What Is a Density Meter? And Guide to Types

What Is a Density Meter?

We are discussing industrial density meters here, not laboratory densitometers. Industrial density meters are devices specifically designed to measure fluid density, performing real-time online density detection and displaying data such as density and temperature. They also support outputs of 4-20 mA, 0-1000Hz, RS485 Modbus RTU, HART, and other signals, facilitating industrial process control.

RFQ

Why is density monitoring needed?

Industrial density monitoring is primarily used for process and quality control, and can also assist in trade transactions.

For example, in the brewing industry, density continuously decreases during fermentation (sugar is converted into alcohol and CO₂). By tracking density changes, the fermentation process and endpoint can be accurately determined, thereby controlling the final alcohol content.

Or in the chemical industry, various chemical solutions (such as acids, alkalis, and alcohols) have a direct, linear relationship between concentration and density. Monitoring density is equivalent to real-time concentration monitoring. For example, in the production or use of sulfuric acid, measuring density directly determines whether it is 98% concentrated sulfuric acid or dilute sulfuric acid, which is crucial for reaction control and safety.

Alternatively, in the trade of petroleum, crude oil, and diesel, density testing can assess product quality. Furthermore, by measuring density and combining it with volume, the total mass of crude oil can be accurately calculated for trade settlement.

4 Types of Industrial Density Meters

The main types of industrial density meters include: tuning fork vibrating density meters, differential pressure density meters, optical density meters, and Coriolis density meters.

Tuning Fork Density Meter 316L — **Tuning Fork Density Meter/Concentration Meter**

Tuning Fork Vibrating Density Meter

A tuning fork vibrating density meter is an instrument that measures the density of liquids online based on the principle of vibration. It is mainly used for continuous monitoring and process control in industries such as petrochemicals, food and beverage, pharmaceuticals, and mineral processing. Its working principle involves a piezoelectric element driving the fork to vibrate; changes in liquid density cause changes in the vibration frequency. The density value is calculated and output by an electronic unit, with a measurement range of 0.5–2.5 g/cc and an accuracy of ±0.002 g/cc. It supports temperature compensation and concentration percentage conversion.

Advantages: Simple installation, plug and play, maintenance-free. It can measure the density of mixed media containing solids or bubbles. Furthermore, our Sino-Inst tuning fork density meters support customization for various special materials such as 316L, Hastelloy, titanium alloy, zirconium, PTFE, and ceramics.

Disadvantages: This density meter is not ideal for measuring media that are prone to crystallization or scaling.

Differential Pressure Density Meter

The differential pressure online density meter continuously measures the concentration and density of liquids online using the differential pressure principle. This device is made of corrosion-resistant materials such as 316L stainless steel, featuring high reliability and simple installation and use. It supports multiple installation methods, including insertion and flange mounting, and outputs a 4-20mA standard signal with an LCD display.

Its working principle is based on Pascal’s principle P=ρgh, calculating density by measuring the vertical differential pressure. An integrated temperature sensor enables automatic temperature compensation. The measurement range is 0-3 g/cm³, with an accuracy of ±0.001 g/cm³, suitable for both flowing and stationary liquids. It is widely used in petrochemical, food and beverage, pharmaceutical, and environmental protection fields, meeting the measurement needs of high-temperature, high-viscosity, and corrosive media.

Optical Concentration Meter

An optical concentration meter is an instrument that measures the concentration of liquids or liquid mixtures using the principle of spectroscopy. It utilizes the propagation laws of spectra in liquids, sampling through a high-resolution spectral sensor, and then analyzing and processing the data using software to obtain the concentration patterns. Temperature compensation is then applied to determine the concentration of various liquids or liquid mixtures. A prerequisite for optical concentration meter measurements is that the liquid must have a certain degree of transparency.

