eDAQ e-corder pH/mV Amp User Manual Download Page 37 | Manualshive

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Appendix A — Technical Aspects

33

The temperature input is effectively a separate eDAQ Amp. It consists of
a bridge circuit that is factory configured for use with RTD temperature
probes. The pH/mV Amp comes supplied with an RTD temperature
probe. The output from the temperature amplifier has been factory set
with the supplied RTD probe to produce 0 – 5 V over 0 – 100 °C.

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Summary of Contents for e-corder pH/mV Amp

Page 1: ...e corder www eDAQ com eDAQ Amp User Manual pH mV Amp pH mV Amp Electrode Reference Temperature ...

Page 2: ...td Chart and Scope are trademarks of ADInstruments Pty Ltd and are used under license by eDAQ EChem is a trademark of eDAQ Pty Ltd Other Trademarks Mac OS and Macintosh are registered trademarks of Apple Computer Inc Windows 98 Windows Me Windows 2000 and Windows XP are trademarks of Microsoft Corporation PostScript and Acrobat are registered trademarks of Adobe Systems Incorporated All other trad...

Page 3: ...the Temperature Amp 14 The Temperature Probe 17 3 pH Calibration Extension 19 Electrode Calibration 20 Temperature Compensation 25 Manual Temperature Compensation 25 Automatic Temperature Compensation 26 Isopotential Point 28 Viewing Electrode Response 28 Manual Compensation Response 29 Removing the Calibration 30 A Technical Aspects 31 pH mV Amp Operation 31 Technical Description 32 B Troubleshoo...

Page 4: ...iv pH mV Amp ...

Page 5: ...ective electrodes ISEs redox or ORP oxidation reduction potentiometric electrodes other high impedance sources up to 2 V requiring electrometer input The in built temperature amplifier can be used to provide automatic temperature compensation ATC for pH and ion selective electrodes This chapter provides an overview of the pH mV Amp and describes its basic features ...

Page 6: ...Q distributor if you encounter a problem You should also become familiar with the basic features of your e corder system which are discussed in the e corder Manual on the Installer CD eDAQ Amps The pH mV Amp is part of a family of preamplifiers known as eDAQ Amps The pH mV Amp is designed for recording signals from pH and other potentiometric electrodes As with other eDAQ Amps it is designed to be...

Page 7: ...tiostat suitable for use with carbon fibre and other microelectrodes Current gain ranges of 10 pA to 100 nA in 1 2 5 steps Bridge Amp suitable for sensors requiring a low drift high gain differential amplifier Also provides DC excitation GP Amp suitable for high output sensors requiring a high impedance single ended or differential amplifier Also provides DC excitation See our web site at www eDAQ...

Page 8: ...4 pH mV Amp ...

Page 9: ...mp This chapter describes how to connect and use your pH mV Amp IMPORTANT Always make sure that the e corder is turned off before you connect or disconnect the pH mV Amp Failure to do this may result in damage to the e corder and or the pH mV Amp ...

Page 10: ...ence socket This is in common with the shield ground of the BNC electrode input connector The Online Indicators When lit these indicate that the software such as Chart or Scope has located and initialized the pH mV Amp If the light does not go on when the software is run check that the pH mV Amp is properly connected There are two indicators one to show connection of the electrode signal and the s...

Page 11: ...d Regulated 17 V DC Regulated 8 V DC Regulated 17 V DC Power lines SCL DSC SDA DSD INT I2C control signals 1 5 9 6 Digital Ground Regulated 17 V DC Regulated 8 V DC Regulated 17 V DC SCL DSC SDA DSD INT I2C control signals Input Output pH Output Input Output I C Bus I C 2 Temp Output pH mV signal BNC connector Temperature signal BNC connector DB 9 pin I2C connectors Figure 2 2 The pH mV Amp back p...

Page 12: ...selection to and from the e corder The pin assignments are shown in Figure 2 3 Connecting to the e corder Your pH mV Amp will have been supplied with an I2 C cable DB 9 pin connectors at either end and two cables with BNC connectors at either end First make sure that the e corder is turned off Then connect the I2 C cable to the I2 C connector on the back panel of the e corder and the other end to ...

