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Page 30

11.2 Dissolved Oxygen Troubleshooting

Symptom

Possible Causes

Remedy

Unit fails to
calibrate, even
with new sensor.

Calibration settings outside
of allowable limits due to
previous failed calibration.

Initialise the unit. See section
10.



Zero calibration

fails (Zero is
greater than
7.0%)



Air calibration

fails (Span is
less than 70% or
greater than
135%).



Unstable or

inaccurate
readings.

1. Membrane is leaking or

broken.

2. Gap between membrane

and gold cathode is dry.

3. Incorrectly fitted

membrane.

4. Sensor is empty.

5. Sensor is faulty.

Replace membrane and refill
sensor.

Undo the barrel 3 turns, then
re-tighten to re-flush the
filling solution.

Membrane should be smooth
and convex with no wrinkles.
Re-fit membrane if
necessary.

Replace membrane and re-
fill sensor.

Return sensor to factory for
repair or replacement

Blackened Silver
anode

Sensor has been exposed to
sulphides or other chemical
poisoning.

Return to the TPS factory for
cleaning and service.

Tarnished or
scratched Gold
cathode.

Sensor has been chemically
poisoned or physically
damaged.

Return to the TPS factory for
cleaning and service.

Meter reads

OVR

ppM

OVR%S

1. Sensor has not yet

polarised.

2. Sensor is faulty

Wait for 2-3 minutes for the
sensor to polarise after the

Aqua-DP

is switched on.

Return sensor to factory for
repair or replacement.

For complete details on the operation, care and maintenance of your
ED1 Dissolved Oxygen sensor, see the separate leaflet that is
supplied with the sensor.

Summary of Contents for Aqua Series

Page 1: ...ns 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 Aqua DP It also contains a full listing of all of the items that you should have received with your Aqua DP Please take the time to read this section as it explains some of items that are mentioned in subsequent secti...

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: ...bration Notes 21 5 3 Millivolt Calibration Messages 21 6 Temperature Calibration 22 6 1 Calibration 22 6 2 Calibration Notes 22 6 3 Calibration Messages 23 6 4 Manual Temperature Setting 23 7 Setting the Salinity Correction Value 24 8 Selecting Buffers for Auto Buffer Recognition 25 9 Battery 26 9 1 Battery Saver Function 26 9 2 Changing the Battery 27 10 Initialising the Aqua DP 28 11 Troubleshoo...

Page 4: ...Page 4 1 Introduction 1 1 Aqua DP Display and Controls ...

Page 5: ...brate all parameters See sections 3 4 5 and 6 Also used to select pH buffers for automatic pH buffer recognition See section 8 Hold this key for 2 seconds to toggle between Saturation and ppM mg L Dissolved Oxygen modes See section 2 Switches the Aqua DP on and off Hold this key for 3 seconds to invoke Battery Saver mode See section 9 and These keys toggle the Aqua DP between Large Display mode an...

Page 6: ...23143 3 123143 5 2 Oxygen sensor 123400 3 Oxygen sensor cable see cable label for part No 1 3 or 5m cable 4 Membrane kit for oxygen sensor 123301 5 pH Sensor see cable label for part No 1 3 or 5m cable 6 pH7 00 Buffer 200mL 121387 7 pH4 01 Buffer 200mL 121381 8 Manual Options that may have been ordered with your Aqua DP 1 Extended cable ordered by the metre 130040 2 Aluminium Carry Case 130057 ...

Page 7: ...r 1 Membrane permeability 2 Solubility in ppM mode Sensor Zero Range 0 to 7 Sensor Span Range 70 0 to 135 0 Calibration One touch automatic calibration in Zero and in Air Additional pH Specifications Temperature Compensation Automatic 0 to 50 0 O C pH Input Impedance 3 x 1012 pH Asymmetry Range 1 00 to 1 00 pH pH Slope Range 85 0 to 105 0 Auto pH Buffer Recognition pH4 01 pH6 86 pH7 00 pH9 18 pH10...

