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Extend the life of your Myron L Meter’s pH Sensor

Posted by 4 Nov, 2014

TweetHow to maximize the life of your Myron L meter’s pH or pH/ORP sensor Your meter uses a general-purpose glass pH sensor. This glass sensor may be used in most applications. To ensure maximum life of your pH meter, read the following procedures. It is the experience of the repair technicians that 90% of all […]

How to maximize the life of your Myron L meter’s pH or pH/ORP sensor


Your meter uses a general-purpose glass pH sensor. This glass sensor may be used in most applications.

To ensure maximum life of your pH meter, read the following procedures. It is the experience of the repair technicians that 90% of all premature pH sensor failures can be prevented with a few maintenance procedures.

The following procedures should be performed after using your meter, or if you plan to store your meter for an extended period of time.

1.      The pH sensor well (fig 1) must be filled with storage solution (preferred) or pH buffer 4, or tap water with table salt added and its protective cap (with foam insert) firmly installed.

 

Figure 1

 

 

 

 

 

 

 

 

Failure to do so will:

•        Allow the glass membrane to dry out. A dehydrated glass membrane will not produce the necessary “Gel layer” on the sensor surface, which is essential to allow the exchange of hydrogen ions (measure pH).

•        Allow airborne contaminants to settle on the glass membrane surface. Once contaminants dry onto the surface of the glass membrane, it will inhibit the transfer of hydrogen ions. (See factory approved cleaning process below.)

•        Allow the reference junction to dry out. The reference junction material is usually a wick or fiber type material that completes the electrical circuit between the reference electrode cell and the solution being tested. Dehydration causes the reference solution to leach out of the electrode cavity, and form crystals in the junction. This is normally referred to as the “Bridging effect”.

Repeated dehydration of the pH or pH/ORP sensor  will cause the instrument to have a slower response time, and be more difficult to calibrate. Dehydration will significantly reduce the normal service life of the sensor.

2.      Store spare pH or pH/ORP sensors in a refrigerator. “Do not Freeze”. Take proper precautions not to allow the temperature to fall below freezing. This will cause the solution to expand and may damage the electrodes inside the sensor. Storage in a refrigerated environment will slow the evaporation of the storage solution, but not prevent evaporation. Always inspect and replace storage solution in spare sensor well on a regular basis.

Note: When using storage solution, it is common for white crystal formations to form around the seal of the pH sensor well and protective cap; this is a normal occurrence as the solution evaporates. Never store the sensor in high purity water (distilled or de-ionized).

Approved factory cleaning process for the pH sensor

During the normal use of your Myron L meter, you must clean your pH sensor bulb. The cleaning is necessary to eliminate the deposits of organic or inorganic contaminates left on the sensor from the solutions being tested. If you think your meter is inaccurate, or the display value drifts, or the response is slow and sluggish, perform the following tests.

Rinse the sensor well (three times) and fill with pH buffer 4 solution. If the pH continues to drift below the pH 4 level (i.e. 3, 2, or 1) repeat the test using buffer 10. If the pH level drifts beyond the pH level of 10 (i.e. 11, 12 etc.) the cleaning procedure outlined below may increase the performance and accuracy of your meter.

While performing the above tests, if the pH levels of the buffer solutions 4 and 10 actually drift towards pH 7, this is an indication that the pH sensor is damaged and needs to be replaced.

Caution: Wear proper eye protection and gloves during the following cleaning procedures.

Try the following to clean and recover the pH or pH/ORP sensors.

NOTE: Not all pH or pH/ORP sensors can be recovered.

1.      Fill the pH/ORP sensor well with 100% Isopropyl alcohol. If not available use additive- free rubbing alcohol (70%). This will remove any oils.

2.      Allow the sensor to soak for 10 minutes.

3.      Rinse with RO or DI water.

4.      Rinse the sensor well (three times) and fill

with storage or pH buffer 4 solution. Replace the protective cap and allow the sensor to recover overnight.

5.      Re-calibrate the instrument according to the operations manual. If the instrument fails to calibrate properly, continue to the next step.

If the above procedure does not recover the pH sensor function, perform the following:

1.      Fill the pH or pH/ORP sensor well with a hot salt solution 60°C (140°F) potassium chloride (KCI preferred) or hot tap water with table salt (NaCl). Allow the solution to cool.

2.      Re-calibrate the instrument according to the operations manual. If the meter doesn’t calibrate properly, the pH or pH/ORP sensor must be replaced.

*CAUTION: If you do not use your Myron L meter on a regular basis, the storage solution in the pH or pH/ORP sensor well will evaporate over time and must be replenished. To prevent premature pH glass sensor failure, we suggest a preventative maintenance program. Failure to do so could void the factory warranty. The use of liquids containing high levels of solvents, such as acetone, xylene, and chlorinated hydrocarbons, or other harsh chemicals in your Myron L meter is not recommended.

