Core Running
The Core Running program actually controls the instrument using the test
sequence pre set via the Sequencer. Individual channels can be switched on or off in the Core Running. Real time data for each channel can be observed using typical Windows features such as Full Screen
Cascade and Tile.
Long Term
Tests that obtain and present data from an electrochemical cell or probe with respect to time
including
Linear Polarisation Resistance; Potentiostatic; Galvanic and Potential monitoring.
Measurements.
Data is presented in real time for instant visual analysis. Typically this technique is used to monitor the corrosion rate in relation to time by using a series of Linear Polarisation Resistance tests. For multiple channel instruments
individual windows simultaneously present the data from each respective channel. These techniques represent the basic tools of long term corrosion testing.
Linear polarisation tests can be controlled in a variety of ways. The two main types are Step and Sweep. Step polarisation’s can be either of the square wave variety or a modified square wave where the cell is left isolated between Anodic and Cathodic
polarisations. Sweep options include sweep from rest potential to start potential and initial delays at start potential.
Cyclic Sweeps
This test is presented on V/ I or V/ Log I graphs typically referred to as Evans Diagrams. Other terms frequently used are Cyclic Voltammetery
Potentiodynamic Sweeps and Polarography. A custom sweep facility enables complex Voltage/ Time graphs to be constructed
which are then used to polarise the cell. A range of typical tools are available to analyse the data including
positioning and measurement of Tafel Slopes and Linear Polarisation Resistance. The corrosion rate may be measured using either the Stearn and Geary or the Current Intercept method. The technique is often used as a traditional way to detect resistance to pitting. To facilitate this
a current limit may be used.
C&V Noise
Electrochemical Current and Voltage Noise and Potentiostatic measurements at a
rate of 50 or 60 per second whilst rejecting mains interference. Typical measurement accuracy is from a few pA upwards.
AC Impedance
AC Impedance uses a scan of test frequencies
normally from a high to a low frequency
to analyse
resistive and capacitive characteristics of a corrosion cell. Data is presented in either Nyquist
Bode Phase or Bode Impedance formats. Curve fitting software is inclusive to calculate the Solution Resistance
Double Layer Capacitance and the Polarisation Resistance. The technique is frequently used in systems with a significant solution resistance
or as a method to analyse the performance of a coating. For very high impedance cells greater than 10 MOhms
the technique is normally used in conjunction with the optional Paint Buffer.
Analysis
Screen shots:
ACM instruments supplies analysis software with its products. This offers the user a number of standard tools which are typically used by electrochemists and corrosion scientists. However for user specific analysis
we recommend the user to transfer data to a typical commercial package such as Excel. Version 4 analysis software offers the following
features:-
Data Management Tools:-
- Browsing data files as thumb nail graphs.
- Selecting data from multiple files into data banks for comparison.
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Exporting individual or batched data files to text or ASCII format suitable for spread sheets.
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Exporting graphs as bitmaps and metafiles for including in reports.
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Storing data in a HTML format suitable for viewing with a web browser or uploading to a web page.
Common Data Manipulation Tools:-
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Cut and paste ability enables graphs to be inserted into text documents with ease.
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Re-definable axis
where an axis type and units can be set.
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Editing of data points and joining any gaps created.
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Zero plot enabling data vs. time graphs with different start times to be referenced to zero on the time axis.
- Inclusion of labels to highlight specific points / areas of the graph.
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Printing the graph to include any labels and rulers displayed.
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Zooming
where the graph can be rescaled manually
automatically or by using the mouse.
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Cursors which can be moved along the data line giving the X and Y co-ordinates as well as data specific information such as average
trend and frequency.
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Smoothing of data by averaging adjacent points can be performed on the data either between cursors
the selected data bank or all of the displayed data.
- Saving data enables modified graphical data to be stored for later retrieval.
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Corrosion rate calculation in mm or mils per year.
Data Specific Features:-
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Circle fit for Nyquist graphs.
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Isotropic Scaling of Nyquist graphs.
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Tafel rulers for calculation of bA
bC and intercepts on V vs LogI graphs.
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Least squares fit and manual line fitting for the calculation of the Linear Polarisation Resistance of a
Voltage vs Current graph.
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Fast Fourier Transform graphs created from Current and Voltage data.
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Point to Point graphs created from Current and Voltage data.
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Graphs area calculated from the base line on Current and Voltage graphs.
