Comparison of two approaches to measurement of electrical impedance of glass microelectrodes designed for evaluation of temperature changes in biological tissues.
We proposed a temperature sensitive microelectrode for rapid measurements of temperature at the cellular level. In principle, the electrical impedance of the tip of the microelectrode changes with temperature. We designed an impulse measurement system (STEP) sensitive to the above changes of impedance. The system is based on a presettable negative input impedance of the current to a voltage converter. We compared the efficiency of the new STEP with the currently used RAMP system. We found following advantages of the STEP system: i) the danger of high voltage oscillations which could mechanically destroy the microelectrode tip is eliminated; ii) this system provides the opportunity to set the maximum sensitivity of the system according to the measured temperature interval. Moreover, the STEP method makes it possible to measure the resistance by using a sinusoidal stimulation signal which has to be preliminarily compensated by a rectangular signal. The shortest sampling period of the new system represents 0.1 ms with a resolution higher than 0.1 K and sensitivity better than 30 mV/K.
Rech
F
F
Institute of Physiology, Czechoslovak Academy of Sciences, Prague.
Dittert
I
I
Vyskocil
F
F
D000818:Animals; D001831:Body Temperature; D017097:Electric Impedance; D008839:Microelectrodes; D012680:Sensitivity and Specificity; D013821:Thermometers