Which pH-meter to choose?
Giorgio Bormac has a lot of instruments available, so it could not be easy to choose the right pH-meter.
The first thing to decide is what kind of instruments do you need: bench meter or portable.
The bench meter instruments have more comfort and accessories than portables.
The portable ones are faster, tougher and suited for measurements on site.
At last we have the pH testers: pocket-sized and low cost instruments, faster than portables but with less accuracy.
How to choose the right electrode...
There are different types of electrodes: they could have different body material, references, junctions, electrolyte and diaphragms.
To make the right choice you need to know what kind of sample you are going to analyse, and then identify the right electrode.
If you’re not sure about your choice or the sample is not in any of our lists, we recommend to contact us for a consultation by one of our technical assistant.
The right electrode, in addition to guarantee more accurate measurements, it will last more than a wrong electrode not suited for the sample under analyse.
How can I measure pH more accurately?
To measure pH more accurately, we recommend to calibrate often using fresh buffer solutions.
The temperature of the buffer solutions must be the same of the samples that are going to be measured.
The pH electrode need to settle in too, so we recommend to let it immersed in the buffer solution for few minutes before starting the calibration.
The last warning is about how to obtain the best measurement: stir gently the electrode in the sample to not create bubbles and to homogenize the solution.
How to set up the pH electrode
Usually the electrode is given ready to use: you just have to connect it to the instrument, remove the protective cap (which contains storage solution), rinse it with distilled water, calibrate it and proceed to measurements.
However the electrode could be asleep at the first measurement, not reactive at all and slow to stabilize.In this case, we recommend to rinse the electrode in the KCL solution or in the pH4.01 buffer solution for at least two hours.
Following this procedure, the membrane will be reactivated and the electrode will be ready to the calibration.
Why to calibrate?
To calibrate means "to fix” the reading of our measurement chain.
You need buffer solutions with known values to do it (there are different families).It is important to have fresh and not contaminated solutions because we must be sure that their values are the same as the values reported on the packaging.
How often to calibrate?
Theoretically, you should calibrate the instrument before every measurement to obtain perfect results.
But it is enough to calibrate the instrument when you need it: for example if you are looking for more accuracy, you should calibrate the instrument more often.
The calibration process lasts few minutes and doing it frequently does not damage the equipment.
What is the automatic compensation of the temperature and why do I need a temperature probe?
Temperature has a significant importance in the pH measurement.Increasing the temperature, the molecular vibrations will increase too. This means that water can create more hydrogen ionsand the pH will fall down.
Basically, when temperature changes, pH value changes too.
A commun mistake is to extract a sample from its ambient and measuring its pH value in a laboratory. From its ambient to the laboratory, the temperature of the sample will be different and so its pH value. Different but not wrong because the new pH value is connected to the new temperature.
We can say that a pH value without a temperature value does not make any sense and the only way to avoid this mistake is to report pH and temperature values of the sample at the same time of the analyse.
Temperature alters the characteristics of the solution and the performance of the electrode too.It is impossible to predict the behavior of the solution, but it is possible to do it with the electrode and the automatic compensation helps us.
Changing the temperature, the mV of the electrode change too leading to a real mistake. The pH instruments with the automatic compensation of the temperature fix this mistake.
Without an automatic temperature probe, the temperature of the solution must be included in the pH meter manually to fix the measurement.The farther the pH of the sample is from pH 7.00, the automatic compensation of the temperature becomes more important, especially in an alkaline ambient.
Do not forget: to obtain the best results in the pH measurement, calibrating and measuring at the same temperature.
Please note: the pH value decreases when temperature increases.
This not means that water becomes more acid at high temperature.A solution is considered acid if there is an excess of hydrogen ions compared to hydroxide ions. In the ultra-pure water there is always the same concentration of hydrogen ions and hydroxide ions, so the water is still neutral (even if the pH value changes). At 100 °C, a pH value of 6,14 is the new neutral point of the scale at this temperature.
What is the best way to maintain my pH electrode?
It is necessary to maintain the electrode in its storage solution. It is a liquid solution that keeps the membrane hydrated and ready to use.The electrode comes out from the factory immersed in the storage solution, but it is necessary to change that solution after few days. We recommend to buy a backup bottle.If the electrode is maintained dry, it will become very slow and unstable until its exhaustion.
Never keep the electrode in water!
How long does it last the pH sensor and what can I do to make it last longer?
