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POM body, open junction. Built for wastewater.
APERA INSTRUMENTS / LABSEN 331 · 333 · 335 / AI3131 / AI3133 / AI3231
LabSen 331, 333 and 335 are non-refillable pH electrodes with a corrosion-resistant POM body, made for wastewater, emulsions, suspensions and other complex solutions that clog regular electrodes. The 331 is a BNC combination electrode, the 333 adds a temperature sensor with BNC/RCA plugs, and the 335 is the 8-pin pH/temperature version for Apera’s PH60/PH60-Z testers with the compatible 8-pin adapter/socket installed.
It reads pH 0 to 13 from 0 to 80°C. Choose the version that matches your meter’s connector from the menu above. Apera warrants LabSen electrodes for six months from delivery.
Only published products are linked. Other cards provide model-comparison information and do not indicate current storefront availability.
Start with your sample. Each card opens an electrode family; on that page, pick BNC, BNC/RCA pH/temperature or 8-pin to match your meter.
AI3101 / AI3121
General water, TRIS buffers
Refillable everyday glass electrode; BNC or BNC/RCA pH/temp.
AI3102 / AI3123
Titration, low ionic strength
Movable sleeve junction: easy to clean, adjustable flow.
AI3111
Wastewater, suspensions
Glass body, open junction and polymer electrolyte.
AI3131 / AI3133 / AI3231
Wastewater, harsh environments
Corrosion-resistant POM body, open junction; BNC, BNC/RCA or 8-pin.
AI3107 / AI3172
Skin, textiles, paper, leather
Flat glass membrane and PTFE ring junction.
AI3108 / AI3137 / AI3233
Pure, DI and RO water
L-type low-resistance glass (<50 MΩ) for low-ionic water.
AI3149
Cold samples to −25°C
L-type conical glass and Protelyte for −25 to 80°C.
BNC versions plug into any pH meter with a BNC input. They have no temperature sensor, so pair them with a separate temperature probe such as Apera’s MP500 where compatible with the meter, for automatic temperature compensation; manual temperature entry is an option only if the meter supports it at the sample temperature. Electrode ratings do not extend the meter’s or separate temperature probe’s operating or compensation limits.
BNC/RCA versions carry a built-in 30 kΩ NTC temperature sensor on an RCA plug for automatic temperature compensation on Apera meters with BNC and RCA inputs, such as the PH700, PH850, PH8500, PH820, PH910 and PH9500. Apera notes they may not work with other brands’ meters because the thermistor might not be compatible.
The 8-pin version is a pH/temperature electrode for Apera meters with an 8-pin socket, including the PH60, PH60-Z, PH400, PH400S and the PC400, PC400S, SX736 and SX751.
PH60/PH60-Z testers require the compatible 60/60-Z-series 8-pin connection adapter/socket to be installed; a standard tester is not a direct plug-in host. Confirm adapter inclusion before ordering. The electrode’s temperature rating does not expand the connected meter’s measurement or compensation range.
Highly resistant to corrosion and suited to harsh environments, per Apera.
Solids have no ceramic pores to block, and there is no electrolyte to refill.
Stable reference potential and long service life, with blue gel inner electrolyte.
All versions share: pH range 0–13; temperature range 0–80°C; body POM; junction open; reference electrolyte polymer.
Dimensions: 331 Ø12 × 120 mm; 333 Ø12 × 120 mm; 335 Ø12 × 115 mm.
The full specification table is in the Product Specifications tab.
Keep the tip in its cap with 3M KCl storage solution whenever it is not measuring.
Never store a pH electrode in pure, deionized or distilled water.
The 331, 333 and 335 are sealed and need no refilling.
Apera’s manual advises avoiding strong acids, strong alkalis and dehydrating media such as absolute ethanol or concentrated sulfuric acid; if exposure is unavoidable, keep immersion short and clean the electrode carefully afterward.
Rinse with distilled or deionized water between samples. For stubborn deposits, use Apera electrode cleaning solution, then recondition and recalibrate.
Apera ships this electrode in these kits: PH700-WW (LabSen 333), PH8500-WW (LabSen 333), PH850-WW (LabSen 333), PH60-WW (LabSen 335), PH60Z-WW (LabSen 335).
Calibrate with fresh pH 7.00, pH 4.00 and pH 10.01 buffers.
LabSen 331, 333 and 335 are non-refillable pH electrodes with a corrosion-resistant POM body, made for wastewater, emulsions, suspensions and other complex solutions that clog regular electrodes.
LabSen 331 (AI3131) is BNC with no temperature sensor; 333 (AI3133) adds a 30 kΩ NTC sensor on BNC/RCA. LabSen 335 (AI3231) is 8-pin for compatible Apera meters; PH60/PH60-Z require an installed 60/60-Z adapter/socket. Confirm inclusion before ordering.
The pH signal is standard BNC, but Apera notes the temperature thermistor may not be compatible with other brands’ meters. Use it on Apera meters with BNC and RCA inputs.
No; it is sealed and needs no refilling.
Keep the tip in its cap with 3M KCl storage solution whenever it is not measuring. Never use pure, deionized or distilled water.
Current US pages specify POM bodies, pH 0–13 and 0–80°C for 331/333/335. Older 331/333 manual tables contain conflicting glass-body or pH 0–14 entries. This offer retains the current US specifications; do not use an older table to expand them or treat the 331 manual as a 335 installation guide.
No. The 331/333/335 body is corrosion-resistant, but that is not universal chemical resistance. Follow the model instructions, avoid strong acids, strong alkalis and dehydrating media, and rinse and clean after use. Store in 3M KCl, not pure water.
Apera warrants LabSen electrodes against defects in material and workmanship for six months from delivery. Accidental damage, improper use and normal wear are excluded.
Check the version, connector and catalog number (AI3131 / AI3133 / AI3231) against your meter and samples, then return to the live price and ordering controls.
APERA INSTRUMENTS, LLC warrants LabSen electrodes to be free from defects in material and workmanship for SIX MONTHS from the delivery.
This limited warranty does NOT cover accidental damage, improper use, normal wear and tear, transportation, storage, failure to follow the product instructions, unauthorized maintenance, modification or repair, or external causes beyond Apera's reasonable control.
Official Apera documents are labeled by model and scope below. Each whole card opens a PDF in a new tab.
Document scope and limits. Document discrepancy: the linked 331 v2.0 manual’s narrative describes POM, but its table says lead-free glass and pH 0–14. Current US 331/333/335 pages specify POM and pH 0–13; those narrower, current specifications are retained here. The 331 manual is not a 333 BNC/RCA or 335 8-pin installation guide. PH60/PH60-Z require the installed 60/60-Z adapter/socket for 335; confirm inclusion. Corrected model-specific 333/335 documentation should be obtained before relying on older conflicting tables.
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