manual rev3.1

8/3/2019 Manual Rev3.1

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UNS-TECH Conductance Detector

Universal NanoSensor Technologies, Inc.

Toronto, Ontario

Canada



Contents

Components list 2

Parts of the detector 3

Installing software 4

Connecting PTFE tubing 4

Features of the software 5

Using the detector 7

Analyzing saved data 8

Example measuring conductance of various NaCl solutions 8

Tutorial on conductance measurements: simultaneously

probing conductivity and dielectric constant via Gx and Gy,respectively 11

Specifications 13

Components list

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USB data key containing software

detector

cable with USB connectors on both ends

peristaltic pump with tubing installed around rotor

DC adapter for peristaltic pump

4 pieces of 8” long x 1/16” outer diameter PTFE tubing

4 pieces of ~1” long tygon tubing

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Parts of the detector

Fig. 1 Photograph of the conductance detector with pump

1. Detector

2. Metal tubing inlet/outlet of detector (inlet/outlet are interchangeable)3. Detector USB port4. Peristaltic ump

5. 1/16” outer diameter PTFE tubing

Caution: The metal tubing inlet/outlet of detector are easily bent. Do not apply strong forces to this tubing.

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Installing software

(1) Insert USB data key and copy UNS-TECH folder from the USB drive to the desktop

(2) Open UNS-TECH folder. Double click on UNS_Installer to run the installer.

Python 2. 7. 1 window comes up.

(3) In Python 2. 7. 1 window, press Next successively 3 times. When User Account Control window comes up, press Continue and press Finish at the end.

(4) In User Account Control , press Allow. When numpy 1. 5. 1 window comes up, press

Next successively 3 times, press Finish and then press Close.

(5) In User Account Control , press Allow again. When matplot lib 1. 0. 1 window comes

up, press Next successively 3 times and finally press Finish.

(6) In User Account Control , press Allow again. When wxpython 2.8 – ansi – py27window comes up, press Next and choose I accept the agreement (if you do) and press Next successively 3 times and finally press Finish at the end where you can closeREADME win 32 from screen.

(7) In User Account Control , press Allow again. When setuptools – 0.6c11 windowcomes up, press Next successively 3 times and finally press Finish at the end.

Installation of the program is completed at this point.

(8) Connect the detector to your PC or Laptop using the cable that has USB connectors at both ends.

Connecting PTFE tubing

Tip: Having the detector upstream of the pump and pulling liquid through the detector

using the pump rather than pushing the liquid is preferable. The preferable flow

direction of the liquid is, therefore, from the detector to the pump.

(1) Place one of the ~1” tygon tubes onto either one of the detector’s metal tubings (see

Fig. 1). Insert one end of a PTFE tubing into this tygon tube. This metal tubing willserve as the inlet to the detector (the metal tubings are interchangeable).

Caution: The metal tubing inlet/outlet of detector are easily bent. Take extra care when

handling this metal tubing. Note that the pressure in the tubing caused by the pump islow, so strong force is not required to hold the tygon/PTFE tubing in place.

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(2) As in step (1), connect one end of PTFE tubing to the other metal tubing of the

detector (which then serves as the detector outlet).

(3) Turn on the pump and note the note the direction of pump rotation. The pump

rotation pushes liquid from the pump inlet to the pump outlet, determining which tubeis the pump inlet and which one is the pump outlet.

(4) Insert the PTFE tubing that is connected to the detector outlet into the pump inlettubing.

(5) Insert another PTFE tubing into the pump outlet tubing.

(6) The PTFE tubing connected to the detector inlet is inserted into the liquid to be

sampled. The PTFE tubing connected to the pump outlet may be inserted either into a

waste container (if the sample is to be discarded after a one-time conductance

measurement) or into the original sample container (for continuous conductancemeasurements).

Features of the software – refer to Fig. 6.2 below

1. Conductance Gx (mS) vs. time:

Real time plot of X component or resistive/in-phase component of conductance being detected.

2. Conductance Gy (mS) vs. time:

Real time plot of Y component or capacitance/out-of-phase component of

conductance being detected.

