The Paton Welding Journal, 2014, #11, 32-35 pages
SYSTEM FOR MEASUREMENT OF TEMPERATURE OF BIOLOGICAL TISSUES IN BIPOLAR HIGH-FREQUENCY WELDING
Yu.N. LANKIN, L.F. SUSHY and E.N. BAJSHTRUK
E.O. Paton Electric Welding Institute, NASU. 11 Bozhenko Str., 03680, Kiev, Ukraine. E-mail: email@example.com
HF welding of soft biological tissues using bipolar electrosurgical instrument is basically similar to resistance spot welding of metals. Physical-biological processes, taking place in tissues during welding, mainly arise from their heating and applied pressure. Thus, information about temperature in contact of tissues during welding is very important. There are virtually no publications on equipment and measuring of temperature in welding of biological tissues. Standard thermocouples with wires of small diameter (70mm), as the tiniest, were used as temperature probes. Heat generation of thermocouple due to welding current passing through it is virtually absent in comparison with heat generation in tissue. Distortion of electric and temperature fields in the vicinity of thermocouple can be neglected. Thermal time constant of chosen thermocouple makes around 8 ms based on reference data. Measurement system consists of chromel-alumel thermocouple with wire of 70 mm diameter, themoEMF amplifier, analog filer of lower frequencies, ADC and laptop. The experiments show that thermocouple can be represented by pure first-order time delay. Thermal time constant of thermocouple is 4.3 ms, time delay makes around 1 ms. Analog filter of lower frequencies completely suppresses welding current noises and determines general band of temperature measurement system of 25 Hz width. Developed system allows for measuring the temperature in contact of biological tissues during HF welding using bipolar electrosurgical instrument without dynamic errors and provides no distortions in tissue temperature field. 9 Ref., 6 Figures.
welding of biological tissues, measurement of temperature, thermocouple, thermal time constant, filtering of welding current noises
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