Objectives:

Design an electronic circuit to measure Celsius temperature.

Model the circuit with Multisim and validate its operatingcharacteristics.

Design Requirements:

A need has arisen for an inexpensive electronic thermometer thatwill measure Celsius temperature over a specified range. The basisfor the design is the property that the forward voltage of a diodedecreases with increasing temperature and can be approximated by astraight-line linear equation. The feasibility as a transducer willbe studied and the specifications are as follows:

               Input Temperature Range: 0^o C to 100^o C

               Realistic Circuit Output Voltage: 0 V to 10 V based on acalibration factor of 0.1 V/^o C

               Voltage Representing Temperature: 0 V to 100 V monitored by VCVSwith a gain of 10

               Accuracy of ±0.5 ^oC at the two extreme inputtemperatures as measured at output of VCVS

               One 1N4148 diode to serve as the basis for the transducer

               No more than three 741 operational amplifiers (preferably two) and± 15 V power supplies

               Resistor values as needed (Assume calibration to an accuracy of 3significant digits.)

               One ideal voltage-controlled voltage source (VCVS) with a gain of10 to monitor the output

Pg. 1       This pagewith data added as requested should be Page 1 of the report.

Pg. 2       Theinstructor will specify a bias current. Connect a DCCurrent Source across thediode.               Perform a Temperature Sweep from 0^o Cto 100^o C and create a Multisim plot of diode voltage               versus Celsius temperature for Page 2. Use the vertical interceptand the slope (dy/dx) to      determine thestraight-line equation that describes the diode voltage as afunction of the         temperature. Then solve for the temperature in terms of the diodevoltage. List the resultsbelow.                                   

               Bias Current:      I.    II.     III.    IV.      V.                        

               

               Diode Voltage as a Function ofTemperature:                                                          

               

               Temperature as a Function of Diode Voltage:

Pg. 3      Design a circuit to provide an output voltage in terms of inputtemperature. Add a Voltage Gain Block with a gainof 10 so that the ideal value of the output voltage is the inputtemperature. Show the Multisim schematic diagram of the circuit onPage 3.

Pg. 4      UseTemperature Sweep to obtain a Multisim plot of theoutput voltage versus input Celsius         temperature. Usecursors to measure the output at the two extreme input values.

                                               

Input Temperature	Expected Output	Measured Output	Error in degrees C
0o C	0 V
100o C	100 V