Replacement pH sensor for Ultrameter II & Digital Dialysate Meters

http://www.myronlmeters.com/Myron-L-RPR-Ultrameter-pH-ORP-Sensor-p/a-rpr.htm

Replacement pH sensor for Portable Analog pH Meters

http://www.myronlmeters.com/Myron-L-RPY-Analog-pH-Sensor-p/a-rpy.htm

Replacement pH sensor for Techpro II meters

http://www.myronlmeters.com/Myron-L-RPG-Techpro-pH-Sensor-p/a-rpg.htm

Replacement pH Sensor PT2: RPT2

http://www.myronlmeters.com/Myron-L-RPT2-Ultrapen-PT2-pH-Sensor-p/a-rpt2.htm

pH/ORP Sensor Storage Solutions: 32 oz

http://www.myronlmeters.com/Myron-L-pH-ORP-Sensor-Storage-Solutions-32-oz-p/s-ssq.htm

pH 4 Buffer: 32 oz

http://www.myronlmeters.com/Myron-L-pH-4-Buffer-32-oz-calibration-solution-p/s-ph4q.htm

Video: Ultrameter II 6P pH Sensor (RPR) Replacement – MyronLMeters.com

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Categories : Care and Maintenance, MyronLMeters.com Service, Technical Tips

New Ultrapen & Ultrameter Solution Sets: Myron L Meters

Posted by 15 Aug, 2014

Tweet              Myron L Meters has made it easy to get the right Ultrapen and Ultrameter solutions – now you can order every Myron L solution you need with one click. When you visit the Ultrameter II 6P  product page, you’ll now see the image above. When you click on the […]

Ultrameter II 6P Solution Set

Ultrameter II 6P Solution Set

 

 

 

 

 

 

 

Myron L Meters has made it easy to get the right Ultrapen and Ultrameter solutions – now you can order every Myron L solution you need with one click.

When you visit the Ultrameter II 6P  product page, you’ll now see the image above. When you click on the VIEW DETAILS button, you go to the Ultrameter II 6P Calibration Solution Set page, where you can order your solutions without having to research them one by one.  Every solution you need for your Ultrameter and Ultrapen is right there on the product page, so make it easy on yourself and order your solutions when you buy your Myron L meter.

It’s never been easier.

 

Categories : Product Updates, Uncategorized

Myron L Ultrameter II 6P

Posted by 27 Jul, 2014

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MyronLMetersUltrameter6P_re

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Real-Time Field Water Analysis with an Ultrameter III 9P: Myron L Meters

Posted by 30 Apr, 2014

Tweet The Ultrameter III 9P Titration Kit allows for fast, accurate alkalinity, hardness & LSI titrations in the field. The Ultrameter III 9P is based on the tried and tested design of the Ultrameter II 6P and measures conductivity, resistivity, TDS, pH, ORP, free chlorine and temperature quickly and accurately. The 9P also features new […]

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The Ultrameter III 9P Titration Kit allows for fast, accurate alkalinity, hardness & LSI titrations in the field.

The Ultrameter III 9P is based on the tried and tested design of the Ultrameter II 6P and measures conductivity, resistivity, TDS, pH, ORP, free chlorine and temperature quickly and accurately. The 9P also features new parameters that allow the user to perform titrations in the field. The Ultrameter III 9P has a unique method of performing alkalinity, hardness and LSI titrations that makes field monitoring fast and feasible.

How does it work?

The 9P titrations are based on conductometric titration methods that are possible with the 9P’s advanced conductivity cell and microprocessor based design. Titrations are chemically equivalent to standard methods using colorimetric techniques, but replace color change identification of equivalence points with changes in conductivity, thereby replacing a subjective, qualitative assessment with a quantitative one. This means the instrument determines the equivalence point instead of the user and the method of analyzing the equivalence point is objective, rather than subjective.

What is a conductometric titration?

A conductometric titration is performed just like a colorimetric titration, only the equivalence point is determined by a change in conductivity rather than a change in color. This is based on the fact that changes in ionic concentration that occur as constituents react with reagents change the electrical conductivity of the solution.

A simple example can be given of the titration of a strong acid with a strong base. The acid solution, before the addition of the base, has a very high conductance owing to the concentration and mobility of the small hydrogen ions.

With the addition of the base, the hydroxide reacts with the hydrogen to form water, thus reducing the hydrogen ion concentration and effectively lowering the conductivity of the solution. The conductivity continues to decrease until all the hydrogen ions are consumed in the reaction, but then sharply increases with the next addition of base, which contains highly conductive hydroxide ions. The solution conductivity then continues to increase with each base addition. The equivalence point in this example would be a clearly defined minimum point of lowest conductivity (see Figure 2).

Not all solutions will give a plot with an equivalence point that is as easy to distinguish as the sharp upturn found in a strong acid-base titration, however. The 9P plots several reagent additions beyond any changes in conductivity and matches the derived curve to the behavior of solutions of known concentration.

Is a conductometric titration a standard method?

(Standard method comparison to methods listed in the Standard Methods for the Examination of Water and Wastewater published by the American Public Health Assn., the American WaterWorks Assn. and the Water Environment Assn.)

Myron L’s conductometric titration methods are chemically equivalent to standard methods that use the same procedure, but with pH indicators. That means that they use the same reagents in the same sequence with the same theoretical approach. The difference lies in the 9P’s ability to determine the equivalence point based on numerical data, rather than subjective observation of a color change.