Page 8: ...24 Character alphanumeric LCD with full text prompts and error messages Power 9V Alkaline Battery for 70 hours operation Battery Saver On Auto switch off after 5 minutes Off Continuous use Dimensions 165 x 85 x 35 mm Mass Instrument only Approx 280g Full Kit Approx 2 0kg Environment Temperature 0 to 45 O C Humidity 0 to 95 R H ...

Page 9: ... mV To select which combination of these two parameters to display 1 Press and hold for 2 seconds 2 The Mode menu is now displayed for example Mode pH Sat Oxy Press the or keys repeatedly to select the desired combination of pH Saturation Dissolved Oxygen pH ppM mg L Dissolved Oxygen mV Saturation Dissolved Oxygen mV ppM mg L Dissolved Oxygen 3 Press to save the selection and return to normal disp...

Page 10: ... readout is not available in this mode Dissolved Oxygen Mode 100 0 Sat 25 0 Dissolved Oxygen data is shown on the top line and Temperature data is shown on the bottom line Select this mode to calibrate Dissolved Oxygen The S is shown after the ppM units when the Salinity correction value is set to greater than 0 0ppK see section 7 Press or to toggle between dual readout or large digit readout pH o...

Page 11: ...mode to set the Salinity Correction value to the salinity of the sample to be measured This setting is only applicable to ppM mg L Dissolved Oxygen readout See section 7 Press or to toggle between regular readout or large digit readout Back to Dissolved Oxygen pH mV Temperature mode Note The decimal point is replaced by a if a Dissolved Oxygen pH mV or Temperature calibration has failed see sectio...

Page 12: ...oint in the temperature reading is replaced by a then the temperature readout is not calibrated 5 Rinse the Dissolved Oxygen sensor in distilled water and blot dry 6 Zero Calibration a Place the sensor into an oxygen free solution This solution may be prepared by dissolving 2g of Sodium Sulphite in 100mL of distilled water A 50g bottle of Sodium Sulphite powder is supplied with a new Dissolved Oxy...

Page 13: ...ings See section 12 1 6 If salinity corrected ppM Dissolved Oxygen readings are required set the salinity correction value before taking sample measurements See section 7 3 2 Dissolved Oxygen Calibration Notes 1 A zero calibration should be performed at least monthly In applications where there is a low level of dissolved oxygen a zero calibration may have to be done weekly 2 An air calibration sh...

Page 14: ...ibration has failed the Aqua DP will display the following message then the failed zero value of the sensor Cal Failed Zero 10 0 3 If an air calibration has been successfully performed the Aqua DP will display the following message and then the span value of the sensor Cal OK Span 100 0 4 If an air calibration has failed the Aqua DP will display the following message and then the failed span value...

Page 15: ... manual temperature compensation 4 Ensure that temperature has already been calibrated or manually set see sections 6 1 and 6 4 NOTE If the decimal point in the temperature reading is replaced by a then the temperature readout is not calibrated 5 Remove the wetting cap from the pH sensor 6 Rinse the pH sensor in distilled water and blot dry 7 Ensure that you are using the buffers which have been s...

Page 16: ...H sensor into a small sample of pH4 01 pH9 18 or pH10 01 Buffer so that the bulb and reference junction are both covered as per the diagram in step 8 DO NOT place the sensor directly into the buffer bottle Discard the used buffer after use pH9 18 and pH10 01 buffers are unstable once the bottles have been opened Discard immediately after use 12 When the reading has stabilised press and hold the ke...

Page 17: ... A full 2 point calibration should be performed at least monthly Of course more frequent calibration will result in greater confidence in results 3 All calibration information is retained in memory when the Aqua DP is switched off even when the battery is removed 4 The Aqua DP displays the value of the pH buffer that it has attempted to recognise at calibration Ensure that the buffer value display...

