Page 1 pH Sensor Preventative Maintenance and Troubleshooting pH Sensor Preventative Maintenance and Troubleshooting Presented by: David Mueller Online Systems Technical Support Supervisor at Hach Company First I would like to welcome everyone, and thank you for attending this presentation on pH sensor maintenance and troubleshooting. My name is David Mueller and I am the Supervisor of the Online Systems Technical Support group with Hach Company. Our technical support group receives many calls and questions each day relating to pH. In most cases, problems related to pH measurement can be traced back to sensor cleaning, maintenance issues, or misapplication issues. My goal today is to provide you with some easy tips, procedures, and troubleshooting techniques to follow in order to make sure that your pH sensors will properly function on a daily basis.
Transcript
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pH Sensor Preventative Maintenance and Troubleshooting
pH Sensor Preventative Maintenance and Troubleshooting
Presented by:David Mueller
Online Systems Technical Support Supervisor at Hach Company
First I would like to welcome everyone, and thank you for attending this presentation on pH sensor maintenance and troubleshooting. My name is David Mueller and I am the Supervisor of the Online Systems Technical Support group with Hach Company.
Our technical support group receives many calls and questions each day relating to pH. In most cases, problems related to pH measurement can be traced back to sensor cleaning, maintenance issues, or misapplication issues. My goal today is to provide you with some easy tips, procedures, and troubleshooting techniques to follow in order to make sure that your pH sensors will properly function on a daily basis.
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What Will We Cover Today?What Will We Cover Today?
How do pH sensors really work?Combination vs. Differential pH electrodesElectrode care, cleaning, and calibrationDifferential sensor regenerationTroubleshootingYour questions
Many of the cleaning and maintenance techniques we will discuss today relate to the proper care of both laboratory and online pH sensors. Let’s take a look at the agenda.
Today we’re going to cover a small amount of theory relating to the operation of pH sensors and how they function.
Next we will discuss the two dominant types of pH sensors, combination and differential, and talk about the differences between the two.
We will go on to discuss electrode care, cleaning, calibration, troubleshooting, and differential sensor regeneration
And finally, I’ll answer your questions.
As we go through the presentation, please feel free to enter your questions into the “Chat Box” in the lower right corner of your screen, then click “Send”. Any questions I am unable to get to before the end of the hour will be responded to after the event.
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Nernst EquationNernst Equation
E = E0 - 2.3RT log ainf
E = 59.16 mV per Decade @ 25°C
E = E0 - 2.3RT log ainf
E = 59.16 mV per Decade @ 25°C
Theory
I’m not going to discuss theory to heavily, but I would like to provide some background into how pH is measured. This foundation is important so that we all understand what exactly we are maintaining and why maintenance of a pH electrode is important.
• A pH probe specifically looks for and measures the hydrogen ion. pH theory is based on the equation on the screen called the Nernst Equation. The only piece of this that is important to remember is that a pH probe will produce 59.16 mV for every 1 pH change in activity at 25ºC. We will discuss this value later in the troubleshooting section.
• This factor will change with temperature. That is why most Hach sensors use temperature compensation.
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Temperature Effects on mV OutputTemperature Effects on mV Output
So how much of an effect can temperature have? The graph on the screen gives you an idea. Note the millivolt output of the sensor at 100 degrees, vs 0 degrees on the legend in the upper right corner of the screen. This 20 mv difference equates to almost a half of a ph, making it very apparent why some type of temperature compensation must be used when measuring pH.
•Hach Sensors use Automatic temperature compensation. This type of compensation is based on the fact that a pH glass electrode’s characteristics will change with temperature. We will discuss how to troubleshoot the temperature compensator later in the presentation.
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Combination SensorCombination Sensor
pHGlass MeasuringElectrode
pHReferenceElectrode
E1E2
E1
E2 E1- E2
100 MEG
With regards to how a pH sensor operates, let’s begin by discussing the combination sensor.
• The combination style electrode is the most commonly used type of pH electrode used in both lab and online applications.
• In a combination sensor, the measuring and reference electrodes are joined together.
• The reference cell is composed of a silver/silver chloride wire immersed in a buffered electrolyte that is normally KCL.