Page 13: ...nput 2 Input 4 pH mV Amp Electrode Trigger Power Status 401 Output Reference Temperature Temp Output pH Output I2C output I2C input Figure 2 5 Connecting multiple pH mV Amps Figure 2 4 Connecting a pH mV Amp to an e corder e corder I2C output I2C input I2C connector cable Electrode signal output ...

Page 14: ...ic tests as described in the e corder Manual Once the e corder is ready open Chart or Scope During initialization you should see these indicators flash briefly and then remain lit the pH mV Amp is ready for use If the indicators do not light check your cable connections and repeat the procedure Appendix B If this does not solve the problem contact your eDAQ distributor Note If only the pH Output i...

Page 15: ...ilar The incoming signal is displayed in real time but is not recorded to hard disk once the signal moves across the display area it is lost Click the OK button to apply the selected settings Signal Display The input signal is displayed so that you can see the effect of changing the settings The average signal value is displayed at the top left of the display area Slowly drifting signals as from p...

Page 16: ...al Average signal amplitude Select filter e corder input channel number Pause Resume button Preview signal Invert signal Gain range sensitivity Select input channel Average signal amplitude Figure 2 7 The pH mV Amp pH dialog box for previewing a signal Chart software on a Windows Computer Figure 2 8 The pH mV Amp pH dialog box for previewing a signal Chart software on a Macintosh Computer ...

Page 17: ... range of approximately one pH unit This relationship is used in Table 2 1 which shows the pH ranges corresponding to the pH mV Amp range settings For general pH measurements a range of 500 mV should be used while the 200 mV range is suited for biological pH monitoring Filtering The pH mV Amp has three low pass filter settings of 2 kHz 50 Hz and 10 Hz The low pass filter will remove high frequency...

Page 18: ...tension Both extensions are available from the eDAQ website www eDAQ com For more information about Units Conversion see the Chart Software Manual or Scope Software Manual Setting up the Temperature Amp Signal Display The input signal is displayed so that you can see the effect of changing the settings no data is actually recorded when setting up the Temperature Amp The average signal value is dis...

Page 19: ...rity that is positive and negative signal values are reversed Units Clicking the button accesses the Units Conversion dialog box allowing calibration of the signal The raw temperature reading will be in volts and must be converted to degrees Celsius Fahrenheit or Kelvin for correct display The Temperature Amp has been factory set to Amplitude axis e corder input channel number Pause Resume buttons...

Page 20: ...e calibrated in degrees Celsius C degrees Fahrenheit F or Kelvin K Clicking the button transfers the signal in the data display area of the dialog box to the data display area of the Units Conversion dialog box Use the Pause button to capture any specific signal that Pause Resume button Select Temperature from the channel menu Select suitable range 5 V up to 100 C 2 V up to 40 C Access Units Conve...

Page 21: ... are both located on the Installer CD The Temperature Probe The pH mV Amp is supplied with a RTD type temperature probe with 100 Ω nominal resistance to which the Temperature Amp is factory set to produce 0 mV at 0 C and an output of 50 mV C Only use these values to calibrate the probe supplied with the pH mV Amp You can substitute other RTD probes for the one provided however the factory calibrat...

Page 22: ...18 pH mV Amp ...

Page 23: ...compensation MTC adjustment or enables automatic temperature compensation ATC if temperature readings are collected on a second channel The resulting calibration information is used to convert the raw voltage signal from the electrode into appropriate units pH pF pNa etc which will then be displayed in the Chart window Multiple point i e more than two points linear or non linear calibration can be...

Page 24: ...ignal values can be entered directly by typing them in it is more usual for the electrode to be immersed in a standard buffer solution of known pH or ion concentration and the signal recorded for a minute or so until it has stabilized If two point calibration is required then the electrode is immersed in a second standard buffer solution of a different pH or ion concentration After recording the r...

Page 25: ... menu Raw signal values Select region of signal for raw value Calibration temperature Decimal places selection Electrode response dialog button Calibration report Temperature compensation Select region of signal for raw value Choose the pH Calibration command from the channel menu Choose the pH command from the channel menu Figure 3 2 The Electrode Calibration dialog box of the pH Calibration Exte...

