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university:courses:electronics:electronics-lab-25 [24 Apr 2017 07:51] – rename Antoniu Miclausuniversity:courses:electronics:electronics-lab-25 [29 Nov 2018 11:23] – add Fritzing + LTspice files Antoniu Miclaus
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 2 - small signal diode (1N914 or similar)\\ 2 - small signal diode (1N914 or similar)\\
  
-===== Description: =====+===== Directions: =====
  
-Construct the circuit of figure 1 using two 1N914 diodes. Connect scope input 1+ to the positive terminal of V<sub>Temp</sub> and connect scope input 1- to the negative terminal of V<sub>Temp</sub>. Use the Scopy Voltmeter or Oscilloscope instruments to monitor the value of V<sub>Temp</sub> using the True RMS measurement display. Use auto-range for the Voltmeter or set the "Volts/Div" scale for the Oscilloscope to its most sensitive value (10 mV) and ensure that Channel 1 is enabled.+Construct the circuit of figure 1 using two 1N914 diodes. 
  
 {{ :university:courses:electronics:a25_f1.png?600 |}} {{ :university:courses:electronics:a25_f1.png?600 |}}
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 <WRAP centeralign> Figure 1 differential temperature circuit </WRAP> <WRAP centeralign> Figure 1 differential temperature circuit </WRAP>
  
-===== Measurements: =====+===== Hardware Setup: ===== 
 + 
 +Connect scope input 1+ to the positive terminal of V<sub>Temp</sub> and connect scope input 1- to the negative terminal of V<sub>Temp</sub>. Use the Scopy Voltmeter or Oscilloscope instruments to monitor the value of V<sub>Temp</sub> using the True RMS measurement display. Use auto-range for the Voltmeter or set the "Volts/Div" scale for the Oscilloscope to its most sensitive value (10 mV) and ensure that Channel 1 is enabled. Connect Vp to the 5V Power Supply. 
 + 
 +{{ :university:courses:electronics:difftemp-bb.png |}} 
 + 
 +<WRAP centeralign> Figure 1 Differential Temperature Breadboard Circuit</WRAP> 
 + 
 +===== Procedure: =====
  
 1. Allow both diodes to reach the same temperature, i.e., T<sub>sense</sub> = T<sub>ref</sub> . Measure and record the voltage offset as V<sub>Temp</sub> set; subtract this offset voltage from your later measurements. 1. Allow both diodes to reach the same temperature, i.e., T<sub>sense</sub> = T<sub>ref</sub> . Measure and record the voltage offset as V<sub>Temp</sub> set; subtract this offset voltage from your later measurements.
 +
 +{{ :university:courses:electronics:difftemp-wav1.png |}}
 +<WRAP centeralign> Figure 3  T<sub>sense</sub> = T<sub>ref</sub> Differential Temperature Waveform</WRAP>
  
 2. Heat the sensor diode by squeezing it between your fingers. Wait for the voltage to stabilize, subtract V<sub>Temp</sub> set, and then record this value as the "body temperature" voltage. You might also try blowing through a straw to direct your warm breath at the sensor diode. 2. Heat the sensor diode by squeezing it between your fingers. Wait for the voltage to stabilize, subtract V<sub>Temp</sub> set, and then record this value as the "body temperature" voltage. You might also try blowing through a straw to direct your warm breath at the sensor diode.
 +
 +{{ :university:courses:electronics:difftemp-wav2.png |}}
 +<WRAP centeralign> Figure 4   T<sub>sense</sub> > T<sub>ref</sub> Differential Temperature Waveform</WRAP>
  
 3. If available, wrap the sense diode in a thin plastic bag and submerge it in ice water to chill the sensor diode. Again, wait for the voltage to stabilize, subtract V<sub>Temp</sub> set, and then record its value as the "freezing point of water" voltage. 3. If available, wrap the sense diode in a thin plastic bag and submerge it in ice water to chill the sensor diode. Again, wait for the voltage to stabilize, subtract V<sub>Temp</sub> set, and then record its value as the "freezing point of water" voltage.
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 What is the purpose of the reference diode in this configuration?\\ What is the purpose of the reference diode in this configuration?\\
 This circuit only measures the difference in temperature not the absolute temperature of either diode. How could you use the temperature dependence of a simple diode circuit like this to determine the actual temperature of the sense diode ( i.e. relative to absolute zero )?\\ This circuit only measures the difference in temperature not the absolute temperature of either diode. How could you use the temperature dependence of a simple diode circuit like this to determine the actual temperature of the sense diode ( i.e. relative to absolute zero )?\\
 +
 +**Resources:**
 +  * Fritzing files: [[ https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/analogdevicesinc/education_tools/tree/master/m2k/fritzing/diff_temp_sensor_bb | diff_temp_sensor_bb]]
 +  * LTSpice files: [[ https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/analogdevicesinc/education_tools/tree/master/m2k/ltspice/diff_temp_sensor_ltspice | diff_temp_sensor_ltspice]]
  
 ===== Further exploration: ===== ===== Further exploration: =====
university/courses/electronics/electronics-lab-25.txt · Last modified: 25 Jun 2020 22:07 by 127.0.0.1

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