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46

17.1.2

 

Slope of a pH Electrode

As mentioned above, a pH electrode produces 0 mV output at around 7.00 pH. As the pH goes up,
an “ideal” pH electrode produces -59mV/pH unit at 25 

O

C As the pH goes down, an ideal pH

electrode pr59mV/pH unit. In practice, pH electrodes usually produce slightly less than
this. The output of a pH electrode is expressed as a percentage of an ideal electrode. For example,
an ideal electrode that produces 59mV/pH unit has “100% Slope”. An electrode that produces
50.15mV/pH unit has “85% Slope” (see Figure 17-2).

-600

-400

-200

0

200

400

600

0

7

14

mV

85% Slope at 25 oC
(50.15mV/pH)

100% Slope at 25 oC
(59mV/pH)

Response of pH Electrode, as a Function of Slope

pH

Figure 17-2

17.1.3

 

Temperature Compensation

The slope of a pH electrode is affected by temperature. This effect is compensated for either by
using an Automatic Temperature Compensation (ATC) probe or by entering the sample temperature
manually. Figure 17-3 shows the slope of a pH electrode at various temperatures.

-600

-400

-200

0

200

400

600

0

7

14

mV

Electrode
Potential (mV) at
0 oC (54mV/pH)

Electrode
Potential (mV) at
50 oC (64mV/pH)

Electrode
Potential (mV) at
100 oC
(74mV/pH)

pH Electrode Response, as a Function of Temperature

pH

Figure 17-3

17.2 Guard Connector

In some circumstances, the Specific Ion, pH or mV readings may become unstable. This may be
due to static charge in the sample vessel, or electrical noise from nearby electrical equipment. In
these cases, a solution guard may eliminate the problem.

A solution earth rod is available from TPS (part no 121360). This connects directly to the 

Guard

socket. Alternatively, run a wire from the 

Guard

 socket to a stainless steel fitting in contact with

the sample.

Summary of Contents for 900-I3

Page 1: ...tion has a diagram and explanation of the display and controls of the 900 I3 It also contains a full listing of all of the items that you should have received with unit Please take the time to read this section as it explains some of items that are mentioned in subsequent sections 3 Main Section The main section of the handbook provides complete details of the 900 I3 including operating modes cali...

Page 2: ...ration Messages 14 4 pH Mode 15 4 1 Selecting pH Mode 15 4 2 Setting the pH Buffer Set 16 4 3 pH Calibration 17 4 4 pH Calibration Notes 18 4 5 pH Calibration Messages 19 5 Absolute Millivolt Mode 20 5 1 Selecting Absolute Millivolt Mode 20 5 2 Absolute Millivolt Calibration 20 6 Relative Millivolt Mode 21 6 1 Selecting Relative Millivolt Mode 21 6 2 Relative Millivolt Calibration 21 6 3 Relative ...

Page 3: ...ode 37 12 2 Recorder Port Configuration in pH Mode 39 12 3 Recorder Port Configuration in Absolute or Relative mV Modes 39 12 4 Recorder Port Specifications 40 12 5 Recorder Port Connections 40 13 Setting the Clock 41 14 Initialising the 900 I3 42 15 Instrument firmware version number 42 16 Troubleshooting 43 16 1 General Errors 43 16 2 Specific Ion pH and mV Troubleshooting 43 16 3 Temperature Tr...

Page 4: ...4 1 Introduction 1 1 900 I3 Display and Controls 1 2 900 I3 Rear Panel Connectors ...

Page 5: ...Relative mV when Relative mV is selected See section 6 2 Press to obtain context sensitive help messages This function is disabled within menus 1 4 Numeric Keypad Used to enter values during set up and calibration A negative sign and decimal point are provided 1 5 Enter Key Press the key to accept default values or those entered on the Numeric Keypad 1 6 Delete Key Press the key to make correction...

Page 6: ...ur 900 I3 1 Flexible arm type electrode holder 130088 2 RS232 Serial Interface Option includes cable 130029 3 Recorder Output Option includes cable 130028 4 RS232 PLUS Recorder Output Option 130049 includes cable 5 Communication software for Windows 3 1 130086 95 and NT 6 Communication software for DOS 130075 7 RS232 Printer 130031 Sensors Your choice of a complete range of Ion Selective Reference...