• The measuring electrode, which is the round glass bulb you see at the bottom of the sensor, has a special ion sensitive glass that searches for the hydrogen ion.
• All of these components are housed in a single body.
• Combination electrodes are normally disposable. If the reference becomes contaminated or the junction gets plugged, the sensor is thrown out and replaced.
• Hach produces many sizes and variations of this type of sensor for use in both laboratory and on-line applications.
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pH Measuring Electrode Typical Problems
pH Measuring Electrode Typical Problems
pH membrane coatingSlow response due to high impedanceAbrasion and/or breakageTemperature shock
Here you see some of the typical problems that can be encountered with the measuring electrode, which is the glass bulb visible onthe end of the sensor.
• All pH glass will coat depending on the application. Once coating begins, response declines as well as accuracy. Coating can occur from hardness in the water, oil, or chemicals.
• Another problem is slow response due to high electrical impedance generated by the glass electrode.
• Viscous processes or a process slurry will abrade the electrode causing measurement errors and thinning of the glass, ultimately leading to glass breakage.
• And finally, removing the electrode from a hot process and placing it into cold water for cleaning, or buffers for calibration, causes the electrode to go into shock or even crack and break. Ample time must be allowed for the electrode to come to temperature equilibrium.
Plugging junctionPoisoning of the internal elementRapid electrolyte depletionGround loops
Reference electrodes are 90% of failures in pH measurement
Some of the typical problems that can occur internally in the Reference electrode are as follows
• The junction may become plugged with precipitates.
• Or, it may dissolve from acids or caustics.
• The electrolyte may become contaminated as the process solution seeps into the chamber.
• The silver/silver chloride wire may be attacked by the process.
• Or if a ground loop is present, it will follow the path of least resistance to ground through the reference electrode and can result in up to a 1 pH error in reading.
• For these reasons, reference electrodes account for 90% of the failures in pH measurement.
Frequent cleaning and electrolyte changes, can help to slow the junction plugging and lengthen the amount of time it takes for the element to poison. Due to the design of this type of junction, however, it will eventually plug or become completely contaminated and the sensor will need to be replaced.
Next we’re going to talk about the differential online pH sensor.
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Hach’s Patented Differential Sensor
Hach’s Patented Differential Sensor
E1 - E3-(E2 - E3)
(E1 - E2)
SolutionGround
Electrode(E3)
TemperatureCompensator
ReferenceElectrode
(E2)
ProcessElectrode
(E1)
Preamplifier
Theory
Hach’s Differential Electrode Technique
The patented Hach Differential Electrode sensor is very similar in operation to the combination electrode with a couple of very important differences:
• The reference electrode is an actual glass measuring electrode rather than a silver-silver chloride wire. This is an extremely important difference as a full glass electrode is easy to clean and will not poison.
•The reference electrode is also immersed in a highly concentrated pH 7 buffered solution rather than a KCL solution.
• A solution ground electrode is used to eliminate ground loops.
•Some other important features include:
• A double junction salt bridge rather than the single junction of the combination electrode providing double the protection from intruding sample.
• And a preamp that converts the normally high impedance signal produced by the sensor to a low impedance signal.
This design allows for:
• Long life
• Replaceable junction which is not usually available in the combination style pH sensor.
• Heavily buffered electrolyte that is more resistant to change.
• Long sensor to analyzer distances up to 3000 feet due to the built in Pre-amp.
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Comparison SummeryComparison Summery
Very resistant to ground interference
Highly susceptible to ground loops causing up to a 1 pH error
Cost effective in nearly all other applications
Cost effective for laboratory instruments and online high purity systems
About 3 times greater chemical resistance
Fair resistance to chemicals
5 minute regeneration providing up to 3X the lifespan of a combination sensor
Disposable
Must use Hach controllerCan use on a broad range of controllers
Differential pHCombination pH
Now let’s compare the two technologies we’ve just discussed.
The combination sensor usually has lower up front costs depending on the manufacturer. Our combination online sensors are typically 40-50% lower in cost compared to our differential sensor. The combination sensor, however, may only last 9 months to a year in a clean process. If the process is dirty, or on the lower or higher end of the pH scale, you may only achieve a 2-4 month life from the sensor. The differential sensor, on the other hand, can last up to 3x as long making it much less expensive in the long run.
