pH meter with automatic calibration function

A pH meter that achieves a reduction in maintenance workload.

The AH-151 pH meter with an automatic calibration function conducts pH measurements, performing chemical cleaning of electrodes and standard solution calibration automatically, enabling significant reduction in maintenance workload. Additionally, by atomizing the calibration solution, the amount used is reduced. The spray volume of the solution can also be adjusted according to the degree of contamination, contributing to cost reduction.


Division: Process Water
Manufacturing Company: HORIBA Advanced Techno Co., Ltd.

Reduction of maintenance workload

A significant reduction of maintenance workload becomes possible by automatically performing electrode cleaning and standard solution calibration, as well as conducting pH measurements.

Reduction in running costs

By atomizing the calibration solution, the amount of solution used has been reduced to 1/5 or less compared to our existing products. *
*with new pH electrodes in use.

Enhanced self-diagnostic functions

Equipped with self-diagnostic functions for detecting measurement anomalies and sensor degradation, enabling prompt response to abnormalities in electrodes and equipment.

Easy operation with a color touch LCD panel

Improved visibility and operability with a 5.7-inch touch panel.  Electrode characteristics during automatic calibration are automatically graphed, making electrode lifespan assessment easy.

Simplified installation through unit delivery

Installation is easy because all parts except for the mounting bracket and the lifting unit are integrated into a single unit.

Product name

pH meter with automatic calibration function


AH-151-CH (dip type), -CF (flow-through type), -FK (water sampling type)

Measuring method

Glass electrode method

Measuring range

pH: 0 to 14    Resolution: 0.01 pH
Temperature: 0 to 100°C    Resolution: 0.1 degree C

Display unit

Touch panel (TFT color LCD)


pH: within ±0.02 pH, Temperature: ±0.3°C (Equivalent input)


pH: within ±0.03 pH, Temperature: ±0.3°C (Equivalent input)

Transmission output

Number of output points: 2, Output form: 4 to 20 mA DC input/output insulation type, Load resistance: Maximum 900 Ω
Output range 1: pH: Can be arbitrarily set within the measuring range
Output range 2: Temperature: Can be arbitrarily set within the range of -10 to 110°C
Hold function: Can be arbitrarily set by selecting from “last value hold,” “any value hold,” and “without hold”

Contact output

Number of output points: 9 and 1 (abnormality alarm), Output form: No-voltage contact output,
Alarm details: Calibration errors (asymmetric potential abnormality, sensitivity abnormality, response time abnormality), electrode abnormalities (glass response membrane crack, short circuiting of temperature sensor, disconnection of temperature sensor), abnormalities of converter (CPU abnormality, ADC abnormality, memory abnormality), shortage of cleaning solution, shortage of calibration solution

Cleaning interval

0.1 to 168.0 hours, Month, day and time of start of next cleaning can be set, Cleaning time: Approx. 2 minutes (default setting)

Calibration interval

1 to 999 hours, Month, day and time of start of next calibration can be set, Calibration time: Approx. 5 minutes (default setting when pH electrode is new)

Contact input

Number of input points: 3, Contact: No-voltage “a” contact for open collector, Contact function: External commands for cleaning performance (automatic cleaning start, automatic calibration start, stand-by commands)

Communication capability

RS-485 two-wire system, Input/output insulation type (not insulated from transmission output)

Combined electrode

Glass electrode 6108

Calibration method

Automatic calibration (lift-up type calibration with standard solution spray) or manual calibration

Cleaning method

Lift-up type cleaning with cleaning solution


Calibration error, Electrode check, System error

Sample conditions

Pressure: Atmospheric pressure, Temperature: -5 to 80°C, Flow velocity: 2 m/sec or less, Flow rate: 10 L/min or less (only for flow-through type), Conductivity: 10 mS/m (100 μS/cm) or more

pH standard solution

Two solutions (pH7 and pH4 or pH9), Consumption: Approx. 30 to 40 mL/min (max. 200 mL/calibration), Capacity: PE tank 3 L (calibration approx. 15 to 50 times possible)

Cleaning chemical

HCI: less than 5 to 10%, Consumption: Approx. 50 mL/cleaning (approx. 75,100 mL/cleaning, adjustable)  Capacity: PE tank 20 L (cleaning approx. 300 times possible, using 50 mL each time)

Water supply

Water quality: Tap water equivalent (industrial water possible), Pressure: 0.2 to 0.75 MPa, Consumption: 10 to 20 L/cleaning, calibration one time (in case of default setting for cleaning time)

Air supply

Air quality: Instrument air, Pressure: 0.3 to 0.7 MPa, Consumption: 10 to 15 L/min


Supply water: Rc1/2, Air: Rc1/4

Cable gland

8 cable glands for φ7 to φ12 (without cable gland, φ21.5 hole)

Operating temperature range

0 to 50°C (no condensation)

Power supply

Voltage range: 100 to 240V AC ±10%, 50/60 Hz, Power consumption: 100V AC, approx. 20 W during steady state and approx. 35 W during auto-calibration


Outdoor setting type: JIS C0920 explosion/splash-proof type (IP54 equivalent), Material of control unit case: SPCC (coated with melamine-based epoxy resin), Metal fittings: SUS304, Stand: SUS304


Operation unit & pole stand: Approx. 60 kg, Metal fittings: Approx. 3 kg, Lifting unit (dip type): Approx. 1.5 kg (except for dip-type holder)

Note: Although a surge arrester (discharge starting voltage: 400V) is installed for transmission output, contact input and communications, please install an appropriate surge absorber on the connecting line, according to the surrounding  environment, equipment installation condition, peripheral equipment, etc.




AH-151  AH-151  AH-151-CH (Dip type)

AH-151-CF (Flow-through type)  AH-151-FK (Water sampling type)



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