Page 7: ...0 pH Slope Range 85 0 to 105 0 Temperature Compensation Automatic 0 to 100 O C Calibration Automatic calibration Automatic recognition of pH4 00 6 88 7 00 9 22 and 10 06 buffers Manual entry of any other buffer value Additional Temperature Specifications Temp Sensor Offset Range 10 0o C to 10 0o C General Specifications Memory 1200 readings including date and time Automatic Logging User set for on...

Page 8: ...within menus Press to access the user friendly menu system as detailed below F1 Calibrate F1 Channel 1 F2 Channel 2 F3 Channel 3 F4 Temperature F2 Notepad F1 Recall F2 Erase F1 Erase All F2 Erase Last F3 Print F4 Program F1 Secs F2 Mins F3 Hours F3 Mode F1 Channel 1 F1 pH F1 1 F2 01 F3 001 F2 mV F1 Absolute F2 Relative F3 Ion See section 3 F2 Channel 2 F1 pH F1 1 F2 01 F3 001 F2 mV F1 Absolute F2 ...

Page 9: ...elect readout in ppK Parts Per Thousand Press to select readout in Press to select readout in Exponential units e g Molar Press to quit without changing the current setting 4 The Ion Resolution screen is now displayed Ion Resolution F1 3 Digits F2 2 Digits Ion Resolution F1 3 Digits F2 2 Digits F3 Auto Rounding F3 Auto Rounding The arrow indicates the current selection Press to select resolution t...

Page 10: ...dards F4 Standards F1 Channel 1 F1 Channel 1 2 The Primary Standard set up screen will now be displayed Enter Primary Standard Enter Primary Standard 0 0 00 ppM 00 ppM Type in the value of the Primary standard including the decimal point Use the key to make any corrections Press to save the Primary standard Alternatively press to quit without changing the current setting 3 The Secondary Standard s...

Page 11: ...power This can be entered as 1 or 2 digits e g 04 04 is treated the same as 4 4 Use the key to make any corrections Press to save the Primary standard Alternatively press to quit without changing the current setting 3 The Secondary Standard set up screen will now be displayed Enter Secondary Standard 0 00 Enter Secondary Standard 0 0010 10 00 00 The Secondary Standard must be at least 2 to 100 tim...

Page 12: ...y been calibrated section 7 1 or manually set section 7 4 NOTE A in place of the decimal point in the temperature readout indicates that temperature is not calibrated 5 Remove the wetting caps from the Ion Selective and Reference electrodes if fitted Rinse the Ion Selective Reference and Temperature sensors in distilled water and blot dry Primary Calibration 6 Place the Ion Selective Reference and...

Page 13: ... electrode s reference junction are both covered as per the diagram in step 6 above Ensure that any Ionic Strength Adjusting Buffer ISAB that may be required has been added see the Ion Selective Electrode s handbook A magnetic stirrer providing constant gentle stirring generally improves stability 10 Select Secondary Calibration for the same Channel as selected in step 7 above e g F1 Calibrate F1 ...

Page 14: ...been successfully performed the 900 I3 will display the following message and the Offset value of the sensor For example 100 100 ppM 25 0 ppM 25 0O O c c Calibration OK mV STD1 0 1mV Calibration OK mV STD1 0 1mV 2 If a Secondary Calibration has been successfully performed the 900 I3 will display the following message and the slope value of the sensor For example 10 0ppM 56 7mV 25 0 10 0ppM 56 7mV ...

Page 15: ...2 The pH Resolution screen is now displayed Select pH Resolution Select pH Resolution F1 0 1 F2 0 01 F3 0 001 F1 0 1 F2 0 01 F3 0 001 The arrow indicates the current selection Press to select 0 1 pH resolution Press to select 0 01 pH resolution Press to select 0 001 pH resolution Press to quit without changing the current selection ...

Page 16: ...6pH The arrow indicates the current selection Press to select pH4 00 and pH9 22 as the Secondary Buffers Press to select pH4 00 and pH10 06 as the Secondary Buffers Press to quit without changing the current setting Notes 1 The selected buffer set will the same for all Channels that are set to pH mode 2 The selected buffer set is kept in memory when the meter is switched off 3 The buffers are re s...

Page 17: ...he bulb and reference junction are both covered as per the diagram below DO NOT place the electrodes directly into the buffer bottle 7 Select pH Calibration for Channel 1 2 or 3 e g F1 Calibrate F1 Calibrate F1 Channel 1 F1 Channel 1 F1 pH F1 pH The display should now look something like this 6 85pH Buffer 6 85pH Buffer 6 6 86 25 0 86 25 0O O c c Press ENTER to Calibrate or Edit Buffer Press ENTER...