3. Resume/Pause button:

When “Resume” is pressed, measurements are performed and displayed. When“Pause” is pressed, measurement stops.

4. Controls for

The minimum and maximum values of the horizontal (time) scale for both Gx and

Gy graphs.

The minimum and maximum values of the vertical scale for the Gx graph.

The minimum and maximum values of the vertical scale for the Gy graph.

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The above maxima/minima values are set automatically by the program if the

respective “Auto” button(s) is (are) selected. You can also override the program’s

choice by setting the respective values manually.

5. File select button

This button allows you to select the file to which measurement data are saved.

6. Saving / not saving button

When the button is pressed and switches from Not Saving to Saving , datarecording to your selected file begins. When the button is pressed and switches

from Saving to Not Saving , data recording stops.

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Fig. 2. A screen shot of a window displaying conductance detector software.



7. Present values of time, Gx, Gy, |G| and Phase angle

Note: The complex conductance G is expressed as G = Gx + iGy where i2 = -1.Gx and Gy are the in-phase and out-of-phase components of the conductance,

respectively. The magnitude of G (|G|) and phase angles, θ, are defined as

22 GyGxG += andGxGyθ =tan .

8. Sampling period

This represents the time between each data measurement. For example if you

choose sampling time of 2s, a data point is taken every 2 s.

9. Calibration button

You can calibrate the detector using a 100 ppm NaCl/H 2O (w/w) solution. Fill the

detector with the solution and press this button. The residual Gx will be displayedand recorded in a file.

Using the detector

(1) Open the UNS-TECH folder and double click on UNS_tec_detector_v1_6.py

(version number, assumed v1_6 here, may vary). The window shown in Fig-2 comes

up to computer screen.

(2) To choose your file for saving data, press Select file and choose your file location.

Then press Save. Any data measured will be saved. If this button is set to “ Not Saving ”, any data measured will be displayed, but not saved.

(3) To start data measurement, press Resume in the interface. This button after pressing

Resume turns to Pause. If you want to stop data measurement, press Pause.

(4) Once the data measurement starts and the “Save” button is displayed, measured

data are plotted and automatically saved in your chosen file in real time.

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Tip: When you start pumping a solution into the detector, use a slow pump rate for

the first few minutes to prevent air bubbles from entering and being trapped in the

detector. Air bubbles in the detector cause irregular and abnormal measurements. However, air bubbles entering the connection at the detector outlet metal tubing is

normal.

Tip: Cleaning the pump’s metal spindle and plastic bearings will help smooth pumping. Alternatively, you can spray a lubricant such as WD-40 on the pump’s

metal spindle and plastic bearings.



Analyzing saved data

Saved data are stored in a document/text file that can be open with Notepad. The data aresaved in 4 columns. Starting from the left, the first column contains the date of a

measurement, the second contains the time of the measurement, and the last 2 columns

contain the Gx and Gy values of the measurement, respectively. The measurement datafile can be transferred to a spreadsheet program such as Excel or Origin for analysis and

plotting.

Example measuring the conductance of various NaCl solutions

Solutions with various concentrations can be prepared as follows:

(1) 1 ppt stock solution1 g NaCl in 1L H2O

(2) 100 ppm solution

Take 1 g of 1 ppt stock solution and add 9 g of H2O.(3) 50 ppm solution

Take 5 g of 100 ppm solution and add 5 g of H2O.

(4) 20 ppm solution

Take 4 g of 50 ppm solution and add 6 g of H2O.(5) 10 ppm solution


(6) 5 ppm solutionTake 5 g of 10 ppm solution and add 5 g of H2O.

(7) 2 ppm solution

Take 4 g of 5 ppm solution and add 6 g of H2O.(8) 1 ppm solution


Measurement results are shown in Fig. 3 and Fig. 4. Fig. 3 shows Gx signal vs. time as

various solutions sequentially flow through the detector, starting from 0 ppm (de-ionized

water) to 100 ppm of NaCl. At 50 ppm and 100 ppm the noise gets slightly larger due tothe high sensitivity of detector. It is normal that the noise apparently appears at high

concentration (> 20mS).

