Thermometer Circuits

The telephone-line tester consists of nothing more than a meter (that`s used to measure line voltage in the on- and off-hook state), three resistors (one of which is variable), a pushbutton switch, and a modular telephone connector...

Digital theremin

The CD4069 or 74C04 hex inverterâ€”is used as^ fixed-frequency oscillator centered around 100 kHz. U2 contains the variable frequency oscillator and balanced modulator. The CD4046 is a phase-locked loop and R3, R4, and C2 determine the center frequency of the on-chip oscillator. The antenna forms a parallel capacitance with C2, which allows the frequency to be shifted several kilohertz by bringing a hand near the antenna. R4, the ZERO control, allows the variable.....

Digital thermometer

The sensor consists of two series-connected lN914s, part of the circuit of a 555 multivibrator. Wired as shown, the output pulse rate is proportional to the temperature of the diodes..

Electronic Thermometer

This thermometer uses an NTC thermistor (RIO) to produce a dc voltage that decreases with temperature, to drive an I..

Temperature-to-frequency converter

The circuit exploits the fact that when fed from a constant current source, the forward voltage of a silicon diode varies with temperature in a reasonably linear way. Diode Dl and resistor R2 form a potential divider fed from the constant current source. As the temperature rises, the forward voltage of Dl falls tending to turn Ql off. The output voltage from Ql will thus rise, and this is used as the control voltage for the CMOS VCO..

Differential thermometer

The 50 k ohm pot trims offsets in the devices whether internal or external, so it can be used to set the size of the difference interval. This also makes it useful for liquid-level detection. ..

Dual over-under temperature monitor

This circuit is ideal for use as an over-under temperature monitor, where its dual output feature can be used to drive HIGH and LOW temperature-indicator lamps, relays, etc. Tl is a 6.3 volt filament transformer whose secondary winding is connected inside a four arm bridge. When the bridge is balanced, ac output is zero, and C5 (or C7) receives no gate signal. If the bridge is unbalanced by raising or lowering the thermistor's ambient temperature, and ac voltage will.....

Temperature control

A couple of transistors and a thermistor in the charging network of the 555 type timer enable this device to sense temperature ^nd produce a corresponding frequency output. ..

Temperature-measuring-add-on-for-dmm-digital-voltmeter

The DVM-to-temperature adapter is built around a single IC, National"s LMlO. That micropower IC contains a stable 0.2 V reference, a reference amplifier and a general-purpose op amp. The circuit is designed for a linear temperature range of 0 to 100Â°C (32 to 212Â°F). The 0.2-V reference and reference amplifier provide a stable, fixed-excitation voltage to the Wheatstone bridge. The voltage is determined by a feedback network consisting of Rl through R6. Switch S2a.....

Centigrade thermometer 0-100c

The ultra-low bias current of the ICL7611 allows the use of large-value gain-resistors, keeping meter-current error under Yt%, and therefore saving the expense of an extra meter-driving amplifier. ..

Digital temperature measuring

The output voltage of a thermocouple is converted into frequency measured by a digital frequency meter. The output thermocouple signal is proportional to the temperature difference between the hot junction and the thermostat kept at 0Â°C, it drives the voltage-to-frequency converter changing the analogue input signal into the output frequency with the conversion ratio adjusted in such a way, that the frequency is equal to the measured temperature in Celsius degrees,.....

Differential-thermometer

The differential thermometer uses two probes and shows the temperature difference betw-een them, rather than the exact temperature. ..

Temperature measurement using two cables

In those cases we want to measure the temperature in an area far from where it is. The imaging unit installed, you should find some way to connect the latter with the necessary sensor. The cables we use most often will have three two conductors for power sensor and one more to carry the signal representing the temperature. But it may have only two, assuming that one will carry the potential of land and the second supply voltage with the signal temperature. This is possible.....

Digital thermometer with zero adjust

This circuit allows zero adjustment as well as slope adjustment..

RTD thermometer

This thermometer is capable of 0.01Â°C accuracy over - 50Â°C to +150Â°C. A unique trim arrangement eliminates cumbersome trim interactions so that zero gain, and nonlinearity correction can be trimmed in one even trip. Extra op amps provide full Kelvin sensing on the sensor without adding drift and offset terms found in other designs. Al is configured as a Howland current pump, biasing the sensor with a fixed current. Resistors R2, R3, R4 and R5 form a bridge driven.....

Thermocouple Temperature Control

This control, with zero-voltage load switching, uses a CA3130 BiMOS op amp and a CA3079 zero-voltage switc..

Electronic-thermometer

This circuit uses the +5 V reference output and the op amp to level shift and amplify the 2.1 mV/Â°C Tempco output into a voltage signal dependent on the ambient temperature. Different scaling can be obtained by selecting appropriate resistors from the table giving output slopes calibrated in degrees Celsius or degrees Fahrenheit. To calibrate, first measure the voltage on the Tempco pin, VTEMPCO. and the ambient room temperature, TA in Â°C. ..

Thermocouple amplifier

Input protection circuitry allows thermocouple to short to 120 Vac without damaging the amplifier. Calibration: Apply a 50 mV signal in place of the thermocouple. Trim R3 for V0UT = 12.25 V. Reconnect the thermocouple...

INDUSTRIAL TEMPERATURE CONTROLLER

This practical temperature controller controls the temperature of any device according to its requirement for any industrial application. It also displays the temperature on an LCD displays in the range of –55°C to +125°C. At the heart of the circuit is the microcontroller from 8051 family which controls all its functions. An IC DS1621 is used as temperature sensor. The DS1621 Digital Thermometer and Thermostat provides 9-bit temperature readings, which indicate the.....