Page 18: ...ibrate the 900 I3 Press to calibrate to the displayed buffer Otherwise enter an alternative buffer using the Numeric Keypad and then press 11 The 900 I3 is now ready for pH measurements for the Channel that was calibrated Discard the used samples of buffer Rinse the pH and Temperature sensors in distilled water and blot them dry before placing them into unknown samples 4 4 pH Calibration Notes 1 A...

Page 19: ...ibration 3 If a 2 point calibration has been successfully performed the 900 I3 will display the following message and the asymmetry and slope of the electrode Slope Asymmetry Calibration Successful Slope Asymmetry Calibration Successful 0 10pH Asym 99 0 Slope 0 10pH Asym 99 0 Slope 4 If a 2 point calibration has failed the 900 I3 will display the following message and the failed slope value of the...

Page 20: ...el 1 F1 Channel 1 F2 mV F2 mV F1 Absolute F1 Absolute The 900 I3 will display the actual millivolts produced by the sensor in this mode 5 2 Absolute Millivolt Calibration The millivolt section of the 900 I3 is factory calibrated There is no user calibration facility for this mode Temperature compensation is not applicable in Millivolt mode ...

Page 21: ...sation is not applied in Relative mV mode so the temperature sensor does not need to be connected 2 Switch the meter on 3 Select Relative mV Mode for Channel 1 2 or 3 e g F3 Mode F3 Mode F1 Channel 1 F1 Channel 1 F2 mV F2 mV F2 Relative F2 Relative 4 The display should now be showing Relative mV on the top line with absolute mV on the bottom line The following example shows all 3 Channels set to R...

Page 22: ...fer a choice of Zeroing any one Channel or all Channels For example 500 0mVR 500 0mVR 500 0mVR 25 0 500 0mVR 500 0mVR 500 0mVR 25 0O O c c Zero F1 Chan1 F2 Chan2 F3 Chan3 F4 All Zero F1 Chan1 F2 Chan2 F3 Chan3 F4 All Press or according to your requirements 9 The 900 I3 Relative mV mode is now zeroed and is ready for use The readout can be re zeroed by repeating the steps detailed above whenever re...

Page 23: ...easured by the mercury thermometer 6 Press the key to calibrate the temperature readout Alternatively press the key to abort temperature calibration 7 2 Temperature Calibration Notes 1 Temperature calibration information is retained in memory when the 900 I3 is switched off even when the power supply is removed This information can be recalled later using the GLP function see section 8 2 Temperatu...

Page 24: ...ture 4 The current temperature setting is now displayed For example Enter Manual Temperature 25 0 Enter Manual Temperature 25 0 O O C C Menu Quits Menu Quits 5 Enter the temperature of the sample using the Numeric Keypad Press to save the new value Alternatively press to quit and retain the current setting 6 The 900 I3 now returns to normal measurement mode Note the flashing M M in the temperature...

Page 25: ...u F4 Setup F4 Setup F3 GLP F3 GLP 3 Select F1 Recall F1 Recall from the menu 4 The instrument model firmware version number and instrument serial number are displayed along with a prompt describing how to scroll through the GLP information 900I3 V3 0 R1234 31 12 98 12 00 900I3 V3 0 R1234 31 12 98 12 00 F4 Next F4 Next 5 Press the key to sequentially scroll through the GLP information for all param...

Page 26: ... 0 31 12 98 11 25 Ion Calibrated F2 Back F4 Next Ion Calibrated F2 Back F4 Next pH2 Asymmetry 0 10pH 31 12 98 11 30 pH2 Asymmetry 0 10pH 31 12 98 11 30 pH Calibrated F2 Back F4 Next pH Calibrated F2 Back F4 Next pH2 Slope 99 0 31 12 98 11 35 pH2 Slope 99 0 31 12 98 11 35 pH Calibrated F2 Back F4 Next pH Calibrated F2 Back F4 Next Ion3 Offset 0 1mV 31 12 98 11 40 Ion3 Offset 0 1mV 31 12 98 11 40 Io...

Page 27: ...witch the meter on 2 Ensure that the 900 I3 RS232 cable is connected to the instrument and to the printer or PC 3 Send the GLP information to the RS232 port F4 Setup F4 Setup F3 GLP F3 GLP F3 Print F3 Print The message Printing GLP Data Printing GLP Data is displayed while sending the data to the RS232 port 4 The GLP information is sent to the RS232 port in formatted ASCII text For example 900I3 V...

