PH485 probes with RS485 / ModbusRTU output

pH sonda s výstupem RS485 / Modbus RTU


  • Reliable and accurate pH measurement without additional transducers and other electronics
  • Basic element for creating RS485 sensor network for PLCs, data loggers and online IoT systems (Lora, Sigfox, NB)
  • Calibration coefficients stored in the probe
  • Measuring ranges 0 to 13 pH; -10 to +60 ° C
  • Self-cleaning design of the reference electrode
  • Service life 2 to 3 years with extended recalibration interval (typically 1 year)
  • Automatic temperature compensation
  • Galvanically separated communication and power supply circuits from the pH electrode itself
  • Wide supply voltage range from 5 to 24 V DC, low current consumption
  • Low purchase price

Variant design of probes for measuring redox potential (ORP485) and voltage of ion-selective electrodes (ISE485)

Basic description

The PH485 probe combines into one compact unit a combined pH electrode with partial self-cleaning ability and extended service life with measuring electronics controlled by a microprocessor.

In order not to influence the measured quantity by the action of earth currents and induced interference potentials, the measuring circuit, including the electrode itself, is galvanically separated from the communication and power supply cable of the probe.

The self-cleaning design of the used electrode ensures a stable and reproducible signal even in the environment of emulsions, suspensions and other adhering impurities of various origins as well as impurities caused by a chemical reaction. The electrode thus largely eliminates, for example, the negative effect of rust, hard water (Ca, Mg compounds in both carbonate and sulfate forms), oil emulsions, adhering organic and inorganic impurities.

Typical use

The compact "smart" probe PH485 with digital data output and calibration coefficients stored in the probe represents a modern solution for accurate and cost-effective online pH measurement in many water supply industries:

  • Water treatment plants and wastewater treatment plants
  • Chemical and food industry
  • Agriculture
  • Research and development projects
  • Environmental monitoring


pH sonda s výstupem RS485 / Modbus RTUElectronic probe circuits

The PH485 probe contains measuring electronics in its body, which, among other things, also performs automatic temperature compensation of the measured pH value and transmits the measured values to the connected superior system via the RS485 bus.

In order not to influence the measured quantity by the action of earth currents and induced interfering potentials into the probe supply line, the measuring circuit inside the probe, including the electrode itself, is galvanically separated from the probe communication and supply cable.

Modbus RTU on RS485

The probe output signal uses the widely used RS485 bus under the Modbus RTU protocol. Via this bus, the probes can be connected at a distance of up to 500 m directly to the control system or to the data logger. In addition to the temperature-compensated pH value, the electrode voltage in mV and the measured temperature can also be obtained from the probe.

The four-core connection and power cable allows easy creation of a sensor network thanks to the possibility of addressing each probe. Thus, several probes of one type or several similar probes for monitoring several quantities can be connected to one RS485 bus - eg ORP485 probes for redox potential measurement or ISE485 type probes for ion-selective electrode potential measurement.

The PH485 probes can also be recalibrated via the RS485 communication bus. The calibration coefficients stored in the probe allow the probes to be recalibrated in the laboratory, and in the field all you have to do is connect the probe to the measuring network.

Mechanical design

The PH485 probe body contains a G 3/4" mounting thread on the electrode side (for mounting the probe in the piping system) and on the cable outlet side (mounting the probe in a holder or sensor).


pH sonda s výstupem RS485 / Modbus RTU
The M12 connector-terminated cable on the PH485-KxM12 probe facilitates mounting of the probe in the TS500 rod sensor (TS1700) and allows for quick probe calibration or easy end-of-life replacement.


Electrode cap KE145

Plastic electrode cap for PH485 probes. The cap is made of a hard and smooth POM tube with an outer diameter of 33 mm and has a length of 145 mm. At one end, the cap has a 3/4" female thread.

iontově selektivní elektrody - amoniová, chloridová

TS500 and TS1700 holders

Stainless steel rod holders are designed for mechanical placement of the PH485 probe in the required location. The holder is available in lengths of 500 mm or 1700 mm - a holder of another non-standard length can be supplied on request.

iontově selektivní elektrody - amoniová, chloridová

Rod holder TS500 equipped with a cable gland and mounted in the holder DE2

At the lower end of the holder there is a G3 / 4" internal thread for screwing on the PH485 probe and at the upper end there is a connector reduction M12 / 4F to M12 / 4M. The lower internal connector inside the M12 / 4F sensor is intended for the connection of a probe of the PH485-K2M12 type (ie a probe with a 2 m long cable terminated with an M12 / 4M connector).

Alternatively, a sensor can be supplied with a simple cable gland at the upper end for routing the cable from the PH485-xM probe (free end of the connecting cable with a length of x).


Holder DE2

An adjustable stainless steel holder DE2 can be ordered for the TS500 or TS1700 holder. It can be fastened to a railing or other vertical structure using brackets. It can also be mounted on a wall or other vertical work surface above the measured object.

The adjustable inclination of the DE2 holder allows, by extending the rod holder, to place the measuring electrode exactly at the required measuring point of the activation tank, the sump or in the open flow profile.

Držák pro snímač ISE485

DE2 holder designed for mounting the TS500 or TS1700 rod holder


pH electrode: combined self-cleaning, gel electrolyte, increased mechanical resistance

pH measuring range: 1.00 to 13.00 pH

Measurement accuracy: ± 0.1 pH

Measuring temperature range: -5.0° C to +60.0° C

Measurement accuracy: ± 0.5° C

Measuring range mV: -1000.0 to +1000.0 mV

Measurement accuracy: ± 2 mV

New probe rise time: <10 sec

Typical recalibration interval: 1 year

PH485-K connection: PUR cable 4x0.34; length 3 m, terminated with sockets without connector

PH485-M12 connection: M12 connector, 4 pins (male), IP67
Interface: RS485, Modbus RTU protocol

Galvanic isolation: 500 V between cable / connector and measuring electrode

Supply voltage: 5 to 24 V DC

Current consumption: <20 mA

Shelf life: 2 to 3 years depending on the composition of the measured medium

Storage temperature: 0 ° C to 60 ° C

Maximum working pressure: 1 bar (up to 10 bar in agreement with the manufacturer)

Dimensions: largest diameter 40 mm, length 170 mm (other electrode lengths can be supplied)

Housing mounting thread: G 3/4”

Case material: POM

Weight including cable: 100 g

Protection: IP68 (PH485-K), IP67 (PH485-M12)


Price list