| 1 | Choose the right sensing technology | Glass electrode | Usually pH 0–14; response commonly about 10–30 seconds in suitable samples | Chemical compatibility, reference junction design, sample conductivity, and cleaning requirements | Use a glass electrode for general laboratory, water, wastewater, food, and process measurements where high accuracy is required. |
| 2 | Compare alternative sensors | ISFET sensor | Typically pH 0–14; fast response is possible, often around 5–15 seconds | Resistance to breakage, sample fouling, temperature range, and calibration stability | Consider ISFET technology for applications requiring a rugged, glass-free sensor, such as field testing or hygienic processing. |
| 3 | Confirm the full temperature range | Glass electrode with temperature probe | Many general-purpose probes operate from 0–100°C; exact limits vary by construction | Continuous operating limit, sterilization temperature, thermal shock resistance, and cable materials | Select a probe rated for the actual process temperature, not only the analyser display range. Check whether 0–100°C operation is continuous or intermittent. |
| 4 | Evaluate automatic temperature compensation | ATC using an integrated temperature sensor | Corrects electrode slope changes caused by temperature; it does not correct the sample's true pH-temperature relationship | Compatibility with Pt100, Pt1000, or thermistor inputs and the stated temperature accuracy | Choose integrated ATC for changing-temperature samples, but interpret results using the process-specific pH-temperature relationship. |
| 5 | Check response time in the real sample | T90 response specification | Often specified as the time to reach 90% of the final reading; clean, well-stirred water is usually faster than viscous or dirty samples | Sample flow, agitation, viscosity, suspended solids, coating, and stabilisation criteria | Request response data for the intended medium. Do not compare response times unless the same test method and T90 definition are used. |
| 6 | Review calibration and accuracy | Two- or three-point calibration with traceable buffers | Common buffer points are pH 4.01, 7.00, and 10.01; practical accuracy is often about ±0.01 to ±0.05 pH, depending on the system | Calibration reminders, slope and offset diagnostics, buffer recognition, and stability checks | Use at least two buffers that bracket the expected sample pH, and replace contaminated or expired buffer solutions. |
| 7 | Plan maintenance and international installation | Reference system, ingress protection, and service support | Replaceable glass electrodes commonly require periodic cleaning, hydration, calibration, and eventual replacement | Spare sensor availability, connector standard, power supply, IP rating, language options, and documentation | For global purchasing, prioritise documented maintenance procedures, readily available consumables, regional voltage compatibility, and long-term technical support. |