Page 28: ...en the RS232 serial Port option is fitted The r r after 900I3 is shown when the Recorder Port option is fitted 2 The serial number is displayed when recalling the GLP information section 8 1 3 The serial number is included on the printout of GLP information section 8 3 4 The GLP information can be downloaded to a PC using the optional Windows software part number 130086 8 5 Additional GLP Features...

Page 29: ...en as required The maximum number of readings that can be stored in the Notepad is 1200 9 2 Recalling Readings from the Notepad To recall records from the Notepad onto the 900 I3 display 1 Select the Notepad menu F2 Notepad F2 Notepad 2 Select F1 Recall F1 Recall from the menu Record number 1 is now displayed For example 10 0ppM 7 00pH 500 0mV 25 0 10 0ppM 7 00pH 500 0mV 25 0O O c c Log 1 F2 Log 1...

Page 30: ...uit without erasing any records 9 4 Printing Records from the Notepad to the RS232 Port This function is only available when the optional RS232 port is fitted 1 Connect one end of the RS232 cable to the RS232 Recorder socket of the 900 I3 2 Connect the other end of the RS232 cable to an RS232 Printer or to the COM1 or COM2 ports of a PC 3 Ensure that the baud rate for the printer or PC and the 900...

Page 31: ...e Logging Printing Period as hours Press to save the Logging Printing Period as minutes Press to save the Logging Printing Period as seconds 5 If the optional RS232 port is fitted the 900 I3 will ask if the records are to be logged into the Notepad or sent directly to the RS232 port The display will look like this Press to log records into the Notepad maximum of 1200 readings Press to send records...

Page 32: ...32 9 Note The clock must be set before the 900 I3 will allow automatic logging to start The message Clock Not Set is displayed if the clock is not set See section 13 for details on setting the clock ...

Page 33: ...l measurement mode This function is disabled if the automatic logging period is set to greater than zero see section 10 Records can be sent directly to the RS232 port rather than stored in memory during automatic datalogging See section 10 for details Press while recalling data on the display see section 9 2 to send that record to the RS232 port 11 3 RS232 Configuration The 900 I3 RS232 configurat...

Page 34: ...mory The data ends with the message ENDS cr Erase logged data E cr Erases all logged records from the 900 I3 memory Returns the message ERASED cr to confirm that the records have been erased Request status information S cr Returns the model name firmware version number instrument serial number and number of logged readings in memory for example 900I3sV3 0sR1234s1200 cr where s are spaces Note that...

Page 35: ...pH for pH readout mV mV for Absolute Millivolts readout mVR mVR for Relative Millivolts readout is one space is one space 22222222 22222222 is Channel 2 Specific Ion pH mV or Relative mV data 8 characters right justified The 900 I3 sends Uncal Uncal when this Channel has not been Primary Calibrated in Specific Ion mode UUU UUU is the unit description which can be any one of those listed in the tab...

Page 36: ...9 0 31 12 1998 11 05 pH1 Asy 0 10pH 31 12 1998 11 10 pH1 Asy 0 10pH 31 12 1998 11 10 pH1 Slope 99 0 31 12 1998 11 15 pH1 Slope 99 0 31 12 1998 11 15 Ion2 Offset 0 1mV 31 12 1998 11 00 Ion2 Offset 0 1mV 31 12 1998 11 00 Ion2 Slope 99 0 31 12 1998 11 05 Ion2 Slope 99 0 31 12 1998 11 05 pH2 Asy 0 10pH 31 12 1998 11 10 pH2 Asy 0 10pH 31 12 1998 11 10 pH2 Slope 99 0 31 12 1998 11 15 pH2 Slope 99 0 31 1...

Page 37: ...n select F2 Recorder F2 Recorder If the Recorder Port option only is fitted then the 900 I3 will jump directly to the Channel Selection screen RECORDER F1 Channel 1 F2 Channel 2 RECORDER F1 Channel 1 F2 Channel 2 F3 Channel 3 F4 OFF F3 Channel 3 F4 OFF The arrow indicates the current selection Press or to select Channel 1 2 or 3 Press to switch the Recorder Port OFF 3 After selecting Channel 1 2 o...