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Combination vs. Differential pH Sensors
Combination vs. Differential pH Sensors
8362sc Online High Purity System
Gel filled Sension Laboratory Sensor
Online Combination Sensors
Online LCP Differential Sensor
Online pHD Differential Sensor
Hach provides pH systems that utilize both technologies:
For example, the 8362sc on-line high purity digital pH system utilizes a combination sensor housed in a special flow through chamber designed for measuring pH at extremely low conductivity levels, like those found in fossil power plants.
To the lower left is a Gel Filled combination pH electrode used in the Hach Sension laboratory pH meters.
In the center is an example of our many on-line combination pH sensors.
And to the right are the LCP and pHD differential on-line electrodes.
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Electrode MaintenanceElectrode Maintenance
We’ve discussed some of the factors that can inhibit your pH electrode from measuring correctly. Let’s now talk about what you can do to prevent and correct some of these issues.
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Sensor Care and Maintenance Comparison
Sensor Care and Maintenance Comparison
Signal can be read and sensor condition determined using digital multi-meter.
LimitedTroubleshooting
Cleaning.5 minute regeneration
of reference junction, and electrolyte.
Limited to cleaning and electrolyte replacement in some models.
Maintenance and Regeneration of Sensor
Same for both Sensor Cleaning
Same for bothTransportation and Storage
DifferentialCombination
To better illustrate how to care for a typical combination sensor and a differential sensor, I’ve included this comparison table..
When it comes to transportation, storage, and cleaning, both thecombination and differential sensors have identical needs.
(Maintenance Read Slide)
Of course Hach sells both for online applications. As I mentioned earlier, lab pH systems are typically combination sensor technology.
The differential sensor is really designed for the type of harsh, fluctuating conditions found in various online process. We’ve seen the differential installed in everything from concrete tank walls in the south Texas heat, to chrome destruct process, to pulp and paper slurries, and everything in between.
So what steps can you take to care for your electrode between maintenance and calibrations? The next few slides will discuss some preventative actions you can take to keep maintenance and costs to a minimum.
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Care of pH ElectrodesCare of pH Electrodes
Transportation
•When transporting or shipping electrodes, use a carrier which will guarantee that the sensor will not freeze.
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Care of pH ElectrodesCare of pH Electrodes
Store between 10 and 30 degrees CUse protective capsKCL or pH 4 buffer solution
Storage
•Electrodes should be stored in ambient conditions, between 10 and 30°C when not in use.
•Protective caps, as well as solution storage caps, should be kept intact and installed onto the end of the sensor.
•Electrodes should be stored in 3 to 3.5 M KCl solution. For short term storage, if you do not have KCL, use either tap water, or pH 4 buffer.
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Care of pH ElectrodesCare of pH Electrodes
DehydrationSlow responseHigh glass resistance
If left out of solution, the pH glass membrane will become dehydrated.
This leads to slow response and higher than normal glass impedance when it is placed back into operation.
Your sensors should always be stored and kept moist.
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Care of pH ElectrodesCare of pH Electrodes
HeatColdVibration
Detrimental factors to electrode life
•Lastly, avoid temperature extremes and mechanical shock both in process and during storage.
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Sensor CleaningSensor Cleaning
Solvent/Solution Application Hot water and detergent For normal applications.
No more than 5% HCL acid For solutions containing lime and hydroxides.
Acetone For solutions containing congealed oils & fats.
Bleaching liquid For solutions with algae, bacteria and molds.
Maintenance
The sensor should be kept reasonably clean to maintain measurement accuracy.
The time between cleanings, is affected by the characteristics of your process and can only be determined by operating experience.
For example, a drinking water facility may be able to perform maintenance and cleaning every 3-6 months depending on the hardness of the water, where an industrial facility, such as a chicken rendering plant, may need to clean daily to remove process coating.
(Read Slide describing different solutions)
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Sensor CleaningSensor Cleaning
Remove contaminant buildup
The next few slides will be spent discussing the proper method for cleaning a pH electrode.
1) Remove most contaminate buildup by carefully wiping the entire measuring end of the sensor, including the process electrode, and salt bridge, and ground electrode if you have a differential sensor, with a soft clean cloth.
Then rinse the sensor with clean, warm water.
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Sensor CleaningSensor Cleaning
Prepare soap solution
AlconoxLiquinoxNon-lanolin dish detergent
2) Next, prepare a mild soap solution.
Use warm water and dishwashing detergent that does not contain lanolin. Lanolin will coat the glass process electrode and may affect sensor performance.
Also, a lab soap such as Alconox or Liquinox works perfectly.
Soak the sensor for 2 to 3 minutes in the soap solution.
3) Use a small bristle brush to scrub the entire measuring end of the sensor, thoroughly cleaning the electrode surfaces.
If the detergent solution cleaning cannot remove surface deposits, use HCL or another of the cleaning solutions we discussed, to dissolve the deposits.
The solution should be as dilute as possible, but yet strong enough to clean. Usually a 3 to 5% concentration of HCL will remove most deposits.
Before cleaning with acid, determine if this would create a hazardous chemical reaction. (Example: Do not put a sensor used in a cyanide bath directly into a strong acid for cleaning because this could produce poisonous cyanide gas.)
Soak the sensor in acid for no more than 5 minutes.
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Sensor CleaningSensor Cleaning
Rinse and Calibrate
4) Rinse the sensor with clean, warm water and then place the sensor back into the mild soap solution for 2 to 3 minutes to neutralize any remaining acid.
Finally, remove the sensor from the soap solution, and rinse thesensor again in clean, warm water.
After cleaning, always recalibrate the sensor.
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Sensor Calibration and Verification
Sensor Calibration and Verification
Which leads us into our next topic of Sensor calibration and verification.
•In order to account for some of the changing conditions we’ve discussed such as contaminates, cleaning, and maintenance over time, a ph sensor must be calibrated at regular intervals.
•As with maintenance, the interval will be process dependant and experience driven. A drinking water facility may find that a calibration only needs to occur monthly, where an industrial facility such as electroplating, may need to clean and calibrate weekly or bi-weekly due to the extreme pH changes and process coating issues.
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pH Sensor CalibrationpH Sensor Calibration
Clean the sensorCalibration keystrokes will depend on analyzer usedA two point buffer calibration preferred7 and 4 pH calibration is ideal
Calibration
•The first step in the calibration is to always clean the sensor using the techniques we’ve just discussed
•Follow the user manual in performing the necessary keystrokes on your analyzer to set the system up for a 2 point buffer calibration.
•If possible, use 7 pH and 4 pH buffer for your 2 point calibration.
•Why not use a 10 pH buffer?
•10 pH buffer is very unstable in the presence of atmospheric CO2 and may begin to acidify over time.
•Large containers of 10 buffer will absorb CO2 the minute the bottle is open.
•If a 10 pH buffer is required, purchase it in smaller quantities, such as 500ml bottles, or in a sealed container that does not allow air in.
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pH Sensor VerificationpH Sensor Verification
Verification should be performed using buffer solutions
Rinse with clean water and dry gently lint free lab clothPlace the sensor in 7pH buffer then 4pH bufferIf the sensor is reading the buffers correctly you do not need to recalibrate
•Verification is the really a big word for checking your sensor periodically to make sure it’s still in calibration.
•The best method of verifying that a calibration is still valid is by using buffer solutions.
•This is because buffers are a known stable value.
•In order to verify that your pH probe is still in calibration:Remove the sensor from the sample or process.
•Rinse with clean water and dry softly with a lint free lab wipe.
•Place the sensor first in fresh 7pH buffer then into 4pH buffer.
•If the sensor is still reading the buffers correctly within +/- 0.1 to 0.2 pH, place the probe back into service. If outside of that range, start a calibration.
•This distance from the known value is again up to the user and the process specifications.
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pH Sensor VerificationpH Sensor Verification
If verifying using a hand-held or portable meter
Calibrate side by side in the same buffer solutionsVerify that both units slope fall within manufacturer specificationsBe realistic with your expectations
•Verifying an online sensor using a lab or portable meter is not ideal for many reasons. Some of which are; Sample error, calibration and slope differences between the two probes, and the time between taking the sample and reading it. If this type of verification is still desired, however, here are some steps to ensure you have the best possible chance of a good verification.
•1. Be sure both the portable and online sensor have been cleaned and maintained.