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Peak counter on Current and Voltage data.
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Load test at cursor on long term LPR step and sweep graphs. This gives the ability to load the sweep or step data relating to the data point at the cursor.
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Ability to analyse data files containing hundreds of thousands of points.
Manual Instrument Control
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The Field machine is supplied with Manual Instrument Control. This is a stand alone single page program which tries to recreate the nostalgia of the Manual
Potentiostat
Sweep Generator and twin channel chart recorder of yesteryear. Rate of movement of the mouse is directly proportional to the rate of change of cell potential. Such tactile feel of an electrochemical cell is typically missing with modern automated systems. It is recommended as an educational or investigative tool. Data is shown in graphical form in real time and stored in an ASCII format for analysis with a typical commercial package such as Excel. |
Specifications
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Case
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47 * 36 * 14 cm
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Power Supply
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110 / 230 VAC 50/60Hz or a 12V source.
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Weight
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9Kg
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Potentiostat
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Compliance Voltage
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+/- 12Volts
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Sweep
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+/- 3Volt
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Sweep Resolution
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0.025mV Maximum
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Current Output
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500mA
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Reference Electrode Input Impedance
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Approximately 1*1012 Ohms
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Frequency Response
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30 Khz with a 1 to 100KOhm load
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Potential Measurement
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21 Bit A/D
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Maximum Potential Resolution
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1µV
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Potentiodynamic Sweep Rate
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Maximum 20mV / second
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Zero Resistance Ammeter
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Current Range
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10pA to 500mA
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Current Ranges
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Eight ranges
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Counter Resistors
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Eight 1
10
100
1K
10K
100K
1M
10M Ohms
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Input Offset Voltage
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10µV
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Galvanostat
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Current Output
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+/- 10pA to 500mA
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Maximum Potential Resolution
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1µV
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Frequency Response Analyser
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Frequency Range
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10µHz to 30KHz
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Amplitude
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1 to 232mV
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Impedance Error
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< 1% for 1
10
100
1K
10K and 100K Loads
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Averaging
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Variable % averaging
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Sample Rate
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1 MHz
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ADC
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12 Bit
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DAC
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12 Bit
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Options for Field Machine
The Field Machine can be fitted with an extensive range of options that can significantly alter both the appearance and the performance of the instrument.
These are listed below followed by a more detailed descriptions for each option.
Sequential Channel
Each Field Machine can be fitted with up to 128 sequential channels. Each channel can be treated as if it is independent from the other sequential channels. The Core Running program provided with the instrument will sort out the timing for the tests on each channel. The user must
be aware that this is a switched system and that with only one Potentiostat
only a single test can be done at any one time.
Additional Software for incorporation in the Sequencer program.
Galvanodynamic Sweeps
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This program enables the instrument to be controlled as a Galvanostat rather than a Potentiostat. The program enables both single and multiple cycle Sweeps to be performed as well as long term tests including Linear Polarisation Resistance and
Galvanostatic tests.
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Harmonic Analysis
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A novel and little used technique for measuring the non linear response to a sine wave polarisation. It is unique in that in one simple measurement
values for Polarisation Resistance and Tafel slopes bA & bC are obtained. The technique can be used as a long term test in order to monitor corrosion rates with respect to time. The technique typically uses a polarisation of about 0.1Hz or less and measures the 1st
2nd and 3rd Harmonic Current response. The Sequencer program allows the operator to use this technique in series with other perhaps more trusted techniques such as LPR in order to compare results. |
IR
Compensation
IR Compensation is used to compensate a Potentiodynamic or Potentiostatic test in real time for the depolarising effects of solution resistance. The solution resistance is first measured using an AC signal. The value of this resistance is used together with the polarisation current to adjust the polarisation potential via Ohms Law. To take a simple case
where the
polarisation resistance and the solution resistance are identical
the
polarisation potential imposed by the Potentiostat is effectively doubled. Unlike interrupt methods
that effectively apply high frequency spikes to the system and have the potential for instability
this method maintains control of the cell at all times without any unwanted high frequency polarisations.
