For a pH electrode, first decide what sample, range and temperature you will measure (a clear aqueous solution, food, slurry or solid, a sample with impurities); then look at the electrode structure (combination or separate, junction type, glass and body, filling method); next look at the connected meter and temperature compensation (high input impedance, transmitter, temperature sensing); after that deal with care, calibration and life (storage, cleaning, number of calibration points, slope and offset). This article is mainly about general pH measurement in the laboratory and the process; pH paper and ion-selective electrodes such as chloride are outside its scope. It is divided into 4 stages:
Stage ① | Sample and measuring range: kind and amount of sample, pH range, temperature, glass type and shape.
Stage ② | Electrode structure and junction: combination or separate, junction type, body material, filling method.
Stage ③ | Meter and temperature compensation: high input impedance, transmitter, temperature sensing, equilibration time.
Stage ④ | Care, calibration and life: storage, cleaning, calibration, slope and offset, replacement.
This article starts from “you already know you need to measure pH”. Each stage below says: how to do it, what public sources say, and what Jiahon can help with; the data and basis of each source are in the “Notes” at the end. This is the general case and still depends on the individual case.
Figure 1: The four stages of pH electrode selection — sample and measuring range, electrode structure and junction, meter and temperature compensation, care, calibration and life (schematic, not to scale).
Stage ①: Sample and measuring range — first look at what is being measured
How to do it:
First write down the sample: a clear aqueous solution, or food, slurry, semi-solid, or something with solids or protein; and how much there is, from a trace to a large container.
Range and temperature: write down the pH range to measure and the sample temperature. At very high pH there is alkaline error, for example pH 12 and above with sodium ion concentration of 0.1 mol/L and above; at very low pH there is acid error.
Glass type: general-purpose glass copes with most everyday laboratory work; for demanding work there are glasses for high temperature, alkali resistance and acid resistance.
Shape of the sensing tip: a spherical tip for ordinary aqueous solutions; a conical tip for slurry, emulsion, semi-solids and solids; a flat tip for surfaces such as skin, leather and paper.
For small samples there are micro electrodes, with examples down to 15 µL or 100 µL.
What public sources say: A web encyclopedia entry on the glass electrode says: at very high pH, with enough alkali metal ions, the response becomes non-linear, usually clear at pH 12 and above with lithium or sodium ions at 0.1 mol/L and above; at extremely high hydrogen ion concentration (about pH below 1) the response also becomes non-linear. An electrode maker’s electrode guide (2017 edition) says: a general-purpose electrode can be used in many situations but is not ideal for every sample, and food, high or low temperature and non-aqueous solutions may need a special one; general-purpose glass has a larger response over the whole pH range; a spherical tip is for ordinary aqueous solutions, a conical tip for slurry, emulsion, semi-solids and solids, and a flat tip for skin, leather and paper; a micro electrode can measure down to 100 µL. Another maker’s booklet (2012) says: general-purpose glass copes with most everyday laboratory work, and for demanding work there are glasses for temperature, alkali and acid resistance; a micro sensor can measure down to 15 µL (Notes table 1).
What Jiahon can help with:
The pH measurement product pages are listed below. For specifications not written on the product pages, please inquire.
pH Analyzer and Electrode: the product page says this is an analyzer and electrode for industrial and process pH measurement, with a specification table in two columns. Analyzer body: measuring range pH 0–14 (some models −2 to 16), resolution 0.01 pH, accuracy ±0.01 pH to ±0.05 pH. Electrode: pH 0–14 (depending on the glass membrane formulation), temperature resistance 0–80 °C (general) or 0–130 °C (high-temperature type), pressure resistance 0–6 bar (general). The page also says the electrode has to be connected to a pH meter or analyzer to read, and does not itself output 4–20 mA.
Combination pH Electrode: the product page says measuring range pH 0–14, temperature range 0–80 °C, hemispherical glass membrane shape; the page also says it is not recommended for samples containing sediment, protein or sulfide, or for non-aqueous titration.
Stage ②: Electrode structure and junction — combination or separate, how to choose the junction
How to do it:
Combination or separate: a combination electrode puts the sensing and reference parts in the same body and is more common now; early on the two half-cells were often sold apart.
