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pH Miniprobe

  • Optical pH sensor
  • Sensor tip only 3mm in diameter
  • Original REDFLASH-technology
  • No need of reference electrode
  • Minimal cross-sensitivity to ionic strength
  • Stainless steel
  • For long-term measurements
  • For small amounts of stirred liquid

This pH miniprobe is based on a unique optical detection principle (REDFLASH technology) and provides a viable alternative to traditional pH measurement devices such as electrodes. The REDFLASH technology utilized red excitation light and uses the NIR emission of the new pH sensor to overcome background fluorescence of the sample which was already successfully applied for our optical oxygen sensors.

The sensor tip is enclosed by a stainless steel tube 3 mm in diameter and 100 mm in length. Other lengths are available on request. The complete sensor tip including its cabling can be submersed into water. The sensing tip has an optical isolation protecting the pH measurement from disturbance by e.g. external illumination or strong luminescent samples.

Different pH ranges. Optical pH sensors work over a confined pH range (2 pH units) at high resolution. We offer sensors for two different ranges for pH measurements between pH 6.0 to 8.0 and pH 7.0 to 9.0. Our pH sensors were especially designed for minimal cross sensitivity to ionic strength and the outstanding photostability of the new sensors enable high sampling rates over long periods. 

Typical Applications

  • General measurements in liquids
  • (Micro)Bioreactors
  • Aquaculture
  • Oceanography
  • Profiling in water

Compatible oxygen meters

FireSting pro (FSPRO-x)

Available Sensors

Item No. Description
(Tip Diameter / Length)
in EU*
PHROB-PK7 pH miniprobe for
pH measurements between pH 6.0 - 8.0
(3mm / 100mm), 2m cable
240 €
PHROB-PK8 pH miniprobe for
pH measurements between pH 7.0 - 9.0
(3mm / 100mm), 2m cable
240 €


Item No. Description Pricing
in EU*
PHCAL4 Buffer capsules for 100ml buffer (pH 4.01), PU = 10 capsules, for calibration of optical pH sensors 44 €
PHCAL10 Buffer capsules for 100ml buffer (pH 10.00), PU = 10 capsules, for calibration of optical pH sensors 44 €

* Only EU-Prices shown. Contact us for pricing outside EU. Not for resale.


Item No. Extension Description Extra Charge
-TLx Optional tip length of x mm of the stainless steel tube (instead of standard 100mm tip length) add 30 €
-CL1 Optional cable length of 1 m (instead of standard 2 m cable length) add 30 €


Given for 2-point calibrated pH sensors (pH 4.0 and 10.0) in physiological solutions at 25°C.

PK7 - Version pH
Optimum measuring range 6.0 - 8.0
Resolution at pH 7.0 0.005
Accuracy at pH 7.0 +-0.05
Drift at pH 7.0 <0.005 / day
PK8 - Version pH
Optimum measuring range 7.0 - 9.0
Resolution at pH 8.0 0.005
Accuracy at pH 8.0 +-0.05
Drift at pH 8.0 <0.005 / day
All versions
Temperature range 5 to 50°C
Photostability Negligible photodegradation
Response time t90 < 60 sec. at 25°C
Interferences Surfactant solutions, organic solvents or commercial buffer solutions (typically contain stabilizer) must not be used
Salinity Compensation of ionic strength (IS) for different application areas (10 mM – 500mM IS) possible
Background fluorescence Minimized due to REDFLASH technology
Cleaning Rinsing with deion. water only
Storage time Original packaging (unpacked) 12 months at room temperature
Calibration 2-point calibration, pH offset adjustment possible
Calibration solution PyroScience buffer capsules or a self-made buffer must be used. Important: other pH buffers must not be used and can damage the sensor irreversibly
Optical isolation The sensor is equipped with an optical isolation to minimize interference from strong external illumination and light-sensitive / fluorescent samples
Connector ST-plug
Cable length 2 m