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In this section: 

Open Circuit Potential .............................................................. 3-1 

 

 

Open Circuit Potential 

The Open Circuit Potential (OCP) of an electrochemical cell is the voltage between the reference and 
working electrodes. When the open circuit potential is measured, a voltmeter with high impedance is 
used to measure the voltage with no current or voltage applied to the cell. 

Because of its high input impedance, your galvanostat can be used to make OCP measurements 
when configured for 4-wire measurements, as shown in the next figure. In this setup, the instrument is 
configured to source 0 A and measure voltage. 

If you measure the OCP before performing any test, you do not have to change any test leads 
between measurements, because your potentiostat or galvanostat can automatically change 
functions. 

Figure 43: Measuring the Open Circuit Potential 

 

To ensure proper instrument operation, the potential difference between the reference electrode 
(RE) and counter electrode (CE) terminals and between the working electrode (WE) and working 
electrode sense (WES) terminals should not exceed 5 V. 

 

Section 3 

Open Circuit Potential 

Содержание KEITHLEY 2450-EC

Страница 1: ...User s Manual 077110402 November 2016 P077110402 077110402 Models 2450 EC 2460 EC and 2461 EC Potentiostats and Galvanostats A Greater Measure of Confidence www tek com keithley...

Страница 2: ...Keithley Instruments Other brand names are trademarks or registered trademarks of their respective holders The Lua 5 0 software and associated documentation files are copyright 1994 2015 Lua org PUC R...

Страница 3: ...s may be connected to mains These instruments will be marked as category II or higher Unless explicitly allowed in the specifications operating manual and instrument labels do not connect any instrume...

Страница 4: ...ead the associated information very carefully before performing the indicated procedure The CAUTION heading in the user documentation explains hazards that could damage the instrument Such damage may...

Страница 5: ...e 2 8 Save or load the test parameter data 2 10 Run the test and view the graph 2 12 Acquire the open circuit potential Eoc 2 13 Save the test data to the flash drive 2 14 View the results saved to th...

Страница 6: ...ew the results saved to the flash drive 5 12 View the Reading Table or measurement Statistics 5 12 View the Event Log 5 13 End the test application 5 13 Chronoamperometry 6 1 Chronoamperometry 6 1 Tes...

Страница 7: ...ction of time Potential Pulse and Square Wave with Current Measure Sources potential at programmable peak and base levels The resulting current at the pulse peak level is recorded Current Pulse and Sq...

Страница 8: ...U key then select Info Manage under System The firmware version is at the upper left of your display The latest firmware is available from the Keithley Instruments website http www tek com keithley Th...

Страница 9: ...he prompt to reboot select Yes Select the high impedance output off state Before making physical connections from the instrument to the test cell set the output of the instrument to the high impedance...

Страница 10: ...can run the test applications from the flash drive or copy the files from the flash drive to the instrument If you choose to copy the applications you must also copy the support files EC_Framework tsp...

Страница 11: ...Figure 3 Copying the file to the instrument Cable assembly details The cable is an electrically shielded 1 m 39 37 in assembly with stackable safety banana plugs on both ends This cable simplifies the...

Страница 12: ...use the supplied cable to connect your electrochemical cell to these jacks The SENSE terminals are used to measure voltage at the device under test DUT When you use sense leads the voltage drop across...

Страница 13: ...he working electrode of your electrochemical cell and connect the CE and RE pair to the counter electrode of the cell Figure 7 Two electrode cell testing cable connections For three electrode applicat...

Страница 14: ...fe secure way to connect to your device Figure 10 Alligator clip attached to accessory cable connector For small cells and electrodes you can use commercially available banana to microclip connectors...

Страница 15: ...and Menu screens in standard mode When you run an electrochemistry test application the default Home and Menu screens are replaced by application specific Home and Menu screens These screens vary dep...

Страница 16: ...ltammetry test application has adjustable parameter settings and enables real time graphing of a voltammogram on the display of the SMU potentiostat without using a computer Test parameters are input...

Страница 17: ...per second 10 mV 350 mV per second scan rate 3500 mV per second Number of cycles 1 to 100 User selectable sampling intervals Points per test 10 to 10 000 Points per cycle 10 to 10 000 Seconds per poi...

Страница 18: ...pt Figure 13 Active script indicator 3 Select the preloaded Cyclic Voltammetry test script potentiostats and galvanostats only or connect the supplied USB drive to your SMU instrument to locate the in...

Страница 19: ...ze Start Test Select this control to immediately begin the test This option becomes Stop Test when the test runs Save Data Select this control to save the test data to a csv file on a flash drive This...

