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TPS WP-81 Manual Download Page 49

Page 49

21.3.3 Temperature Compensation

The slope of a pH sensor (section 21.3.2) is affected by temperature. This
effect  is  compensated  for  either  by  using  an  Automatic  Temperature
Compensation  (ATC)  sensor  or  by  entering  the  sample  temperature
manually.  Figure  21-3  shows  the  slope  of  a  pH  sensor  at  various
temperatures.

-600

-400

-200

0

200

400

600

0

7

14

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

E

le

c

tr

o

d

e

R

e

s

p

o

n

s

e

(

m

V

)

pH

Figure 21-3

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Summary of Contents for WP-81

Page 1: ...b sections have also been included to enable you to find the information you need at a glance 2 Introduction The introduction has a diagram and explanation of the display and controls of the WP 81 It also contains a full listing of all of the items that you should have received with your WP 81 Please take the time to read this section as it explains some of items that are mentioned in subsequent s...

Page 2: ...ty Ltd ABN 30 009 773 371 Unit 6 253 Leitchs Road Brendale QLD Australia 4500 Phone 07 32 058 027 International 61 7 32 058 027 Fax 07 3808 4871 International 61 7 3808 4871 Email tps tps com au Web www tps com au ...

Page 3: ...ibration 18 7 Temperature Calibration 19 7 1 Calibration Procedure 19 7 2 Calibration Notes 19 7 3 Calibration Messages 20 7 4 Manual Temperature Setting 20 8 Good Laboratory Practices GLP 21 8 1 To recall GLP information on the display 21 8 2 Failed Calibration 22 8 3 Printing GLP Information to the RS232 Port 22 8 4 Instrument Serial Number 23 8 5 Additional GLP Features 23 9 Notepad Function 24...

Page 4: ...16 Selecting k 0 1 or k 10 Conductivity Sensors 37 17 Selecting Buffers for Auto Buffer Recognition 38 18 Initialising the WP 81 39 19 Instrument firmware version number 39 20 Troubleshooting 40 20 1 General Errors 40 20 2 Conductivity Troubleshooting 41 20 3 pH and mV ORP Troubleshooting 43 20 4 Temperature Troubleshooting 44 21 Appendices pH and Conductivity Sensor Theory 45 21 1 Care Cleaning a...

Page 5: ...Page 5 1 Introduction 1 1 WP 81 Display and Controls ...

Page 6: ...ed within the menu system on the WP 81 Press to access the user friendly menu system which makes the WP 81 a breeze to operate and The and keys are used for calibrating the temperature value section 7 1 setting the manual temperature compensation section 7 4 setting the clock section 15 1 setting the automatic logging period section 10 and displaying GLP information section 8 1 The key is also use...

Page 7: ...or 5m cable 4 Conductivity Standard 200mL 2 76 mS cm 122306 or 58 0 mS cm 122315 or 150 0 uS cm 122320 5 pH7 00 Buffer 200mL 121387 6 pH4 01 Buffer 200mL 121381 7 Battery charger 130037 8 Manual Options that may have been ordered with your WP 81 1 Extended cable 130040 2 RS232 Serial Interface Cable 130041 3 Communication software for Windows 95 and later 130086 4 USB to Serial Adaptor requires 13...

Page 8: ...M k 1 0 Sensor 0 ppM to 10 00 ppK k 10 Sensor 0 ppM to 100 0 ppK Resolution 0 1 of selected range Accuracy 0 5 of full scale of selected range at 25 O C Salinity k 0 1 Sensor 0 to 0 10 0 PSU to 1 0 PSU k 1 0 Sensor 0 to 1 19 0 PSU to 11 9 PSU k 10 Sensor 0 to 8 00 0 PSU to 80 0 PSU Resolution 0 01 0 1 PSU Accuracy 0 5 of full scale of selected range at 25 O C pH Range 0 to 14 00 pH Resolution 0 01...

