WTW SenTix HWD pH electrode with ground joint diaphragm and temperature sensor, 170 mm shaft, 1 m cable, 103731

The ground-joint sleeve of the WTW SenTix HWD is made of plastic and is fixed with a heat-shrink tube at the factory. Before commissioning, the tube is carefully removed without damaging the sleeve. The sleeve is then loosened by hand; this ground-joint electrode does not need a special key. The analogue glass electrode has a built-in NTC temperature sensor, a 1 m fixed cable and measures from 0 to 14 pH at sample temperatures ranging from -5 to 100 °C.

Ground joint diaphragm and spherical membrane

The glass shaft is 170 mm long and has a diameter of 12 mm. The membrane is spherical; according to WTW, it offers consistent measurement quality and low resistance due to its large surface area. The membrane resistance is less than 600 MΩ. The reference electrolyte is 3 mol/l KCl, Ag+-free, and can be refilled. The refill opening remains open during calibration and measurement; the electrolyte level is at least 2 cm above the sample level. For the ground joint diaphragm, the minimum immersion depth has to be observed.

Sensor, cable and plug

The NTC sensor (30 kΩ) measures the sample temperature. The cable terminates in a waterproof DIN plug (DIN 19262) and a 4 mm banana plug for the sensor. A version with S7 plug head and without sensor is the SenTix HW, although according to WTW only for 0 to 60 °C.

Typical applications according to WTW

• Low-ionic-strength media: boiler feed water, condensate, distilled and fully demineralised water
• Emulsions, suspensions and sulphide-containing liquids
• Salt solutions, cooling water, dye solutions and electroplating baths
• Seawater, surface water, rainwater and soil extract
• Beer, lemonade, fruit juice, vegetable juice, wine, mineral water, milk, coffee extract, vinegar, yoghurt, quark, honey and jam
• Hair dye, mouthwash, shampoo and household cleaners
• Enzyme solutions, gastric juice, infusion solutions, protein-containing liquids, serum, Tris buffer solutions and urine

Storage and care

For short measurement breaks, immerse the electrode in reference electrolyte (KCl 3 mol/l, Ag+-free) with the refill opening open. Overnight and for longer periods, it stays in the wetting cap, filled with reference electrolyte, with the refill opening closed. According to WTW, storing the electrode in a dry state or in deionised water can cause permanent damage. If the cap has dried out, the electrode needs at least 24 hours in reference electrolyte. As with any pH electrode, strong acids and alkalis, hydrofluoric acid, organic solvents, oils, fats and proteins shorten its service life.

Technical details

Scope of delivery

• 1 WTW SenTix HWD pH electrode with wetting cap
• Dropper bottle for refilling (included according to the WTW instructions)
• 1 m fixed cable with DIN and banana plugs, permanently attached to the electrode

Accessories and procurement service

Reference electrolyte KCl 3 mol/l and buffer solutions for calibration are also available. The procurement service can answer any questions regarding the selection of WTW ground-joint electrodes.