WTW digital IDS precision pH electrode SenTix 980, 1.5 m fixed cable, 103780

A liquid electrolyte means keeping an eye on the fill level and refilling now and then. In return, WTW cites fast response times. The WTW SenTix 980 is a digital IDS pH electrode in a glass shaft with a platinum wire junction and KCl 3 mol/l (Ag+-free) as reference electrolyte. Its calibration data is stored in the sensor. It measures from 0 to 14 pH at sample temperatures of 0 to 100 °C.

Refilling and operation

The electrode is filled at the factory. In operation, some electrolyte flows through the junction into the sample; if the level drops too far, it is topped up through the refill opening. The opening stays open during calibration and measurement. According to the WTW instructions, a dropper bottle is included: cut the tip off straight, press it into the opening and pump electrolyte into the shaft. During short measurement breaks, the electrode stands in reference electrolyte with the opening open; overnight, it stays in the wetting cap filled with it, with the refill opening closed.

Shaft, membrane and junction

The shaft is 120 mm long and has a diameter of 12 mm. The membrane is conical and, according to WTW, impact-resistant. According to the product page, the membrane resistance is below 600 MΩ. According to WTW, the platinum wire junction ensures optimum electrolyte flow without clogging. An NTC temperature sensor (30 kΩ) is built in; according to WTW, the IDS electronics measure with pH ±0.004, ±0.2 mV, ±0.1 °C (±1 digit in each case). The SenTix 950 is the plastic version with ceramic junction and temperatures up to 80 °C.

Typical applications according to WTW

• Dilute acids, salt solutions, emulsions and suspensions
• Drinking water, mineral water, lake water, surface water and seawater
• Soil extract, paper extract and coffee extract
• Beer, lemonade, fruit juice, vegetable juice, wine, milk and vinegar
• Hair dye and household cleaners
• Enzyme solutions, gastric juice, infusion solutions, protein-containing liquids, serum, Tris buffer solutions and urine (pharma, biology, medicine; application category according to WTW, not a statement on suitability for medical devices)

Cable and care

The electrode has a permanently attached 1.5 m cable with a waterproof IDS plug. It is 4.3 mm thick; according to WTW, the smallest permissible bending radius is 20 mm for fixed installation and 60 mm in flexible use. If stored dry or in deionised water, the electrode can be permanently damaged according to WTW; dried-out caps require at least 24 hours of conditioning in reference electrolyte. Strong acids and alkalis, hydrofluoric acid, organic solvents, oils, fats and proteins shorten the service life. According to WTW, salt deposits on the cap do not affect the measurement and can be removed with deionised water.

Technical details

Scope of delivery

• 1 WTW SenTix 980 pH electrode with wetting cap
• Dropper bottle for refilling (included according to the WTW instructions)
• Operating instructions
• Fixed cable 1.5 m with IDS plug, permanently attached to the electrode

Regulatory information

As an electrical device, the digital IDS electrode falls under the ElektroG. The manufacturer Xylem Analytics Germany GmbH (WTW brand) is registered under the WEEE registration number DE 29884659. How to return old appliances is described on the page Environment and disposal.

Accessories and procurement service

Also available are reference electrolyte KCl 3 mol/l for refilling and buffer solutions for calibration. Enquiries about further IDS electrodes go through the procurement service.