Page 9: ...d Recognition 150uS cm 1413uS cm 2 76mS cm 12 88mS cm 58 0mS cm Cond Sensor Span Range k 0 1 Sensor k 0 075 to k 0 133 k 1 0 Sensor k 0 75 to k 1 33 k 10 Sensor k 7 5 to k 13 3 Temperature Use a reference thermometer Temperature Sensor Offset 10 0o C to 10 0o C Memory 3600 readings including date and time Automatic Logging User set for one reading every 1 to 90 seconds 1 to 90 minutes or 1 to 24 h...

Page 10: ... Good Laboratory Practices Date Time and Value of last Conductivity pH and Temperature calibration are stored and can be recalled or sent to the RS232 port at any time Power 6V NiMH Rechargeable Battery for approx 40 hours operation Dimensions 195 x 110 x 55 mm Mass Instrument only Approx 520g Full Kit Approx 2 5kg Environment Temperature 0 to 45 o C Humidity 0 to 95 R H ...

Page 11: ...e for the WP 81 menu functions F1 Cal F1 Cond F2 pH F3 Temp F2 Notepad F1 Recall F2 Erase F3 Print F4 Prog F1 Min F2 Sec F3 Hr Set Period F3 Mode F1 Cond TDS Sal F1 Cond F2 TDS F3 Sal F1 F2 PSU F3 pH F4 mV F4 Setup F1 Batt F1 OFF Battery Saver F2 ON Battery Saver F2 Clock F3 GLP F1 Recall F3 Print F4 Baud F1 300 F2 1200 F3 9600 F4 19200 ...

Page 12: ...ivity mode Press to select TDS mode You will now be asked to enter the TDS Factor 0 65 TDS factor Set F1 Save Press to select Salinity mode menu Select units F1 F2 PSU Press to select units Press to select PSU units Press to quit and retain the current selection 3 2 Selecting pH or ORP mV Mode To select pH or ORP mV mode 1 Select the Mode menu F3 Mode F1 Cond TDS Sal F3 pH F4 mV 2 Press to select ...

Page 13: ...Plug the Conductivity sensor into the Conductivity socket If a k 0 1 or k 10 sensor is being used ensure that the WP 81 is set to the correct k factor before using the instrument see section 16 2 Switch the meter on 3 Rinse the Conductivity sensor in distilled water Shake off as much water as possible Blot the outside of the sensor dry DO NOT BLOT THE SENSOR WIRES 4 Zero Calibration Let the sensor...

Page 14: ...glass bodied sensors immerse the sensor at least to the vent hole in the glass body DO NOT place the sensor directly into the bottle of standard Discard the used sample of standard after use It is advisable to use a narrow sample vessel to minimise the use of standard solution 7 Select Conductivity Calibration F1 Cal F1 Cond 8 When the reading has stabilised press the key to calibrate The will now...

Page 15: ...section 8 5 The WP 81 displays the value of the standard to which it will attempt to calibrate Ensure that the standard value displayed corresponds to the standard that you are using 6 If the WP 81 does not recognise the standard it will display the message NOT STD during calibration Calibration will fail if this message is displayed 4 3 Calibration Messages 1 If a Zero calibration has been succes...

Page 16: ... in the temperature reading is shown by a then the temperature value is not calibrated 4 Remove the wetting cap from the pH sensor Rinse the pH and Conductivity sensors in distilled water and blot them dry 5 Ensure that you are using buffers which have been selected for automatic buffer recognition See section 17 for a detailed explanation 6 Place both sensors into a small sample of pH7 00 or pH6 ...

Page 17: ...he will now be replaced by a decimal point if calibration was successful 13 The WP 81 is calibrated for pH and is ready for taking pH measurements Discard the used samples of buffer 5 2 Calibration Notes 1 A 1 point calibration should be performed at least weekly In applications where the sensor junction can become blocked such as dairy products mining slurries etc a 1 point calibration may have t...

Page 18: ... 50pH Hi or 1 Point Cal Fail Asy 1 50pH Lo 3 If a 2 point calibration has been successfully performed the WP 81 will display the following message and the asymmetry and slope of the sensor For example 2 Point Cal OK Asy 0 10pH then 2 Point Cal OK Slope 100 0 4 If a 2 point calibration has failed the WP 81 will display the following message and the failed slope value of the sensor For example 2 Poi...

