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Download opamp application using lm335-semiconductor temperature sensor
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BME 325 MEDICAL ELECTRONICS OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR TEMPERATURE SENSOR EXPERIMENT 04 OPAMP APPLICATION USING LM335-SEMICONDUCTOR TEMPERATURE SENSOR Objective: The aim of this experiment is the realization of a celcius thermometer using Lm335 series semicondutor temperature sensor and measuring various temperatures, comparing the results intended. Sensor output voltage must be set to show ° c unit on the screen of the multimeter using opamp circuits (amplifiers and adder, and so on). Theory: LM335 is a precision, easily calibrated, integrated circuit temperature sensor with an operating range of -40oC to 100oC. The low impedance and linear output makes interfacing to a control circuit simple. The sensor comes in a TO-92 package and provides an output voltage directly proportional to the absolute temperature at the rate of +10mV/oK. The output is calibrated with an external potentiometer to provide a 2.98 V output at 25oC. When calibrated at 25oC, the LM335 has an error of less than 1oC over a 100oC range. Output at ant temperature can be calculated using the formula below 𝑇 𝑉𝑜𝑢𝑡 𝑇 = 𝑉𝑜𝑢𝑡 𝑇𝑜 𝑥 𝑇𝑜 Knowing output voltage at a reference temperature output voltage at any temperature is calculated using equation. For example at 40°C output of the LM335 is 3.13Volts. Then the output at 100°C is given by V (100) = V (40) (273+100) / (273+40) = 3.13 x 1.19 = 3.724 Volts. Preliminary Work: 1) Calculate LM335 output at 20,25,30,35 °C Figure 1 1 BME 325 MEDICAL ELECTRONICS OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR TEMPERATURE SENSOR 2) In the figure a dc power source V2 is used instead of LM335 and it is output is 3.03V. output of U1,U2 and U3 are indicated. Calculate the unknown values for the circuit in figure 1 (including V3 DC source) so that the output voltage of the circuit will be Output voltage equal changetoper degree change in but temperature known as temperature sensitivity. temperature in °C in mVs. isFor example at 40°C output of the LM335 is LM335 is designed for 10mV/°C. This makes an ultra sensitive temperature STS is 3.18Volts approximately 3.13Volts or atit45°C output of the LM335 issensor. approximately biased using a but regulated power supply. biasingby current is within 400µA to 5mA for and 45mV the circuit output The measured a multimeter must be 40mV, LM335 and family. Figure 2 (for shows a STS biased using a dc power supply. A series resistor respectively. further information inspect LM335 datasheet). limits current (1.6mA) within the prescribed range. !!! ANYBODY WHO DID NOT PREPARE PRELIMINARY WORK CAN NOT JOIN THE EXPERIMENT !!! Procedure: 1) Calibrate LM335 as defined below. Output voltage change per degree change in temperature is known as temperature sensitivity. LM335 is designed for 10mV/°C. This makes it an ultra sensitive temperature sensor. STS(semiconductor Tempereture Sensor) is biased using a regulated power supply. The biasing current is within 400µA to 5mA for LM335 and family. Figure 2 shows a STS biased using a dc power supply. A series resistor limits tput voltage change per degree change in temperature is known as temperature sensitivity. M335 is designed for 10mV/°C. Thiscurrent makes it an(1.6mA) ultra sensitivewithin temperature sensor. STS is the prescribed range. (If you want to use a single DC power sed using a regulated power supply. The biasing current is within 400µA to 5mA for source for the positive voltage values for the whole circuit calculate the resistor value + Adj. M335 and family. Figure 2 shows a STS biased using a dc power supply. A- series resistor mits current (1.6mA) within the prescribed range. that must be used instead of 5.6k) Figure 1, Base Diagram LM 335 5.6K 9V 5.6K LM335 Vo 9V TP1 LM335 10K Vo - + Adj. Figure 2 PinLM Connection Figure 1, Base Diagram 335 Lm335 Figure 3 Figure 2, Biasing STS a) Uncalibrated b) Calibrated 5.6K 5.6K STS output is calibrated to read exact temperature in degree Kelvin using a potentiometer as TP1 Vo 9V LM335 Vo 10K Table-1 shown in Figure 2. In this calibration process the wiper of the potentiometer is connected to Device Temperature the adjustment terminal. Once calibrated at oneRange temperature the potentiometer is undisturbed. Figure 2, Biasing STS a) Uncalibrated b)LM125 Calibrated -55°C to 150°C 2) Construct the LM225 circuit in figure 3.125°C For accurate results you are advised to use -40°C to Table-1 potentiometers LM335 so that you can adjust accurately. -40°C to 100°C Device Temperature Range LM125 -55°C to 150°C Family of STS 9V LM335 LM225 LM335 -40°C to 125°C -40°C to 100°C Family of STS STS output is calibrated to read exact temperature in degree Kelvin using a 10-turm trimpot of the trimpot is connected to the trimpot is undisturbed. as shown in exact Figure 2b. Inin degree this calibration process the wiper S output is calibrated to read temperature Kelvin using a 10-turm trimpot shown in Figure 2b. In this calibration process the wiper of the trimpot is connected to the adjustment terminal. Once calibrated at one temperature the ustment terminal. Once calibrated at one temperature the trimpot is undisturbed. measure theTo temperature the STS make contact the with the surface of body. However, measure theshould temperature STS should make contact with the surface measure temperature of water or liquid STS is not dipped directly. The process of dipping tothemeasure water or liquid STS isliquid not dipped directly. The Liquid shorts terminals oftemperature the STS and STSof may spoil. Therefore to measure of body. However, process of dipping in Liquid shorts the terminals of the STS and STS may spoil. Therefore to measure liquid 2 BME 325 MEDICAL ELECTRONICS OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR TEMPERATURE SENSOR 3) Measure different temperetures in a range as wide as possible, compare your results with a thermometer afill the table below and draw temrepereture vs. volts diagram for the thermometer,sensor and circuit output. Fill the report by necessary measured values and graphs Question: Explain the use and purpose of each opamp. Equipment List: • • • • • • 3 741 Opamp 6 x 10 k , 1x5,6k, 1 x 1 k resistor, 3 x 10 k potentiometer 1 piece LM335 temperature sensor Multimeter Power supply (+15V,-15V,+9V,+5V) 3 Student ID # : Name : BME 325 MEDICAL ELECTRONICS OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR TEMPERATURE SENSOR REPORT: 1. V3 : R1 : R5 : R2 : R6 : R3 : R7 : R4 : Sensor Output (V) Tempereture (°C) Measured 2. (°C) V 3. Answer of the Question 4 Calculated Circuit Output (V0)