Compact density meter

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Short description
YUNYI Portable Inline Tuning Fork Density Meter is a compact, battery-powered measurement instrument designed for real-time density detection in liquid process lines. Combining high-precision frequency-tracking technology with a rugged plug-in probe, the unit delivers instant density and concentration readings directly from pipelines, open tanks, and sealed vessels — no bypass loops or additional sampling equipment required. Ideal for field applications where laboratory analysis is too slow or impractical, this meter helps operators maintain consistent product quality, optimise blending operations, and reduce waste through on-the-spot process control.

Working Principle
The meter operates on the resonant tuning-fork principle. A piezoelectric drive excites the fork tines at their natural frequency, while a separate piezoelectric sensor monitors the resulting vibration. When the fork is immersed in a liquid, the added mass changes its resonant frequency relative to the fluid’s density. A built-in PT100 temperature sensor continuously compensates for thermal effects, eliminating temperature drift and ensuring consistent readings across varying process conditions. The device converts measured density into concentration, specific gravity, or directly calculated mass/volumetric values according to pre-programmed correlation curves for the specific fluid.

Technical Specifications (table)
Parameter : Specification
Measurement Range : Density: 0 – 2.0 g/cm³ (expandable to 3.0 g/cm³ on request); Concentration: 0 – 100% (local range can be calibrated as needed)
Accuracy : ±0.001 g/cm³ (density) / ±0.5% (concentration)
Repeatability : ±0.0001 g/cm³ (density) / ±0.1% (concentration)
Resolution : Density: 0.0001 g/cm³ / Concentration: 0.1%
Response Time : ≤ 2 seconds
Fluid Temperature : –25℃ ~ +120℃ (customizable up to 150℃)
Ambient Temperature : –25℃ ~ +85℃
Maximum Viscosity : ≤ 2000 cP
Wetted Materials : 316L stainless steel / Hastelloy / Titanium (custom)
Process Connection : Flange (ANSI/DIN), Clamp (tri-clamp), Thread (NPT/G-thread)
Power Supply : Built-in 3.7 VDC rechargeable lithium battery (charger included)
Output Signals : 4-20 mA (two-wire/four-wire), RS485 Modbus RTU, HART
Electrical Interface : M15×1 / M20×1.5 / ½” NPT
Protection Rating : IP65 (optional IP66)
Insertion Depth : ≥125 mm (Standard, custom up to 2 m)
Cable Length : 5 m (standard, custom lengths available)

Main Features

• True portability – Self-contained battery operation and compact instrument case allow rapid deployment across multiple measurement points without external power or wiring.
• Inline installation – Plug-in design enables direct mounting into process pipelines, open tanks, and sealed vessels without cutting pipes or constructing bypass stations.
• Real-time digital display – Backlit LCD shows density, concentration and temperature simultaneously.
• Automatic temperature compensation – Built-in PT100 sensor and integrated compensation algorithm maintain measuring accuracy across fluctuating process temperatures.
• Maintenance-free operation – No moving parts, no seals to wear out, and no routine calibration required under normal operating conditions.
• Versatile outputs – 4-20 mA analog signal for PLC/DCS integration plus RS485 Modbus for digital data logging and remote monitoring.
• Corrosion-resistant construction – Wetted parts available in 316L stainless steel, Hastelloy, or titanium, with PTFE / electropolished coating options for aggressive media.

Typical Applications & Industries (table)
Industry / Typical Measurement Purpose
Petrochemical : Multi-product pipeline interface detection; oil-water-sediment separation monitoring
Chemical processing : Acid/alkali concentration control; evaporator endpoint detection; solvent separation in batch reactors
Food & beverage : Brix/concentration monitoring; brewing density control; sugar / juice concentration measurement
Pharmaceutical : Alcohol blending; active ingredient concentration; fermentation process monitoring
Battery & electrolyte : Lithium hydroxide concentration; sulfuric acid solution monitoring; electrolyte density control
Mineral processing : Slurry density; clay / carbonate / silicate suspension measurement; flotation circuit monitoring
Wastewater & environmental : Ammonia water concentration; lime slurry consistency; effluent density trending
Power generation : Desulfurisation slurry density (FGD); scrubber feed monitoring
Additional uses include inline blending verification, reactor endpoint detection, separator interface tracking, and concentration-to-mass flow conversion when paired with a volumetric flow meter.

Installation Guidelines (Pipe Mounting)
Horizontal Pipe Installation

• Mount on the side wall of the pipe (not the top or bottom) to avoid air accumulation.
• Orient the tuning-fork gap vertically so that bubbles rise and solids settle out of the measurement path.
• Minimum pipe diameter: ≥100 mm (4″). For smaller diameters, accuracy may be affected.
• Preferred fork area flow velocity: ≤1 m/s; maximum absolute main-pipe velocity: 5 m/s (with flow conditioning).

Vertical Pipe Installation

• Install on the side wall, not directly in the main vertical stream.
• Preferred flow direction: upward (ensure the tuning fork is always submerged).
• Minimum pipe diameter: ≥150 mm (6″) to provide adequate clearance around the fork.

Important
The tuning fork must remain fully immersed at all times for stable readings. When installing in open tanks, keep the probe at least 200 mm from walls and 50 mm from the tank bottom to avoid wall effects and sediment accumulation.

caractéristiques / spécifications techniques

• Measurement Range: Density 0–2.0 g/cm³ (expandable to 3.0 g/cm³); Concentration 0–100% (calibratable)
• Accuracy: ±0.001 g/cm³ (density) / ±0.5% (concentration)
• Repeatability: ±0.0001 g/cm³ (density) / ±0.1% (concentration)
• Resolution: Density 0.0001 g/cm³; Concentration 0.1%
• Response Time: ≤ 2 seconds
• Fluid Temperature Range: –25℃ to +120℃ (up to 150℃ customizable)
• Ambient Temperature Range: –25℃ to +85℃
• Maximum Viscosity: ≤ 2000 cP
• Wetted Materials: 316L SS / Hastelloy / Titanium (options)
• Process Connections: Flange (ANSI/DIN), Tri-clamp, Thread (NPT/G-thread)
• Power: Built-in 3.7 VDC rechargeable lithium battery (charger included)
• Outputs: 4-20 mA, RS485 Modbus RTU, HART
• Electrical Interface: M15×1, M20×1.5, ½” NPT
• Protection Rating: IP65 (optional IP66)
• Insertion Depth: ≥125 mm (standard, up to 2 m customizable)
• Cable Length: 5 m standard (custom lengths available)