Fig. 4 shows plots of Gx signal vs concentration of NaCl from 1 ppm to 100 ppm (main

panel) and from 1 ppm to 10 ppm (inset). Both plots show a high R (correlation

coefficient value) that is particularly robust for very low concentration detection usingUNS Tech’s conductance detector.

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0 20 40 60 80 100

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40 R = 0.99986

X - S i n g a l ( m S )

Concentration (ppm)

0 2 4 6 8 10

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R = 0.99945

X - S i n g a l ( m S )

Concentration (ppm)

Fig. 4

R = 0.99945



Tutorial on conductance measurements: simultaneously probing

conductivity and dielectric constant using Gx and Gy, respectively

In a conductance measurement, a sinusoidal drive voltage applied across a pair of

electrodes induces a sinusoidal current to flow across the electrodes. A sample mixture

flowing between the electrodes can be interrogated by analyzing this current response.

For example, the drive voltage may cause a so-called external current, iext, to

flow across the surfaces of the electrodes and through the sample mixture by inducingmobile charges in the sample mixture to flow; and/or, the drive voltage may cause so-

called displacement current, idisp, to flow by charging/discharging the electrodes and

polarizing/depolarizing the sample mixture as a function of time.

In a linear approximation and assuming parallel electrodes, if a voltage difference,

ΔV, is applied between a pair of electrodes and no displacement current flows between

the pair of electrodes, the external current that flows between the electrodes is

proportional to ΔV and is given by

iext = ΔV Gx (1)

where

Gx = σ A /L = 1/R (2)

σ is the conductivity of the sample mixture and depends on type and concentration of

mobile charges species present, A is the cross section area of the electrodes throughwhich the external current flows, L is the separation between the electrodes and R is the

resistance of the sample mixture.

Also in a linear approximation and assuming parallel electrodes, if a voltage

difference, ΔV, is applied between a pair of electrodes and no external current flows (i.e.

the sample mixture is in a insulating liquid, e.g. hexane), then just displacement currentflows between the electrodes and is given by

idisp = ΔV Gy (3)

where

Gy = iωε A/L = iωC (4)

where i is an imaginary number such that i2 = -1, ω is the angular frequency of the

voltage difference assumed to vary sinusoidally with time, ε is the dielectric constant, Ais the cross sectional area over which the displacement current flows, L is the separation

between the electrodes and C is the capacitance of the sample mixture.

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Since Gx is real, Eq. (1) implies that the voltage drive and external current

response are “in-phase”. Since Gy is pure imaginary, Eq. (3) implies that the voltage

drive and external current response are 90 degrees “out-of-phase”. The in-phase and the90 degree out-of-phase current responses can be separately measured and given the

magnitude of the voltage drive, Gx and Gy can be determined.

Note that Gx is proportional to conductivity, and Gy is proportional to dielectric

constant of the sample mixture. Both are also proportional to A/L, which therefore serves

as “geometrical amplification” factor for small changes in either conductivity and/or dielectric constant. Small changes in either conductivity and/or dielectric constant are

more easily measured with larger A/L. In UNS Tech’s conductance detector, A/L is

very large, enabling simultaneous measurements of BOTH Gx and Gy; i.e. it

simultaneously functions as a conductivity and dielectric constant detector. The latter is a unique feature of UNS Tech’s proprietary technology and provides a means for

characterizing conductivity with great sensitivity and for characterizing even insulating

sample mixtures via their dielectric constant.

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Detector specifications

Conductance (tested with NaCl solution)Range: 0 to 300 mS

Resolution: 6 significant digits down to 1 nS

Reliable Accuracy: +/- 0.5 %

Salinity:

Range: 1 ppb to 100ppm (NaCl equivalent)Resolution: 6 significant digits down to 1 nS

Relative Accuracy: +/- 0.5%

Temperature:tested at room temperature

Cell Constant:

0.001 to 0.010 cm-1

Cell volume:1 to 10 µL

Connection to computer:USB mini connection

Power:

power supply from USB (no external power supply required).

Dimensions:Detector, 11cm(L), 7.5cm(W), 2.5(D), or 4-1/4”(L), 3”(W), 1”(D)

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manual rev3.1

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