Differential Temperature Sensor

Differential temperature sensor is used to measure temperature difference in two different area.  Here is the schematic diagram of the circuit: Please note that the connection from pin 2 to pin 3 of LM308 shouldn’t be  there, just break the connection so we get valid configuration like as we see in other differential amplifier.  [Source: STMicroelectronics Application Note]

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LM135/235/335 Centigrade Thermometer

LM135/235/335 temperature sensor is designed ease absolute temperature reading, giving all positive value for any frequency, that’s why we read 2.7315V at 0 Celsius degree. To read directly in Celcius, we can use the following circuit: This circuit works by nothing more than providing a 2.7315 voltage reference, so you must connect the meter the sensor output and this reference […]

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Temperature Measurement via Thermocouple

This is a temperature measurement circuit using thermocouple. This is a low-frequency application. It will allow the OPA335 to be switched directly into the signal path. This circuit has low noise, high accuracy, and low drift. Here is the circuit : The 4.096-V bridge supply is provided by a precision voltage reference. A negative temperature coefficient of  diode D1’s forward […]

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Ultrasonic Proximity Detector

This is ultrasonic proximity detector circuit. This circuit consist of micropower opamp and a pair of matched piezo-ceramic tranducers. It uses a 9V battery as power supply. This circuit uses the radar principle, when the objects or people is nearby it will reflect the transmitter’s steady tone back to the reciever. Here is the circuit : First circuit is a […]

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