The alkalinity titration is modeled after standard method 2320. The sample is titrated with sulfuric acid and conductivity changes are recorded at each titration point.

The hardness titration is modeled after standard method 2340. To reduce the affects of high alkalinity in the form of bicarbonate, acid is first added to the sample. This shifts the bicarbonate toward carbonic acid, then carbon dioxide (reference the carbonic acid equilibrium), which is gassed off the sample. The sample is buffered above pH 10 (effectively pH 12) by the addition of sodium hydroxide. EDTA reagent is then added incrementally, with conductivity measured after each addition.

The LSI titration uses a simplified version of the thermodynamic equations for the determination of the scaling tendency of water developed in 1936 by Dr. Wilfred Langelier. The user simply titrates for alkalinity and hardness, then measures pH and temperature, and the 9P generates the saturation index value automatically.

Conductometric vs. Colorimetric

The benefits of determining the equivalence points by conductometric titrations are that the user does not have to interpret any results. The 9P does it for you using objective measurements. And the 9P is a faster method. For example, a typical colorimetric titration for hardness can take up to 30 drops of reagent, while the 9P method for the same concentration only requires six to eight drops. Colorimetric distinctions are sometimes hard to make, as well, especially when adding reagents drop by drop while trying to carefully observe the precise point at which the color changes—and that can lead to inaccurate data. This is especially true in colored or turbid solutions.

The conductometric method can also be used with very dilute solutions or for solutions for which there is no suitable indicator. The conductometric titration method gives you empirical results that are calculated for you, eliminating potential sources of error. And the measurements can be stored in memory for later data transfer using the optional U2CI software and bluDock Bluetooth hardware installed on the 9P . This makes data analysis and reporting seamless.

What else can the Ultrameter III 9P do?

Alkalinity, hardness, pH and temperature values used to compute the saturation index of a sample can be manipulated in the LSI Calculator function, allowing you to perform on the spot analysis of water balance scenarios. You can use historical or theoretical data to populate the required values in the calculator.

And the 9P titration kit comes with all required accessories, reagents, and calibration solutions (see Figure 6). Streamline your field testing with an Ultrameter III 9P from MyronLMeters, where you can save 10% when you order online.

Myron L Meters is the premier online retailer of accurate, reliable, and easy-to-use Myron L meters like the Ultrameter III 9P.  Save 10% when you order online at MyronLMeters.com. Find out more about the Ultrameter III 9P in our Myron L Meters – Ultrameter III 9P Titration Kit Overview video.

 

Categories : Case Studies & Application Stories, Product Updates

pH Calibration of the Ultrameter 6PFCE: MyronLMeters.com

Posted by 23 Mar, 2014

Tweet  *Note: This procedure applies to the Ultrameter, PoolPro, TechPro, and D-6 Dialysate meter. IMPORTANT: Always “zero” your Ultrameter II with a pH 7 buffer solution before adjusting the gain with acid or base buffers, i.e., 4 and/or 10, etc. a. pH Zero Calibration (6PFCE) 1. Rinse sensor well and cell cup 3 times with […]

 

*Note: This procedure applies to the Ultrameter, PoolPro, TechPro, and D-6 Dialysate meter.

IMPORTANT: Always “zero” your Ultrameter II with a pH 7 buffer solution

before adjusting the gain with acid or base buffers, i.e., 4 and/or 10, etc.

a. pH Zero Calibration (6PFCE)

1. Rinse sensor well and cell cup 3 times with 7 buffer solution.

2. Refill both sensor well and cell cup with 7 buffer solution.

3. Press

pH

 

 

 

 

to verify the pH calibration. If the display shows 7.00, skip the pH

Zero Calibration and proceed to pH Gain Calibration.

4. Press

CAL key

 

 

 

 

 

to enter calibration mode. “CAL”, “BUFFER” and “7” will appear on the display.

display

 

 

 

 

 

 

 

Displayed value will be the uncalibrated sensor.

NOTES: If a wrong buffer is added (outside of 6-8 pH),“7” and “BUFFER

will flash, and the Ultrameter II will not adjust.

The uncalibrated pH value displayed in step 4 will assist in determining

the accuracy of the pH sensor. If the pH reading is above 8 with pH 7

buffer solution, the sensor well needs additional rinsing or the pH sensor

is defective and needs to be replaced.

5. Press

Up

 

 

 

 

or

Down

 

 

 

 

until the display reads 7.00.

NOTE: Attempted calibration of >1 pH point from factory calibration will

cause “FAC” to appear. This indicates the need for sensor replacement

or fresh buffer solution. The “FAC” internal electronic calibration is not intended to

replace calibration with pH buffers. It assumes an ideal pH sensor. Each “FAC”

indicates a factory setting for that calibration step (i.e., 7, acid, base).

You may press

CAL key

 

 

 

 

 

to accept the preset factory value, or you may

reduce your variation from factory setting by pressing

Up

 

 

 

 

or

Down

 

 

 

 

6. Press to accept the new value. The pH Zero Calibration

is now complete. You may continue with pH Gain Calibration or

exit by pressing any measurement key.

b. pH Gain Calibration (6PFCE)

IMPORTANT: Always calibrate or verify your Ultrameter II with a pH 7

buffer solution before adjusting the gain with acid or base buffers, i.e.,

4 and/or 10, etc. Either acid or base solution can be used for the 2nd

point “Gain” calibration and then the opposite for the 3rd point. The

display will verify that a buffer is in the sensor well by displaying either

Acd” or “bAS”.

1. The pH calibration mode is initiated by either completion of the

pH Zero Calibration, or verifying 7 buffer and pressing the

CAL key

 

 

 

 

 

key twice while in pH measurement mode.

2. At this point the “CAL”, “BUFFER” and “Acd” or “bAS

will be displayed (see Figures 7 and 8).

Capture

 

NOTE: If the “Acd” and “bAS” indicators are blinking, it indicates

an error and needs either an acid or base solution present in the sensor

well.

3. Rinse sensor well 3 times with acid or base buffer solution.

4. Refill sensor well again with same buffer solution.

5. Press

Up

 

 

 

 

or

Down

 

 

 

 

until the display agrees with the buffer value.

6. Press

CAL key

 

 

 

 

 

to accept the 2nd point of calibration. Now the

display indicates the next type of buffer to be used.

Single point Gain Calibration is complete. You may continue for the 3rd

point of Calibration (2nd Gain) or exit by pressing any measurement key.

Exiting causes the value accepted for the buffer to be used for both acid

and base measurements.

To continue with 3rd point calibration, use basic buffer if acidic buffer

was used in the 2nd point, or vice-versa. Again, match the display to the

known buffer value as in step 2 and continue with the following steps:

7. Repeat steps 3 through 6 using opposite buffer solution.

8. Press

CAL key

 

 

 

 

 

to accept 3rd point of calibration, which completes the Calibration procedure.

Fill sensor well with Sensor Storage Solution and replace protective cap.

You can find technical advice and videos, the calibration solutions you need, and reliable Myron L meters
at MyronLMeters.com
Categories : Application Advice, Care and Maintenance, Product Updates, Technical Tips

TDS Calibration on the Ultrameter II 6PIIFCe: MyronLMeters.com

Posted by 23 Mar, 2014

Tweet  *Note: This procedure applies to the Ultrameter, PoolPro, TechPro, and D-6 Dialysate meter. a. Fill and rinse the conductivity cell three times with a 442 standard solution. In this example, we’re using 442-3000. b. Refill conductivity cell with same standard solution you rinsed with. c. Press           then press   […]

 

*Note: This procedure applies to the Ultrameter, PoolPro, TechPro, and D-6 Dialysate meter.

a. Fill and rinse the conductivity cell three times with a 442 standard solution. In this example, we’re using 442-3000.

b. Refill conductivity cell with same standard solution you rinsed with.

c. Press

TDS

 

 

 

 

 

then press

 

.CAL key

 

 

 

 

The “CAL” icon will appear in the top center of the display. In this example, the reading shows 2988.

d. Press

Up

 

 

 

 

 

or

Down

 

 

 

 

 

to step the displayed value toward the standard’s value.

In this example, we’re pressing

 

Up

 

 

 

 

 

to go down from 2988 to 3000. You can also hold a key down to scroll rapidly.

e. Press

 

CAL key

 

 

 

 

 

once to confirm the new value and end the calibration.

You can find technical advice and videos, the calibration solutions you need, and reliable Myron L meters
at MyronLMeters.com
 
 

 

Categories : Application Advice, Care and Maintenance, Product Updates, Technical Tips

Conductivity Calibration on the Ultrameter II 6PIIFCe: MyronLMeters.com

Posted by 23 Mar, 2014

Tweet  *Note: This procedure applies to the Ultrameter, PoolPro, TechPro, and D-6 Dialysate meter. a.  Fill and rinse the conductivity cell three times with a KCL standard solution. In this example, we’re using KCL-7000. b. Refill conductivity cell with same standard solution you rinsed with. c. Press         then press .   […]

 

*Note: This procedure applies to the Ultrameter, PoolPro, TechPro, and D-6 Dialysate meter.

a.  Fill and rinse the conductivity cell three times with a KCL standard solution. In this example, we’re using KCL-7000.

b. Refill conductivity cell with same standard solution you rinsed with.

c. Press

COND

 

 

 

 

then press

CAL key

.

 

 

 

The “CAL” icon will appear on the display.

display

 

 

 

 

 

 

 

 

 

 

 

d. Press

Up

 

 

 

or

Down

 

 

 

 

to step the displayed value toward the standard’s value.

In this example, we’re pressing

Down

 

 

 

 

to go down from 7032 to 7000. You can also hold a key down to scroll rapidly.

e. Press

CAL key

 

 

 

 

 

once to confirm the new value and end the calibration.