Page 19: ...display and the value you are going to set is shown on the left For example 25 0 20 0o c Set F1 Cal 6 When the reading on the right has stabilised press the and keys until the reading on the left shows the same temperature as the mercury thermometer 7 Press the key to calibrate the temperature value The will now be replaced by a decimal point if calibration was successful Alternatively press the k...

Page 20: ...e sensor is not used in its place the temperature of the sample solution must be set manually for accurate pH measurements A separate thermometer will be required for this NOTE The Conductivity sensor has a separate sensor built in for automatic temperature compensation for Conductivity TDS and Salinity 1 Switch the meter on 2 Measure the temperature of the sample 3 Select Temperature Calibration ...

Page 21: ...rmware version number and instrument serial number are displayed along with a prompt describing how to scroll through the GLP information 5 Press the key to sequentially scroll through the GLP information for all parameters Press the key to scroll back to previous data The sequence of information displayed is shown below Press to abort at any time WP81 V6 0 S1234 More Back Cond Zero 0 00uS 31 12 0...

Page 22: ...ing 8 3 Printing GLP Information to the RS232 Port The GLP information stored in the instrument s memory can be sent to a printer or PC via the RS232 port Switch the meter on 1 Ensure that the WP 81 RS232 cable is connected to the instrument and to the printer or PC 2 Send the GLP information to the RS232 port F4 Setup F3 GLP F3 Print 3 The GLP information is sent to the RS232 port in formatted AS...

Page 23: ...Con TDS Sal pH o C where S1234 is the serial number The serial number is display when recalling the GLP information section 8 1 The serial number is included on the print out of GLP information section 8 3 8 5 Additional GLP Features Another GLP requirement is to record the date and time of every reading The WP 81 does this for you when readings are recorded either with the Notepad function sectio...

Page 24: ...3 Repeat steps 1 2 as often as required The maximum number of readings that can be stored in the Notepad is 3600 9 2 Recalling Records from the Notepad To recall records from the Notepad onto the WP 81 display 1 Select the Notepad menu F2 Notepad 2 Select F1 Recall from the menu 3 Record number 1 is now displayed for example 2 76mS 7 00pH 25 0o c 1 F2 Clk 4 Press to alternatively display the date ...

Page 25: ... Charger RS232 socket of the WP 81 The charger optional solar panel or optional battery leads can be connected into the spare socket on the cable for long term use if required 2 Connect the other end of the RS232 cable to an RS232 Printer or to COM1 or COM2 of a PC 3 Ensure that the baud rate for the printer or PC and the WP 81 are the same If necessary alter the baud rate of the WP 81 see section...

Page 26: ... 4 When the logging period has been correctly set select whether this period is in minutes seconds or hours Press to save the period as minutes Press to save the period as seconds Press to save the period as hours For example if the period was set to 05 followed by then the WP 81 will automatically log a record every 5 seconds 5 The WP 81 will ask if the records are to be logged into the Notepad o...

Page 27: ... The WP 81 will beep each time a record is sent to the RS232 port 8 Press to stop automatic logging Notes 1 The clock must be set before the WP 81 will allow automatic logging to start The message Clock Not Set is displayed if the clock is not set 2 The Battery Saver function section 13 is disabled while the meter is in Automatic Data logging mode to stop the meter switching off while logging data...

Page 28: ...ection 10 Records can be sent directly to the RS232 port rather than stored in memory during automatic data logging See section 10 for details 11 3 RS232 Configuration The WP 81 RS232 configuration is 8 bits No Parity 1 Stop Bit XON XOFF Protocol 11 4 Communication and Statistical Software Communication between the WP 81 and a PC can be handled with any RS232 communication software WinTPS RS232 co...

Page 29: ...y The data ends with the message ENDS cr Erase logged data E cr Erases all logged records from the WP 81 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 eg WP81 V1 0 S1234 9999 cr where are spaces Note that the number of l...

