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YOKOGAWA PH150-AS-AA
Product Introduction:
The PH150-AS-AA is a compact 2-wire pH/ORP transmitter from Yokogawa designed for continuous measurement of pH and ORP (Oxidation-Reduction Potential) in industrial process environments. The AS option indicates compatibility with analytical sensors featuring built-in automatic temperature compensation (ATC). The AA suffix denotes specific output and configuration settings.
Detailed content
Technical Specifications:
| Parameter | Value |
|---|---|
| Measurement Range (pH) | -2.00 to 16.00 pH |
| Measurement Range (ORP) | ±1500 mV |
| Accuracy (pH) | ±0.005 pH |
| Accuracy (ORP) | ±1 mV |
| Temperature Compensation | Automatic (ATC), -5°C to 105°C |
| Output Signal | 4–20 mA DC (2-wire) |
| Supply Voltage | 12–42 V DC |
| Response Time (pH) | ≤ 30 seconds (95% of final value) |
| Response Time (ORP) | ≤ 15 seconds (95% of final value) |
| Operating Temperature | -10°C to +60°C |
| Protection Rating | IP67 (NEMA 4X) |
| Process Connection | 1/2″ NPT / DIN 11851 (tri-clamp) |
| Materials (Wetted Parts) | PPS (Polyphenylene Sulfide) / PTFE |
| Certifications | ATEX Zone 1/2, IECEx, FM, CSA |
| Option AS | Analytical sensor with ATC (Automatic Temperature Compensation) |
| Option AA | Standard output configuration, 4–20 mA with HART |
Functional Features:
- 2-wire loop-powered operation — no separate power supply needed
- Built-in automatic temperature compensation (ATC) eliminates need for separate temperature sensor
- HART 7 protocol communication for remote configuration, calibration, and diagnostics
- Dual-measurement capability: pH and ORP selectable via configuration
- Self-diagnostic functions: electrode impedance check, sensor life indicator, signal quality monitoring
- Two-point or multi-point calibration with automatic buffer recognition (USA, NIST, DIN)
Material Composition:
- Sensor Body: PPS (Polyphenylene Sulfide) — chemically resistant to acids, bases, and solvents
- Electrode: Glass pH electrode with Ag/AgCl reference (gel or liquid junction)
- Cable: PVC jacket, 5 m standard length (extendable to 50 m)
- Housing: PPS with PTFE O-ring seals
Structural Features:
- Compact immersion-type design — total length approx. 190 mm
- 1/2″ NPT thread process connection with optional tri-clamp adapter
- Integral DIN rail mount bracket included for panel mounting
- LED indicator for status and calibration prompts
Working Principle:
The pH electrode generates a millivolt signal proportional to hydrogen ion activity (Nernst equation: 59.16 mV/pH at 25°C). The ORP electrode measures the redox potential difference between a platinum/gold sensing electrode and an Ag/AgCl reference. The ATC sensor contains an integrated Pt1000 temperature element that automatically corrects the pH/ORP reading to the standard reference temperature. The transmitter converts the millivolt signal to a 4–20 mA output using a high-impedance, low-drift amplifier circuit.
Advantages & Highlights:
- Automatic temperature compensation removes manual temperature correction errors
- IP67 rated — suitable for direct immersion in harsh process fluids
- HART communication enables predictive maintenance and remote troubleshooting
- Wide pH range (-2 to 16) covers virtually all industrial applications
- Long sensor life with gel-filled reference junction
Applicable Industries:
- Water & Wastewater Treatment
- Chemical / Petrochemical Processing
- Food & Beverage (CIP/SIP compatible)
- Pharmaceutical (USP <645> compliant)
- Mining & Mineral Processing
- Pulp & Paper
Installation Requirements:
- Install sensor fully immersed in process fluid; minimum immersion depth 50 mm
- Mount transmitter on DIN rail or wall bracket within 50 m of sensor (max cable length)
- Ensure no air bubbles trapped at electrode tip
- Provide adequate flow velocity (> 0.3 m/s) at sensor location for accurate readings
- Ground the transmitter at one point only to prevent ground loops
Usage Precautions:
- Calibrate at least every 3 months or when measurement drift exceeds ±0.05 pH
- Do not operate above 105°C — will damage ATC element and glass electrode
- Store electrode in KCl storage solution (3 mol/L) when not in use
- Do not expose to HF (hydrofluoric acid) — attacks glass electrode
- Replace sensor every 12–24 months depending on process conditions
