Measuring ORP: MyronLMeters.com

Posted by 12 Apr, 2014

Tweet Ultrapen PT3 ORP tester Though the measurement of free chlorine concentration is often indicated for the disinfection of water and disinfectant byproduct control, there is a better way. Because free chlorine works through oxidation, ORP instrumentation can be used to monitor and control its effectiveness. ORP measures the actual oxidation power of the solution, […]



Ultrapen PT3 ORP tester Ultrapen PT3 ORP tester



Though the measurement of free chlorine concentration is often indicated for the disinfection of water and disinfectant byproduct control, there is a better way. Because free chlorine works through oxidation, ORP instrumentation can be used to monitor and control its effectiveness. ORP measures the actual oxidation power of the solution, specifically the strength and number of oxidation and reduction reactions in solution. This yields a clear picture of the efficacy of the chlorine present, regardless of the concentration or ratio of chlorine species in solution.
Measuring ORP directly reflects the sanitizing power of free chlorine or any other oxidizing or reducing chemicals. The measurement of ORP is precise, empirical and requires no user interpretation, making it ideal for water quality and industrial process control.
What is ORP?
ORP stands for Oxidation Reduction Potential, sometimes called REDOX. ORP is a differential measurement of the mV potentials built up when electrodes are exposed to solutions containing oxidants and reductants. ORP describes the net magnitude and direction of the flow of electrons between pairs of chemical species, called REDOX pairs.
In a REDOX pair, one chemical loses electrons while the other chemical gains electrons. The chemical in the REDOX exchange that acquires electrons is called the oxidant (HOCL, OCl-, ClO2, bromine, hydrogen peroxide, etc.). The chemical in the REDOX exchange that gives up electrons is called the reductant (Li, Mg2, Fe2+, Cr2, etc.). Oxidants acquire electrons through the process of reduction, i.e., they are reduced. Reductants lose their electrons through the process of oxidation, i.e., they become oxidized.
How is ORP measured?
ORP sensors are basically two electrochemical half-cells: A measurement electrode in contact with the solution being measured and a reference electrode in contact with a reservoir of highly concentrated salt solution.
When the solution being measured has a high concentration of oxidizers, it will accept more electrons than it loses so that the measurement electrode develops a higher electrical potential than the reference electrode. A voltmeter placed in line with the two electrodes will display this difference in potential between the two electrodes. Once the entire system reaches equilibrium, the resulting net potential difference represents the ORP. A positive reading indicates an oxidizing solution, and a negative reading indicates a reducing solution. The more positive or negative the value, the more powerful the oxidants or reductants, the greater their concentrations or both.
What does ORP measure?
ORP can be used to determine the efficacy of chemical disinfectants that work via the oxidation or reduction of the structures of microbial contaminants. For example, chlorine, an oxidant, will strip electrons from the negatively charged cell walls of some bacteria. Because ORP measures the total chemical activity of a solution, ORP measures the total efficacy all oxidizing and reducing disinfectants in solution: Hypochlorous acid, monochloramine, dichloramine, hypobromous acid, sodium hypochlorite, UV, ozone, peracetic acid, bromochlorodimethylhydantoin, etc.
ORP indicates the effectiveness of only those disinfectants that work through oxidation and reduction. ORP cannot be used to detect the presence of any one particular chemical or chemical species. Nor can it alone be used to determine the concentration of a known species of chemical in solution. This means that although ORP is the best way to know whether or not your sanitizer is working, it can’t tell you how much or what kind of sanitizer is working.
What factors affect ORP measurement?
While the accuracy of ORP sensors is relatively stable, which is why they do not require calibration, there are factors that affect their response time. Changes in temperature can affect response times by altering the kinetic rates of the reactions being measured, for example. Low temperatures reduce the kinetic rates and lengthen sensor response times.
