APERA INSTRUMENTS / SX620 / AI223

A slim pH tester.
Three buffers and replaceable sensing.

SX620 combines a narrow replaceable probe, temperature display and automatic calibration in a compact case. Supplied pH buffers and 3M KCl storage solution support routine testing of compatible water-based samples. Its 0.01 pH resolution makes small reading changes visible without guaranteeing that accuracy for every sample.

Choose SX620 for regular aqueous solutions and vessels that accommodate its probe. Current US kit AI223 is a standalone pH/temperature tester, not a connected meter or specialist electrode.

A narrow probe, not a universal fit

The current SX625 replacement specification gives a 10 mm probe diameter. Check your vessel opening, available immersion depth and clearance before use. The original test-tube photograph illustrates one arrangement, not a promise to fit every tube or measure a specified minimum volume. Avoid pressing the glass tip against the vessel.

Keep the meter when the probe ages

The sensing assembly is replaceable. Apera currently identifies SX625 for SX620, while the linked US manual contains an inconsistent SX615 replacement reference. Use the current SX625 compatibility listing when ordering. Replace a probe that cannot meet your response or verification requirements after appropriate cleaning and calibration; lifespan estimates are not guarantees.

pH and temperature together

The LCD shows pH, temperature and completed-calibration icons. One CAL/power button handles operations. Temperature units switch between Celsius and Fahrenheit; the tester shuts down after ten minutes without operation. The display illustration is an example, not a performance certificate.

Know what this configuration supplies.

Routine aqueous checks

Applications include compatible hydroponic solutions, pool water and aquaculture water. This tester does not measure chlorine, conductivity or dissolved oxygen; pH alone cannot establish water quality.

Small-vessel teaching

The slim form supports demonstrations of rinsing, calibration and stabilization in suitably sized vessels. Compare samples at consistent temperatures and record the conditions. The pocket-case photograph illustrates portability; actual pocket fit depends on clothing and how the case is carried.

Select chemistry before selecting range

Apera limits ordinary glass-bulb probes to general water solutions at moderate temperature. Strong acids or alkalis, organic solvents, protein-rich, viscous, turbid and low-ion samples need an appropriately selected electrode. The electronic pH range is not a chemical-compatibility guarantee.

Start at pH 7.
Use standards that bracket the work.

Rinse the probe with distilled water and gently remove excess rinse water. Immerse it in fresh pH 7.00 buffer, stir gently, then hold still until the reading stabilizes. Hold CAL for about two seconds to enter calibration. Let the automatic sequence complete before moving to another standard.

Rinse between standards. Add pH 4.00 for acidic samples, pH 10.01 for alkaline samples, or both for work spanning a broader range. The manual recommends calibration at least weekly; your procedure may require more frequent checks. No user-entered custom-buffer calibration is documented. Automatic recognition does not eliminate stabilization time or contaminated-buffer errors.

After calibration, rinse again and immerse in the sample without striking the sensing tip. Stir gently, hold still and wait for a stable result. The manufacturer specifies automatic temperature compensation over 0 to 60°C, but the current SX625 probe listing limits the probe to 0 to 50°C. Do not treat compensation as permission to exceed probe limits.

Rinse the sensor.
Store with the recommended solution.

After measurement, rinse with distilled water, gently remove excess water and replace the protective cap. The exact SX620 manual recommends a few drops of the supplied 3M KCl storage solution in the cap. Rinse water and storage solution serve different purposes; do not substitute a rinse-water bath for the specified storage routine.

For contamination, the manual describes soap-water cleaning with a soft brush, followed by distilled-water rinsing and recalibration after several hours. Handle the glass bulb gently rather than scrubbing or scraping it. Protect electrical connections during replacement. IP57 is the manual's enclosure rating, not approval for unrestricted immersion or chemical exposure.

Read the scale. Check calibration.

Use the controls only for the measurement and calibration functions documented for this exact tester. Check the displayed value, unit and any documented calibration indicator before assigning a result to a sample. Screen values in photographs are illustrative, not sample results. The model-specific record and output workflow is explained below.

Follow the exact parameter-specific calibration procedure, using the required standard, solution or calibration atmosphere. Temperature compensation does not make different sample temperatures, preparation methods or chemistry equivalent. Follow the model-specific meter and electrode instructions before extending the method to a new sample.

Read directly.
Record the sample context yourself.

No app, Bluetooth, stored-result memory or export is documented. Record sample identity, pH, temperature and calibration checks yourself. Calibration icons indicate completed points, not independent certification of a sample reading.

The manual specifies a temperature display range of 0 to 60°C, 0.1°C resolution and ±0.5°C accuracy. ATC addresses the electrode's temperature-dependent response, not every temperature-driven change in sample chemistry. Compare readings under controlled conditions rather than assuming compensation converts every sample to a common reference-temperature pH.