Junction: porous ceramic is common; porous PTFE is chemically resistant and durable and is used in industry; open and sleeve types have a large flow and do not clog easily and are used for solids, semi-solids and emulsions; a cloth-core junction lets a short length be drawn out to refresh it; a double junction clogs less easily and keeps the silver-free electrolyte in contact with the sample.
Body: plastic where it is easily dropped or broken, glass for corrosive samples and high temperature.
Filling method: for those that can be refilled, keep the liquid level and open the fill-hole cap during measurement; some gel types need no refilling, just routine calibration and cleaning.
Temperature sensing: for an electrode with a temperature sensor built into the body, the meter can compensate temperature automatically.
What public sources say: An electrode maker’s electrode guide (2017 edition) says: combination electrodes that put sensing and reference together are the more commonly used today, while before the 1970s the two half-cells were often sold apart; porous ceramic is a common junction and porous PTFE is used in industrial sensors, open and sleeve types have a high flow, do not clog easily and are used for solids and emulsions; a cloth-core junction lets a short length be drawn out to refresh it; a double junction clogs less easily and keeps silver-free electrolyte in contact with the sample; a refillable electrode needs its liquid level kept and the fill-hole cap opened during measurement, and some gel types need no refilling. A web encyclopedia entry says: the reference electrode is often silver chloride or calomel; many meters use a combination probe. Another maker’s booklet (2012) says: the reference element is commonly silver and silver chloride, but silver precipitation can clog the junction, so an open or diaphragm (ceramic or PTFE) junction can be chosen; plastic bodies are for places where things are dropped or broken, glass for corrosive samples and high temperature; for a probe with a built-in temperature sensor, automatic temperature compensation is assured (Notes table 2).
What Jiahon can help with:
Combination pH Electrode (the page of stage ①): the product page says this is a combination type (including the reference electrode), shaft of polypropylene and glass, lower part of fluoro rubber; ceramic liquid junction; reference electrolyte c(KCl) = 3 mol/L, electrolyte flow rate 3–10 µL/h (10 cm water column), a low-leakage reference system; built-in Pt1000 temperature sensor; cable 1.2 m fixed cable. Whether it can be refilled and whether the connector fits your meter, please inquire.
pH Meter U-Type Electrode: the product page says this is a U-type double-junction pH electrode, where the U-tube structure separates the electrolyte from the sample; the sample examples on the page are samples containing organic solvent, protein or a high heavy-metal content. The title of the product page once calls it a reference electrode while the specification table says combination electrode; which one it is, please inquire to confirm; the measuring range and temperature are not written on the product page, please inquire.
Stage ③: Meter and temperature compensation — what the electrode is connected to
How to do it:
High input impedance: a glass electrode has a very high resistance, about 50 to 500 MΩ, so it has to be connected to a meter with high input impedance, such as a pH meter or a potentiometer.
Meter: what a pH meter actually measures is a voltage, shown in pH units; which meter or transmitter to connect depends on the measuring setting.
Temperature compensation: when temperature changes, the measured pH changes too; automatic compensation needs a temperature probe, built in or separately connected; manual compensation means re-entering the value every time the temperature changes.
Sample volume: automatic temperature compensation works better when the sample is over 10 mL; with a very small sample the sensor may not have time to equilibrate and the temperature can be misread, so leave enough time.
What public sources say: A web encyclopedia entry on the glass electrode says: the resistance of glass pH electrodes is always very high, about 50 to 500 MΩ, so a measuring device with high input impedance, such as a pH meter or a potentiometer, is needed. A web encyclopedia entry on the pH meter says: the display is a voltmeter in pH units; temperature changes affect pH, and some meters take a temperature input to adjust. Another maker’s booklet (2012) says: automatic temperature compensation works quickly when the sample is over 10 mL; a sensor with a built-in temperature probe lets the meter compensate automatically, and one without needs a probe connected separately; manual compensation is accurate but time-consuming and must be entered at every temperature change; with a very small sample the sensor may take too long to equilibrate, so its temperature is taken as the sample temperature. An electrode maker’s electrode guide (2017 edition) says: the meter needs high input impedance to read the electrode’s voltage; temperature compensation gives an accurate measurement (Notes table 3).