Linear Polarisation Resistance Noise (Patent
applied for)
A new corrosion monitoring technique that employs the virtues of LPR and Noise. The method is good for multi phase environments
such as
those experienced in splash zones and multi phase flow. The technique may also be of assistance when used with Rotating Disc Electrode systems. In multiple phase environments such as splash zones or in multiple phase oil / brine solutions
the technique gives two
results: the average monitored corrosion rate and the corrosivity of the conductive phase. In many cases
it is the corrosivity of the conductive phase that is most important. Especially as in the case of an oil/brine mixture
the more corrosive brine has a chance of separating out and causing enhanced corrosion rates at a place where a probe does not exist. Note that as far as I am aware
no other technique including Electrochemical Noise and Electrical Resistance can do this. Further details on the technique are available under
application notes.
Advanced Options for Field Machine
Voltage Input
Voltage inputs can be used to monitor other parameters that have a voltage output
such as temperature
pressure or velocity. Each voltage input can be selected as a test within the Sequencer program enabling a
voltage measurement to be taken at the start or end of any electrochemical test. These inputs can be configured and scaled for display with the correct units together with the long term electrochemical data. Up to four voltage inputs per Gill AC are available on board. Additional voltage inputs are available on request. If requested
voltage Inputs can be configured at 0 or 4 to 20mA inputs at no additional charge. A small additional charge is made for direct measurement of a thermocouple.
Paint Buffer
The Paint Buffer is fitted with ultra high impedance components and switches that can handle low currents of the order of 10pA
with a good level of resolution below that. It is recommended for use with high impedance cells such as those that are coated or for miniature electrodes. It is housed in a small die-cast box and connects via a cable to the rear panel of appropriately fitted Gill AC’s.
DC Weld Test option
This option enables the host instrument to test multiple electrode couples with up to five elements
such as encountered with welds or mixed metal systems. Each element in the couple is attached to its own Zero Resistance Ammeter complete with automated current ranges. Thus the individual current response from each element is monitored in both the galvanic and polarisation mode. Versions of the following programs are supplied with this
option: Long Term; Cyclic Sweeps and C&V Noise. These programs are operated through the sequencer program in the normal way. The maximum read rate for C&V Noise is reduced to one reading per second whilst using this option. The specification of the additional ZRAs is as
follows:-
- Current Range 10pA to 500mA
- Seven Current Ranges per ZRA.
- Seven
Counter Resistors 10
100
1K
10K
100K
1M
10M Ohms
- Input Offset Voltage 10µV
AC Weld Test option
This option enables AC Impedance tests to be applied to the multiple electrode couple. The individual current response to a polarising AC signal is obtained from each of the test electrodes whilst it remains
galvanically coupled to the other test electrodes in the cell. It includes the same hardware as with the DC weld test option.
Offsetting Ability for Weld Test option
This technique enables more than one electrode to be tested in the same cell at the same time. Each test is performed around each
electrode's rest potential
as if it were isolated from the other electrodes in the couple. A typical use for this technique may be to test 100 painted sample simultaneously during an accelerated exposure test
thus reducing the immersion time and also ensuring the test time occurs at the same time for all samples being tested. Letting our minds run free and with quite a bit more complexity
the technique enables each of the electrodes in the multiple electrode system to be running completely different tests at the same time
whilst still using a single Auxiliary and Reference Electrode. We would like to do a product like this
trouble is finding a customer who wants one!
Instrument Control DLL
The Instrument Control DLL is a library of commands that enables operators to control the instrument using their own software. It can be used in Microsoft’s or Borlands C type programming languages. A version that can be controlled from other languages can be supplied at an additional charge.
Electrical Resistance
This option enables the instrument to measure an Electrical Resistance Probe with high resolution. A lot has been made of high accuracy ER measurements in recent times and indeed the electronics is perfectly capable of giving very high resolution measurements and corrosion
rates. However
to obtain high accuracy it is important to have very stable temperatures with no variations. In our opinion
even temperature fluctuations between the corroding and check elements of a 1/1
000 °C will lead to significant errors when trying to calculate
the corrosion rate over a short period of time
especially when the corrosion rates are low. Operators can reduce external temperature variations by insulating the probe with waterproof material to reduce the chance of cooling by evaporation. Other than that
it comes down to probe design. For higher accuracy
try to select a probe that endeavours to reduce any heat difference between the corroding and check elements. ACM can get an indication of the accuracy of the measurement by measuring the resistance of the check element. If this
resistance remains constant throughout the test period
there is a good likelihood that the corrosion measurements obtained are satisfactory. By measuring the check elements resistance at a set temperature
the temperature of the probe whilst in use can be calculated
provided the materials thermal coefficient of resistance is known. Our software will include a list of materials with such coefficients.