•2. Calibrate both the portable and online sensor side by side in the same container using the same buffer and stabilization time.
•3. Once the calibration is finished, make sure both units calibration slope falls within acceptable manufacturer specifications.
•4. Take a grab sample of the process water and place both sensors side by side into the grab sample.
•By doing this, you are assured that both sensors are reading exactly the same sample.
•5. And, be realistic with your expectations!
•If you have two different probes, with all of their associated variables, matching to within 0.2 pH of each other, call it good. There will always be slight variation between sensors. Remember, most portable pH electrodes are combination style electrodes. Depending on the age of the electrode, there may be fill solution contamination, plugging of the junction, or poisoning of the reference wire that will cause deviation from the differential electrode.
Though I’ve made mention already of the advantages of the Differential electrode, to this point most of the cleaning, maintenance, and calibration procedures we’ve discussed apply to all pH electrodes.
We’re now going to focus on the differential on-line sensors, and the extended steps you can take to troubleshoot and rejuvenate this particular sensor to achieve the extended life and cost reductions we’ve been telling you about.
Unlike combination on-line and lab pH sensors, the differential sensor technology incorporates a replaceable salt bridge and reference buffer solution. This allows you to recondition the sensor back to proper working condition rather than replacing it as with the combination probe.
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Maintenance for pH SensorsMaintenance for pH Sensors
What is a Salt Bridge?A double junction barrier between the process and the standard cell solution This barrier extends the time between calibrations and reduces maintenance requirementsThe “Oil Filter” in the sensor
So what exactly is a salt bridge? (read slide)
In a way, they are like the oil filter in your automobile acting to prevent contaminants from getting into the engine.
Combination electrodes actually employ a similar barrier, though they are typically a single junction and are not replaceable.
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“Inside” Hach’s Differential pH Sensors
“Inside” Hach’s Differential pH Sensors
Salt Bridge
Standard Cell
Solution Fill Chamber
and Reference Electrode
ProductsChanging the salt bridge and internal Standard Cell Solution in the differential electrode is a very simple procedure that can be done in the field in less than 5 minutes.
There are currently two differential electrode designs that have slightly different salt bridges.
The LCP/Ryton sensor on the left has a 9/16” double junction salt bridge that looks like a small bolt.
The pHD on the right has a larger salt bridge encompassing the entire end of the electrode.
Both sensors have a full glass reference electrode located in the Standard Cell Solution chamber.
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Maintenance for Differential pH Sensors
Maintenance for Differential pH Sensors
What is Standard Cell Solution?Standard cell solution is highly concentrated pH 7 buffer A 100 to 1 dilution would represent a change in measured pH of only 0.05 unitsThe “Oil” in the sensor
What is standard cell solution? (read slide)
What makes standard cell solution so resistant to change?
Unlike a combination sensor which uses a KCL solution as the reference buffer, Standard cell solution is a highly concentrated 7 pH solution with a higher concentration of buffer salts, and other salts that help to maintain the ionic strength of the solution.
Why is this important?
7 pH is the ideal reference point for the electrode, therefore, a fill solution that resists change away from 7 pH creates a better, more stablereference half cell for the sensor.
Following the previous analogy, this would be the oil in the car. Once it becomes contaminated it must be replaced.
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Frequency of Salt-Bridge/Standard Cell Solution Maintenance
Frequency of Salt-Bridge/Standard Cell Solution Maintenance
How often do I need to change the salt-bridge and reference solution?
This is process dependent, but generally at least twice a year
What symptoms indicate the Saltbridge/standard cell solution need to be changed?
Poor calibration slopeThe offset is greater than +/-20 mV
The frequency of salt bridge and standard cell solution maintenance is very much dependent on the process the sensor is placed into.
For example: In a drinking water final effluent, where pH levels are very close to 7pH, you may find that the salt bridge will last 6-12 months before replacement. On the other hand, in a very dirty or highly caustic process consistently running around 9-12 pH, you may need to perform the maintenance every 3-6 months.
The bottom line with all pH electrodes, whether they are combination or differential, is that the further away from 7pH, or neutral, your process is, the faster the reference junction and inner fill solution will contaminate. Again, the major difference is that in a differential sensor, you can easily replace the contaminated parts in 5 minutes and be back on line. With a combination sensor, you will have to replace the probe.