Page 18: ...If a 1 point calibration has failed the Aqua DP will display the following message then the failed asymmetry value of the sensor 1 point 7 00 Cal Failed then Asym 1 50pH 3 If a 2 point calibration has been successfully performed the Aqua DP will display the following message and then the asymmetry and slope of the sensor 2 point 4 01 Cal OK then Asym 0 10pH Slope 99 5 4 If a 2 point calibration ha...

Page 19: ...to the BNC socket this is the metal socket Automatic temperature compensation is not applicable to mV mode so it is not necessary to connect the Dissolved Oxygen sensor 4 Remove the wetting cap from the ORP sensor 5 Rinse the ORP sensor in distilled water and blot dry 6 Ensure that you are using the buffers which have been selected for automatic buffer recognition See section 8 for a detailed expl...

Page 20: ...both covered as per the diagram below Discard the used standard after use 9 When the reading has stabilised press and hold the key for 2 seconds to calibrate The will now be replaced by a decimal point if calibration was successful 10 The Aqua DP is calibrated for mV and is ready for use in this mode ...

Page 21: ...bration information is retained in memory when the Aqua DP is switched off even when the battery is removed 5 3 Millivolt Calibration Messages 1 If calibration has been successfully performed the Aqua DP will display the following message and the offset of the sensor For example ORP Cal OK Zero 0 mV 2 If calibration has failed the Aqua DP will display the following message and the failed offset va...

Page 22: ...emperature throughout the beaker 5 When the reading has stabilised press and hold the key for 2 seconds 6 The reading from the sensor is now displayed on the top line and the value you are going to set is on the bottom line For example Enter 25 0 Temp 26 0 7 Press the and keys until the bottom line shows the same temperature as the mercury thermometer 8 Press the key to calibrate the temperature r...

Page 23: ...al Temperature Setting 1 Switch the Aqua DP on 2 Select Temperature mode see section 2 3 Manual temperature setting is only available if the Dissolved Oxygen sensor is not connected 4 Press and hold the key for 2 seconds The current Manual Temperature Setting is now displayed for example Enter Manual Temp 25 0 5 Press the and keys until the bottom line shows the temperature which you wish to set T...

Page 24: ...eter is in Salinity mode see section 2 The currently selected salinity correction value is displayed 4 Press and hold the key for 2 seconds 5 The display should now look like this Enter Manual Sal 36 0 6 Press the and keys until the bottom line shows the salinity value obtained in step 1 7 Press the or key to set the salinity correction value NOTES 1 For non salinity corrected readings in ppM mode...

Page 25: ...played 4 The display will now show the currently selected primary buffer for example 7 00pH Select or 6 86pH Select 5 Use the or keys to alternate between pH7 00 and pH6 86 buffers 6 Press the key to save the primary buffer 7 After the message Buffer 2 Select the display will now show the currently selected secondary pH buffers for example 4 01 9 18pH Select or 4 01 10 0pH Select 8 Use the or keys...

Page 26: ...he meter already switched on press and HOLD the key for 3 seconds 3 The battery saver menu is now displayed For example ON 9 00V 4 In this mode use the or keys to toggle the battery saver function on or off NOTE The display also shows the battery volts This gives the operator an idea of how much battery life is remaining The symbol flashes when the battery volts drops below 7 50 volts At 6 00 volt...

Page 27: ...See the diagram below 2 Raise the fold out stand so it is out of the way and then fully loosen both screws It is not necessary to pull the screws all the way out Lift off the battery cover 3 Replace the battery with a new alkaline 9V battery 4 Re fit the battery cover and tighten the screws Do not over tighten ...

Page 28: ...may be required if an sensor is replaced To initialise the Aqua DP 1 Switch the Aqua DP off 2 Press AND HOLD the key while switching the Aqua DP on 3 The following messages are now displayed Memory Cal Reset You MUST Re Calibrate TPS AQUA DP V1 1 S1234 4 The meter then displays Dissolved Oxygen pH and Temperature Note that the decimal points have been replaced with a to indicate that the unit requ...

