What is a 4-20mA Output？

The signal current of general instruments is 4-20mA, which means that the minimum current is 4mA and the maximum current is 20mA.

The industry generally needs to measure various non-electrical physical quantities. For example, temperature, pressure, speed, angle, etc. They all need to be converted into analog electrical signals before they can be transmitted to the control room or display equipment hundreds of meters away. This device that converts physical quantities into electrical signals is called a transmitter. The most widely used in the industry is to use 4-20mA current to transmit analog quantities.

In the industrial field, to complete signal conditioning and long-term transmission, the following problems will occur:

1. Since the transmitted signal is a voltage signal, the transmission cable will be interfered by noise;
2. The distributed resistance of the transmission cable will produce a voltage drop;
3. How to provide the working voltage of the instrumentation amplifier in the field is also a problem.

In order to solve the above problems and avoid the influence of related noise, we will use current to transmit signals. