DEVELOPMENT OF OPEN CODE APPLICATION FOR

REMOTE MEASUREMENTS

Simone Müller Vidal, Haroldo Stark Filho, Keiko Ono Fonseca, Alexandre de Almeida Prado Pohl

Centro Federal de Educação Tecnológica do Paraná (CEFET-PR)

Programa de Pós-Graduação em Eng. Elétrica e Informática Industrial

Av. Sete de Setembro, 3165 - CEP 80230-901 - Curitiba-PR – Brasil

Keywords: Java-based instruments, open source software, remote measurement

Abstract: New Web-based monitoring and control system applications have been developed to allow remote control

of equipments. Although interesting and useful, such applications present hidden costs related to software

development tools, annual software licensing, regular maintenance and upgrades. This paper presents an

application tool for controlling instruments over the Web developed using open code resource, such as

Linux, JAVA and CamServ. The application shows a potential use for laboratories dealing with different

types of equipment conformance testing. The developed tool allows access to the instrument’s screen

through a video streaming process, an alternative towards similar application, in which data is first acquired

and then plotted using graphical tools. First tests over a 10 Mbps LAN Network and 1 Gbps Ethernet Inter-

Universities Network evaluated latency times and the video quality versus video signal acquisition system.

Specification and development issues are described, as well testing and validation schemes of the developed

application.

1 INTRODUCTION

The world wide use and evolution of computer-

based communications, through which the Internet is

its best example, has made it possible to create and

develop new types of tools and services that are

intended to offer new alternatives and even replace

the way human activities are performed. One

example is the area of Industrial Automation and

Measurement, which has seen a great number of

innovations and improvements concerning the

remote control of instruments through web-based

techniques.

Beginning in the late 90´s a series of experiments

has shown the feasibility of doing remote

measurements over the web using simple

instruments like oscilloscopes, digital multimeters

and signal generators (Leitão, 2001; Gillet, 2001;

Ko, 2001; Ferrero, 2003). Most part of it was

foreseen as didactic laboratories, which could be

mainly justified as a cost-reduction attempt to bring

expensive instruments to a large audience of

students. Besides, the continuous spread of Local

Area Networks (LAN) in the industrial environment

has facilitated the intervention on and control of

dedicated measurement systems using a client-server

architecture based on Internet Protocol (IP) networks

(Schmid, 2001). Another example of remote

measurement system is drawn from the area of

conformance testing, in which product or equipment

shall be tested in order to verify their specifications

according to parameters established by norms and

standards. Usually, such tests should be carried on

by an experienced technician and require specific

instrumentation.

Following this line of research, this paper

presents the main features of an application tool

based on open code software developed for

controlling measurement instruments. Particularly,

an example is given using an instrument for

measuring baseband video signal. An important

characteristic of such tool is the possibility of

viewing the instrument screen, which displays the

online results of a given command. In contrast to

other tools, that usually send data and plot results in

a scope-like chart using graphic resources at the

client side, the application takes advantage of the

video output existing in many instruments to send

this signal over the Web. Alternately, a web cam or

a CCD may be used to capture the instrument’s

screen output and send it along with the commands

that the operator wishes to set. It facilitates the

de Almeida Prado Pohl A., Müller Vidal S., Stark Filho H. and Ono Fonseca K. (2004).

DEVELOPMENT OF OPEN CODE APPLICATION FOR REMOTE MEASUREMENTS.

In Proceedings of the First International Conference on E-Business and Telecommunication Networks, pages 33-38

DOI: 10.5220/0001393600330038

 SciTePress

observation of results on one side, but may be a

burden in low capacity networks imposing a great

delay to the streamed video signal. However, we

believe the upgrade of communication networks to

support higher capacities (e.g. GigaEthernet) and

Quality of Service (QoS) guarantees will drastically

reduce or avoid this problem.

This paper is structured as follow: Section 2

identifies the application context and related

requirements, its basic functions and architecture,

and some development issues; Section 3 describes

its operation through a remote measurement

experiment example. Functional and conformance

tests of the initial requirements are presented and

discussed at Section 4. Finally, Section 5 presents

our conclusions about the application tool

functionalities and results and outlines some future

research works on the same subject.

2 DESCRIPTION OF THE

APPLICATION BASIC

FUNCTIONS

2.1 Concept and Architecture

Every single application designed as a tool for

performing remote measurements should be first

concerned with the type of tests to be done. If its

purpose is only a didactic one, then instruments may

be interfaced apart of each other and each

experiment may run independently. If this is the

case, the application should consider simultaneous

access by several users limiting the users number by

the available number of instruments/experiments one

may have access to (Ko, 2001). However, if the

designers have in mind an application that needs to

follow a norm or standard and a sequence of tests

needs to be performed with one or more instruments

interconnected, then requirements are very strict and

most probably only one user will be allowed to

execute the application at a time. So, a previous

knowledge of the way the application works should

be available for the potential clients as, for instance,

by providing information at the appropriate web

page.

The tool can be represented by its basic

building blocks: a block that grants access to users

(authentication block), a block with general

information about the application and specific

information on every test that may be performed and

a block through which the user call the routines

needed for commanding the instruments. The

authentication block can also checks the tool

availability and sends warnings about the current

access status.