Clean the electrode with water and neutral soap and properly store it in the storage solution are the basic operations to make the electrode last longer (generally it lasts from 9 to 24 months, depending on the application). Solvents, acids, corrosive chemicals and high temperature are the worse enemies of the pH electrode.It is necessary to choose the right electrode based on the sample to analyse.
When do I know it is time to change the pH sensor?
When readings become slower and unstable and it is not possible to calibrate the electrode, it could be the right moment to change it.
Ultra-pure water compensation
Do you have difficulties to measure pH in distilled, deionized or ultra-pure water?
The reason is that distilled, deionized or ultra-pure water have not many hydrogen ions and it is complicated for the electrode to read them.This means unstable measurements.But sink water has enough hydrogen ions so the pH readings are easier.
Do not forget that water (distilled, deionized, ultra-pure water, ecc.) has not an accurate pH value of 7.00 because the effect of the air creates carbonic acid (H2CO3) that acidifies the pH value.
To measure correctly the pH value in treated waters it is essential the "ultra-pure water compensation” function in our XS 80 Series and in multiparameter XS ReVio.This instrument bears in mind the ionic strength of water and gives a very accurate measurement.
Why to measure the conductivity?
The conductivity reveals how the solution is able to conduct electricity.
This characteristic is due to dissolved mineral salts in the solution.
We can find how many elements are dissolved in our solution through the conductivity measure.
How to measure the conductivity?
The measurement needs a conductivity sensor and a probe temperature (usually combined in the same body).
After the calibration, insert the sensor in the solution and start measuring.
The new measuring instruments, like the XS Instruments, are able to measure conductivity and temperature of the sample and then give back the measurement already standardize at 25 °C (or any temperature between 15 and 30 °C).
Changing temperature changes also the measurement but, unlike the pH, for the conductivity is possible to predict precisely this variation.
How to clean and store the conductivity cells?
Immerse the cell in ethyl alcohol for a couple of minutes to remove residues of dirt.
NEVER rub the cell.
Rinse the cells with distilled or deonized water and calibrate againg before the use.Instead of pH and ORP sensors, the conductivity cells can be preserved dry.
How and when to calibrate the conductivity meter?
Consult the manual of your instrument to know more about the calibration process.
Choose the calibration solution between the buffer solutions available for sale.
Pick the closest values to the sample under analysis.
The most commun buffer solutions are 84 µS, 1413 µS and 12.88 mS.The regularity of calibration is established by the accuracy required, the sample analysed and working mode.We recommend to calibrate the instrument at least once a week for frequent use.
What does it mean cell costant?
The cell costant (C) is the correlation between distance and surface of the conductivity sensors.
The 2 poles cells have 3 possible options:
C = 0,1: for low conductivity measurements (< 100 µS).
C = 1: for average value measurements.
C = 10: for high conductivity measurements (> 20 mS).
It is important to choose the right cell according to the expected values and to set up the exact value of the cell constant on the instrument.
Why to measure dissolved oxygen?
The dissolved oxygen (DO) could indicate the health and quality of the water.
Oxygen is essential for water-based ecosystem and few chemical reactions, but too much oxygen could be dangerous too.
What does influence DO levels in water?
The dissolved oxygen concentration in water is influenced by:
- Water temperature - high temperatures influence DO levels.
- Mineral waters - oxygen is less soluble in water with high salinity levels.
- Atmospheric pressure - it decreases the oxygen pressure in different altitudes.
An oxymeter should consider all these parameters.
What is the difference between polarographic and optical sensor?
Polarographic sensors have to heat up before to calibrate and polarize the electrodes.
Optical sensors are always ready to work, they don’t need any polarization periods.
Also, the optical sensor does not need maintenance, instead of the polarographic sensor that needs regular maintenance, cleaning and electrolyte refill.
How frequently calibrate the oxymeter?
It is not possible to establish how frequently calibrate the oxymeter.
To obtain perfect values, the instrument should be calibrated before each measurements.
More frequently calibrations mean more accurated measurements.
How to calibrate an oxymeter?
The XS oxymeter can be calibrated in air with a dissolved oxygen value of 100%.
The calibration does not need buffer solutions, it takes just few seconds and it can be done whenever you want.
Also it is possibile to linearize the scale calibrating on a second point (0%) using single-use solution.
This process can be done less frequently.
When to change the membrane of the sensor?