Coriolis Density Meter

A Coriolis density meter is an online density meter based on the Coriolis force principle, and is a derivative of the Coriolis mass flow meter. It is currently one of the most accurate density measurement instruments on the market. It is suitable for high-precision measurement of the density of flowing mixed solutions in pipelines. Normal accuracy is 0.001-0.002 g/cm³, with high accuracy reaching 0.0005 g/cm³.

It features high repeatability, stable measurement, and is unaffected by the type and properties of the liquid. It is largely unaffected by different operating conditions such as high and low pressure, flow rate, temperature, and the length of the preceding and following straight pipe sections. Pipe diameters range from DN1 to DN150, and the output signal is mostly 4-20mA. It supports HART communication protocol, RS485 communication, and bus communication (DP/FF/PA), enabling multi-functional remote transmission and control.

FAQ

Density is one of the important physical parameters of a substance, defined as the mass per unit volume, commonly expressed in g/cm³ or kg/m³. Measuring density can guide us in quality control, process optimization, and physical property analysis.

For example, density can be used to determine the grade of oil products and is an important basis for adulteration and measurement. This applies to gasoline, diesel, lubricating oil, naphtha, etc. Or, for products like beer, wine, and juice, density is often used to indirectly control the formulation and production process.

A density meter is also called a concentration meter.

We’ll illustrate these with examples from our company:

In ammonia preparation, an online ammonia density meter is installed to monitor ammonia concentration in real time. Suitable for pipelines and tanks, it displays the reading upon insertion into the liquid. Remote calibration and monitoring are possible via a 4-20mA signal output, making it directly applicable to ammonia industrial production.
In large power plant desulfurization processes, limestone slurry is used as the desulfurization absorbent. The quality of the limestone slurry is a key factor influencing desulfurization efficiency and effectiveness. Limestone slurry density is a crucial parameter reflecting its quality. A desulfurization and denitrification limestone slurry concentration meter can monitor the density/concentration of the limestone slurry in real time.
In chemical plants, tuning fork density meters are installed to monitor the density of silica solution after ultrafiltration in real time, enabling automated production measurement and control.
In solar cell manufacturing processes, the concentration of isopropanol solution is monitored online to control the percentage concentration.
In the pharmaceutical industry, the concentration process of traditional Chinese medicine concentration requires control of concentrations at each stage. In pharmaceutical manufacturing, online drug concentration monitors can be installed on evaporators. Real-time monitoring of drug concentration changes improves production efficiency and drug quality, while conserving raw materials.

Intelligent industrial densitometers can display density values in real time. Commonly used units include g/cc, kg/m³, b/ft², g/L, g/ml, and g/cm³. They can also display concentration percentages and temperature values.

You can also remotely read the density using signals from 4-20 mA, 0-1000Hz, RS485, Modbus RTU, and HART.

Density meters can be used for density measurement in both laboratories and industrial process sites. Laboratories typically use benchtop or handheld densitometers, such as those supplied by Anton-Paar. These are primarily suitable for monitoring the density of media samples.

Industrial process sites generally use the four types of densitometers analyzed in this article: tuning fork densitometers, Coriolis densitometers, optical densitometers, and differential pressure densitometers.

Many industries require monitoring the density of fluids. These include the petrochemical, brewing, food, pharmaceutical, and mineral processing industries (such as clay, carbonates, and silicates). Specific applications include interface detection in multi-product pipelines, density detection of stirred mixtures, endpoint monitoring in reaction vessels, and interface detection in separators.

Sino-Inst specializes in the research and development and manufacturing of process control instruments, including online density meters, concentration meters, pressure transmitters, flow meters, level gauges, and temperature gauges. We have extensive research and field application experience, particularly in online concentration and density measurement. We have established close partnerships with numerous universities, research institutes, and other scientific research organizations. We are now a comprehensive automation solution provider integrating instrumentation research and development, software development, and system integration.

We supply over 20 different digital density meters, widely used in factories across the US, UK, UAE, Indonesia, Singapore, and other countries. Online purchasing is supported.