1110PK - Wireless pH Sensor Pack

• This general-purpose electrode is non-refillable. 
• Keep the pH sensitive membrane wet, at all times. For the ion exchange process to occur properly, the glass needs to be hydrated. Check and maintain the level of storage solution. 
• If the electrode should inadvertently become dry, place in the storage solution for several hours. in an attempt to recondition the glass. 
• Care should be taken to avoid handling the glass membrane. Any damage to the surface, such as abrasion, may cause inaccuracies and result in a slow response time. 
• Stirring of a sample will achieve a faster electrode response, but the glass membrane tip is very thin and requires care to prevent accidental damage. Broken glass bulbs are not covered by warranty. 
• Some magnetic stirrers can generate sufficient heat to change the temperature of the test solution. If this is the case, place a piece of insulation material such as polystyrene under the beaker. 
• The working temperature of the pH electrode is 0 to 80 ̊C. The operating range of the adaptor is 0 to 40 ̊C and 0 to 95% RH (non-condensing). Do not subject to extreme heat or cold. 
• The pH adaptor is not waterproof. It may be cleaned using a damp cloth. Do not immerse in water or detergent. 
• Do not place the pH adaptor in an environment in which high humidity levels are possible, as this may result in damage or malfunction. 
• If the sensor has been left in the cold, let it warm to near room temperature before waking it from sleep. 
• Do not expose to direct sunlight for extended periods of time. 
• pH electrodes have a finite lifespan due to their inherent properties. How long a pH electrode lasts will depend on how it is cared for and the solutions it is used to measure. Even if the electrode is not used, it will still age. 
• Always use freshly prepared pH buffers. When not in use, pH buffers should be stored in sealed containers. High pH buffers are less stable as they tend to absorb atmospheric CO2 which lowers their pH. During calibration only open the bottle of buffer to pour it into a beaker. Never leave the bottle open. 
• Buffers and sample solutions should be at the same temperature when measuring pH. The resistance of glass electrodes partially depends on temperature. The lower the temperature, the higher the resistance. It will take more time for the reading to stabilise if temperatures are cold. 
• To allow the pH adaptor to be used with any suitable pH electrodes with a BNC connector, automatic temperature compensation has not been built in. 
• This sensor can also be used with alternative probes, such as Ion Selective Electrodes (ISE) and the Oxidation Reduction Potent (ORP) Probes using the mV range. 

Conditions to avoid:

• Never store the electrode in deionised or distilled water, as this will cause the migration of the electrode’s fill solution. 
• To maximise electrode life, avoid pH/ temperature extremes whenever possible. High temperature, strong acids or caustics (greater than 1.0 mol dm-3) shorten electrode life. If used at high temperatures, the electrode’s life is drastically reduced. The higher the range of temperature, the shorter the life of the electrode e.g. typical electrode life when used at ambient temperature is 1 – 3 years, if used at 80 ̊C this will be reduced to less than 4 months. 
• Never expose to temperatures below -12 ̊C, as freezing will damage the electrode. 
• Coatings on the glass or junction surfaces e.g. proteins, will prevent proper operation (see maintenance on page 9). Avoid frequent or prolonged periods of use in these solutions. 

Sensor Ranges

pH Range

This range is the pre-set default calibration that is suitable for most investigations. The calibration is set for operation at a temperature of 25 ̊C.

±1000 mV Range

This range gives the reading in mV and can be used in experiments on calibrating a pH sensor using buffer solutions of known pH values.

An ideal would be that the potential is zero mV when the pH is 7, but in a real pH system this is rarely so. It is normally between -20 mV and +20 mV. 

This range can also be used with ion-selective electrodes (ISE) and oxidation reduction probe (ORP). All ISE’s work in the same manner as a pH electrode, in fact the pH electrode is really an H+ ISE. Ions have either a positive charge or a negative charge. The ISE measures the electrical energy created by the presence of the charged particles. An Ion Selective membrane controls the flow of the ions to the electrode; it is this membrane that makes the electrode particular to an ionic species. The production of a calibration curve is required to convert the mV reading to ppm or Log ion concentration reading. Refer to the manufacturer’s guide for the ion-selective electrodes (ISE) and oxidation reduction probes (ORP) for details of dilutions for calibration and mV slope values.

User Calibration

If required, the calibration constants of a pH electrode can be adjusted. The settings for an electrode will be stored in the Adaptor as the User pH calibration. 

Note: Mark the pH electrode and adaptor combination so they are used as a pair. 

Standardised buffer solutions are used to adjust the sensor reading at either two or three points in its range. A slope adjustment is made using these points and will affect the whole range, between and beyond these points. The accuracy of the user calibration will depend upon the number of calibration points used, and their spacing. Ideally, the buffer solutions used should encompass the expected pH range and be as close as possible to the pH of the samples being measured. 

A User calibration is best used when the:

• Experiment requires a very accurate calibration.
• Electrode has aged to the point where its glass membrane has changed resistance.
• Samples to be measured are at a lower or higher temperature than 25 ̊C. The buffer solutions used to set values must be at the same temperature as the samples in the experiment. Buffers values are temperature sensitive, enter a pH value for the buffer at that temperature.

Values of pH buffers a various temperatures:

*Please note that high pH buffers are less stable as they tend to absorb atmospheric CO2 which lowers their pH. Only open the bottle of buffer to pour into a beaker, never leave the bottle open.

How to Calibrate

1. Change the sensor’s range to User pH 
2. Select the Calibrate button. 
3. If only two samples of buffers are being used select the down symbol for Calibration Type, then select 'Two point' from the list. 
4. Type in the value of all the buffers being used to set points into the appropriate boxes. 
5. Rinse the electrode in distilled water. 
6. Wipe off the excess, and suspend the electrode in the value one buffer, stir and select Calibrate. 
7. After the 20 second count, rinse the electrode in distilled water, wipe off excess, suspend in the value two buffer, stir, and select Next. 
8. After the next count down, rinse the electrode in distilled water, wipe off excess, and suspend in the value 3 buffer, stir, and select Next. 
9. After the next count, a message will say ‘Your sensor has been calibrated’. Select Finish. 

Note: Mark the pH electrode and adaptor combination so they are used as a pair.