What Jiahon can help with:
Combination pH Electrode (the page of stage ①): the product page says built-in Pt1000 temperature sensor, membrane impedance 200–400 MΩ.
pH Analyzer Transmitter: the product page says this is a multi-channel panel-mount transmitter (½ DIN), with 1, 2 or 4 channels to choose from, specified when ordering; 5.7-inch color touch screen; the sensor interface supports both analog and digital; measured parameters pH / ORP, with dissolved oxygen, conductivity, turbidity and others also listed; protection rating IP66; power AC 100–240 V or DC 20–30 V; analog output 4–20 mA; digital communication lists Profinet, EtherNet/IP, HART and FOUNDATION Fieldbus; with relay outputs. The page also says whether it works with your existing sensors or control system, please ask Jiahon sales.
pH/ORP Online Analysis Transmitter: the product page says measured parameters pH / ORP (configurable); power wiring two-wire or four-wire (by model); analog output 4–20 mA (HART); communication HART, Modbus; protection rating IP67; LCD backlit display of pH value, temperature and electrode status. The page also says a standard glass electrode can be connected, but the electrode impedance has to meet the specification; what the specification is, the page does not say, please inquire.
Stage ④: Care, calibration and life — what starts after you buy
How to do it:
Storage: keep it moist, soaked in the maker’s storage solution; do not leave it in pure water (reverse osmosis, deionized or distilled water); one that has dried out can be soaked in storage solution for at least 1 hour.
Calibration: use at least two buffers covering the range to be measured; general use can take pH 4.00 and 10.00; for a wide range use three points. Examples of frequency: for very precise work before every measurement, for general work once a day.
Cleaning: after measuring, rinse with distilled or deionized water and blot gently dry; choose the cleaning solution by the contaminant; one source suggests cleaning weekly, soaking for 15 to 20 minutes, after which it has to be rehydrated and calibrated again.
Check the state: for example, offset within ±30 mV and slope of 85% to 105% mean the electrode is in the normal range; if it is still outside after cleaning and fresh solution, replacement may be needed.
Life: one source says an average of 12 to 18 months; the slope falls over months, and an aging electrode takes longer to equilibrate.
What public sources say: An electrode maker’s electrode guide (2017 edition) says: do not leave the electrode in reverse osmosis, deionized or distilled water, because ions are lost from the glass membrane and the reference electrolyte; a dried-out electrode can be soaked in storage solution for at least 1 hour; calibration frequency depends on how accurate you need to be, and calibrating every day is ideal; do at least a multi-point calibration, choosing points that cover the expected range; clean the sensing tip weekly, soaking for 15 to 20 minutes; offset within ±30 mV and slope of 85% to 105% mean the electrode is normal, and if the offset is still outside ±30 mV after cleaning and fresh solution, replacement may be needed; the average life is 12 to 18 months, which needs correct use and matching to the application. A web encyclopedia entry on the pH meter says: calibrate with solutions of known pH, usually before each use; for very precise work before every measurement, for general work once a day; use at least two buffers covering the range, and for general use pH 4.00 and 10.00; a clean probe is the key to accuracy; after each measurement rinse with distilled or deionized water and blot with wiping paper; as an electrode ages the equilibration time gets longer; makers provide their own cleaning and care instructions. A web encyclopedia entry on the glass electrode says: the electrode slope usually falls within several months; a glass electrode must be calibrated before use, commonly with standard buffers; the membrane must not dry out. Another maker’s booklet (2012) says: use pH 7 first, then pH 4 or 10; a wide range needs a three-point calibration; calibrate over the whole measuring range (Notes table 4).
What Jiahon can help with:
Combination pH Electrode: the product page says electrode zero point ±15 mV, electrode slope above 0.97 (factory specification; not the same kind of number as the normal in-use range written by the sources above); for long-term storage, soak the glass membrane in the maker’s storage solution.
pH Meter U-Type Electrode: the product page says that when not in use it should be kept in the maker’s storage solution (3 mol/L KCl or a special solution) and not stored dry, otherwise the glass membrane dehydrates and needs a longer time to equilibrate again.
pH/ORP Online Analysis Transmitter: the product page says that when the electrode is replaced, a two-point calibration has to be done again (pH 4 and pH 7 buffers). This again is not exactly the same as the calibration points written by the two sources above (pH 4.00 and 10.00, or pH 7 first and then pH 4 or 10); each says its own, and the maker’s data prevails.
pH Analyzer and Electrode: in the specification table of the product page, the electrode life row says 6–24 months (the page notes this is the general case and still depends on the individual case); this is an example from a different source than the average of 12 to 18 months written above, and the two cannot be compared directly.
