Digital guide
You are here:
Yokogawa PH450G-A-A/UM
Working Principle: The PH450G uses a glass electrode (for pH) or metal electrode (for ORP) combined with a reference electrode. The potential difference between the measuring electrode and reference electrode is proportional to the hydrogen ion activity (pH) or oxidation-reduction potential (ORP). The internal high-impedance amplifier converts the millivolt signal into a 4–20 mA DC output proportional to the measured value. Automatic Temperature Compensation (ATC) is performed using a built-in or external temperature sensor (Pt1000).
Detailed content
Model Breakdown:
| Code | Meaning |
|---|---|
| PH450G | 2-Wire pH/ORP Transmitter Series |
| A | Output: 4–20 mA DC (2-wire) |
| A | Configuration Code A (Standard configuration) |
| /UM | Sensor Connector: UM Type (Universal Module Connector — BNC-style with integrated temperature sensor) |
Technical Specifications:
| Parameter | Specification |
|---|---|
| Measurement Type | pH and/or ORP (Redox) |
| pH Range | -2.00 to +16.00 pH |
| ORP Range | -1500 to +1500 mV |
| pH Accuracy | ±0.05 pH (at 25°C) |
| ORP Accuracy | ±2 mV |
| Resolution | pH: 0.01 pH; ORP: 1 mV |
| Output Signal | 4–20 mA DC (2-wire, HART 5/7 compliant) |
| Temperature Compensation | Automatic (ATC) via Pt1000, Range: -5°C to +105°C |
| Operating Temperature | -5°C to +60°C (23°F to +140°F) |
| Process Temperature | 0°C to +100°C (32°F to +212°F) — standard; up to +130°C with high-temp electrode |
| Process Pressure | Maximum 0.3 MPa (43 psi) — standard; up to 0.6 MPa with high-pressure variant |
| Power Supply | 12–36 V DC (2-wire loop powered) |
| Loop Load Resistance | Maximum 600 Ω (at 24 V DC supply) |
| Protection Rating | IP67 / NEMA 4X |
| Explosion Proof | Ex d IIC T6 / Ex ia IIC T6 (available on request) |
| Communication | HART 5 / HART 7 Protocol |
| Response Time (pH) | ≤ 30 seconds (95% of step change) |
| Response Time (ORP) | ≤ 15 seconds (95% of step change) |
| Electrode Impedance | ≤ 400 MΩ (measuring electrode); ≤ 15 kΩ (reference electrode) |
| Calibration | 2-point or 3-point automatic calibration (pH 4.01/7.00/10.01 buffers) |
| Dimensions (Transmitter) | Approximately 159 × 98 × 134 mm (6.3 × 3.9 × 5.3 inches) |
| Weight (Transmitter) | Approximately 1.1 kg (2.4 lbs) |
| Certification | CE, ATEX, IECEx, FM, CSA, EAC |
Material Composition:
- Transmitter Housing: PPS (Polyphenylene Sulfide) — chemical resistant
- Sensor Connector (UM): PPS with stainless steel BNC connector
- Electrode (sold separately): SUS316L Stainless Steel body, Glass pH bulb (or Au/Pt ORP element)
- Cable Entry: PG13.5 cable gland (M20 × 1.5)
- Terminal Block: Screw-type, 2.5 mm² max wire size
Structural Features:
- Wall-mount or pipe-mount design with adjustable bracket
- UM connector allows quick sensor replacement without breaking the process seal
- Internal temperature sensor for ATC
- HART communication via 4–20 mA loop
- IP67 sealed housing — submersible in short-term immersion
Applicable Industries:
- Water & Wastewater Treatment
- Chemical & Petrochemical
- Food & Beverage
- Pharmaceutical
- Power Generation (Cooling Water, Boiler Water)
- Pulp & Paper
- Mining
Advantages & Highlights:
- 2-wire design — reduces wiring cost and simplifies installation
- UM connector — enables fast, tool-free sensor replacement
- HART communication — remote calibration, diagnostics, and configuration
- Automatic Temperature Compensation — eliminates manual temp correction
- Glass electrode (pH) provides long-term stability and accuracy
- Wide pH range (-2 to 16) covers virtually all industrial applications
Installation Requirements:
- Mount transmitter at same level or below process connection (for submersion)
- Ensure minimum 150 mm immersion depth of electrode in process fluid
- Use shielded cable for signal wiring — ground shield at transmitter end only
- Verify loop power supply ≥ 12 V DC with sufficient headroom for 600 Ω load
- Install flow-through assembly or immersion fitting for proper electrode exposure
Usage Precautions:
- Never operate with dry electrode — will permanently damage glass bulb
- Calibrate at minimum every 3 months (more frequently in dirty or high-temperature processes)
- Clean electrode regularly with appropriate cleaning solution (pH electrode: pepsin/HCl; ORP: dilute acid)
- Replace reference electrolyte every 6–12 months
- Store spare electrode with protective cap filled with KCl storage solution (3 mol/L)
- Do not exceed maximum process temperature of +100°C (standard) or +130°C (high-temp variant)