Page 30: ...he unit description sent as pH or mV TTTTTT is the Temperature Data Maximum 6 characters right justified ttt is the Temperature unit description The WP 81 sends oC for real temperature data or oCm when manual temperature compensation is being used dd mm yy is the date month and year data hh mm ss is the hours minutes and seconds data Notes 1 When requested by a PC with the D or R commands section ...

Page 31: ...command section 11 5 the computer must respond with a character after receiving each line For example WP81 V6 0 S1234 31 12 03 12 00 Conductivity Zero 0 00uS 30 03 11 11 05 Conductivity k 1 00 2 76mS 30 03 11 11 10 pH Asy 0 00pH 30 03 11 11 25 pH Slope 100 0 30 03 11 11 30 Temperature Offset 1 0oC 20 03 11 11 35 ENDS ...

Page 32: ...e Open 2 In the Files of type pull down box choose Text Files prn txt csv 3 Navigate to the folder where your data file is stored and double click it to start the Text Import Wizard Note The default data folder for the WinTPS software is C My Documents WinTPS 4 In step 1 of the Text Import Wizard select Fixed width as per the sample screen below then press Next Continued over the page ...

Page 33: ...ss Next after the column breaks have been inserted 6 Simply press Finish at step 3 of the Text Import Wizard TPS recommends that the data format for each column be set once the data is in spreadsheet format For help on formatting the data columns charting graphing or other operations please consult the Microsoft Excel help file Alternatively please contact TPS and we will try to provide further as...

Page 34: ...ble the battery saver function for continuous use Press to enable the battery saver function The meter will switch itself off if no key has been pressed for five minutes Press to quit the battery saver menu and retain the current setting Notes 1 For troubleshooting purposes the battery volts can also be displayed in the battery saver menu Press to display battery volts 2 The symbol flashes when th...

Page 35: ...harge the battery 1 Plug the battery charger solar panel or car cigarette lighter adaptor into the Charger RS232 socket DO NOT plug into the Conductivity TDS socket as this will damage the WP 81 2 Charge for approximately 8 hours for full capacity The WP 81 has special circuitry to prevent overcharging so the charger can be used continuously To ensure optimum battery life and capacity the WP 81 sh...

Page 36: ...e minutes Press the and keys until the minutes are correct 8 Check that the date and time are correct Press to save the settings If any changes are needed press the key to move left to the desired position Press to quit without resetting the clock Notes 1 The WP 81 does not test for a valid day of the month when setting the clock eg attempting to enter 30 03 11 is not corrected 2 The WP 81 does te...

Page 37: ...d only if the k 0 1 or k 10 sensor is connected Select F1 k 0 1 k factor F2 k 10 The arrow indicates the current selection 5 Press to select a k 0 1 sensor Press to select a k 10 sensor Press to quit buffer selection and retain the current setting Notes 1 The manual k factor selection is kept in memory when the meter is switched off even if the battery is removed 2 The manual k factor selection is...

Page 38: ...7 00pH Buffer F2 6 86pH The arrow indicates the current selection 4 Press to select pH7 00 as the primary buffer Press to select pH6 86 as the primary buffer Press to quit buffer selection and retain the current setting 5 The display will now show the currently selected high pH buffer Select F1 9 18pH Buffer F2 10 0pH The arrow indicates the current selection 6 Press to select pH9 18 as the high p...

Page 39: ...r WP 81 is shown when the RS232 serial port option is fitted 4 The meter then displays Conductivity pH and Temperature Note that the decimal points have been replaced with a to indicate that the unit requires re calibration Notes 1 The TDS Factor is reset to 0 65 when the meter has been initialized 2 When the WP 81 is initialised the manual k factor selection is re set to k 10 See section 16 if yo...

Page 40: ...elf off when the battery falls below 5 00 volts Meter displays the word OFF and switches off Battery is below 5 00 volts Recharge the battery If this fails check the charger If charger OK replace the battery Meter will not turn on 1 Battery is exhausted 2 Faulty Instrument Recharge the battery If this fails check the charger If charger OK replace the battery Return to factory for repair Battery do...