Usually the membrane tend to be contaminated and get ruined in different ways depending on the conditions of use.
We recommend to always have a spare membrane ready to use.
When measurements become unstable or too slow, or when the calibration in air gives back a mistake, it is time to change the membrane.
Polarographic sensors get ruined before than optical sensors.
When and how to clean the sensor?
You have to clean the sensor after each measurements rinsing it with distilled water.
Do maintenance if it is necessary, as it explained in the manual.
General features of different sensors (PT100, Thermocouples, NTC)
The PT100 is a platinum thermoresistance with 100 ? nominal resistance at 0 °C. The main characteristics of these probes are excellent accuracy, more stability, characteristic curve almost linear and medium-low temperature range.
The Thermocouple is made of the different metals connected at one extremity. When the intersection of the two metals heats up or cools down, it produces a tension connected to the temperature that can be detected using a thermometer for thermocouple. There are different types of thermocouple: K, J, T, E, N, B, S, R. They are made of different kind of metals that define the areas of application.K type: chromium and nickel with yellow plug. J type iron and constantan with blue plug. Thermocouples reach higher temperatures than PT100 sensors.
A thermistor sensor (or a NTC probe) is a temperature detection tool made of a sintered semiconductor material that, when there is a small temperature variation, shows a wide resistive variation. Its working range is shorter than PT100 and Thermocouples temperature sensors. Below there is a table with some technical specifications about different kind of sensors. On the right side, the table shows the percentage of the temperature real value on the X axis and the time stated in seconds on the Y axis. The conclusion is that PT100 sensors are more accurated than thermocouples but slower to reach the real temperature. Instead thermocouples are less accurated but much faster.
Choosing the temperature probe…
The choice of the temperature probe is an important decision because you have to focus your attention on certain points to find the right sensor for your application.
The list below will help you to choose the appropriate sensor: if you already have a thermometer, you should verify what kind of sensor and plug the instrument can identified; if you do not have a thermometer, choose the sensor according to your application.
terminal type (air/liquids, penetration or contact).
All these informations are necessaries to understand what kind of sensor should be used. If you can not find the sensor that you are looking for on our catalog, we recommend to send an e-mail to firstname.lastname@example.org with all the characteristics and values you need: with the help of our technical assistants we will try to find the best solution for you, if it is possible.
Che durata ha un certificato Accredia?
Il certificato non ha una scadenza e non vi è un termine entro il quale deve essere effettuata una nuova taratura.
La scelta dell’intervallo di taratura deve essere fatta in base a diverse variabili. Si dovrà anche tener conto del Registro della Qualità dell’utilizzatore.
Talvolta la taratura viene richiesta annualmente, mentre in altri casi si adotta la certificazione biennale.
I termometri checker sono certificabili Accredia?
Visto il costo dei termometri. Giorgio Bormac s.r.l. non invia tali termometri in certificazione. Consigliamo l’acquisto di uno strumento di livello superiore se l’utilizzatore necessitasse di un certificato Accredia.
Can I use infrared thermometers to detect temperature from liquids and reflective surfaces?
Measuring a reflective surface or a liquid, the thermometer picks up radiations from other sources and reflected by the sample. So the result shown by the thermometer will be falsify. For reflective surfaces, the temperature can be measured by placing an opaque "target” on the sample. After the sample has transmitted its temperature to the target, use the infrared thermometer on it.
For example, if you want to measure the temperature of a glass bottle, just apply a paper label on the bottle and "shoot" on it.
What does it mean D:S in the infrared thermometer?
"D” means distance and "S” means spot, it is just a ratio between distance and target.
If the thermometer has a D:S of 11:1, it means that with a distance of 110 cm from the target, it will measure the radiation of a 10 cm diameter area.
What is the emissivity in the infrared thermometer?
The emissivity is a measurement of the efficiency in the surface emission of a thermal radiation.
This value has not unit of measure and its value can change from 0 to 1.
Some infrared thermometers have the possibility to change this value, in others it is fixed at 0,95 (most commun value for a lot of surfaces).
Which infrared thermometers to measure the body temperature?
Not all infrared thermometers can measure the body temperature because the accuracy value is not high enough.
In 2020 Giorgio Bormac s.r.l. introduced a new infrared thermometers called BodyTemp for body temperature (and sufraces too) measuremets.
This thermometer is classified among the medical devices (CND) available for consultation on the Health Minister web site.