#1 TEMPERATURE DETECTION USING LM35 AND NI MYDAQ

Temperature measurement in today’s industrial environment encompasses a wide variety of needs and applications. To meet this wide array of needs the process controls industry has developed a large number of sensors and devices to handle this demand. In this experiment you will have an opportunity to understand the concepts and uses of many of the common transducers, and actually run an experiment using a selection of these devices. Temperature is a very critical and widely measured variable for most mechanical engineers. Many processes must have either a monitored or controlled temperature. This can range from the simple monitoring of the water temperature of an engine or load device, or as complex as the temperature of a weld in a laser welding application. More difficult measurements such as the temperature of smoke stack gas from a power generating station or blast furnace or the exhaust gas of a rocket may be need to be monitored. Much more common are the temperatures of fluids in processes or process support applications, or the temperature of solid objects such as metal plates, bearings and shafts in a piece of machinery. 

In my application, I used LM35 as a temperature sensor, whose output voltage varies linearly with respect to temperature, and is directly proportional to temperature. Let us 1st discuss about this sensor LM35-

1. Detectable range -   -55 deg.C to 150 deg.C

2. Linear with 0.5 deg.C ensured accuracy at +25 deg.C

• In this project, +Vs used is 15 V
• The output at 36 deg.C is 0.36V and the output at 21 deg.C is 0.21 V
• The above equations serve as the design equations for the block diagram of LABVIEW.

INTERFACE WITH NI MYDAQ :

The above figure shows the interface of the sensor circuit with Mydaq. After connecting the circuit as shown in the figure, the analog output is taken by AI 0 channel of Mydaq, the supply voltage to LM35 is given from the fixed voltage +15V from Mydaq. 

After the completion of interface, with the help of Labview, the data which is into the analog input of Daq is processed and calibrated to show the correct temperature by multiplying the output of Daq assistant with a numeric constant '100'.

Output of the project is shown as below- 

When the temperature is less than 40 deg.C, green light will be visible as shown above

 When the temperature exceeds 40 deg.C , red light will be visible and a dialogue box appears as shown in the figure indicating 'DANGER'

This concludes the project work on Temperature detection using LM35 and NI Mydaq. For further information about this project and about LABVIEW block diagram, contact me -  +Prajwal Kotamraju