Measurement of temperature using Thermistor temperature sensor and perform its data logging using NI USB 6008 and LabVIEW.

Objective:

Measurement of temperature using Thermistor temperature sensor and perform its data logging using NI USB 6008 and LabVIEW. Design the front panel as shown in fig.

Apparatus Required:

• 10K Thermistor temperature sensor.
• Breadboard
• Jumper wires
• NI USB 6008 multifunction DAQ
• 1K resistor.

Theory:

Thermistor: It is a resistive temperature sensor. It has Negative Temperature Coefficient (NTC) of resistance, means the resistance of thermistor increases as the temperature decreases and vice versa. It is very highly sensitive temperature sensor and the relation between temperature and resistance is non-linear.

NI USB 6008: It is a multi-function DAQ, because it has both Analog and Digital I/O lines with 5V power supply. It is connected through a USB cable to the PC. It has

• 8 analog inputs (12 bits, 10Ks/sec)
• 2 analog outputs (12 bits)
• 12 digital I/O lines. 

Procedure:

• Connect the sensor with the DAQ as per the diagram shown above.
• Connect the USB cable of DAQ to one of the USB ports of the PC.
• Open the LabVIEW software and create a new VI. Bring the DAQ Asst function into the block diagram by right clicking over it go to Express------>Inputs-------->DAQ Asst.
• Select the proper channel of the DAQ as Acquire Signals------->Analog Input------->Voltage------>AI 0 then click on finish.
• A configuration window will be opened and change some parameters in the configuration window such as:

         Voltage range (max=5, min=0)

         Terminal configuration (RSE)

         Acquisition Mode (Sample on Demand), then click on OK.

• Now the LabVIEW will configure the DAQ and Build all the parameters you have changed.
• A ‘DAQ Asst’ function block will appear on the block diagram and it has an output variable named ‘Data’. It has an outward arrow (input for the VI) means the data acquired by the DAQ is ready for further processing in the VI.
• The value of the variable ‘Data’ is the real time data in Voltage.
• Now find the resistance of the thermistor (R_t) at temperature ‘t’ using this formula:

\[{R_t} = \frac{{V{R_S}}}{{{V_{CC}} - V}}\]

Where

V = voltage obtained from the DAQ

R_S = Series Resistance = 1K

V_CC = Supply Voltage = 5V

Now from R_t, find the temperature (T) using the following formula:  

\[T = \frac{1}{{a + b\ln {R^{'}} + c\ln {R^{'2}} + d\ln {R^{'3}}}}\]

Where

T = temperature in Kelvin

R’ = R_t/R

R = Thermistor resistance = 10K

a= 0.00335401

b= 0.000290967

c= 3.632136 X 10^-6

d= 7.1922 X 10^-7

Convert the temperature from Kelvin to Celsius and make the file system to log the data in the following format:

Date	Time	Thermistor voltage	Thermistor Resistance	Temperature	Status

Note: For the status give a high and low threshold limit of the temperature, within that limit the temperature is ‘NORMAL’ otherwise ‘ABNORMAL’