Buffers, storage solutions, cleaning solutions and calibration certificates were not seen among the product names on the site; please inquire, and attach the sample and the frequency of use.
When you need to match a type, please prepare six items first: the kind and amount of sample, the pH range and temperature, the electrode structure and junction wanted, the connected meter, the arrangement for calibration and care, and the frequency of use. You are welcome to contact Jiahon.
Notes: Sources and Exceptions
This is for readers who need to check; skipping it does not affect the practice above. Where your system specification and the written specifications of the electrode and meter makers differ from this article, theirs prevail.
Where each stage comes from
| Source | Where it is used, and where it comes from |
|---|---|
| Source 1 | Stages ① to ④: alkaline and acid error, high impedance, slope, membrane. A web encyclopedia entry on the glass electrode (edited by many people, changes over time) |
| Source 2 | Stages ② to ④: reference electrode, display and temperature, calibration, cleaning, storage. A web encyclopedia entry on the pH meter (edited by many people, changes over time) |
| Source 3 | Stages ① to ④: electrode choice, junction, filling, storage, cleaning, state and life. An electrode maker’s electrode guide (version 1.4, back cover marked 08/17, reprinted on a distributor’s site; vendor material) |
| Source 4 | Stages ① to ④: glass, micro, body, temperature compensation, calibration. A maker’s pH booklet (September 10, 2012, 1st edition; vendor material) |
| Jiahon material | “What Jiahon Can Help With”. From Jiahon product pages |
Table 1 | Sample and measuring range
| Item | Content |
|---|---|
| Alkaline error | At low hydrogen ion concentration with enough alkali metal ions, the response becomes non-linear; usually clear at pH 12 and above with lithium or sodium ions at 0.1 mol/L and above (source 1) |
| Acid error | At extremely high hydrogen ion concentration (about pH below 1) the response becomes non-linear (source 1) |
| General and special | A general-purpose electrode can be used in many situations and is not ideal for every sample; food, high or low temperature and non-aqueous solutions may need a special one (source 3) |
| Glass | General-purpose glass has a larger response over the whole pH range (source 3); for demanding work there are glasses for temperature, alkali and acid resistance (source 4) |
| Shape of sensing tip | Spherical for ordinary aqueous solutions; conical for slurry, emulsion, semi-solids, solids; flat for skin, leather, paper (source 3) |
| Micro | A micro electrode can measure down to 100 µL (source 3), 15 µL (source 4) |
Sources: 1, 3, 4
Table 2 | Electrode structure and junction
| Item | Content |
|---|---|
| Combination or separate | A combination electrode puts sensing and reference in one body and is more common now; before the 1970s the two half-cells were often sold apart (source 3) |
| Reference electrode | Often silver chloride or calomel; many meters use a combination probe (source 2) |
| Junction | Porous ceramic is common; porous PTFE is used in industry; open and sleeve types have a high flow and do not clog easily; cloth core can be refreshed; double junction clogs less easily and keeps silver-free electrolyte in contact with the sample (source 3) |
| Silver precipitation | The reference element is commonly silver and silver chloride, and silver precipitation can clog the junction; an open or diaphragm (ceramic or PTFE) junction can be chosen (source 4) |
| Body | Plastic where it is easily dropped or broken; glass for corrosive samples and high temperature (source 4) |
| Filling method | Refillable types need the liquid level kept and the fill-hole cap opened during measurement; some gel types need no refilling (source 3) |
| Temperature sensing | A probe with a built-in temperature sensor assures automatic temperature compensation (source 4) |
Sources: 2, 3, 4
Table 3 | Meter and temperature compensation
| Item | Content |
|---|---|
| High input impedance | The resistance of a glass electrode is about 50 to 500 MΩ, so a pH meter or potentiometer with high input impedance is needed (sources 1, 3) |
| Display | A pH meter is a voltmeter that displays in pH units (source 2) |
| Temperature and pH | Temperature changes affect pH; some meters take a temperature input to adjust (sources 2, 3) |
| Automatic compensation | Works quickly with samples over 10 mL; one with a built-in temperature probe compensates automatically, and one without needs a probe connected separately (source 4) |
| Manual compensation | Accurate but time-consuming, entered at every temperature change (source 4) |
| Small samples | The sensor may take too long to equilibrate and its temperature is taken as the sample temperature (source 4) |
