Labview software

NI Labview 2011 a program development environmental was used with

the NI ELVIS II. Labview uses a graphical symbol programming language to

create programs in block diagram form. The graphical language is named G,

Labview is commonly used for instrument control, data acquisition and industrial

automation on various system platforms including Windows, Unix, Linux and

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The programming language in Labview is a data flow programming

language. Labview programs are named virtual instruments, vi, because their

symbolic appearance and ability to emulate real instruments such as oscilloscopes

and multimeters. The vi programs contains three main parts; the block diagram,

the front panel and the symbol/connector.

The vi for impedance measurement consists of two main parts, generating

waveform and the other undertaking the analogue input measurement.

XSC1 A B Ext Trig + + _ _ + _ XFG1 ELVIS II PC + Labview Syramed uSP 6000 Magnetic Stirrer Hot plate 100 ml Borosilicate glass Sensor

Flexible tubing for methoxide injection Waveform generator

Osciloscope

Figure 6.6 The schematic diagram of impedance measurement

The voltage excitation is vpp ± 5 volt 15 khz generated by function

generator (FGen), both sensor input is connected to function generator as well as

one input analogue input scope0 (ai0). The sensor output which measures the

voltage of the resistor is connected to analogue input scope1 (ai1). FGen of

ELVIS II can be activated using fgen vi to generated sinusoidal waveform,

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Figure 6.6 shows the layout of the conducted experiment, syramed dozing

machine has been used to inject methoxide in to the bottom of the experiment

flask. The flask with vegetable oil was put on magnetic stirrer with controller hot

plate. ELVIS II unit connected with computer with NI LABVIEW, the output

waveform was connected to sensor and the sensor output was link to Aio.

Figure 6.7 Impedance measurement block diagram

Figure 6.7 shows the impedance measurement block diagram, the

waveform which was generated by function generator was physically route to the

sensor, and the output from sensor as an input for ai0 (analogue input 0) and

ai1(analogue input 1) of the National Instrument hardware. The output signal from

the sensor then converted from dynamic data into numeric data. extract single tone

information vi is used to extract information from the data such as frequency,

amplitude and phase input. By comparing two signal from original waveform with

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Figure 6.8 is function generator express vi, the variable can be adjusted is

amplitude and frequency output. It can be seen from block diagram, the

connection from function generator is physically connected to the sensors. The

BNC connectors are connected to the input sensor and analog input scope0, this

connection has the purpose of capturing the sinusoidal waveform source. The

other pair connectors are connected to the shunt resistant. The data output from

scope0 and scope1 cannot directly used as the output in the form of waveform

dynamic data. It is necessary to convert dynamic data to numeric with the other

express vi or function, the output dynamic data was processes by convert form

dynamic data vi, the conversion can be in the form of numeric, Boolean or array

in this case the data was converted into numeric. Figure 6.9 shows the express vi

convert form dynamic data.

Figure 6.8 NI ELVISmx Function Generator

In Labview a vi which can be configured through a dialog box is called an

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built in express vi’s. Express vi can be configured by setting options in the

configuration dialog box and it is appear on the block diagram as expandable

nodes.

a B

Figure 6.9 Convert from Dynamic Data Express VI and extract single tone information vi

Figure 6.10 NI ELVISmx Oscilloscope

Figure 6.10 shows the express VI for oscilloscope function, there are two

channel input for ID sensor application. The scope has 1 MS/s multiplexing and

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is limited to 500 kS/s. However this speed is more than enough for the impedance

experiment using 15 kHz excitation waveform.

The output from convert form dynamic data vi then split into two wired

connections. One connection is joined with build array vi to create real time

signal visualisation in the front panel software, it is appear as signals on front

panel in the function of signal magnitude and time.

This graphical signal show in figure 6.11 is important as it enables the user

to check whether the waveform is properly configured. The wired from sensor

output has goes to extract single tone information vi to extract the signal

waveform into frequency, amplitude and phase.

Figure 6.11 Impedance measurement front panel

The extracted frequency, amplitude and phase both input and output then

fed into write to measurement file in numeric value. There are some choices to

save the file in binary file using TDMS file and based text file LVM, in this

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measurement vi has some interface to check frequency and amplitude parameters

have properly setting. Figure 6.12 shows the layout of the biodiesel impedance

measurement layout inside fume cupboard.

Figure 6.12 Equipment for biodiesel single frequency impedance measurement

The experiment divided into two sections, initial experiment which was

using digital multimeter with capacitance measurement and further experiment

using waveform and impedance measurement. Early experiment conducted to

evaluate the possibility using capacitance measurement using digital multimeter to

measure chemical reaction in biodiesel transesterification process. Based on first

investigation, the ideas is further expanded using impedance measurement which

is capable to measure both conductance and permittivity.