Page 41: ...n fails and k factor is greater than 0 133 1 33 or 13 3 depending on k factor of sensor 1 Sensor is not immersed deeply enough 2 Sensor may have a build up of dirt or oily material on sensor wires 3 Platinum black coating has worn off 4 Standard solution is inaccurate 5 Sensor is faulty 6 Faulty instrument 7 k factor incorrectly set if using k 0 1 or k 10 sensor Immerse sensor at least to the vent...

Page 42: ...y have a build up of dirt or oily material on sensor wires 2 Platinum black coating has worn off Clean sensor as per the instructions detailed in section 21 1 Sensor requires replatinisation Return to the factory or see details in section 21 2 Readings drift 1 Sensor may have a build up of dirt or oily material on sensor wires Clean sensor as per the instructions detailed in section 21 1 Readings ...

Page 43: ... been set see section 17 Clean glass bulb as per instructions supplied with the sensor Attempt rejuvenation as per instructions supplied with the sensor If not successful replace sensor Dry in a warm place Replace buffers Unstable readings 1 Sensor chamber needs to be refilled 2 Reference junction blocked 3 Glass bulb not clean 4 Bubble in glass bulb 5 Faulty connection to meter 6 Reference juncti...

Page 44: ...ernal stem cracked Replace sensor Display flashes ATC and LIMIT The Temperature is not within the ATC limits Cool Heat solution before taking measurements 20 4 Temperature Troubleshooting Symptom Possible Causes Remedy Displays OVR o C when sensor is plugged in 1 Faulty sensor 2 Faulty instrument Fit new sensor part number 122201 Return to factory for repair Temperature inaccurate and cannot be ca...

Page 45: ...urement and rinse well with distilled water Conductivity sensors can be stored dry Ensure that the sensor is stored in a covered container to avoid dust and dirt build up 21 1 2 Cleaning of Conductivity of Sensors Platinised platinum Conductivity sensors can only be cleaned by rinsing in a suitable solvent DO NOT wipe the sensor wires as this will remove the platinum black layer 1 Rinsing in disti...

Page 46: ...l in distilled water c Immerse the sensor in platinising solution at least to the vent hole in the white plastic cover Platinising solution is available from TPS part no 122300 d Alternatively platinising solution can be prepared by dissolving 1g of Hydrogen Chloroplatinate H2PtCl16 in 30mL of distilled water and including about 0 01g of Lead Acetate CH3COO 2Pb and a drop or two of concentrated HC...

Page 47: ...nction 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 21 3 1 Asymmetry of a pH Sensor An ideal pH sensor produces 0 mV output at 7 00 pH In practice pH sensors generally produce 0 mV output at slightly above or below 7 00 pH The amount of variance from 7 00 pH is call...

Page 48: ...practice pH sensors usually produce slightly less than this The output of a pH sensor is expressed as a percentage of an ideal sensor For example an ideal sensor that produces 59mV pH unit has 100 Slope An sensor that produces 50 15mV pH unit has 85 Slope see Figure 21 2 600 400 200 0 200 400 600 0 7 14 85 Slope at 25 oC 50 15mV pH 100 Slope at 25 oC 59mV pH Response of pH Electrode as a Function ...

Page 49: ... Compensation ATC sensor or by entering the sample temperature manually Figure 21 3 shows the slope of a pH sensor at various temperatures 600 400 200 0 200 400 600 0 7 14 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 Electrode Response mV pH Figure 21 3 ...

Page 50: ...ipment incorrect calibration incorrect operation or from interpretation of information derived from the equipment Specifications are subject to change without notice This warranty becomes invalid if modifications or repairs are carried out on this unit by unauthorised persons There are no express or implied warranties which extend beyond the face hereof Procedure for Service Please read service de...

Page 51: ...r equipment will be repaired and returned to you by express air freight where possible For instruments beyond warranty period a repair cost will be calculated from parts and labour costs and emailed to you If you decline to have the equipment repaired the complete instrument will be returned to you freight paid not serviced TPS Pty Ltd has only one service location which is located at our factory ...

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