You can find technical advice and videos, the calibration solutions you need, and reliable Myron L meters
at MyronLMeters.com
Categories : Application Advice, Care and Maintenance, Product Updates, Technical Tips

Testing Fountain Solutions: MyronLMeters.com

Posted by 6 Mar, 2014

TweetNeed to know the best meter for your application? Review our Bulletins which explain in clear detail the best model for your needs. If you have more questions, visit our FAQ section or send our Experts a question using the contact form. We’ll respond as quickly as possible! Visit MyronLMeters.com for videos, operations manuals, FAQ, […]

Need to know the best meter for your application? Review our Bulletins which explain in clear detail the best model for your needs. If you have more questions, visit our FAQ section or send our Experts a question using the contact form. We’ll respond as quickly as possible! Visit MyronLMeters.com for videos, operations manuals, FAQ, MSDS, and more information about Myron L meters.

Fountain Solutions
Accurate fountain (dampening) solution concentration control is essential for consistent, high-quality results in lithography. Low concentration can cause drying on the non-image area of the plate resulting in tinting, scumming, blanket piling, etc. High concentrations, on the other hand, bring about over-emulsification of the ink. This results in weakening of color strength and changes in ink rheology (body and flow properties). Correct concentration will allow the non-image areas of the plate to be appropriately wetted.

Ways to Test

Traditionally, pH was the test relied on to determine fountain solution concentration. Today, however, conductivity testing is recognized as a much more accurate method. Many modern dampening solutions are pH stabilized (or buffered), so only small changes in pH are seen even when dramatic changes occur in solution strength. Conductivity measurement is a fast and easy test which is more indicative of fountain solution concentration than pH. This is true for all neutral, alkaline, and many acid type solutions.

pH is still important, however, with unbuffered acid fountain solutions. Checking both conductivity and pH can provide valuable information. Acid fountain solution is a mixture of gum arabic, wetting agents, salts, acids, buffers, etc. Conductivity will tell you if the proper amount of most ingredients are present, but pH is necessary to check acid concentrations. pH will also determine how effective one ingredient, gum arabic, will be.

Conductivity Testing

What is conductivity? Conductivity is the measurement of a solution’s ability to conduct an electrical current. It is usually expressed in microsiemens (micromhos). Absolutely pure water is actually a poor electrical conductor. It is the substances dissolved in water which determine how conductive the solution will be. Therefore, conductivity is an excellent indicator of solution strength. To properly measure the conductivity of fountain solutions:

Test and write down the conductivity of the water used to prepare the solution.
Mix the fountain solution concentrate with the water, using the manufacturer’s recommendations or as experience dictates.
Measure the conductivity of the mixed solution.
Subtract the water conductivity value obtained in step 1. This is necessary because tap water quality can change from day to day.

The resulting number is an accurate indicator of fountain solution strength. Caution: because alcohol will lower a solution’s conductivity, always test solution conductivity before and after the addition of alcohol.

Determining the best concentration of fountain solution is mostly ‘trial and error.’ It can be very useful to make a graph, recording readings for every one-half or one ounce of concentrate added to a gallon of water. Record readings on a graph with the vertical axis representing conductivity values and the horizontal axis representing ounces/gallon. Such a graph will help ‘fine tune’ your system during future press runs.
For ‘on the spot’ fountain solution tests, Myron L meters are fast, accurate, and reliable. Measurements are made in seconds simply by pouring a small sample of solution into the instrument cell cup and pressing a button. Automatic temperature compensated accuracy and reliability have made our instruments popular in pressrooms worldwide.

pH Testing

Even though pH usually is not the best method to check the concentration of fountain solution, it is still very important and must be checked regularly. The pH of acid dampening solution affects sensitivity, plate-life, ink-drying, etc. Also, pH can change during a run if the paper has a high acid or alkaline content. pH, therefore, must be maintained at the proper level for good printing.

A convenient and accurate way to test pH (as well as temperature) is the waterproof ULTRAMETER II Model 6P or TECHPRO II TH1. The 6P has a 100 reading memory and the TH1 has a 20 reading memory to store test results onsite. The 6P also measures conductivity. All electrodes are contained in the cell cup for protection. Model M6/PH also measures pH and conductivity.

Continuous Control

For continuous monitoring and/or control of fountain solution concentration, we offer a complete series of in-line conductivity instruments. These economical, accurate, and reliable models use a remotely installed sensor and a panel/wall mount meter enclosure. Most contain an adjustable set point and heavy duty relay circuit which can be used to activate alarms, valves, feed pumps, etc. All models contain a 0-10VDC output for a chart recorder or PLC (SCADA) input, if required, (4-20mA output is also available).

The 750 Series II with dual set point option has become quite popular in pressrooms. The two set points allow a ‘safe zone’ for controlling fountain solution concentration.

Litho-Kit

Ultrameter II 6P, 512M5 and M6/PH are available with the useful LITHO-KIT. This accessory includes a foam-lined, rugged all-plastic carrying case with calibrating solutions and buffers. In addition, a syringe to simplify drawing samples and a thermometer for testing fountain solution temperature are also included.