Standard client-server architecture is used for

implementing the remote laboratory. Fig. 01 shows

this architecture, where the remote client accesses a

video and instrument server through a web page.

The instrument server functions as the

communication interface to the required instruments

and should carry out the necessary interfaces (digital

I/O, A/D and D/A boards, RS232, IEEE 488, etc)

through which the commands with the instruments

are exchanged. It also bears the video capture cards

that are necessary for visualizing the instruments´

screen. The communication between the video and

the instrument server may occur over a local

network or even in specific cases over a WAN.

2.2 Development Issues

The application was developed using open code

software such as the JAVA language (JAVA, 2004)

running on a LINUX platform (Kernel version:

2.4.20; Slackware distribution). LINUX has been

widespread, but still presents difficulties concerning

appropriate drivers for the different devices used in

the servers. Particularly, drivers for video capture

cards and IEEE 488 interfaces may be hard to find

for different LINUX versions. JAVA is a platform

independent language that was developed for the

implementation of secure distributed systems. Its use

in the present application is fundamental; it enables

an interface between JAVA and programs written in

another language (for example, C for the interface

between the VM700T, a Waveform Analyzer, and

instrument server) called Java Native Interface (JNI)

and distributes data through the web, between the

JAVA Applet and the instrument server, known as

Remote Method Invocation (JAVA RMI). The JNI

has been developed for interfacing the developed

Java classes to the low-level drivers of the

Figure 1: Remote Laboratory Architecture

ICETE 2004 - GLOBAL COMMUNICATION INFORMATION SYSTEMS AND SERVICES

instruments (see Figure 2). This is an important

issue, as instrument manufacturers have a great

variety of native codes through which the instrument

functions may be remotely commanded. The JAVA

RMI enables the creation of distributed JAVA

technology-based to JAVA technology-based

applications, in which the methods of remote JAVA

objects can be invoked from other JAVA virtual

machines.

A video streaming tool is necessary for

visualizing the instrument display of the remote

controlled instrument. Commercial tools such as

Windows Media Player and Real Video Player are

available. These tools may be downloaded free but

limited for a short number of users. However, under

the guideline of using open code software, a

streaming tool known as CamServ (CamServ, 2004)

was used in our application. This video server

presents the following features:

• Downloadable;

• Encoder and server are in one

application;

• Easy to install;

• Not much configuration is needed for it

to run;

• Relatively small when compared to other

video server applications;

• Use multipart JPEG.

The application tool can be executed through an

URL address using a browser such as Internet

Explorer, Netscape or Apache.

2.3 Data Flow Information

In order to use an instrument via Internet, the client-

server model was adopted as described in the

Section 2.1. Fig. 03 shows the data flow information

of this architecture on a remote measurement

experiment with a Waveform Analyzer, VM700T.

On the server side the instrument is connected to the

controller (instrument server) using the GPIB

(General Purpose Interface Bus – IEEE 488) bus

The GPIB describes a standard interface for

communication between instruments and controllers

from different manufacturers. In the server the

instrument is accessed by a JAVA code that interacts

with the instrument driver via JNI. The client is

represented by means of an applet JAVA that is

downloaded using a standard browser. This applet

will connect with the server using the

communication model RMI.

To control the instrument from a personal

computer (PC), a GPIB bus was used as shown at

Figure 3. This networked system has all the features

that are required to create a measurement system.

Remote control of instruments is one aspect of these

features, but there are other more important features

Any communication interface can be used. Usually,

measurement equipments support GPIB, RS232 and the new ones

USB or Ethernet (IEEE 802.3) communication interfaces.

ure 3: Remote Laborator

lementation

ure 2: JNI Interface

ure 4: RMI Structure

DEVELOPMENT OF OPEN CODE APPLICATION FOR REMOTE MEASUREMENTS

Figure 5: VM700T (Waveform Analyzer) GUI

like data handshake for reliable operation and real-

time response capability, only to name a few.

The JNI allows JAVA code, which runs within

a JAVA Virtual Machine (JVM), to operate with

applications and libraries written in other languages,

such as C, C++ and Assembly. JNI has defined

standardized naming and calling conventions used

by the JVM to call native methods and functions.

Fig. 03 shows how the JNI ties the C-based side of

an application to the JAVA side (Chaitas, 2004).

Particularly, the software used to drive the

instrument by the controller was written in C. The

VM700T main JAVA program (or applet) connects

to the real device through drivers written in C.

To implement a remote instrument control the

RMI mechanism is used. The applet will be

downloaded through a standard browser when the

remote user connects to the measurement site. It has

to communicate with the remote object that resides

on the server in order to transfer commands to, and

take results from the instrument. Globally RMI

works as follow: a RMI server is declared and

bounded to the HTTP server of the local server. A

remote object, which implements a remote interface,

is declared to this server. The remote object has data

members and methods distributed between the

server and client side by using “stub” and “skeleton”

layers. “Stub” and “skeleton” are directly build from

the remote object. The “stub” is the client side

interface for the remote object, and the “skeleton”

the server side. Fig. 04 shows the general structure

of RMI (CGAL, 2004).

