study introduced roller shaped structure for electrical line contact. Proto-type transducer was developed and measurement characteristics were compared with a commercialized product. When the displacement was varied with steps of 5 mm, 1 mm, and down to 0.1 mm, the correlation coefficient between resistance and displacement decreased lower than 0.9 in the commercialized product while the proto-type transducer maintained values higher than 0.99. Therefore, the measurement resolution was enhanced by approximately 10 times. Since manufacturing also seemed easier, the present results would enable more accurate and less expensive manufacturing of variable resistance displacement transducer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.1
• /
• pp.32-37
• /
• 2014

The thermal contact resistance (TCR) is one of the important resistance components in cryogenic systems. Cryogenic measurement devices using a cryocooler can be affected by TCR because the device has to consist of several metal components that are in contact with each other for heat transfer to the specimen without a cryogen. Therefore, accurate measurement and understanding of TCR is necessary for the design of cryogenic measurement devices using a cryocooler. The TCR occurs at the interface between metals and it can be affected by variable factors, such as the roughness of the metal surface, the contact area and the contact pressure. In this study, we designed a TCR measurement system at variable temperature using a cryocooler as a heat sink. Copper was selected as a specimen in the experiment because it is widely used as a heat transfer medium in cryogenic measurement devices. We measured the TCR between Cu and Cu for various temperatures and contact pressures. The effect of the interfacial materials on the TCR was also investigated.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.2
• /
• pp.48-51
• /
• 2013

The thermal contact resistance (TCR) is one of the important components in the cryogenic systems. Especially, cryogenic measurement devices using a cryocooler can be affected by TCR because the systems have to consist of several metal components in contact with each other for heat transferring to the specimen without cryogen. Therefore, accurate measurement and understanding of TCR is necessary for the design of cryogenic measurement device using a cryocooler. The TCR occurs at the interface between metals and it can be affected by variable factors, such as roughness of metal surface, contact area and contact pressure. In this study, we designed TCR measurement system at various temperatures using a cryocooler as a heat sink and used steady state method to measure the TCR between metals. The copper is selected as a specimen in the experiment because it is widely used as a heat transfer medium in the cryogenic measurement devices. The TCR between Cu and Cu is measured for various temperatures and contact pressures. The effect of the interfacial materials on the TCR is also investigated.

• Journal of the Korean Society of Safety
• /
• v.33 no.6
• /
• pp.22-27
• /
• 2018

Fire fighters are exposed to the risk of many accidents during fire suppression, especially near the high voltage circuit. In order to prevent and analyze the electric shock accidents, measurement of water resistance is crucial. However, this has been one of the overlooked research areas and it has been very difficult to measure the mixed up resistance components separately. In this paper, we measured a total resistance of apparatus and regarded it as a serial resistance of contact resistance and length dependant resistance. Measuring the resistance by varying the length of water stream, the variable resistance and fixed contact resistance appear, which are used to calculate the both components of resistances. In addition, the resistance of fire hose can be calculated from the parallel circuit which is formed by grounding the fire hose with the resistance of water stream. Results show that we can successfully measure the resistance per unit length of water stream and fire hose, thereby proving that this method is a facile way to measure water and fire hose resistance. However, many experiments are still required to obtain the precise contact resistance of ground under various condition and the resistance between the human body and fire hose.

• Progress in Superconductivity and Cryogenics
• /
• v.25 no.3
• /
• pp.38-42
• /
• 2023

The evaluation of no-insulation (NI) high-temperature superconducting (HTS) typically uses the lumped equivalent circuit (LEC) model. Constant parameters in the NI HTS LEC model accurately predict voltage and central magnetic field at currents below the critical current. However, it is difficult to find constant circuit parameters that simultaneously satisfy the measured voltage and magnetic field under overcurrent conditions. Recent research highlights changes in contact resistance during transient conditions, which may impact power loss estimation in NI HTS coils. Therefore, we confirm the influence of contact resistance changes on loss calculation in the transient state for NI HTS coil. To achieve this, we introduce a measurement data analysis method based on the LEC model and compare it with the LEC model using constant circuit parameters.

• Journal of Power System Engineering
• /
• v.12 no.2
• /
• pp.41-47
• /
• 2008

This article deals with the stress analysis of the friction drive, which transmits the power via the rolling resistance on the contract area between the two rotating bodies. On the contact area, friction drives are normally involved with shear stress due to the transmitted force, as well as normal stress. Thus the stress analysis including the shear stress is necessary for the design of the friction drive. Hertzian results can be used to estimate the normal stress distribution and elastic deflection of the contact area, although the shear stress distribution is not well defined. In order to investigate the shear stress distribution and its effects in a friction drive, we have performed the stress analysis of the spherical continuously variable transmission(CVT) using finite element method. The spherical CVT is one of friction drives, which is used in small power applications. The numerical results show that the normal stress distribution is not affected by the transmitted shear force, and the maximal shear stress is increased in small amount along with the shear force.

• Polymer(Korea)
• /
• v.37 no.4
• /
• pp.431-436
• /
• 2013

Polycarbonate (PC) films have been irradiated with various kinds of ions according to energy and dose. Change of the optical transmittance and chemical characteristics were confirmed by UV-VIS and FTIR (ATR) spectroscopy respectively. These UV-A block in 400 nm was variable from 10 to 100% according to energy and doses. Surface electrical resistance of PC film irradiated by ion beam was $10^6-10^{13}{\Omega}/cm^2$, which reveal variation of conduction. Contact angle of film irradiated by ion beam was decreased than the pristine film. Polymer surface morphology was examined by means of atomic force microscopy (AFM). As expected, degradation of polymer film was higher after irradiation with heavier Xe ions but the roughness in the polymer surface morphology were more pronounced for Ar ions. This observed effect can be explained by stronger compaction of polymer surface layer in the case of Xe irradiation, connected with a reduction of free volume available.

• Proceedings of the KIEE Conference
• /
• 1997.07b
• /
• pp.406-408
• /
• 1997

This paper presents the new method of a nondestructive spot welding state inspection system using neural networks. The learning process of neural networks makes the inspection system to adapt the variable welding parameters. The inspecting process is working with on-line real-time after off-line learning process. This neural network based inspection system shows reliable results through the field test for variations of applied voltages, currents, and contact area of the welding electrode.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.1
• /
• pp.37-43
• /
• 2011

In this paper, the optimized doping condition of crystalline silicon solar cells with $156{\times}156\;mm^2$ area was studied. To optimize the drive-in temperature in the doping process, the other conditions except variable drive-in temperature were fixed. These conditions were obtained in previous studies. After etching$7\;{\mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in 400-425-450-550-$850^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $830^{\circ}C$ to $890^{\circ}C$to obtain the sheet resistance $30{\sim}70\;{\Omega}/{\box}$ with $10\;\Omega}/{\box}$ intervals. Solar cell made in $890^{\circ}C$ as the drive-in temperature revealed 17.1% conversion efficiency which is best in this study. This solar cells showed $34.4\;mA/cm^2$ of the current density, 627 mV of the open circuit voltage and 79.3% of the fill factor.