WTW analogue precision pH electrode SenTix 91, glass shaft, 170 mm, 103695

The WTW SenTix 91 analogue precision pH electrode is an analogue combination pH electrode for pH measurement in demanding laboratory applications. Designed for use with classic analogue pH meters from the WTW inoLab and Profiline series, this glass electrode offers reliable signal transmission and high measurement accuracy.

Traditional analogue technology and integrated temperature compensation

The measured potential is transmitted via a high-quality, shielded fixed cable directly to the analogue input stage of the pH meter. A key functional feature is the 30 kOhm NTC temperature sensor integrated into the sensor head. This sensor measures the sample temperature simultaneously with the pH value, enabling the connected meter to perform automatic temperature compensation in real time. As a result, no separate temperature sensor needs to be immersed in the sample.

High-quality platinum diaphragm and refillable reference system

The materials-science-based design is optimised for precision and fast response times. The electrode features a chemically highly resistant glass shaft and a proven spherical membrane made of special glass. A liquid electrolyte (3 mol/l KCl) serves as the reference system; this can be easily topped up or completely replaced via a sealable opening at the top of the glass shaft. A standout technological feature is the integrated platinum diaphragm. This specialised diaphragm ensures a continuous and uniform flow of electrolyte without the risk of blockages, even with challenging sample media such as emulsions, suspensions or slightly viscous solutions.

Extended geometry for deep sample vessels

To ensure optimum ergonomics in everyday laboratory use, the SenTix 91 features an extended glass shaft with a total length of 170 mm. This design allows for deep, contact-free immersion in narrow-necked flasks, measuring cylinders, reactors or deep sample vessels, without the sensitive plug-in head coming into contact with the sample. The connection to the pH meter is via a permanently attached, 1-metre-long cable, which terminates in a standard DIN plug and a 4 mm banana plug. This standardised plug combination is compatible with a wide range of analogue measuring stations.

Technical details

Measurement & sensor technology

• Sensor type: Analogue pH combination electrode
• Model: SenTix 91
• pH measurement range: 0 to 14 pH
• Temperature element: Integrated NTC 30 kOhm temperature sensor
• Operating temperature range: 0 to 100 °C

Construction & dimensions

• Shaft material: Highly chemically resistant glass shaft
• Membrane shape: High-quality spherical membrane
• Electrolyte: Liquid electrolyte (3 mol/l KCl, refillable)
• Diaphragm: Reliable platinum diaphragm
• Shaft length: 170 mm (extended version)
• Shaft diameter: 12 mm
• Connection type: Fixed cable, length 1.0 m
• Connector combination: DIN plug (for pH) and 4 mm banana plug (for temperature)

Operating conditions

• Maintenance: Refillable (KCl solution replaceable)
• Main applications: Demanding laboratory measurements, deep vessels, chemical analysis, difficult sample media, general aqueous media

Scope of delivery

• 1 x WTW SenTix 91 analogue pH glass electrode with 1 m fixed cable (MPN: 103695)
• 1 x wetting cap with original storage solution
• 1 x dropper bottle with refill electrolyte (3 mol/l KCl)

Important note: pH buffer solutions for regular calibration and the analogue pH meter itself are not included as standard and must be configured separately.

Individual requirements & accessories

To ensure consistently high measurement accuracy of the WTW SenTix 91, regular calibration of the measuring station is recommended. Our range includes WTW technical buffer solutions in practical dosing bottles (pH 4.01, pH 7.00 and pH 10.01). For the proper care and storage of the pH-sensitive glass membrane during measurement breaks, we recommend the use of the original 3 mol/l KCl storage solution. Should the electrode ever become contaminated with stubborn sample residues during the rigours of everyday laboratory work, we offer special cleaning concentrates for gentle regeneration. Please make use of our technical procurement service when putting together your laboratory equipment.