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Thermocouple Sensitivity Measurement using ExpEYES and ADS1115

Author : Dr. Ujjwal Ghanta

  • Extra equipment/sensors Needed : ADS1115 16-bit ADC , PT1000
  • Approx Cost: < 400 Rs

Overview

This project aims to measure the sensitivity of a thermocouple by analyzing thermo-emf as a function of temperature using ExpEYES, an ADS1115 analog-to-digital converter, and a PT1000 temperature sensor.

Download the “ET_Curve.exe” file and run directly.

Required Apparatus :

  1. ExpEYES latest model (SEELAB 3.0, with I2C expansion bus)
  2. Analog to digital converter (ADS1115)
  3. Temperature Sensor (PT1000)
  4. T/K-type thermocouple
  5. Jumper wires (with alligator clips, optional)
  6. Glass beaker (100 ml)
  7. Mini Immersion water heater (optional)

Procedure:

Experimental Setup

  1. Preparation: Take 40 ml of hot water (~90°C).
  2. Sensor Setup: Submerge PT1000 and T/K-type thermocouple in hot water.
  3. Connections:
  4. Connect PT1000 between SEN and Ground.
  5. Connect ExpEYES (VCC, GND, SCL, SDA) to ADS1115 (VCC, GND, SCL, SDA).
  6. Connect thermocouple between A0 of ADS1115 and ground.
  7. Data Acquisition:
  8. Connect ExpEYES to PC via USB.
  9. Run the provided ET_Curve.exe file.
  10. Set time interval (20 or 30 sec).
  11. Data (time, temperature, thermo-emf) will be saved to “ET.dat”.
  12. Graphing:
  13. Plot 2nd and 3rd column
  14. Fit Linear to estimate the thermocouple sensitivity (slope) and room temperature (extrapolation)

Python Source code

Source Code 
''' Program for ET Curve with ADS1115 and
    using PT1000 and T-type thermocouple
    on 05/07/2024 
    Copyright: Dr Ujjwal Ghanta 23/Jul/24
'''

# Establish Connection
import eyes17.eyes
p = eyes17.eyes.open()

# Import python library 
import time, math
import numpy as np
from eyes17.SENSORS import ADS1115 

# Define the function to mesaure the temperature
def temperature():
    """Function to measure the instanteneous temperature"""
    R0 = 1000                    # PT1000 (RTD Name)
    Alpha = 3.85/1000            # Temperature coefficient 
    t0 = time.time()             # Time initialization
    n = 1                        # NO of measurements for averaging
    Rsum = 0
    for x in range (0,n):        # Loop for averaging
        r = p.get_resistance()   # Measure the resistance in ohm
        Rsum = Rsum+r            # Sum of resistance
    R = Rsum/n                   # Average resistance
    T = (1/Alpha)*((R/R0)-1)     # Calculate Temperature from Resistance
    return T 


t0=time.time()                     # Time initialization
while True:
    T = temperature()    
    ADC = ADS1115.connect(p.I2C)   # Measure the ADC
    ADC.setGain('GAIN_SIXTEEN')    # options : 'GAIN_TWOTHIRDS','GAIN_ONE','GAIN_TWO','GAIN_FOUR','GAIN_EIGHT','GAIN_SIXTEEN'
    emf = ADC.readADC_SingleEnded(0) # ADC reading in Channel A0
    ts=time.time()                   # current time
    t=ts-t0                         # Time difference
    print("%4.2f" % t, "S", "%4.2f" % T, "°C", "  ","%4.2f" % emf,"mV")
    file = open ("ET.dat", "a") # Appending file
    file.write("{0:4.2f} {1:4.2f} {2:4.2f}\n".format(t,T,emf))
    time.sleep(20)

NOTES :

  • Don’t forget to delete the existing data file “ET.dat”, if you are running the ET_Curve.exe file multiple times.
  • Reference_data (i.e, “T-type.dat”) and graph (“ET Curve.png”) for T-type thermocouple are provided.

Experimental Setup and Connections :

Experimental_Setup Experimental_Connections

NOTES :

  • A sample data (‘T-type.dat’) and the corresponding graph (‘ET Curve.png’) for the t-type thermocouple are also provided for reference.
  • Please see the ‘Experimental Setup.jpeg’ and ‘Connections for ET Curve.jpeg’ images for setup and connection.

Results:

Raw Data 
0.06 58.80 1.85
20.15 76.35 1.94
40.27 74.75 1.81
60.41 72.20 1.70
80.61 70.20 1.59
100.72 68.21 1.49
120.90 66.09 1.40
141.07 64.39 1.32
161.22 62.38 1.24
181.41 61.18 1.17
201.58 59.83 1.11
221.72 58.33 1.04
241.83 57.61 0.98
261.96 56.24 0.93
282.15 55.24 0.88
302.35 54.46 0.84
322.48 53.35 0.78
342.66 52.32 0.73
362.86 51.36 0.69
383.06 50.55 0.65
403.26 49.84 0.62
423.49 48.82 0.59
443.65 48.30 0.54
463.80 47.83 0.52
483.95 47.03 0.48
504.10 45.86 0.45

Obtained ET Curve from “T-type.dat” :

E T Curve

Special thanks to:

  • Heartfelt thanks to Dr. Jithin B.P. from CSpark Research for his invaluable assistance and support. His expertise and guidance were instrumental in the successful completion of this project. Dr. Jithin, your unwavering help and dedication are deeply appreciated.

  • Wholehearted thanks to the entire Inter-University Accelerator Centre (IUAC), New Delhi, India team especially Er. V.V.V. Satyanarayana, Mr. Abhijit Sarkar, and Dr. Ajith Kumar B. P. for developing the device and conducting the training program.

License

This work is licensed under a Creative Commons Attribution 4.0 International License. CC BY 4.0

Author

  • Dr. Ujjwal Ghanta

Github Page