Page 29: ...e been lost or corrupted Re calibrate the instrument Both a Zero and an Air calibration are required for Dissolved Oxygen section 3 a 2 point calibration for pH section 4 and a 1 point calibration for temperature section 5 Meter displays the word OFF and switches off Battery is below 6 00 volts Replace the battery Meter will not turn on Battery is exhausted Replace the battery Flashing symbol Batt...

Page 30: ...g solution Membrane should be smooth and convex with no wrinkles Re fit membrane if necessary Replace membrane and re fill sensor Return sensor to factory for repair or replacement Blackened Silver anode Sensor has been exposed to sulphides or other chemical poisoning Return to the TPS factory for cleaning and service Tarnished or scratched Gold cathode Sensor has been chemically poisoned or physi...

Page 31: ...er instructions supplied with the sensor Flush with distilled water and replace electrolyte 2 Point calibration fails Slope is less than 85 0 1 Incorrect primary buffer 2 Glass bulb not clean 3 Sensor is aged 4 Connector is damp 5 Buffers are inaccurate Ensure that you are using the buffers which the Aqua DP has been set to automatically recognise See section 8 Clean glass bulb as per instructions...

Page 32: ... sensor Flick the sensor to remove bubble Check connectors Replace if necessary Ensure that the bulb AND the reference junction are fully immersed Rinse electrolyte chamber with warm distilled water until dissolved Replace electrolyte Inaccurate readings even when calibration is successful Reference junction blocked Clean reference junction as per instructions supplied with the sensor Displays 7 0...

Page 33: ...ck connectors Replace if necessary Ensure that the platinum tip AND the reference junction are fully immersed Inaccurate readings even when calibration is successful Reference junction blocked Clean reference junction as per instructions supplied with the sensor Displays 0mV for all solutions Electrical short in connector 1 Check connector Replace if necessary 3 Replace sensor 11 5 Temperature Tro...

Page 34: ...tained behind a plastic membrane In this case the plastic is 0 001 inch PTFE Teflon sheet It must be realised that using membranes of very different thicknesses will result in an error in the temperature compensation that is applied in the instrument for the membrane permeability This coefficient is 4 2 o C at 25o C for this thickness membrane A polarising voltage of about 800 millivolts is applie...

Page 35: ... with the Dissolved Oxygen sensor for details on how to change the membrane 12 1 3 Sensor Storage The Dissolved Oxygen sensor should be kept moist when not in use to prevent the thin film of electrolyte behind the membrane from drying out To achieve this the sensor can be stored with the tip in water Alternatively use a wetting cap such as those supplied with pH sensors For long term storage of se...

Page 36: ...s the importance of correct interpretation of the salinity The Clark Sensor measures the partial pressure of oxygen diffusing through a membrane The current is a linear measure of this partial pressure assuming sufficient liquid flow conditions With air at sea level the 20 9 oxygen exerts about 15 5 cm of Mercury pressure Water in equilibrium with air and with no oxygen demand C O D B O D etc is s...

Page 37: ...sor in the sensor c Salinity correction is performed automatically once the Salinity value of the solution is entered section 7 12 1 5 Equilibrium Conditions Whilst Saline Water has a lower ppM than does Fresh Water it does not mean it necessarily has less biologically available oxygen Both have 100 Saturation presuming no Chemical Oxygen Demand C O D Biological Oxygen Demand B O D etc because bot...

Page 38: ...nce the flow is sufficiently high Tests with this sensor have shown that flow rates above 0 2 litres minute past the membrane give results indistinguishable from those with appreciably higher flow rates 5 litres minute Fluctuations in readings due to air bubbles passing through the membrane are a different matter however With the type of sensor to be used with this instrument very little change in...

Page 39: ...unction 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 12 2 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 cal...

Page 40: ...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 12 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 41: ... 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 12 3 12 3 Instrument software version number If you need to phone or fax TPS for any further technical assistance the version number of your Aqua DP firmware may of benefit to us Please obtain the version number before phoning or faxing The version number is di...

Page 42: ...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 43: ...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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