2.4 Instrument Graphic Interface

Independently of which instrument and setup is

necessary for the measurements, the client shall have

an interface with which he can interact by inserting

the input data to the experiment, setting the range of

relevant parameters or even the chain of commands

for operating the equipment. With this regard, an

interface was developed which simulates the

instrument front panel. The development was done

by using NetBeans IDE 3.5.1 development

environment, Apache HTTP Server 1.3 (Apache,

2004), J2SE 1.4.2 and CamServ 0.5.1. As an

example, Fig. 05 shows the interface developed for

the Waveform Analyzer, VM700 (Tektronix,

2004). The display of the instrument is viewed by

means of the video streaming application, described

above.

3 REMOTE MEASUREMENTS

3.1 Test Setup

In order to check the functionality of the application

a test setup was constructed. The setup is intended to

measure baseband video parameters, such as Bar

Line Time, Chrominance-Luminance Delay,

Differential Gain, Differential Phase, H_Blank,

V_Blank, etc, and uses the Waveform Analyzer,

VM700. This configuration consists of a signal

source (which may be a standard signal generator or

a baseband signal that outputs a VCR or a DVD) and

the waveform analyzer. Depending on the device

under test (DUT), such as a modulator, a more

sophisticated apparatus may also include a

demodulator, which is placed before the signal

analyzer.

3.2 Trial Tests

First tests were made in a local environment, where

both video and measurement servers were connected

to a hub. Several attempts to capture the image of

ICETE 2004 - GLOBAL COMMUNICATION INFORMATION SYSTEMS AND SERVICES

the analyzer’s screen were made. The screen of the

analyzer is very rich on information that is mainly

displayed in its upper or bottom part. Such

information is important for the equipment operation

and for displaying test results. The first attempt

placed a standard web cam (3Com Bigpicture Video

Camera - it captures 30 frames per second at 640-by-

480 pixel resolution) directly in front of the

instrument’s screen. The captured image was poor in

the sense that valuable information could not be read

in the reproduced image, though ordinary

communication lines barely support 176-by-144

resolution and rarely transfer more than 5 or 6

frames per second. So, in the second attempt a CCD

camera (Gradiente SC60) was used. The resolution

of the image was much better, mainly due to the

camera’s higher pixel density and also the quality of

its lens. It was also observed that the display of the

instrument might be an issue regarding the image

quality. The analyzer used in the setup presented a

slightly rounded display in the corners, which

provokes image distortion. This way, the third

attempt used the instrument’s VGA video output.

However, a video capture card with such a connector

would be needed. Unfortunately, no card was found

with such an interface. Instead, the instrument’s

video output was connected to a computer monitor

with a flat panel. This last setup showed a

reasonable image resolution.

Fig. 06 shows the result of a synchronism

signal measurement viewed at the video server,

which was performed in the local environment.

Besides the touch buttons, there is also a round

button (see instrument’s right bottom panel in Fig.

05), which is driven by spinning it with the hand

around its central axis in the real instrument. This

button is responsible for selecting the individual

signal lines, from which a frame is composed. In the

virtual instrument, this function is implemented by

dragging the knob with the mouse in the

(anti)clockwise direction.

4 VALIDATION OF THE

APPLICATION IN THE WEB

Several tests have been performed in order to verify

the proposed structure. In particular, several

accesses have been made from clients directly

connected to the university LAN and clients

connected to Internet through the ReMAV, an

advanced Metropolitan Area Network used for

research and education purposes.

The most significant contribution to the

equivalent latency time is given by the video

transmission viewed at the VM700 display. Taking

in account that the client already has a web browser

with the right plug-in installed, the delay time for the

video streaming into the university LAN is 7

seconds while, into the ReMAV, this time decreases

to 4 seconds.

5 CONCLUSION

An application for controlling instruments over the

Web was developed using open code resources such

as LINUX, JAVA and CamServ. Any known Web

browser may access the application, although the

performance differs significantly from each other.

Also, the available output display supported by the

instrumentation reflects on performance levels of the

remote display results. Two main bottlenecks were

identified: capacity and QoS support of the

communication network and processing power of

the video server. The main contribution of this paper

is the description of development issues of an open-

source Web-based measurement system based on

video streaming process. We believe our solution

greatly minimizes development time and costs by

avoiding the deployment of graphical tools to each

output file format of measurement equipments. A

next step aiming application performance

improvements requires the testing of other open

source video streaming tools, such as VideoLAN

(VideoLAN, 2004), which provides video

compression before streaming . Also, new

performance tests should lead to better specifications

for designing the video server.

Figure 6: Measurement at Video Server

SinaleasSigMeasurement

DEVELOPMENT OF OPEN CODE APPLICATION FOR REMOTE MEASUREMENTS

ACKNOWLEDGEMENTS

The authors would like to thank the Conselho

Nacional de Desenvolvimento Científico e

Tecnológico (CNPq), Brazil, for supporting this

project by means of the research grant CNPq

552342/2001-7.

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ICETE 2004 - GLOBAL COMMUNICATION INFORMATION SYSTEMS AND SERVICES