How will you know when this maintenance needs to be done?? (read the two bottom diamond bullets on the slide).
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How Do I Perform the Salt Bridge Maintenance?
How Do I Perform the Salt Bridge Maintenance?
Step 1. Remove the salt bridge by holding the sensor in an upright position and turn the salt bridge counterclockwise using a 9/16 inch socket wrench or nut driver. Take care not to damage the glass electrode.
If you are using the pHD differential sensor you will need an adjustable wrench, for example a crescent wrench, to remove the larger salt bridge, but the principle behind the replacement is the same.
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How Do I Perform the Salt Bridge Maintenance?
How Do I Perform the Salt Bridge Maintenance?
Step 2. Pour out the aged standard cell solution, then thoroughly flush the standard electrode chamber with fresh standard cell solution.
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How Do I Perform the Salt Bridge Maintenance?
How Do I Perform the Salt Bridge Maintenance?
Step 3. Fill the standard electrode chamber to the top of the thread with fresh standard cell solution.
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How Do I Perform the Salt Bridge Maintenance?
How Do I Perform the Salt Bridge Maintenance?
Step 4. Install the new salt bridge, making sure the O-ring is intact. Turn the salt bridge clockwise until finger tight. Then tighten with a socket wrench or nut driver approximately 1/4 turn. Do not over tighten.
Step 5. Calibrate the system using the methods discussed earlier and return the sensor to the process.
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pHD Differential SensorpHD Differential Sensor
The five step process we just covered used the LCP encapsulated differential sensor as an example. This slide shows the pHD differential sensor, but the regeneration steps are identical.
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Hach’s Differential On-Line pH Sensors
Hach’s Differential On-Line pH Sensors
Sensor Troubleshooting
Hach’s differential sensor incorporates a built in pre-amplifier that converts the normally high impedance signal produced by a pH electrode to a low impedance signal.
This allows us a maximum sensor to analyzer distance of up to 3000 feet.
It’s also very helpful in troubleshooting possible sensor problems as we can drive the signal directly to a Digital Multi-Meter for interpretation.
This cannot typically be done with a combination sensor unless an external pre-amplifier is purchased.
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Testing and Troubleshooting the Differential pH Sensor
Testing and Troubleshooting the Differential pH Sensor
Temperature compensatorSignal measured between yellow and black300 ohm thermistorInversely proportional to temperatureMeasure between yellow and black300 ohms at 25 degrees CFailures are normally an “open” or “short”
Testing The Sensor
To test the temperature compensator, a digital multi-meter can be directly connected to the yellow and black sensor wires.
The resistance is inversely proportional to temperature, therefore, as temperature goes up, resistance will go down.
In a well functioning sensor, resistance should be between 250-350 ohms at 25 degrees C.
Normally if a thermister is failing it will show either open or short on the multi-meter.
If the thermistor has failed the sensor will need to be replaced.
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Testing and Troubleshooting a Differential pH Sensor
Testing and Troubleshooting a Differential pH Sensor
Theoretical pH signals in bufferMeasure between Red and Black wire59.16 mV per pH7 pH is isopotential point, 0 mV4 pH is +177 mV10 pH is -177 mVOffset is the mV signal in 7 pH bufferSpan is the mV signal in 4 or 10 pH buffer
Testing the Sensor
Again, due to the built in preamplifier of the differential sensor, you can also easily test the measuring electrodes functionality in the field with a Digital Multi-Meter.
•If you’ll remember from the earlier equation, the ideal mv output of the sensor is 59.16 mv/ph.
•By disconnecting the Red active electrode wire and the green reference electrode wire from the analyzer and connecting them directly to a Digital multimeter, this output can be measured.
•In a perfect world, ideal mv readings are 0mv in 7ph, +177mv in 4ph, -177mv in 10ph.
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Testing and Troubleshooting a Differential pH Sensor
Testing and Troubleshooting a Differential pH Sensor
Acceptable Offset and Span Tolerances
Signal measured between red and green wiresOffset should be 0 mV +/- 20 mVSpan should be at least 160 mV from offset
Testing a Differential Sensor
Of course there are variables that can affect the mv output of the sensor such as temperature, thickness of the electrode glass, the quality and cleanliness of the buffer solutions, and the age of the salt bridge and sensor.