 

Capture

Categories : Case Studies & Application Stories

Ultrameter: Measuring Conductivity, TDS and Resistivity: MyronLMeters.com

Posted by 1 Mar, 2014

TweetPlease note:  These procedures apply to Ultrameters, Pool Pros, Tech Pros, and D-4 and D-6 dialysate meters. Measuring Conductivity & TDS 1. Rinse cell cup 3 times with sample to be measured. (This conditions the temperature compensation network and prepares the cell.) 2. Refill cell cup with sample. 3. Press COND or TDS. 4. Take […]

Please note:  These procedures apply to Ultrameters, Pool Pros, Tech Pros, and D-4 and D-6 dialysate meters.

Measuring Conductivity & TDS

1. Rinse cell cup 3 times with sample to be measured. (This conditions

the temperature compensation network and prepares the cell.)

2. Refill cell cup with sample.

3. Press COND or TDS.

4. Take reading. A display of [- – – -] indicates an over range condition.

Measuring Resistivity

Resistivity is for low conductivity solutions. In a cell cup the value may drift from trace contaminants or absorption from atmospheric gasses, so measuring a flowing sample is recommended.

1. Ensure pH protective cap is secure to avoid contamination.

2. Hold instrument at 30° angle (cup sloping downward).

3. Let sample flow continuously into conductivity cell with no aeration.

4. Press RES key; use best reading.

NOTE: If reading is lower than 10 kilohms display will be dashes: [ – – – – ]. Use Conductivity.

If you have further questions, please watch our Ultrameter 6P product overview video here: http://blog.myronlmeters.com/ultrameter-ii-product-review/

 IV. AFTER USING THE ULTRAMETER II

Maintenance of the Conductivity Cell

Rinse out the cell cup with clean water. Do not scrub the cell. For oily films, squirt in a foaming non-abrasive cleaner and rinse. Even if a very active chemical discolors the electrodes, this does not affect the accuracy; leave it alone.

Myron L Meters is the premier internet retailer of Myron L meters, solutions, parts and accessories. Save 10% on the Ultrameter II 6PFCe when you order online at MyronLMeters.com.

Categories : Application Advice, Technical Tips

Conductivity Conversion to TDS in the Ultrameter: MyronLMeters.com

Posted by 1 Mar, 2014

TweetElectrical conductivity indicates solution concentration and ionization of the dissolved material. Since temperature greatly affects ionization, conductivity measurements are temperature dependent and are normally corrected to read what they would be at 25°C. A.           How It’s Done Once the effect of temperature is removed, the compensated conductivity is a function of the concentration (TDS). Temperature […]

Electrical conductivity indicates solution concentration and ionization of the dissolved material. Since temperature greatly affects ionization, conductivity measurements are temperature dependent and are normally corrected to read what they would be at 25°C.

A.           How It’s Done

Once the effect of temperature is removed, the compensated conductivity is a function of the concentration (TDS). Temperature compensation of the conductivity of a solution is performed automatically by the internal processor with data derived from chemical tables. Any dissolved salt at a known temperature has a known ratio of conductivity to concentration. Tables of conversion ratios referenced to 25°C have been published by chemists for decades.

B.           Solution Characteristics

Real world applications have to measure a wide range of materials and mixtures of electrolyte solutions. To address this problem, industrial users commonly use the characteristics of a standard material as a model for their solution, such as KCl, which is favored by chemists for its stability.

Users dealing with sea water, etc., use NaCl as the model for their concentration calculations. Users dealing with freshwater work with mixtures including sulfates, carbonates and chlorides, the three predominant components (anions) in freshwater that Myron L calls “Natural Water”. These are modeled in a mixture called “442™” which Myron L uses as a calibration standard, as it does standard KCl and NaCl solutions.

The Ultrameter II contains algorithms for these 3 most commonly referenced compounds. The solution type in use is displayed on the left. Besides KCl, NaCl, and 442, there is the User choice. The benefit of the User solution type is that one may enter the temperature compensation and TDS ratio by hand, greatly increasing accuracy of readings for a specific solution. That value remains a constant for all measurements and should be reset for different dilutions or temperatures.

C.           When does it make a lot of difference?

First, the accuracy of temperature compensation to 25°C determines the accuracy of any TDS conversion. Assume we have industrial process water to be pretreated by RO. Assume it is 45°C and reads 1500 µS uncompensated.

1.         If NaCl compensation is used, an instrument would report 1035 µS compensated, which corresponds to 510 ppm NaCl.

2.         If 442 compensation is used, an instrument would report 1024 µS compensated, which corresponds to 713 ppm 442.

The difference in values is 40%.

In spite of such large error, some users will continue to take data in the NaCl mode because their previous data gathering and process monitoring was done with an older NaCl referenced device.

Selecting the correct Solution Type on the Ultrameter II will allow the user to attain true TDS readings that correspond to evaporated weight.

If none of the 3 standard solutions apply, the User mode must be used.

TEMPERATURE COMPENSATION (Tempco) and TDS DERIVATION

The Ultrameter II contains internal algorithms for characteristics of the 3 most commonly referenced compounds. The solution type in use is displayed on the left. Besides KCl, NaCl, and 442, there is the User choice. The benefit of User mode is that one may enter the tempco and TDS conversion values of a unique solution via the keypad.