GPS Tracking System
This technique enables the location of the corrosion measurement to be recorded
with the data for later cross referencing. It does not include the GPS device
itself which will interface with the PC. ACM can provide this part with the
system if required. The option gives the ability to pre-program the instrument
with sequences of electrochemical tests for specific probe locations
such that
as the operator goes from probe to probe
the instrument knows the location of
the probe and which tests it is programmed to perform. The data will
automatically be added to previous data for that probe.
Bubble Test Software
The Bubble Test program is designed for the repetitive testing of corrosion inhibitors. Unlike our standard Sequencer based software
which gives great flexibility
the Bubble Test program appears to already know what is required of it. Once its initial parameters are set
it is ready to perform tests on inhibitors day after day
with minimum operator intervention. Tests are typically done in triplicate to gain a level of confidence in the results. Results
are presented in a report-ready
graphical form
that can be printed out at the end of a test
including:-
- LPR graph showing LPR; corrosion current or corrosion rate vs time.
- As above but with markers and labels showing the corrosion rate immediately before the inhibitor was added and the corrosion rate and % inhibition after 1
2
5
10 and 15 hours.
- As above but with operator set titles above and below the graph.
- Corrosion rate bar graph displaying the corrosion rate on each channel immediately before the inhibitor was added
2 hours after and 16 hours after. Parameters can be changed.
- % inhibition bar graph displaying the % inhibition on each channel at 2 hours and 16 hours after the inhibitor was added. Parameters can be changed.
- Result table displaying the results from the above two bar graphs in a table format with titles and extra information above and below the table.
- Cyclic Sweep or Tafel type graph showing the results of a Cyclic Sweep done at the end of the Bubble Test. Titles can be added both above and below the Tafel graph.
Traditionally we have used multiple channel sequential instruments for the Bubble Test
such as the Gill 12. This
can lead however
to a timing error between inhibitor injection and the actual time the measurement is taken. This is especially the case between channel 1 and channel 12
as channels 2 to 10 are tested first. To prevent this
we can now supply the Bubble
Test software to work with multiple instrument systems. For instance a 12 channel system could comprise of 12 separate instruments all performing their tests at exactly the same time. This would also apply to tests done on different days provided the same settings are used.
Option for BTS: Bubble Test Software including Linear Polarisation Resistance Noise.
This option uses the same software as the Bubble Test program
however it enables ACMs patent applied for technique to be used. Linear Polarisation Resistance Noise can give the same results as LPR
however it comes into its own when used in multiple phase environments. In multiple phase flow the technique gives two readings
the average monitored corrosion rate and the corrosivity of the conductive phase.
Critical Pitting Temperature Test
This is an automated test to detect the pitting temperature of passivated metals. The option comprises of a small enclosure that couples to the rear of the host instrument and a remote temperature probe for insertion into the cell. The CPT enclosure is capable of measuring both the remote 7mm diameter temperature probe and switching a mains supply that is used to heat the cell. The software enables the following to be set:-
Potentiostatic Polarisation; Temperature Ramp Rate (either as a sweep or as predefined
steps); the critical pitting current or current density; critical current continuously exceeded time and the time taken to isolate the test after the critical current continuously exceeded time has been exceeded itself.
Limited Distance Modem
This option enables the host instrument to be operated several kilometres away from the host PC using limited distance modems. This method
uses a base station instrument close to the PC fitted with modules for each instrument
controlled by the Limited Distance Modem method.
Customised Software and Automated Emailing and Internet Storage of Data
Our reliable Sequencer and Core Running programs form the backbone of our standard software. However these programs have been designed in a way that accommodates customisation. Typical forms of customisation include:
- Test customised to specific requirements.
- Real time presentation of data
possibly involving dials.
- Alarms
both audible and visual
triggered by monitored levels.
- Automated control.
- Written operator input
perhaps indicating action taken due to an alarm.
- Schematic visualisation of the monitored system.
- Automated emailing of data.
- Automated transfer of data to a web site for storage and access.
Such customisation is normal at ACM Instruments
hence the depth of options. Just ask for what you want and we will be pleased to supply it.
Replacement Electrode Cables
Replacement cables can be provided to any length required or with any type of termination. It is quite common for operators to specify a complete set of straight through cables for connection directly to a specific
probe.
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Field
Machine