Страница 20: ...wn in the next figure You can select up to four voltage potential vertices which are defined as E1 or E initial E2 E3 and E4 in the next figure The slope of the lines is determined by the the scan rat...

Страница 21: ...vertices Figure 19 Scan Settings menu defining four vertices 5 Enter each vertex value in the range of 20 V After you define the vertices select the potential reference Eref or Eoc If you select Eref...

Страница 22: ...ring the experiment You can select a scan rate of 0 1 mV per second to 3500 mV per second To select the Scan Rate 1 From the Scan Settings menu select Scan Rate Figure 21 Scan Settings menu selecting...

Страница 23: ...active buffer of the instrument cvBuffer The buffer can hold a maximum of 100 000 readings The following table describes the available interval units and accompanying range of values Sampling rate uni...

Страница 24: ...t measurement range 1 From the Measure Settings screen select Current Range Figure 25 Measure Settings menu selecting the Current Range When the test runs your potentiostat will limit the magnitude of...

Страница 25: ...five test parameter configurations can be stored To save the test parameters 1 From the Menu screen select Save Settings If you have saved a settings file previously with the same File Selection numbe...

Страница 26: ...instrument model on which they were created and saved For example you cannot load test parameter settings created with a 2450 EC to a 2460 EC 1 From the Menu screen select Load Settings Figure 29 Sel...

Страница 27: ...port of the potentiostat by simultaneously pressing the HOME key and the ENTER key The file name has the format imgmmdd_xxxxxx png where mmdd represents the instrument month and day and xxxxxx is a sy...

Страница 28: ...pted by the test application as shown in the next figure Figure 32 Prompt for Eoc measurement If you select Yes the instrument measures the open circuit potential Eoc of your electrochemical cell If y...

Страница 29: ...ve the test data to the flash drive 1 Make sure your flash drive is inserted into the front panel USB port 2 From the test application home screen select Save Data 3 Specify a file name then select OK...

Страница 30: ...these events You can also specify which events are shown in the event log which ones are logged and which ones generate popup messages Figure 36 Viewing the Event Log See your Keithley Instruments 245...

Страница 31: ...ith respect to the reference electrode The resulting current i flowing to the working electrode is measured with the ammeter AM This process is usually repeated for a range of E An example procedure t...

Страница 32: ...n reverses again and the voltage is swept until it reaches E4 From the potential sweep important information about the experiment can be derived and analyzed Keithley galvanostat scan theory The 2450...

Страница 33: ...a fixed point t for each discrete voltage step which may not be at the same time for each step See the following figure Figure 40 Voltage step measurements Conversely the 2450 EC 2460 EC and 2461 EC u...

Страница 34: ...pplied to the cell This voltage measurement is made using the galvanostat to source current and measure voltage see the next figure The instrument sources 0 A on the 1e 6 range using a 4 wire configur...

Страница 35: ...igured for 4 wire measurements as shown in the next figure In this setup the instrument is configured to source 0 A and measure voltage If you measure the OCP before performing any test you do not hav...

Страница 36: ...C and 2461 EC Potential measure ranges 200 mV 2 V 7 V 10 V 20 V Sample interval 0 75 s sample interval 100 s Number of samples 1 to 100 000 Run the Open Circuit Potential test application To run the t...

Страница 37: ...data This is useful for constraining all of the data to the screen s viewing size Start Test Select this control to immediately begin the test This option becomes Stop Test when the test runs Save Da...

Страница 38: ...the Potential Range 1 Press the MENU key then select Measure Settings 2 Select Potential Range Figure 48 Measure Settings menu selecting Potential Range 3 Choose a value Note that the choices are dif...

Страница 39: ...fy the sample interval time in seconds per point The sample interval time is illustrated in the next figure You can choose an interval from 0 75 to 100 seconds per point Figure 51 Sample Interval time...

Страница 40: ...ve test parameter configurations can be stored To save the test parameters 1 From the Menu screen select Save Settings Note that your Menu screen options are different depending on the test you are ru...

Страница 41: ...You are notified when the load completes 4 Select OK to clear the prompt Run the test and view the graph To start the experiment and view the graph or data 1 Press the HOME key 2 Select Start Test Th...

Страница 42: ...to select Stop Test before selecting End App Stop Test turns off the instrument s output Hazardous voltages may be present on all output and guard terminals To prevent electrical shock that could caus...

Страница 43: ...program on a computer Current voltage time and general parameters for the test are included in the file View the Reading Table or measurement Statistics When the test completes you can view the indiv...

Страница 44: ...w these events You can also specify which events are shown in the event log which ones are logged and which ones generate popup messages Figure 60 Viewing the Event Log See your Keithley Instruments 2...

Страница 45: ...e Various parameters of the pulse wave are displayed in the figure below Though not pictured there is also a brief latency period between the end of the measurement and the end of the pulse to allow t...

Страница 46: ...3600 s 100 ms pulse width 0 99 period Current measure range 1 A 4 ms period 3600 s 2 ms pulse width 0 99 period Sample time Minimum is 166 667 s Maximum is lesser of 166 667 ms and pulse width 1 ms N...

Страница 47: ...or 3 Select the preloaded Potential Pulse and Square Wave test script potentiostats and galvanostats only or connect the supplied USB drive to your SMU instrument to locate the included Potential Puls...

Страница 48: ...est data to a csv file on a flash drive This option is only visible after the test runs Cursor Select this control to cycle through the available cursor placements None Vertical Horizontal and Both Re...

Страница 49: ...Enter a value Figure 67 Entering a Base Potential 3 Select OK Next you will adjust the Peak Potential This setting allows you to adjust the maximum potential that the instrument will attempt to force...

Страница 50: ...our expected maximum current Setting the current range also sets a current limit which can be used to stop the test or otherwise protect your DUT Your potentiostat will limit the current to 105 percen...

Страница 51: ...se Width 3 Select OK The Sample Time is the length of time over which the actual measurement is taken The Sample Time cannot exceed the Pulse Width minus 1 ms PW 1 ms The measurement is taken at the e...

Страница 52: ...le the Number of Cycles the Program Time is disabled Conversely if you enable the Program Time the Number of Cycles condition is disabled The Source Limit setting is independent of the other two setti...

Страница 53: ...the waveform if the current level reaches the programmed source or compliance limit The source limit is set to 105 percent of the selected current measure range To enable the Source Limit end conditi...

Страница 54: ...saved test parameters Test parameters can only be loaded to the same instrument model on which they were created and saved For example you cannot load test parameter settings created with a 2450 EC to...

Страница 55: ...o the USB port of the potentiostat by simultaneously pressing the HOME key and the ENTER key The file name has the format imgmmdd_xxxxxx png where mmdd represents the instrument month and day and xxxx...

Страница 56: ...e flash drive 1 Make sure your flash drive is inserted into the front panel USB port 2 From the test application home screen select Save Data 3 Specify a file name then select OK 4 Select OK on the co...

Страница 57: ...ed by your instrument Through the Event Log menu you can view these events You can also specify which events are shown in the event log which ones are logged and which ones generate popup messages Fig...

Страница 58: ...rious parameters of the pulse wave are displayed in the figure below Though not pictured there is also a brief latency period between the end of the measurement and the end of the pulse to allow the i...

Страница 59: ...00 ms period 3600 s 100 ms pulse width 0 99 period Ipeak or Ibase 1 05 A 4 ms period 3600 s 2 ms pulse width 0 99 period Sample time Minimum is 166 667 s Maximum is lesser of 166 667 ms and pulse widt...

Страница 60: ...ndicator 3 Select the preloaded Current Pulse and Square Wave test script potentiostats and galvanostats only or connect the supplied USB drive to your SMU instrument to locate the included Current Pu...

Страница 61: ...e the test data to a csv file on a flash drive This option is only visible after the test runs Cursor Select this control to cycle through the available cursor placements None Vertical Horizontal and...

Страница 62: ...Enter a value Figure 89 Entering the Base Current 3 Select OK To adjust the Peak Current 1 From the Pulse Settings screen select Peak Current 2 Enter a value Figure 90 Entering the Peak Current 3 Sel...

Страница 63: ...ercent of the selected range Now you will adjust the Period This setting lets you specify the duration of one cycle of the pulse wave The Period and Pulse Width settings are related You cannot set the...

Страница 64: ...end of the pulse A brief latency period between the end of the measurement and the end of the pulse allows the analog to digital converter in your galvanostat to complete the measurement To adjust the...

Страница 65: ...t On 4 Select the Number of Cycles Value control 5 Enter a value then select OK Use the Program Time end condition to stop generating the waveform after a specified time interval The pulse wave stops...

Страница 66: ...test parameter configurations can be stored To save the test parameters 1 From the Menu screen select Save Settings Note that your Menu screen options are different depending on the test you are runn...

Страница 67: ...You will be notified when the load completes 4 Select OK to clear the prompt Run the test and view the graph To run the test and view the graph 1 Press the HOME key 2 Select Start Test The output tur...

Страница 68: ...select Stop Test before selecting End App Stop Test turns off the instrument s output Hazardous voltages may be present on all output and guard terminals To prevent electrical shock that could cause...

