Health transistor thermometer
This device allows for no more than 5 seconds to measure the patient's temperature with an accuracy of ±0,05° C. the measurement range is from 34 to 42° C. the Device is powered by two elements of type FMC consuming current is not more than 1 mA.
The device (see diagram) is a bridge, one arm of which includes the sensor - thermistor KMT-14 with a DC amplifier with two transistors T1 and T2 of type A13-p. An indicator is a measuring device of the type M-24 on talk 200 MCA, the scale of which is calibrated in degrees Celsius.
When the contact with the human body resistance of the thermistor changes, the bridge balance is disturbed, and the current in the diagonal of the bridge is amplified by transistors 20-50 times and deflects the arrow tool. The shift range of the measured temperature is achieved by selection of the resistor R2, and the expansion or contraction of the spectrum, the selection of resistors R5 and R6.
The VC switches 1a and 1B VC (switch) are used for the simultaneous inclusion of both batteries. Instrument calibration at the beginning of the scale (34° C) is carried out by the potentiometer R9 when open contacts of the circuit breaker BK2, and temperature measurement of the patient when the closed contacts BK2.
All parts and elements of the supply unit are accommodated in duraluminium body size HH mm.
Sensor-the thermistor is connected to the instrument via the two-wire cord.
Calibration of the instrument is as follows: the thermistor is placed in a thermostat with water, stir the impeller. Laboratory thermometer monitor the temperature of the water and the bridge DC MO-62 fix the thermistor resistance at the desired temperature range. Then in the shoulder of the bridge instead of the thermistor include the same axle (like the resistor) and the resistor R2, R5 and R6, set the desired temperature measurement range.
Author: A. Masuk; Publication: N. Bolshakov, rf.atnn.ru