The condition of the electrode will also alter response times by changing the “exchange current density” (the amount of electrons exchanged per unit area of exposed electrode). The lower the exchange current density, the more sluggish the sensor response. The typical measurement electrode is made from pure platinum (Pt) because it is a noble metal and, therefore, highly unreactive, i.e., the potential being measured is most likely due to the activity of the chemicals in the water and not reactions between the solution and the Pt itself. Even though Pt is a noble metal, it will form a thin oxide layer on the surface of the platinum when exposed to dissolved oxygen. This oxide layer facilitates the ORP measurement when it is very thin, one molecule thick, by attracting, or “adsorbing,” hydrolyzed oxidant or reductant molecules to the surface of the electrode.
Unfortunately, when the oxide layer becomes more than one molecule thick, the resulting lowered exchange current density offsets this benefit. Also, the adsorbed molecules cause a “memory effect.” If a sensor is placed in a less oxidizing solution after measuring a more oxidizing solution, it can take a very long time for the sensor to equilibrate to the new sample. Though the sensor response time is much slower, the final ORP reading will be the same.
ORP electrodes never require recalibration because there is no drift in zero point (as is the case with pH sensors). Any deviation from expected readings is most likely due to surface contamination of the electrodes or buildup of the oxide layer, both of which can easily be remedied by cleaning with a light abrasive, such as Softscrub®. Exposing the sensor to an “ORP conditioning solution” will help reduce the memory effect due to adsorption.
Can ORP be used as a surrogate parameter for free chlorine?
Yes. ORP measures the oxidizing power and, therefore, the actual residual sanitizing strength of the solution being tested. Simply counting how much chlorine is present is misleading because certain changes in water chemistry, such as pH or the addition of cyanuric acid, dramatically alter the oxidizing power of chlorine and, therefore, its efficacy, without changing how much chlorine is present.
When correlated with established disinfection control parameters, measurements and bacterial plate counts, this type of measurement gives a very accurate picture of the sanitizing activity. For this correlation to be valid, the water undergoing treatment must be characterized so that all chemical constituents are known. The pH and temperature values should be reported and held constant. ORP will report an empirical value or a hard number that indicates how active the sanitizer is. However, you have to make certain that microbial contamination is responding to the treatment. Once a correlation is established in a stable system, ORP is a very efficient and effective way to monitor microbial control.
ORP has long been used in bathing waters as the only means for automatic chemical dosing. In fact, the World Health Organization (WHO) suggests an ORP value of between 680-720 mV, depending on the sensor and the particular context, for safe bathing water. In the disinfection of drinking water, an ORP value of ~800 mV is required for oocyst inactivation.
For the purpose of pretreatment screening to detect chlorine levels prior to contact with chlorine-sensitive RO membranes, influent must first be screened to determine which chemicals besides chlorine are present that contribute to the ORP value. With these interferants characterized and pH and temperature held constant, ORP can be correlated to specific sanitizer concentrations, such as chlorine, in their known forms. Some manufacturers of RO membranes and other water quality treatment equipment will also specify an ORP tolerance value for prescreening and influent control. The same holds true of effluent screening.
Why ORP?
ORP is a faster, simpler empirical measurement than titration with DPD or other methods, and in many cases it gives the most accurate picture of the effect of all oxidizing and reducing chemicals in solution. No in-depth knowledge or training is required to obtain accurate repeatable results. User error is virtually eliminated because ORP readings require no subjective, visual interpretation, nor do they require calibration.
Using ORP disinfectant control can be automated because the measurement produces an electrical signal that can trigger switches when outside established control parameters. And ORP sensors are relatively low-maintenance. If you’re not using ORP to monitor and control chemical additions that work through REDOX, you should. You’ll save yourself time, hassle and money.
Myron L Meters is the premier internet retailer of accurate, reliable Myron L meters like the Ultrapen PT3, ORP pen tester.
Categories : Case Studies & Application Stories

