WTW SenTix ORP Redox Electrode with Platinum Sensing Element, Liquid Electrolyte, S7 Connector, 103648

The SenTix ORP from WTW is a redox electrode with a platinum measuring element for laboratory use. The measuring element is a platinum disc with a diameter of 4 mm; the shaft is made of glass. The reference system is Ag/AgCl in 3 mol/l KCl (Ag⁺-free), which can be refilled. The electrode does not have a temperature sensor and is supplied without a connection cable.

Configuration of the redox measurement chain

The potential between the platinum disc and the Ag/AgCl reference system is measured. A ceramic diaphragm is situated between the reference electrolyte and the sample. The electrode is 120 mm long with a shaft diameter of 12 mm and is approved for use between 0 and 100 °C. It is supplied with a water-sealing cap fitted, which is also used for storage.

S7 plug head and connection cable

The connector is an S7 plug; the cable is supplied separately. The input on the measuring instrument determines which cable is suitable: S7/DIN 1 m (item no. 108110), S7/DIN 3 m (item no. 108112) or S7/BNC 1 m (item no. 108114). These same cables are also used with pH electrodes featuring an S7 connector, such as the SenTix 60.

Converting measured values to the standard hydrogen electrode

The meter displays the voltage relative to the Ag/AgCl system. To reference the standard hydrogen electrode, UH = UMeas + URef. URef depends on the temperature and, for the SenTix ORP, is, for example, +224 mV at 0 °C, +207 mV at 25 °C and +180 mV at 60 °C. The full table can be found in the operating instructions; see also DIN 38404-6. As the electrode does not have its own temperature sensor, the sample temperature must be known separately.

Refilling, Storage, Cleaning

During measurement, the refill opening must be open, and the electrolyte level should be at least 2 cm above the level of the sample. If the level drops, top up with KCl-250 (item no. 109705), for example using a dropper bottle. During short breaks in measurement, the measuring chain should be left standing in the reference electrolyte; overnight, it should be placed in the filled wetting cap with the refill opening closed. Grease and oil can be removed with water containing washing-up liquid; limescale and hydroxide deposits with 10 per cent citric acid; and proteins with the pepsin cleaning solution PEP/pH (item no. 109648) for about an hour. Redox measuring chains are consumables. Strong acids and alkalis, hydrofluoric acid, organic solvents, oils, fats, bromides, sulphides, iodides, proteins, high temperatures and sharp changes in temperature or pH shorten their service life.

Typical applications

• Redox measurement in the laboratory (ORP measurement) in aqueous samples up to 100 °C
• Checking the measuring chain with redox buffer solution RH 28 (UH = 427 mV, 250 ml, item no. 109740)

For argentometry, the same series includes the SenTix Ag with a silver measuring element and a different electrolyte (KNO3 with a small amount of KCl). Those measuring redox potentials use the ORP with platinum. For argentometry, the Ag is used.

Technical details

Scope of delivery

• 1 WTW SenTix ORP redox electrode with irrigation cap

The scope of delivery does not include connection cables, which must be ordered separately.

Individual requirements and procurement service

Connection cables in the required length, reference electrolyte, redox buffer solution, cleaning solution or the STH 650 bench stand (item no. 109809): You can enquire about these items together with the electrode via lt-laborhandel.com/service. The procurement service will also clarify whether ORP or Ag is suitable for the measurement task.