Yokogawa SC41-SP34

Core Technical Specifications

• Power Supply Mode: Two-wire 24VDC loop power supply, loop load resistance maximum 500Ω
• Measurement Range: 0.001 μS/cm ~ 200 mS/cm, auto-ranging automatic range switching
• Cell Constant of SP34 Matching Probe: K=0.1 cm⁻¹ high-purity water dedicated electrode
• Temperature Compensation Range: 0°C ~ 100°C, built-in Pt1000 temperature sensor for automatic temperature compensation
• Measurement Accuracy: ±0.5% full scale; temperature measurement precision ±0.1°C
• Output Signal: Standard 4–20mA DC analog signal, HART 7 digital communication overlay
• Response Speed: 90% measured value stabilization within 3 seconds after liquid contact
• Process Pressure Tolerance: Maximum 1.0 MPa working pressure at 25°C
• Process Liquid Temperature Range: 0 ~ 100°C continuous medium temperature
• Enclosure Protection Grade: IP65 waterproof and dustproof transmitter housing
• Wetted Material of SP34 Probe: PEEK electrode body, 316L stainless steel measuring electrodes, EPDM sealing gaskets
• Mounting Form: Threaded pipeline insertion mounting, 1/2 NPT standard process connection
• Operating Ambient Temperature: -20°C ~ +60°C; storage temperature: -40°C ~ +85°C
• Humidity Range: 10%–90% RH non-condensing
• Dimension: Transmitter body 92mm (W) × 130mm (H) × 68mm (D); probe insertion length 120mm
• Total Weight: 0.65kg

Functional Features

1. Integrated transmitter and SP34 conductivity probe assembly, factory pre-calibrated to eliminate on-site separate calibration steps
2. Built-in Pt1000 temperature sensor achieves real-time automatic temperature compensation, eliminates conductivity measurement deviation caused by liquid temperature fluctuation
3. Auto-ranging measurement circuit automatically switches internal detection range according to liquid conductivity value, ensures full-range high measurement precision
4. HART 7 communication function supports remote range adjustment, calibration zero/span setting, electrode fault diagnosis and historical data query
5. Multiple electrode self-diagnosis functions: electrode scaling coating, probe breakage, temperature sensor failure, with corresponding 4–20mA alarm current output
6. Local integrated digital display screen, on-site real-time viewing of conductivity value, medium temperature and equipment fault codes without handheld communicator
7. Anti-pollution electrode surface design, effectively reduces scaling adhesion in high mineral content water medium
8. Two-wire loop power supply design, simplifies field wiring construction, only two signal cables required for both power supply and signal transmission
9. Reverse power connection protection circuit, prevents circuit burnout caused by on-site positive/negative wiring reversal
10. Multiple liquid medium compatible, applicable to pure water, boiler feed water, chemical dilute solution, industrial wastewater monitoring

Working Principle

Material Composition & Structural Characteristics

• Transmitter Outer Housing: Die-cast aluminum alloy with anti-corrosion polyurethane coating, IP65 silicone rubber sealing gasket
• Circuit PCB: Conformal coated industrial grade FR-4 circuit board, isolated excitation signal circuit to avoid measurement noise
• SP34 Probe Main Body: Medical grade PEEK plastic, high temperature and chemical corrosion resistant
• Measuring Electrodes: Polished AISI 316L stainless steel, anti-oxidation surface treatment
• Temperature Sensing Element: Pt1000 platinum resistance temperature sensor encapsulated inside probe body
• Process Sealing Components: EPDM rubber gaskets, resistant to weak acid and weak alkali liquid medium
• Connection Structure: Integrated quick plug connector between transmitter and probe, sealed waterproof locking design

Application Scenarios

• Electronic industry ultra-pure water production line real-time conductivity monitoring
• Thermal power plant boiler feed water, condensed water water quality detection
• Pharmaceutical factory purified water and injection water quality monitoring system
• Chemical factory dilute solvent concentration on-line measurement
• Municipal wastewater treatment plant effluent water quality analysis
• Food beverage production process water ion concentration monitoring

Installation Requirements

1. Install probe vertically downward on pipeline or tank side wall, avoid horizontal upward installation to prevent air bubbles adhering to electrode surface and causing measurement error
2. Process pipeline must install ball valve front of probe for convenient probe extraction and cleaning without system shutdown
3. Two-core shielded twisted pair signal cable for 4–20mA HART wiring, shield single-end grounding at DCS control cabinet
4. Ensure the probe measuring section is fully immersed in flowing liquid, avoid installation in static dead water area
5. Process medium pressure shall not exceed 1.0MPa; install pressure reducing valve for high-pressure pipeline working conditions
6. Avoid installation near pipeline heating sections to prevent local medium over-temperature exceeding probe rated temperature range
7. HART communication wiring length shall not exceed 1000 meters to guarantee stable digital signal transmission

Operation & Maintenance Precautions

1. Regularly extract SP34 probe every 1–3 months to clean electrode surface scaling with dilute hydrochloric acid cleaning solution
2. After electrode cleaning, perform zero and span calibration via local display or HART handheld communicator to restore measurement accuracy
3. Do not scratch the polished surface of stainless steel measuring electrodes with hard tools, scratches will cause permanent measurement deviation
4. Avoid long-term exposure of probe to strong oxidizing acid liquid medium, which will corrode electrode surface
5. If measurement value drifts abnormally, first check for air bubble adhesion on electrode surface instead of replacing transmitter
6. HART firmware upgrade requires stable 24VDC loop power supply; power loss during upgrade will damage measurement calibration parameters
7. Store spare probes in clean pure water sealed container to prevent electrode surface oxidation and contamination