Страница 69: ...rogram on a computer Current voltage time and general parameters for the test are included in the file View the Reading Table or measurement Statistics When the test completes you can view the individ...

Страница 70: ...these events You can also specify which events are shown in the event log which ones are logged and which ones generate popup messages Figure 103 Viewing the Event Log See your Keithley Instruments 24...

Страница 71: ...U potentiostat can repeat this process for up to ten defined steps Key timing parameters are shown in the figure below Note that there is always a measurement at the beginning of each step Figure 104...

Страница 72: ...mum is 166 667 s Maximum is lesser of 166 667 ms and sample interval 5 ms and step duration 5 ms Maximum number of samples 100 000 total for all steps Models 2460 EC and 2461 EC Step potential 20 V Es...

Страница 73: ...ns to run immediately and the following screen is displayed Figure 107 Chronoamperometry test home screen The test home screen controls include End App Select this control to immediately stop the test...

Страница 74: ...the Menu screen depending on the application The following graphic shows the Chronoamperometry main Menu You will learn the function for each option later in this section Figure 108 Chronoamperometry...

Страница 75: ...e MENU key then select Step Settings 2 Select Number of Steps 3 Enter a value then select OK The next figure shows three steps defined Figure 110 Step Settings menu Next you must define the Potential...

Страница 76: ...device under test DUT Make sure to choose a range higher than your expected maximum current Setting the current range also sets a current limit which can be used to stop the test or otherwise protect...

Страница 77: ...Save or load the test parameter data You can save your test parameters to the front panel flash drive at any time Up to five test parameter configurations can be stored To save the test parameters 1...

Страница 78: ...saved test parameters Test parameters can only be loaded to the same instrument model on which they were created and saved For example you cannot load test parameter settings created with a 2450 EC to...

Страница 79: ...USB port of the potentiostat by simultaneously pressing the HOME key and the ENTER key The file name has the format imgmmdd_xxxxxx png where mmdd represents the instrument month and day and xxxxxx is...

Страница 80: ...flash drive 1 Make sure your flash drive is inserted into the front panel USB port 2 From the test application home screen select Save Data 3 Specify a file name then select OK 4 Select OK on the con...

Страница 81: ...ed by your instrument Through the Event Log menu you can view these events You can also specify which events are shown in the event log which ones are logged and which ones generate popup messages Fig...

Страница 82: ...lvanostat can repeat this process for up to ten defined steps Key timing parameters are displayed in the figure below Note that there is always a measurement at the beginning of each step Figure 123 P...

Страница 83: ...um is 166 667 s Maximum is lesser of 166 667ms and sample interval 5 ms and step duration 5 ms Maximum number of samples 100 000 total for all steps Models 2460 EC and 2461 EC Step current 7 35 A Iste...

Страница 84: ...on begins to run immediately and the following screen is displayed Figure 126 Chronopotentiometry test home screen The test home screen controls include End App Select this control to immediately stop...

Страница 85: ...ill learn the function for each option later in this section Figure 127 Chronopotentiometry main Menu Configure the Step and Measure Settings Select Step Settings to specify the number level and durat...

Страница 86: ...The next figure shows three steps defined Figure 130 Step Settings menu Next you must define the Current and Duration for each step To define the Current and Duration 1 From the Measure Settings menu...

Страница 87: ...ross the device under test DUT Make sure to choose a range higher than your expected maximum potential Setting the Potential Range also sets a potential limit which can be used to stop the test or oth...

Страница 88: ...e Save or load the test parameter data You can save your test parameters to the front panel flash drive at any time Up to five test parameter configurations can be stored To save the test parameters 1...

Страница 89: ...saved test parameters Test parameters can only be loaded to the same instrument model on which they were created and saved For example you cannot load test parameter settings created with a 2450 EC t...

Страница 90: ...nostat by simultaneously pressing the HOME key and the ENTER key The file name has the format imgmmdd_xxxxxx png where mmdd represents the instrument month and day and xxxxxx is a system generated num...

Страница 91: ...e flash drive 1 Make sure your flash drive is inserted into the front panel USB port 2 From the test application home screen select Save Data 3 Specify a file name then select OK 4 Select OK on the co...

Страница 92: ...ted by your instrument Through the Event Log menu you can view these events You can also specify which events are shown in the event log which ones are logged and which ones generate popup messages Fi...

Страница 93: ...operty of Keithley Instruments All other trademarks and trade names are the property of their respective companies Keithley Instruments Corporate Headquarters 28775 Aurora Road Cleveland Ohio 44139 44...

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