Complete Industrial Solution for Automation in

Temperature and Humidity Monitoring using

LabVIEW

Rohit Agrawal School of Electronics Engineering

VIT University

Vellore, India rohit4849@gmail.com

Saumitra Mohan School of Electronics Engineering

VIT University

Vellore, India saumitra90@gmail.com

Abstract Temperature and humidity are key issues to be taken care of in manufacturing plants and particularly that of

electronic assemblies. Lack of control over any of them will not

only affect the component and equipment but also the process

and the operators comfort, all ultimately leading to loss in production. This paper aims to provide a solution for similar

problem. The system provides for remote monitoring of the

temperature and humidity levels of different parts of the plant

with the help of the Wireless Senor Network Module by National

Instruments and is based on labView software platform. In

addition, it has the functionalities of a secured access for login,

easy reconfiguration, alarm facility in case of over limit and data

logging capability for further analysis. All these make it ideal for

industrial applications.

Keywords-monitoring; industry; labview; automation.

I. INTRODUCTION

Electronics assembly units work under a controlled

environment with temperature in the range of 16C-28C and

relative humidity in the range of 35% -65%. Lack of control

may influence defects in the SMT applications and soldering

process [1]. Low humidity can cause ESD issues and improper

solder joints (due to premature drying of the paste). Moisture

sensitive surface mount devices may experience popcorn

defects in high humidity environment due to sudden changes

in the temperature during reflow operations [2]. On the other

hand, variations in temperature leads to defects like improper

solder joints, bridging and extra oxidation of boards, solder

and components. Apart from the environment, specific

machines like solder paste refrigerator and desiccators for

storage of paste and bare PCB respectively also call for control

over these parameters.

Looking at their importance, it is kept mandatory in industries

to monitor the above environmental parameters which when

done manually is overlooked due to tediousness.

There have been works done in this regard but with lesser

consideration on the application side and deployment in

industrial environment. The temperature and humidity detector

mentioned in [3] does not provide for remote wireless

monitoring. In [4], the authors have presented a digital

temperature measurement system using labVIEW with

automatic control as well. But since, they make use of USB

Data collecting cards, wireless functionality is deprived.

Moreover, most of the works like mentioned in [3], [4], [5]

concentrate only on the temperature aspect overlooking the

humidity parameter.

There are various reasons for choosing labVIEW as the

platform for development of this system. LabVIEW provides

the ease of graphical programming and is very useful for

building an efficient user interface through various designs.

Moreover, most importantly, the availability of large no. of

toolkits with hardware support for almost all kinds of

applications make it an ideal software platform for developing

these kind of industrial solutions. Also it helps to relieve the

developer of the low level hardware and software issues

experienced during design so that he/she may lay more time

on the bottlenecks related to application [6].

The complete system architecture is depicted in Fig. 1. And

the hardware setup in Fig. 2. The rest of the paper has been

divided into 3 parts illustrating about the system hardware

details, application software and finally the conclusion.

Fig. 1 System Architecture

Battery Powered

External Power

Fig. 2 Hardware Setup

II. HARDWARE DEVELOPMENT

A. Wireless Sensor Network Module

The NI WSN system is built on an IEEE 802.15.4

wireless mesh network and provides for reliable

communication of measurement data across its various

devices. It consists of the NI-WSN-9791Gateway and WSN-

3226 nodes.

1) Gateway (WSN-9791): It communicates with the

Wireless nodes to acquire data wirelessly and send them to

the host PC via an Ethernet data acquisition interface [7]. It

acts as the network coordinator, in charge of node

authentication, message buffering, and bridging from the

802.15.4wireless network to the wired Ethernet network. The

gateway can be directly connected to the host PC or into a port

onto the local/other subnet, accordingly it needs to be

configured in Measurement and automation Explorer (MAX).

It works on an input voltage range of 9 to 30V and maximum

input power of 4.5 W. The 9V input is required during the

power up whereas it normally operates at 6 V.

2) Wireless Node (WSN-3226): It is a wireless

voltage/resistance device which works with the other nodes

and the gateway to form a wireless sensor network [8]. It has

got four channels which can be configured in either voltage

mode or in resistance/RTD mode. In our application, we are

making humidity measurements (voltage mode) on channel 1

and temperature measurements (RTD mode) on channel 2.

These nodes work in a voltage range of 3.6 to 7.5V. Powering

them with 4 AA 1.5 V batteries and keeping the sample

interval to be 60 sec or more can make the battery life to last

for 3 years. They can also be used to power up the sensors at

12V but the battery life has to be compromised.

B. Humidity and Temperature Sensor Combination

The humidity sensor used in our application works on a

voltage input of 3.5-5.5V. It consumes a current of around 0.5

mA and has an analog output voltage of 0-3.3V corresponding

to relative humidity of 0-100% which is scaled accordingly in

the software. For temperature measurements we have used a standard Pt-

100 RTD with temperature coefficient of resistance (TCR) equal to 3851 mu-ohm/ohm/C. The 3226 node makes the resistance measurement of the RTD and calculates the temperature on the basis of the Callendar-Van Dusen equation [8].

RT = R0[1 + A T + B T2 + C T3 (T 100 C)]

( for temperature < 0C )

RT = R0[1 + AT + BT2]

(temperature >0C)

Where: RT = RTD resistance at temperature T

R0

A = 3.9083 x 103 B = 5.775 x 107 C = 4.183 x 1012

A, B and C vary for different TCRs.

These sensors shown in Fig. 3 have been customized in the

form of a single box Fig. 4 to make them more rugged and

easily mountable for industrial applications.