Ultrapen PT3 ORP Pen Features: MyronLMeters.com

Posted by 4 Apr, 2014

Tweet                    The ULTRAPEN™ PT3 ORP Pen is designed to be extremely accurate, fast, and simple to use in diverse water quality applications. Advanced features include highly stable microprocessor-based circuitry; automatic temperature compensation from 15ºC to 30ºC while in calibration mode; user-intuitive design; and waterproof housing. A […]

 

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The ULTRAPEN™ PT3 ORP Pen is designed to be extremely accurate, fast, and simple to use in diverse water quality applications. Advanced features include highly stable microprocessor-based circuitry; automatic temperature compensation from 15ºC to 30ºC while in calibration mode; user-intuitive design; and waterproof housing. A true one-handed instrument, the PT3 is easy to calibrate and easy to use. To take a measurement, you simply push a button then dip the PT3 in solution. Results display in seconds.

FEATURES
1. Push Button — turns PT3 on; selects mode and unit of measurement preferences.
2. Battery Cap — provides access to battery for replacement.
3. Pocket Clip — holds PT3 to shirt pocket for secure storage.
4. Battery Indicator — indicates life remaining in battery.
5. Display — displays measurements, menu options, battery indicator, and
firmware revision (during power-up).
6. LED Indicator Light — indicates when to dip PT3 in solution, when measurement is in progress, and when to remove PT3 from solution.
7. ORP Sensor — measures oxidation-reduction potential or redox of solution.
8. Soaker Cap — contains a sponge soaked with Sensor Storage Solution to maintain sensor hydration. To remove, twist soaker cap while pulling off. To replace, fi soaker cap with storage solution just until sponge is covered. Squeeze and release tip of soaker cap so sponge will saturate with solution, then pour out any excess solution. Twist soaker cap while pushing back on.
CAUTION: Do NOT overfill the soaker cap as solution can squirt out while you are
pushing the cap back on.
9. Scoop — used to hold sample solution when dipping is not possible. To install, push scoop onto sensor while shifting side-to-side. To remove, pull scoop off while shifting side-to-side. Verify ORP sensor r
into PT3. If not, reinstall per ORP Sen page 5. To use, pour solution into scoop or hold scoop directly under a vertical stream to collect sample.
10. Holster — feed belt through strap in back of holster for hands-free portability.
11. Lanyard — attach through hole in top of pocket clip.
12. ORP Electrode Cleaning Paper — for deep cleaning the platinum electrode.

Technical Specs

ORP Range: -1000 mV to +1000 mV
ORP Accuracy: ± 10 mV
ORP Resolution: 1 mV ORP
Temperature Range: 0 – 71° C / 32 – 160° F
Temperature Accuracy: ± 0.1 ºC / ± 0.1 ºF
Temperature Resolution: 0.1ºC/0.1ºF
Time to Reading Stabilization: 10-45 seconds
Power Consumption: Active Mode 37 mA, Sleep Mode 2 μA
Temperature Compensation: Automatic In Calibration Mode From 15ºC to 30ºC
Physical Dimensions: 17,15 cm L x 1,59 cm D or 6.75 in. L x .625 in. D
Weight: 50,4 g / 1.78 oz. (without soaker cap and lanyard)
Case Material: Anodized Aircraft Aluminum with Protective Coating
Battery: One N type, Alkaline, 1.5V
Calibration Solutions: ORP80, ORP260, ORP470
Operating/Storage Temperature: 0 – 55ºC or 32 – 131ºF
Enclosure Ratings: IP67 and NEMA6
EN61236-1: 2006 – Annex A: 2008: Electrostatic discharge to the PT3 may cause it to spontaneously turn on. If this occurs, the PT3 will turn off.

* Temperature compensation in calibration mode: Temperature affects the reaction potentials for all chemicals differently. True ORP is the direct measurement of electron activity during an oxidation-reduction reaction, regardless of temperature. However, for maximum accuracy and ease of calibration, the Myron L Company has developed three calibration solutions with known dissolved species. We derived the temperature compensation (from 15ºC to 30ºC) for those solutions, and embedded automatic temperature compensation into the calibration function of your PT3. Note: To verify calibration while in measurement mode, you must manually correct for any variation in temperature. Example: @25ºC, ORP2602OZ calibration solution will read 260mV, however @ 20.0ºC ORP2602OZ will read 265mV.

MyronLMeters.com is the premier internet retailer of the Ultrapen PT3 and other reliable Myron L meters. Save 10% on Myron L meters when you order online HERE.

Categories : Product Updates

The Ultrameter II™ in Disaster Response: MyronLMeters.com

Posted by 29 Oct, 2013

TweetWhen disaster strikes, people are scared and disorganized. They need resources — safe water and proper sanitation — that aren’t easy to come by in the aftermath. Without the help of humanitarian organizations to provide assistance, large populations of survivors are subject to epidemics of cholera, diarrhea, meningitis, and other diseases as they struggle to […]

Ultrameter II 6P

Ultrameter II 6P

When disaster strikes, people are scared and disorganized. They need resources — safe water and proper sanitation — that aren’t easy to come by in the aftermath. Without the help of humanitarian organizations to provide assistance, large populations of survivors are subject to epidemics of cholera, diarrhea, meningitis, and other diseases as they struggle to meet these basic needs.

Qualified Help
Dr. Roddy Tempest, a leading designer and manufacturer of water purification systems has headed the efforts of public and private aid organizations, such as the United Nations and AmeriCares, in responding to people in crisis all over the world for over 15 years.

Dr. Tempest contributed his expertise and experience in such situ- ations as the aftermath of Hurricane Andrew in 1992, the Kosovar refugee crisis in the Balkans, the devastating earthquakes in Tur- key and the flood and mudslides that ravaged the coastal states of Venezuela in 1999. He has assisted in disaster relief efforts in Japan, Africa, Central America, and Taiwan, as well.

So when AmeriCares launched its water purification program for the inhabitants of Sri Lanka following the devastation of the tsunami on December 26, 2004, it turned to Dr. Tempest.

For this heroic effort, Dr. Tempest used two Ultrameter II 6P portable, handheld water testing instruments. Dr Tempest said the instruments gave him “a good, quick first-brush assessment of the possible water sources.”

The Ultrameter II reported and recorded instant precise measurements of Conductivity, Resistivity, TDS, ORP (REDOX), pH, and Temperature. But creating a livable situation for hundreds of thousands of displaced survivors wasn’t as easy as testing the water.

Water Doctor to the Rescue
From his offices in the United States, Dr. Tempest responded to the call for help by first reviewing satellite maps that showed the location of potential water sources in relation to groups of survivors, or Internally Displaced Persons (IDPs). He assessed the total situation of the potential water sources, trying at a glance to deter- mine possible contamination by flooding or infiltration of seawater. Upon his arrival in Sri Lanka, Dr. Tempest worked 24 hours a day to determine a suitable survival supply of water for the IDPs. As indicated in the World Health Organization’s Environmental Health in Emergencies and Disasters, the required water per person per day is 15 liters / 3.963 gallons.

Faced with this daunting task, Dr. Tempest surveyed the land via helicopter and fixed wing aircraft to record the extent of the damage, the location of IDPs, and the viability of potential water sources. Some of the photographs reveal the mammoth challenge he had ahead of him. Debris lay everywhere, indicating the likelihood of surface water and well contamination. Filtration was a must.

Dr. Tempest then combined satellite imagery, the photographs and sketches of water sources from his survey and a list of supplies to determine which water sources would be targeted for testing.

Following World Health Organization guidelines, Dr. Tempest considered as many potential water sources as possible, not just the most obvious ones. These included surface and groundwater near the groups of IDPs and tankered or bottled water brought in from a distance – though this would not be suitable for the long- term supply. The preferred source would have been groundwater, especially for the long-term.

Ultrameter II in Action
Dr. Tempest used the Ultrameter II 6P to screen these sources for their potential disinfection and filtering.
First, Dr. Tempest considered whether or not potential water sources could be protected from pollution and secured. Any potential source water had to be filterable and sanitizable. If the water was brackish, it would require a certain treatment method. If it was high in turbidity, then it would require another. If the pH needed adjusting, then yet another. If the source water was not easily treatable, then the source had to be discarded as an option and a better alternative found.

The Ultrameter II provided Dr. Tempest with fast, reliable, accurate initial information on whether or not to pursue further testing and treatment of a potential source. Dr. Tempest used a multiparameter approach and tested for Total Dissolved Solids (TDS), pH, ORP (REDOX), and temperature (recorded with every reading taken.) He also tested for turbidity and bacteria using other instrumentation.

Initially, Dr. Tempest used a measurement of the mineral salt concentration using TDS calibrated to a sodium chloride solution and TDS calibrated to a natural water standard.

Right away Dr. Tempest knew whether or not the water was too saline or saturated to be filtered  economically. If the TDS is too high, filtration systems that work by reverse osmosis can be overwhelmingly expensive to operate in a disaster area, especially considering electrical costs alone. At the very least, the systems become less efficient as the TDS increases and a burden in operation and maintenance costs. This is critical for the short-term disaster response, where Dr. Tempest has to get as much safe water to IDPs in as short amount of time as possible.

High TDS can also indicate an unacceptable level of specifically known inorganic contaminants caused by industrial pollution.
And though it is not a health consideration, high TDS water often has an unpleasant taste that deters people from using it. People may try to return to old wells or other sources of previously safe drinking water that have been contaminated in the disaster. The old source may be more trusted than one that tastes “polluted.” So even though TDS is a secondary water quality standard, it can profoundly impact whether or not the new source is acceptable.

Dr. Tempest also took instant electronic pH readings using the Ultrameter II. The pH directly affects the potential to disinfect the water. pH levels beyond 8 will require substantial increases in the amount of disinfectant required or the length of time the water must be disinfected before safe consumption. And at a pH beyond 9, a residual disinfectant is extremely difficult to maintain.

pH is also critical in the long-term disaster recovery planning. pH that is too low or too high affects water balance, as well, and can contribute to either corrosion or scaling of filtration and disinfection system components and plumbing. An electronic meter is the best choice in this application as compared to colored strips or solutions or other colorimetric methods that do not produce the accuracy required to consistently and correctly balance water and maintain proper disinfection levels. The more precisely the pH is maintained, the less costly safe water production is.

Dr. Tempest also took quick ORP (REDOX) measurements using the Ultrameter II. ORP (REDOX) is the oxidation reduction potential of the water and indicates the state of the water for gaining or losing electrons. Unlike pH, which measures the water’s ability to donate or receive hydrogen ions, ORP (REDOX) values reflect the presence of all oxidizing and reducing agents — not just acids and bases. Initially, the ORP (REDOX) value gave Dr. Tempest a rough idea of the organic load in the water. A reading of 650 mV or greater indicated good water quality that could effectively be sanitized by a minimal amount of free chlorine. A value like 250 mV indicated that the organic contaminants would significantly increase chlorine demand and thereby significantly increase operation and management costs.

ORP (REDOX) is not only a good first indicator about the viability of a water source, but it also is the best way of measuring the disinfectant present in the water after treatment has begun.

Putting It All Together
Using all of the results from these parameters and based on his knowledge of the location of IDPs in relation to potential water sources, Dr. Tempest decided which source would satisfy the needs of each specific location of groups of IDPs. Where possible, water treatment technology would be designed around the quality of the source waters tested where IDPs had gathered, since it was not practical to re-locate large groups of people to distant water sources. Unfortunately, in the case of the Tsunami in Sri Lanka, oftentimes the water closest to IDPs could not be filtered and relocation was necessary.

Dr. Tempest found after his first quick assessment of potential water sources that it was not practical to supply the IDPs in parts of the Batticoloa and Ampara Districts along the eastern coast, because the source water was too saline from seawater intrusion. With limited electricity, this
made the use of reverse osmosis or desalination equipment impractical.

He ended up settling on sites that were more inland, using source waters from man-made reservoirs. IDPs were then settled inland near the cleaner water source.

However, the water in the man-made reservoirs was heavily contaminated with toxic blue-green algae.

Dr. Tempest chose microfiltration and ultrafiltration water treatment systems in the eastern district locations, taking algae-infested water over the salt-saturated, so that treatment and operation costs would be significantly less. Dr. Tempest designed, built and commissioned 4 large transportable water treatment systems, each capable of producing over 500,000 liters/day.

Plans then continued to follow through with long-term water treatment using the Tempest Environmental Systems equipment for the Sri Lankan Ministry of Urban Development and Water Supply and their National Water Supply & Drain- age Board (NWSDB). The NWSDB has 14 Ultrameter II 6Ps in current use in Sri Lanka, which are providing continuing confidence checks to ensure system equipment remains up and running properly.

The Ultrameter II 6P is an excellent multiparameter water quality meter used by thousands of water treatment professionals. The instrument can test for pH, total dissolved solids, conductivity, resistivity, oxidation reduction potential, temperature, and has the capability of testing for free chlorine. This meter handles the job of SIX single parameter testers using one single water sample. Save 10% on the Ultrameter II 6P at MyronLMeters.com.

 

 

Categories : Case Studies & Application Stories

The Ultrapen PT-3: MyronLMeters.com

Posted by 12 Jun, 2013

Tweet Myron l Meters Ultrapen PT-3 from Myron L Meters

Myron l Meters Ultrapen PT-3 from Myron L Meters
Categories : Product Updates

Ultrapen PT3 pen – Tests ORP / REDOX and Temperature – MyronLMeters.com

Posted by 23 Sep, 2012

TweetThe All NEW ULTRAPEN PT3 pen tests ORP / REDOX and Temperature with great reliability. Advanced features include highly stable microprocessor-based circuitry; automatic temperature compensation from 15ºC to … [Learn more about the ULTRAPEN PT3 pen NOW!]

The All NEW ULTRAPEN PT3 pen tests ORP / REDOX and Temperature with great reliability. Advanced features include highly stable microprocessor-based circuitry; automatic temperature compensation from 15ºC to … [Learn more about the ULTRAPEN PT3 pen NOW!]

Ultrapen PT3 instrument diagram

Categories : Product Updates