A. Conductivity Characteristics
When taking conductivity measurements, the Solution Selection determines the characteristic assumed as the instrument reports what a measured conductivity would be if it were at 25°C. The characteristic is represented by the tempco, expressed in %/°C. If a solution of 100 µS at 25°C increases to 122 µS at 35°C, then a 22% increase has occurred over this change of 10°C. The solution is then said to have a tempco of 2.2 %/°C. Tempco always varies among solutions because it is dependent on their individual ionization activity, temperature and concentration. This is why the Ultrameter II features mathematically generated models for known salt characteristics that also vary with concentration and temperature.

B. Finding the Tempco of an Unknown Solution

One may need to measure compensated conductivity of some solution unlike any of the 3 standard salts. In order to enter a custom fixed tempco for a limited measurement range, enter a specific value through the User function. The tempco can be determined by 2 different methods:

1. Heat or cool a sample of the solution to 25°C, and measure its conductivity. Heat or cool the solution to a typical temperature where it is normally measured. After selecting User function, set the tempco to 0 %/°C as in Disabling Temperature Compensation, pg. 15 (No compensation). Measure the new conductivity and the new temperature. Divide the % decrease or increase by the 25°C value. Divide that difference by the temperature difference.

2. Heat or cool a sample of the solution to 25°C, and measure its conductivity. Change the temperature to a typical measuring temperature. Set the tempco to an expected value as in User Programmable Temperature Compensation, pg. 15. See if the compensated value is the same as the 25°C value. If not, raise or lower the tempco and measure again until the 25°C value is read.

C. Finding the TDS Ratio of an Unknown Solution

Once the effect of temperature is removed, the compensated conductivity is a function of the concentration (TDS).

There is a ratio of TDS to compensated conductivity for any solution, which varies with concentration. The ratio is set during calibration in User mode as in User Programmable Conductivity to TDS Ratio, pg. 16.
A truly unknown solution has to have its TDS determined by evaporation and weighing. Then the solution whose TDS is now known can be measured for conductivity and the ratio calculated. Next time the same solution is to be measured, the ratio is known.

ph and ORP (6PFCE)

1. pH as an Indicator (6PFCE)

pH is the measurement of Acidity or Alkalinity of an aqueous solution. It is also stated as the Hydrogen Ion activity of a solution. pH measures the effective, not the total, acidity of a solution.
A 4% solution of acetic acid (pH 4, vinegar) can be quite palatable, but a 4% solution of sulfuric acid (pH 0) is a violent poison. pH provides the needed quantitative information by expressing the degree of activity of an acid or base. In a solution of one known component, pH will indicate concentration indirectly. However, very dilute solutions may be very slow reading, just because the very few ions take time to accumulate.

2. pH Units (6PFCE)

The acidity or alkalinity of a solution is a measurement of the relative availabilities of hydrogen (H+) and hydroxide (OH-) ions. An increase in (H+) ions increases acidity, while an increase in (OH-) ions increases alkalinity. The total concentration of ions is fixed as a characteristic of water, and balance would be 10-7 mol/liter (H+) and (OH-) ions in a neutral solution (where pH sensors give 0 voltage).
pH is defined as the negative logarithm of hydrogen ion concentration. Where (H+) concentration falls below 10-7, solutions are less acidic than neutral, and therefore are alkaline. A concentration of 10-9 mol/liter of (H+) would have 100 times less (H+) ions than (OH-) ions and be called an alkaline solution of pH 9.

3. The pH Sensor (6PFCE)

The active part of the pH sensor is a thin glass surface that is selectively receptive to hydrogen ions. Available hydrogen ions in a solution will accumulate on this surface and a charge will build up across the glass interface. The voltage can be measured with a very high impedance voltmeter circuit; the dilemma is how to connect the voltmeter to solution on each side.
The glass surface encloses a captured solution of potassium chloride holding an electrode of silver wire coated with silver chloride. This is the most inert connection possible from a metal to an electrolyte. It can
still produce an offset voltage, but using the same materials to connect to the solution on the other side of the membrane causes the 2 equal offsets to cancel.
The problem is, on the other side of the membrane is an unknown test solution, not potassium chloride. The outside electrode, also called the Reference Junction, is of the same construction with a porous plug in place of a glass barrier to allow the junction fluid to contact the test solution without significant migration of liquids through the plug material. Figure 33 shows a typical 2 component pair. Migration does occur, and this limits the lifetime of a pH junction from depletion of solution inside the reference junction or from contamination. The junction may be damaged if dried out because insoluble crystals may form in a layer, obstructing contact with test solutions.

Capture

Figure 33

 

Glass Surface

H+ ions

Junction plug
Platinum button

 

KCl solution

 

 

Glass

 

 

Electrode wires

 

 

 

4. The Myron L Integral pH Sensor (6PFCE)

The sensor in the Ultrameter II (see Figure 34) is a single construction in an easily replaceable package. The sensor body holds an oversize solution supply for long life. The reference junction “wick” is porous to provide a very stable, low permeable interface, and is located under the glass pH sensing electrode. This construction combines all the best features of any pH sensor known.