| Need for compensation | Temperature compensation is needed to get an accurate measurement (source 3) |
Sources: 1, 2, 3, 4
Table 4 | Care, calibration and life
| Item | Content |
|---|---|
| Storage | Keep moist, soaked in the maker’s storage solution; not in pure water (reverse osmosis, deionized, distilled); a dried-out one soaked in storage solution for at least 1 hour (sources 2, 3) |
| Membrane | The membrane must not dry out (source 1) |
| Calibration points | At least two buffers covering the range; general use pH 4.00 and 10.00 (source 2); pH 7 first, then pH 4 or 10, three points for a wide range (source 4) |
| Calibration frequency | Usually before each use; for very precise work before every measurement, for general work once a day (source 2); calibrating every day is ideal (source 3) |
| Cleaning | A clean probe is the key to accuracy; after measuring, rinse with distilled or deionized water and blot dry (source 2); choose the cleaning solution by the contaminant; clean weekly, soak 15 to 20 minutes, then rehydrate and calibrate again (source 3) |
| State | Offset ±30 mV and slope 85% to 105% are normal; if the offset is still outside ±30 mV after cleaning and fresh solution, replacement may be needed (source 3) |
| Life | Average of 12 to 18 months (source 3); the slope falls within several months (source 1); equilibration time gets longer with age (source 2) |
Sources: 1, 2, 3, 4
This is the general case and still depends on the individual case.
Exceptions and limits
What was seen and not seen: this article looked at two web encyclopedia entries (edited by many people), one electrode maker’s electrode guide of the 2017 edition (vendor material, reprinted on a distributor’s site) and one maker’s pH booklet of 2012 (vendor material). The full text of a pH measurement standard was not read; the specification sheet of any Jiahon product was not read; the sources contain no standardized table of buffer values, and this article does not give one.
The numbers are examples: pH 12 and 0.1 mol/L, 50 to 500 MΩ, 10 mL, 15 and 100 µL, pH 4.00 and 10.00, ±30 mV, slope of 85% to 105%, 12 to 18 months, weekly cleaning of 15 to 20 minutes are all examples from the sources and not selection thresholds; sources 3 and 4 are makers’ recommendations.
The sources differ: on the calibration points, source 2 writes that general use takes pH 4.00 and 10.00, while source 4 writes pH 7 first and then pH 4 or 10; the text sets them side by side and picks none. On how long a buffer can be kept after opening, the two makers’ documents give different answers, and the text gives no period.
Single-source items: the classification and use of junction types, gel types needing no refilling (some), no pure water for storage, weekly cleaning, the normal ranges of offset and slope, and the average life of 12 to 18 months are in source 3 alone (vendor material); automatic temperature compensation working better over 10 mL and temperature being misread on very small samples are in source 4 alone (vendor material); the high impedance of 50 to 500 MΩ is in source 1 alone.
Sources with a standpoint: sources 3 and 4 are vendor material, and sources 1 and 2 are web encyclopedias edited by many people; none is a standard itself or a third-party test report.
This article’s own summary: the text does not use a “this article’s summary” marker, and each statement can be matched to the sources above.
Scope: this article is a selection summary; pH paper and ion-selective electrodes such as chloride are outside its scope; model comparison by maker, price and lead time are not discussed either.
Equipment and products: the numbers and statements under “What Jiahon Can Help With” are text read from the product pages on October 13, 2026; the product images were not looked at and no specification sheet was read, and they were not verified by this article; specifications follow the product pages, and for anything the product pages do not say, please inquire. The model numbers, series codes and makers’ brands on the product pages are not written here; the “also see”, selection advice, calibration advice and marketing wording of the product pages are not quoted. Some specification tables on the product pages are factory specifications and some are usage suggestions, which are not necessarily the same kind as the examples from the sources and cannot be compared directly.
This article is a summary of the general case; it is not a restatement of the clauses of a standard, not an endorsement of any maker, equipment maker or service provider, and not an assurance for your equipment and process. Take your system specification, the written specifications of the electrode and meter makers, and your own validation as the reference; this describes the general case and still depends on the individual case.