HP-300, Field-Installation Type pH Meter HP-300, HORIBA

The HP-300 is a 2-wire loop-powered field-installation type pH transmitter from HORIBA, designed for straightforward continuous pH monitoring in industrial and environmental applications. Unlike 4-wire instruments, the HP-300 draws its operating power directly from the 4–20 mA signal loop, eliminating the need for a separate AC power supply and simplifying cable routing and installation costs. The instrument is part of HORIBA's long-selling H-1 Series and benefits from the same broad lineup of compatible glass electrodes and cleaning devices — including ultrasonic cleaners that require no water or air supply — making it equally suited to new installations and retrofits. The reflective monochrome LCD provides clear reading in direct sunlight, while the IP65-rated aluminium alloy housing with SUS304 stainless steel fittings ensures reliable outdoor operation across harsh industrial environments.

Key Features HP-300

• 2-wire loop-powered design: powered from the 4–20 mA signal loop (24 V DC, 0.6 W max.) — no separate AC supply required, simplified wiring and installation.
• pH measurement range pH 0 to 14 (display pH −1 to 15); resolution 0.01 pH; repeatability and linearity within ±0.03 pH.
• Single isolated 4–20 mA DC transmission output; max. load resistance 600 Ω at 24 V DC (load-voltage curve available); linearity and repeatability within ±0.08 mA.
• Automatic temperature compensation over 0–100 °C; supports Pt 1 kΩ and multiple NTC thermistors; sensor type detected automatically or set manually.
• 1, 2, or 3-point auto or manual calibration using pH 2, 4, 7, 9, and 10 standard solutions; automatic detection of solution type and potential stability; calibration history stored.
• Comprehensive self-diagnostics: glass membrane cracking, reference electrode impedance error, temperature sensor faults, CPU/ADC/EEPROM errors.
• IP65 protection (IEC60529 / JIS C0920); pole (50 A) or wall mount; aluminium alloy housing, SUS304 stainless steel fittings and hood.
• CE marked: EMC EN61326-1 Class A, RoHS EN50581; FCC Part 15 Class A.

Applications

The HP-300 is well suited to continuous pH monitoring in industrial process water, municipal and industrial wastewater treatment, drinking water facilities, environmental water monitoring, and any application where simplified 2-wire installation is preferred. Its compatibility with the full HORIBA electrode and cleaner lineup allows adaptation to a wide variety of sample conditions.

Installation and Safety Notes

Power the HP-300 from a 24 V DC source (operating range 21–32 V DC) via the 4–20 mA signal loop. Maximum load resistance depends on supply voltage — consult the power supply voltage vs. load resistance curve in the product documentation. When sensor, transmission, or contact input cables are extended by 30 m or more, additional surge absorption elements must be fitted on all connection lines; the CE marking surge test does not apply to such extended runs. An internal arrester (spark-over voltage 400 V) is provided for transmission output and contact input terminals. Operating temperature: −20 to 60 °C; storage: −25 to 65 °C; humidity: 5–90% RH non-condensing.

Technical Specifications