Fig. 3 RTD and Humidity Sensor

Fig. 4 Customized Sensor Combination

Host Computer

Wireless Node

Sensor

Combination

DAQ Card

Gateway

Power Supply

Buzzer

RTD

Humidity Sensor

RTD Wires

Humidity Sensor

Wires

Sensor Power

C. Buzzer Module

A USB Daq-6008 has been interfaced to the host PC to

actuate an electronic buzzer whenever the humidity or

temperature values cross the specified limits.

III. APPLICATION SOFTWARE

The application is based on Lab VIEW 2011 platform

which is a graphical programming environment widely used

today to develop measurement, test and control systems

through virtual instrumentation. Its programs are called Virtual

Instruments which consist of the front panel (a user interface

with controls and indicators) and the block diagram (code to

control the front panel).

In order to provide a more scalable solution to the

temperature and humidity monitoring problem in industries,

several features have been added to the system which are

shown in the start-up screen in Fig. 5.

Fig. 5 Start-up Screen

A. User Authentication

There is an amount of skill set/training required in the

operators before they start to operate or run any particular

machine and as a result all the machines in industries are

password protected to ensure selective access to them. Similar

functionality has been illustrated in Fig. 6 which is the front

panel of the login vi wherein the operators name gets

displayed after he/she successfully logs in. The names of the

various users and their corresponding passwords are also

stored to provide multiple accesses.

Fig. 6 User Authentication

B. Configuration

There are a total of four wireless nodes used in our system shown as Channel 1, 2, 3 and 4. They can be placed anywhere as from the drop down list and accordingly operator has to select the exact location of placement. He can then specify the upper and lower bounds of temperature and humidity depending on the area requirements like the shop-floor needs temperature 16-28 Deg C and humidity 35-65% RH. This illustrates that even the operator can easily reconfigure the system depending upon his requirements without having any software knowledge. After entering these values, they have to be used so that the user does not need to configure the system every time he logs in. Clicking load button directly loads the fields with previously saved values. A view of the front panel and the block diagram are given in Fig. 7 and Fig. 8 respectively.

Fig. 7 Cofiguration Front Panel

Fig. 8 Cofiguration Block Diagram

C. Acquire and Display Alarm

The present temperature and humidity status can be viewed

by clicking the Acquire Button on the main screen. A dialog box pops up immediately after the button is clicked which asks

the user to enter a file name and choose a location for the

creation of a data log file with a DAT extension. The user may

see the temperature and humidity values with names of their

specific areas configured in the form of plot names. These

values are available both numerically and graphically along

with time stamp. Start logging button has to be clicked whenever the user wants to start the logging operation.

Whenever these values cross the specified limits, a red alert

message pops up either for temperature or humidity and it can

be seen which particular area it is. Moreover, the buzzer also

rings when the limits are crossed to alert the user properly.

Fig. 9 and Fig. 10 give a view of this features front panel and block diagram respectively.

Fig. 9 Acquire Front Panel

Fig. 10 Acquire Block Diagram

D. Analysis

The data log created previously is available for subsequent

analysis. The Analysis button when clicked from the main screen prompts the user to enter a file name that he would like

to analyze. This function shows a plot of the values recorded

previously with the start time/date and stop time/date. These

values depicted in the graph can also be seen on Microsoft

Excel by exporting them. Fig. 11 shows its front panel.

Fig. 11 Analysis Front Panel

CONCLUSION

The system being introduced in this paper not only automates the monitoring process of temperature and humidity

but also caters to other industrial problems of remote access,

authentication, reconfiguration, data logging and alarming.

Another big advantage of such a system is customizing it for

control applications also according to the needs of the user.

This paves way to work out ways to automate the process of

taking counter acting measures in case the temperature

and humidity goes out of the limits. Connecting the Building

Management System (BMS) it and switching on the Air

conditioning Units automatically seems one plausible solution.

REFERENCES

[1] Circuitnet, What should be the average temperature and humidity level in an electronic assembly facility, Ask the Experts.

[2] Technical Brief, Guidelines for handling and Processing Moisture Sensitive Surface Mount Devices (SMDs), Intersil.

[3] Yang Jingwei , Sun Rongxia, Ji Na, Li Lei, Chen Zhangle, The Portable Temperature and Humidity Monitor Based on Intelligent Sensor, Proceedings of. The 1st International Conference on Information Science and Engineering (ICISE2009)

[4] Wenlian Li, Sun Yang Li and Fan Xiao, The Design and Implementation of Digital Temperature Measurement and Automatic Control System, Proceedings of. 2010 International Conference on Computer Application and System Modeling (ICCASM 2010).

[5] Charles Castello, Asad Davari, Sun Ruei-Xi Chen, Temperature Control Framework Using Wireless Sensor Networks and Geostatistical Analysis for Total Spatial Awareness, Proceedings of. 10th International Symposium on Pervasive Systems, Algorithms, and Networks.

[6] Prasanna Ballal, Vincenzo Giordano, Pritpal Dang, Sankar Gorthi, Jose Mireles Jr., Frank Lewis, A LabVIEW Based test-bed with off-the-shelf components for research in mobile sensor networks, Proceedings of. 2006 IEEE International Symposium on Intelligent.

[7] NI WSN-9791 Ethernet Gateway Userguide and Specifications.

[8] NI WSN-3226 4-Channel, 20-Bit Voltage/RTD Node Userguide and Specifications.

[9] Bingsheng Wu, Chaozhi Cai, Remote Data Acquisition and Signal Processing System Based on LabVIEW, Proceedings of. International Conference on Measuring Technology and Mechatronics Automation 2009.

[10] Xinrong Zhang, Bo Chang, Research of Temperature and Humidity Monitoring System based on WSN and Fuzzy Control, Proceedings of. International Conference on Electronics and Optoelectronics (ICEOE 2011.