For these reasons we do allow for acceptable Offset and Span tolerances.
If you have a sensor that is outside these tolerance ranges, clean the sensor and perform a salt bridge and Standard Cell Change.
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The Differential Cost Advantage$$$
The Differential Cost Advantage$$$
Up to 3 times the life of a combination sensorSensor can be rejuvenated many times
Sensor will not stop running until electrode glass actually wears out
2 year savings of more than $600 per sensor installation.Backed by a Warranty unmatched in the industry.
During my time in Technical Support, I have seen hundreds of different applications utilizing both combination and differential online pH sensors.
As we discussed earlier, the most common failure seen in these sensors is internal contamination of the reference electrode.
The fact that the differential sensor uses a full glass internal reference electrode, very similar to the glass electrode you see on the end of the probe, reference contamination issues can be easily solved.
Customers who use the differential sensor realize significant overall cost savings due to extended sensor life, versus customers who use the combination sensor and must throw it away and buy new every few months.
Even combination sensors with flowing junctions or triple wood junctions only extend the life by 10%.They are all designed to be discarded and replaced when their voltage-based reference electrode becomes contaminated.
Hach offers the best warranty in the industrythe best warranty in the industry.
One year warranty.Covering defects in materials or workmanship, within one year from date of shipment
Thirty month pro-rate replacement.If the sensor fails for ANY reason, including physical damage, within 30 months, Hach will provide a replacement at a substantially reduced price
Products
If you haven’t tried differential technology for your online applications, I encourage you to do so. Hach is so confidant in this proven technology, first introduced and patented by GLI in the 1970’s, that we stand behind it with an impressive warranty and pro-rate replacement plan which covers the sensor for 2 and a half years.
This is unmatched by the industry.
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Technical Support ContactsTechnical Support Contacts
Contact us by phone at: 1-800-227-4224Or email us at [email protected]
What if you have done all of the maintenance, cleaning, and troubleshooting we have discussed and you still believe your sensor is not functioning properly? Or, what if you just need to order replacement salt bridges, standard cell solution, or electrodes?
Hach is here as a free technical resource from 6:30 am to 5 pm mountain time M-F, and we will be happy to help you answer any questions.
Please feel free to take advantage of this, as our Technical Advisors can help on any instrument, whether it is lab or process, that Hach sells.
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How Can I Learn More?How Can I Learn More?
Helpful links in “Thank you” email“What is pH, and how is it measured? A technical handbook for industry” by Fred KohlmannCopy of this presentation with speaking notes
Visit us on the web at www.hach.comwww.hach.comKnowledge baseLearning libraryDocumentation downloads
How can you learn more about pH?
•We also offer many Technical Bulletins, application notes, and blue books on the Hach website at www.hach.com.
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Hach pH InstrumentationHach pH Instrumentation
Products
Hach Company offers a diverse selection of sensors and systems to measure pH in virtually all applications.
We offer several different sensor body materials allowing for exceptional chemical resistance in aggressive process solutions.
With our broad range of sensors and systems we can measure pH invirtually any industrial, municipal, or laboratory application.
I'd also like to note that Hach recently dropped the price on our LCP differential probes by about $100 and substantially lowered the price on many of our longer sensor cables making our pH product line even more affordable.
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Questions???Questions???
This concludes our pH Sensor Preventative Maintenance and Troubleshooting presentation. We will now take time to answer some of the questions that we have received throughout the presentation.
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pH Sensor Preventative Maintenance and Troubleshooting
pH Sensor Preventative Maintenance and Troubleshooting
Please email any questions relating to this presentation to [email protected].
Include in the subject line:“Attn: pH maintenance presentation”
I would like to thank everyone for attending and I hope you have found the suggestions and troubleshooting techniques beneficial.
It has been my experience that the large majority of issues with measuring pH can be traced back to a lack of regular cleaning and maintenance. I truly believe that by developing a regular cleaning and maintenance schedule, many headaches and system downtime hours can be avoided.
Again, if your questions were not addressed today, or you have any further questions you would like answered, you may email them to [email protected]. Be sure to include in the subject line, “Attn: pH maintenance presentation”.