Page 26: ...d two markers and indicate the maximum and minimum data points in the selection Figure 3 4 Usually a region of steady signal is selected Figure 3 4 and then clicking the Value button enters the raw signal value the Figure 3 3 Selection of raw mV data from two buffer solutions for use in electrode calibration Figure 3 4 Selecting different regions of the electrode signal ...

Page 27: ...you cans also define new units or delete unwanted ones Unit names are stored in a preferences file and become available to other files Choose Define Unit from the Units pop up menu to access the Define Unit dialog box Figure 3 7 to enter a new unit name Results of double point calibration Results of single point calibration Click on arrow to enter average signal value Enter buffer pH Select region...

Page 28: ...nd return to the Chart window click the button To abandon the changes click the button Ionic Charge Use the pop up menu Figure 3 7 to select the value for the number of electrons transferred at the electrode This usually corresponds to the charge of the ion and thus for pH sodium or potassium measurements n 1 for magnesium or calcium n 2 while for halides or nitrate n 1 The value of n is used to c...

Page 29: ...d as a basis for compensation of the readings The pH extension offers two types of temperature compensation manual temperature compensation MTC Used where the measurements are made at a constant temperature but where Tm Tc Automatic temperature compensation ATC Used where temperature fluctuations are expected to occur during the experiment that is when Tm is not constant In these cases temperature...

Page 30: ...When the Automatic option is chosen the pH extension will use temperature data from one of the Chart channels to correct the pH channel for variations in temperature To choose the automatic temperature compensation option click in the radio button next to the Automatic option The channel selection pop up menu can select the channel on which temperature was recorded Recording Temperature To use a t...

Page 31: ...3 10 Select Temperature from the channel menu Select suitable range 5 V up to 100 C 2 V up to 40 C Access Units Conversion for temperature signal Preview of temperature signal 0 V 0 C and 5 V 100 C are the factory default settings for the RTD probe Figure 3 9 Uncalibrated temperature channel warning alert Figure 3 10 Previewing the temperature signal and setting up units for the temperature channe...

Page 32: ...ppendix D for more information on how to determine the isopotential point Viewing Electrode Response The pH extension plots the voltage response of the electrode versus pH or other ion giving a calibration graph of the electrode Click the button in the pH dialog box Figure 3 1 and Figure 3 2 Typical electrode responses are shown in Figure 3 11 The isopotential point will be set to zero unless temp...

Page 33: ...ibration temperature and a second plot showing the response at the specified temperature The calibration response can be identified as the line with one or two calibration points on it These are represented as dots The information displayed on the right of the dialog shows the calibration points and the values used for the Nernst equation Calibration point Calibration points Single point calibrati...

Page 34: ...t Removing the Calibration The calibration can be turned off at any time by choosing the command from the channel pop up menu Figure 3 1 and Figure 3 2 This displays the raw electrode signal in millivolts or volts again Response at 65 C Isopotential point Response at 25 C Figure 3 12 Electrode Response dialog box when using manual temperature compensation ...

Page 35: ...odification of the equipment voids your rights under warranty pH mV Amp Operation The pH mV Amp and other eDAQ Amps have been designed to be used with an e corder system The pH mV Amp is an extension of the e corder s analog input channels It provides a very high impedance amplifier suitable for direct connection to pH or other ion selective electrodes software controlled filtering for the pH chan...

Page 36: ...e pH input amplifier of the pH mV Amp is an electrometer type amplifier with extremely high input impedance The input also has provision for connection to a reference electrode which is connected to the analog ground of the amplifier The input amplifier can be software set to a gain of 1 or 10 depending on the required sensitivity The output of the electrometer amplifier is fed to a 2 pole 10 Hz l...

Page 37: ...DAQ Amp It consists of a bridge circuit that is factory configured for use with RTD temperature probes The pH mV Amp comes supplied with an RTD temperature probe The output from the temperature amplifier has been factory set with the supplied RTD probe to produce 0 5 V over 0 100 C ...

Page 38: ...34 pH mV Amp ...