Page 38: ...nential mode type in 3 significant digits of the value that will produce full scale The decimal point is fixed for you in this mode Now press for 10 or press for 10 Enter the power This can be entered as 1 or 2 digits e g 04 04 is treated the same as 4 4 Use the key to make any corrections Press to save the value Alternatively press to quit without changing the current setting The 900 I3 will conf...

Page 39: ... the 900 I3 will display the Recorder Port configuration for 3 seconds before returning to normal measurement mode Channel 1 pH selected Channel 1 pH selected 0pH 0 volts 14pH 2 volts 0pH 0 volts 14pH 2 volts 12 3 Recorder Port Configuration in Absolute or Relative mV Modes 1 Select the Ports Set up menu F4 Setup F4 Setup F1 Ports F1 Ports 2 If the both the Recorder and the RS232 port options are ...

Page 40: ...et to 1000ppM then 10 ppM 0 mV 1000 ppM 2000 mV pH 0 to 14 000 pH 0 to 14 00 pH 0 to 14 0 pH 0 to 2000 mV for all resolutions 7 00 pH 1000 mV Absolute mV ISE mV 1500 to 1500 mV 0 to 2000 mV 0 0 mV 1000 mV 750 mV 1500 mV 600 mV 600 mV Relative mV 1500 to 1500 mVR 0 to 2000 mV 0 0 mVR 1000 mV 750 mVR 1500 mV 600 mVR 600 mV Output Impedance Approximately 1000 Ohms Resolution Approximately 2 mV 12 5 R...

Page 41: ...will now show the current date for example Date is now 31 12 1998 Date is now 31 12 1998 Enter new date Enter new date 3 31 12 1998 dd mm yyyy 1 12 1998 dd mm yyyy 6 Use the Numeric Keypad to enter the current date then press 7 Alternatively press menu to quit and retain the current setting Notes 1 The 900 I3 tests that a valid day of the month is entered If an invalid date is entered e g 31 02 19...

Page 42: ...brated before use then 900I3srV3 0 R1234 C 1998 TPS Pty Ltd 900I3srV3 0 R1234 C 1998 TPS Pty Ltd Three Channel Ion pH mV and Temperature Three Channel Ion pH mV and Temperature The s s after 900I3 is shown when the RS232 serial Port option is fitted The r r after 900I3 is shown when the Recorder Port option is fitted 4 The meter then displays pH Temperature Date and Time Note that the decimal poin...

Page 43: ...on standards or pH Buffers are inaccurate Ensure that you are using Specific Ion standards as per the Standards set up see section 3 2 For automatic pH buffer recognition ensure that you are using buffers that match the selected buffer set see section 4 2 Otherwise ensure that the buffer value is entered correctly at pH calibration Clean glass bulb as per instructions supplied with the electrode A...

Page 44: ...nnector 2 Faulty temperature probe Check the connector and replace if necessary Fit new temperature probe part number 121245 Displays flashing M M when temperature probe plugged in 1 Faulty TEMP socket 2 Faulty temperature probe Return the instrument to the TPS factory for service Fit a new temperature probe part number 121245 ...

Page 45: ... the reference junction A saturated solution of KCl is used to make contact with the sample It is vital that the KCl solution has an adequate flow rate in order to obtain stable accurate pH measurements 17 1 1 Asymmetry of a pH Electrode An ideal pH electrode produces 0 mV output at 7 00 pH In practice pH electrodes generally produce 0 mV output at slightly above or below 7 00 pH The amount of var...

Page 46: ... electrode is affected by temperature This effect is compensated for either by using an Automatic Temperature Compensation ATC probe or by entering the sample temperature manually Figure 17 3 shows the slope of a pH electrode at various temperatures 600 400 200 0 200 400 600 0 7 14 mV Electrode Potential mV at 0 oC 54mV pH Electrode Potential mV at 50 oC 64mV pH Electrode Potential mV at 100 oC 74...

Page 47: ...junction as per the instructions supplied with the pH electrode 5 Re calibrate the 900 I3 and repeat the test 6 If the value obtained is still outside 7 06 0 02 pH then the electrode should be replaced 17 5 Determining if an instrument or pH electrode is faulty The following test can be performed to help determine if the 900 I3 or the pH electrode is faulty 1 Plug the pH electrode into a different...

Page 48: ...need of repair please re read the manual Sometimes instruments are received for repair in perfect working order This can occur where batteries simply require replacement or re charging or where the electrode simply requires cleaning or replacement TPS Pty Ltd has a fine reputation for prompt and efficient service In just a few days our factory service engineers and technicians will examine and rep...

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