pH Sensors / CS525-L
This product is no longer available and has been replaced by: CS526-L. Some accessories, replacement parts, or services may still be available.
CS525-L ISFET pH Probe
More Durable, Safer
Elimination of glass bulb allows longer time in field
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications


Campbell Scientific’s CS525 pH probe provides reliable, accurate pH measurements that are fully temperature compensated. This probe makes general pH measurements in aqueous or semi-solid solutions, and can be submersed or inserted into tanks, pipelines, and open channels.

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Benefits and Features

  • Compatible with the CWS900-series interfaces, allowing it to be used in a wireless sensor network
  • Electronics are safely embedded in a durable resin body
  • Elimination of the glass-bulb makes the probe more durable and safer to use
  • Fully temperature-compensated
  • Innovative ISFET pH-sensing element used as measurement electrode
  • Designed and manufactured under stringent quality control conditions in an ISO 9001 environment, ensuring good measurements
  • Each sensor individually tested
  • Compatible with all contemporary dataloggers (including the CR200X series)

The "-L" on a product model indicates that the cable length is specified at the time of order.


Detailed Description

The CS525 uses SENTRON’s high-tech, Ion Sensitive Field Effect Transistor (ISFET) semi-conductor as its pH-sensitive element, and includes a silver/silver chloride-potassium chloride reference system. The ISFET technology is the most powerful pH monitoring technology available today. This technology considerably reduces the number of acidic or alkaline errors in extreme pH conditions. It allows the CS525 to monitor pH in liquids containing high solids, aggressive chemicals, or biological materials that would clog or contaminate the junction of the traditional glass-bulb pH probes.

The CS525’s rugged design makes it suitable for just about any liquid pH-monitoring application, from laboratory to harsh field applications. The probe’s electronics are safely embedded in a durable PEEK body. Elimination of the glass-bulb removes the possibility of broken glass, making the CS525 more durable and safer to use.

Note: The CS525-L ISFET pH Sensor is highly susceptible to ground looping and galvanic conditions. The best isolation technique to overcome these issues is to use a CWS900-series Wireless Sensor Interface. In many cases, the CS525 can also be isolated by NOT grounding the datalogger to an earth ground. Please discuss your application with Campbell Scientific before purchasing the sensor.


CE Compliance CE Compliant
pH Range 0 to 14
Power Requirements 4.5 to 5.5 Vdc
Current Consumption 2 mA (nominal)
Measurement Time 200 ms < 67% < 500 ms
Accuracy ±0.1 pH (with two-point calibration)
Operating Temperature 0° to 70°C
Allowed Water Pressure 0 to 30 kPa (0 to 45 psi)
Cable Type Two-twisted pair, 22 AWG cable with Santoprene jacket
Sensor Material Polyaryletheretherketone (PEEK)
Diameter 16 mm (0.63 in.)
Maximum Cable Length 300 m (1000 ft)
Length 190 mm (7.48 in.)
Weight 318 g (11.2 oz) with 3.05-m (10-ft) cable


-NOTE- Output range used depends on which wires are connected to the datalogger.
Range A
  • 0 to 5000 mV
  • +2700 mV at pH7 and 25°C with a sensitivity of 270 mV to 330 mV/pH at 25°C
Range B ±400 mV with a sensitivity of -45 mV to -50 mV/pH at 25°C


Datalogger Considerations

Compatible Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR5000 CR7X CR9000X

*The CR200(X)-series dataloggers require the VDIV2:1 2-to-1 Voltage Divider; contact Campbell Scientific about using this sensor with a retired datalogger.