Page 39: ... connected Check that the cable is firmly connected to the BNC connector on the back panel of the pH mV Amp and to a BNC input on the front panel of the e corder Either or both on line indicators fail to light when the application is opened and the pH mV Amp is not accessible from Chart or Scope The I2 C cable from the pH mV Amp to the e corder may not be properly Check to see that the I2 C cables...

Page 40: ...36 pH mV Amp ...

Page 41: ... V full scale in 13 steps combined e corder and pH mV Amp Input resolution 16 bits 0 0015 of range Input impedance 1013 Ω typical Amplifier noise 1µV rms 4 µV p p with a bandwidth of DC 10 Hz Maximum Input 10 V Input Connection type Insulated BNC Low pass filter 10 Hz 3 dB frequency Low pass filter accuracy 3 0 Low pass filter type Bessel 2 pole ...

Page 42: ...0 1 5 V 100 0 05 2 V 40 0 02 1 V 20 0 01 500 mV 10 0 01 Input connection 3 pin mini audio jack Control Port I2 C input and output Male and female DB 9 pin connectors Provides control and power Power requirements 17 V DC 8 V DC 3 W Physical Configuration Dimensions h w d 50 76 260 mm 1 96 3 0 10 2 inches Weight 0 8 kg 1 8 lb Operating conditions 0 35 C 0 90 humidity non condensing eDAQ reserves the...

Page 43: ...the gas constant 8 314 J K 1 mol 1 T is the temperature in Kelvin F is the Faraday constant 96487 C mol 1 n is the number of electrons transferred at the electrode usually the charge of the ion pY log10 Y where Y is the activity of the ionic species Note that if pY is plotted against E then the Nernst equation predicts that a straight line should be obtained of intercept E0 and a slope of RT nF Fo...

Page 44: ...emains constant as temperature changes Most pH electrodes are constructed so that the isopotential is about 0 mV which for most pH electrodes also corresponds to pH 7 However it is not uncommon to find that even in new pH electrodes this value may be anywhere between 50 mV and that the value also changes as the electrode ages Ion selective electrodes may have an isopotential completely outside the...

Page 45: ... Calibration Both single and two point calibration assume that the electrode has a linear response to ion activity Experimentally there will always be some deviation from linearity in the response This is most noticeable at very high or low concentrations In these instances a non linear calibration technique must be used for accurate work Also if you need to calibrate an electrode directly in term...

Page 46: ...42 pH mV Amp In either case the Chart Multipoint calibration extension can be used for non linear electrode calibration See our web site at www eDAQ com for more information ...

Page 47: ...eDAQ Amps 10 E eDAQ Amps Bridge Amp 3 GP Amp 3 pH Amp 2 pH mV Amp 2 Picostat 3 Potentiostat 3 electrode isopotential point 28 electrode calibration 19 ATC 26 MTC 29 non linear 41 report 30 undoing 30 electrode connector pH mV Amp 6 electrode response 28 30 determination 40 electrode response dialog axis scaling 28 printing or copying 30 F filtering 13 front panel pH mV Amp 6 G GP Amp 3 I I2C conne...

Page 48: ...r Scope 10 pH calibration extension 19 30 pH electrode isopotential point 28 pH range settings 13 pH mV Amp 2 Picostat 3 Potentiostat 3 preferences file 23 problems 35 R reference connector pH mV Amp 6 T technical specifications 37 38 Temperature Amp dialog box 12 13 16 setting the sensitivity 15 setup 14 17 Units conversion 15 temperature compensation 25 28 automatic 26 manual 25 26 troubleshooti...

Page 49: ...efective product at your expense We will pay return shipping The product should be packed safely preferably in its original packaging and have the RAN on the shipping label Returns sent without a RAN may be refused delivery This warranty does not cover hardware that has been modified by the user in any way been subjected to unusual physical electrical or environmental stress This includes damage d...

Page 50: ...Macintosh OS 10 2 the software version you are using for example Chart v5 1 2 We endeavor to answer all your questions but in some cases for example where the problem relates to the other equipment that you are using a nominal fee may be charged Jurisdiction eDAQ Pty Ltd is bound by the laws of New South Wales in Australia and any proceedings shall be heard by the Supreme Court of New South Wales ...

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