5. Sources of Error (6PFCE)

The most common sensor problem will be a clogged junction because a sensor was allowed to dry out. The symptom is a drift in the “zero” setting at 7 pH. This is why the Ultrameter II 6PFCE does not allow more than 1 pH unit of offset during calibration. At that point the junction is unreliable.

b. Sensitivity Problems

Sensitivity is the receptiveness of the glass surface. A film on the surface can diminish sensitivity and cause a long response time.

c. Temperature Compensation

pH sensor glass changes its sensitivity slightly with temperature, so the further from pH 7 one is, the more effect will be seen. A pH of 11 at 40°C would be off by 0.2 units. The Ultrameter II 6PFCE senses the sensor well temperature and compensates the reading.

B. ORP/Oxidation-Reduction Potential/REDOX (6PFCE)

1. ORP as an Indicator (6PFCE)

ORP is the measurement of the ratio of oxidizing activity to reducing activity in a solution. It is the potential of a solution to give up electrons (oxidize other things) or gain electrons (reduce).
Like acidity and alkalinity, the increase of one is at the expense of the other, so a single voltage is called the Oxidation-Reduction Potential, with a positive voltage showing, a solution wants to steal electrons (oxidizing agent). For instance, chlorinated water will show a positive ORP value.

2. ORP Units (6PFCE)

ORP is measured in millivolts, with no correction for solution temperature. Like pH, it is not a measurement of concentration directly, but of activity level. In a solution of only one active component, ORP indicates concentration. Also, as with pH, a very dilute solution will take time to accumulate a readable charge.

3. The ORP Sensor (6PFCE)
An ORP sensor uses a small platinum surface to accumulate charge without reacting chemically. That charge is measured relative to the solution, so the solution “ground” voltage comes from a reference junction – same as the pH sensor uses.

4. The Myron L ORP Sensor (6PFCE)

Figure 34, pg. 45, shows the platinum button in a glass sleeve. The same reference is used for both the pH and the ORP sensors. Both pH and ORP will indicate 0 for a neutral solution. Calibration at zero compensates for error in the reference junction. A zero calibration solution for ORP is not practical, so the Ultrameter II 6PFCE uses the offset value determined during calibration to 7 in pH calibration (pH 7 = 0 mV). Sensitivity of the ORP surface is fixed, so there is no gain adjustment either.

5. Sources of Error (6PFCE)

The basics are presented in pH and ORP, pg. 44, because sources of error are much the same as for pH. The junction side is the same, and though the platinum surface will not break like the glass pH surface, its protective glass sleeve can be broken. A surface film will slow the response time and diminish sensitivity. It can be cleaned off with detergent or acid, as with the pH glass.

C. Free Chlorine

1. Free Chlorine as an Indicator of Sanitizing Strength Chlorine, which kills bacteria by way of its power as an oxidizing agent, is the most popular germicide used in water treatment. Chlorine is not only used as a primary disinfectant, but also to establish a sufficient residual level of Free Available Chlorine (FAC) for ongoing disinfection.

FAC is the chlorine that remains after a certain amount is consumed by killing bacteria or reacting with other organic (ammonia, fecal matter) or inorganic (metals, dissolved CO2, Carbonates, etc) chemicals in solution. Measuring the amount of residual free chlorine in treated water is a well accepted method for determining its effectiveness in microbial control.

The Myron L  FCE method for measuring residual disinfecting power is based on ORP, the specific chemical attribute of chlorine (and other oxidizing germicides) that kills bacteria and microbes.

2. FCE Free Chlorine Units

The 6PIIFCE is the first handheld device to detect free chlorine directly, by measuring ORP. The ORP value is converted to a concentration reading (ppm) using a conversion table developed by Myron L Company through a series of experiments that precisely controlled chlorine levels and excluded interferants.

Other test methods typically rely on the user visually or digitally interpreting a color change resulting from an added reagent-dye. The reagent used radically alters the sample’s pH and converts the various chlorine species present into a single, easily measured species. This ignores the effect of changing pH on free chlorine effectiveness and disregards the fact that some chlorine species are better or worse sanitizers than others.

The Myron L 6PIIFCE avoids these pitfalls. The chemistry of the test sample is left unchanged from the source water. It accounts for the effect of pH on chlorine effectiveness by including pH in its calculation. For these reasons, the Ultrameter II’s FCE feature provides the best reading-to-reading picture of the rise and fall in sanitizing effectivity of free available chlorine.

The 6PIIFCE also avoids a common undesirable characteristic of other ORP-based methods by including a unique Predictive ORP value in its FCE calculation. This feature, based on a proprietary model for ORP sensor behavior, calculates a final stabilized ORP value in 1 to 2 minutes rather than the 10 to 15 minutes or more that is typically required for an ORP measurement.

The Myron L Ultrameter II 6PFCe is available at MyronLMeters.com, the premier internet retailer of Myron L products. Save 10% on the Myron L Ultrameter II6 PFCe when you order online here: http://www.myronlmeters.com/Myron-L-6P-Ultrameter-II-Multiparameter-Meter-p/dh-umii-6pii.htm

 

Categories : Application Advice, Technical Tips