HM SERIES — CERAMIC CAPACITIVE TECHNOLOGY
HM21R Anti-Corrosive Submersible Level Transmitter
The HM21R combines German-engineered Al₂O₃ ceramic capacitive dry-cell sensing with a titanium alloy flat membrane, delivering unmatched chemical resistance and anti-clogging performance for sea water, corrosive chemicals, and viscous liquid level measurement applications.
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Ceramic Capacitive Sensing for Harsh Chemical Environments
The HM21R Anti-Corrosive Submersible Level Transmitter is purpose-built for liquid level measurement in environments where standard piezoresistive sensors fail. By combining a high-purity Al₂O₃ ceramic capacitive sensing element with a titanium alloy flat diaphragm, the HM21R eliminates the two most common failure modes in corrosive service: sensor membrane corrosion and silicone oil leakage. The ceramic dry-cell design contains no oil fill whatsoever — the ceramic diaphragm directly contacts the process medium, making it inherently immune to chemical attack from a wide range of acids, alkalis, sea water, and organic solvents.
Unlike conventional submersible level transmitters that rely on thin 316L stainless steel diaphragms bonded to piezoresistive silicon chips with silicone oil coupling, the HM21R’s ceramic capacitive sensor measures pressure through the deflection of the ceramic diaphragm itself. This architecture provides several critical advantages: no risk of oil leakage contamination, inherent chemical inertness of the Al₂O₃ ceramic surface, and significantly higher overload capacity (3× rated pressure versus the typical 2×) due to the ceramic’s superior elastic properties.
The titanium alloy flat membrane further enhances corrosion resistance while providing an anti-clogging design. The large flat diaphragm surface has no recessed cavities, small pressure ports, or dead zones where viscous media or suspended particles can accumulate. This self-cleaning geometry is essential for applications involving slurries, wastewater with high solids content, or high-viscosity process fluids. Combined with IP68 protection and optional Ex ia IIC T5 explosion-proof certification, the HM21R delivers reliable level measurement in the most demanding industrial environments.
Technical Specifications
| Parameter | HM21R Specification |
|---|---|
| Measuring Range | 0–0.5 m to 200 m |
| Overload Capacity | 3× maximum rated pressure |
| Overall Accuracy | ±0.1% FS / ±0.25% FS / ±0.4% FS / ±1% FS (selectable) |
| Long-Term Stability | Typical ±0.1% FS/year, Max ±0.2% FS/year |
| Sensing Technology | Ceramic Capacitive (Al₂O₃) — dry cell, no oil fill |
| Operating Temperature | Integrated: −20°C to +70°C | Split: −20°C to +80°C |
| Temperature Drift (Zero) | Typical ±0.02% FS/°C, Max ±0.05% FS/°C |
| Power Supply | 12–36 V DC (typically 24 V DC) |
| Output Signal | 4–20 mA / 1–5 V DC / 0–5 V DC |
| Wetted Materials | Membrane: Titanium alloy | Enclosure: 316L SS (optional) | Seal: Fluoro-silicone rubber |
| Media Compatibility | Sea water, acids, alkalis, viscous media (compatible with Al₂O₃ ceramic) |
| Protection Rating | IP68 (fully submersible) |
| Explosion-Proof | Ex ia IIC T5 (optional) |
| Response Time | ≤ 2 ms |
| Resolution | 1/100,000 (practical) |
| Structural Forms | Integrated (0–200 m) | Split (0–10 m) | Inserted (0–4 m) |
| Weight | Approx. 250 g |
Key Features
Ceramic Capacitive Dry-Cell Sensing
High-purity Al₂O₃ ceramic sensor with no silicone oil fill — inherently resistant to chemical attack from acids, alkalis, sea water, and solvents. Zero risk of oil leakage contamination.
Titanium Alloy Flat Membrane
Large flat diaphragm design with no recessed cavities or small pressure ports. Self-cleaning geometry resists clogging from viscous media, slurries, and particulate-laden fluids.
3× Overload Tolerance
Withstands 3× maximum rated pressure without damage or zero shift — significantly higher than the typical 2× rating of piezoresistive sensors. Superior protection against pressure surges and water hammer.
±0.1% FS High Accuracy
Selectable accuracy classes from ±0.1% FS to ±1% FS to match application requirements. Long-term stability of ±0.1% FS/year ensures reliable readings over extended deployment periods.
Ultra-Fine 1/100,000 Resolution
Extremely fine measurement resolution enables detection of subtle level changes in precision monitoring applications. Practical resolution of 1/100,000 of full scale.
IP68 Fully Submersible
Complete waterproof protection rated IP68 for permanent underwater installation up to 200 meters depth. Optional Ex ia IIC T5 explosion-proof certification for hazardous area deployment.
Typical Applications
Sea Water Level Monitoring
Coastal installations, desalination plants, offshore platforms, and marine infrastructure. The titanium alloy membrane and ceramic sensor both resist chloride-induced corrosion that destroys conventional stainless steel sensors.
Chemical Storage Tanks
Acid and alkali tank level monitoring in chemical processing plants. The Al₂O₃ ceramic surface is inert to virtually all common industrial chemicals including sulfuric acid, hydrochloric acid, and sodium hydroxide.
Wastewater Treatment
Municipal and industrial wastewater level measurement in aeration basins, settling tanks, and chemical dosing systems. IP68 protection and anti-clogging flat membrane handle high-solids effluent reliably.
Pulp & Paper Industry
Level measurement in black liquor tanks, pulp digesters, and chemical recovery systems. The flat membrane design prevents buildup of fibrous materials and high-viscosity process fluids.
Mining & Slurry Processing
Abrasive and corrosive slurry level measurement in thickeners, leach tanks, and tailings ponds. The 3× overload capacity provides protection against sudden pressure surges from slurry movement.
Food & Beverage Processing
Hygienic level monitoring in CIP systems, brine tanks, and acidic beverage storage. The ceramic sensor with no oil fill eliminates any risk of process contamination from sensor failure.
Ordering Guide
Example model code: HM21R (0~10m) — C1 — 2 — A1 — E
Select each parameter below to configure your HM21R to match your application requirements. Our engineering team can assist with custom configurations.
| Code | Parameter / Options |
|---|---|
| Range | Measuring Range: 0–X m or 0–X kPa (specify required range) |
| C1 / C2 / C3 | Structural Form: C1 = Integrated (0–200 m) | C2 = Split (0–10 m) | C3 = Inserted (0–4 m) |
| 0 / 1 / 2 / 3 | Accuracy: 0 = ±0.1% FS | 1 = ±0.4% FS | 2 = ±0.25% FS | 3 = ±0.1% FS |
| A1 / V1 / V2 | Output Signal: A1 = 4–20 mA | V1 = 1–5 V DC | V2 = 0–5 V DC |
| E / F / F1 / F2 | Options: E = Ex-proof (Ex ia IIC T5) | F = Lightning protection | F1 = G1½ thread | F2 = DN20 flange |
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Frequently Asked Questions
Need a Corrosion-Resistant Level Transmitter?
Our engineering team specializes in corrosive and harsh-environment level measurement solutions. Whether you need a standard HM21R configuration or a fully customized system with explosion-proof certification, we can help you select the right sensor for your specific media, temperature, and range requirements.
Our engineers typically respond within 12 business hours with detailed technical specifications and pricing.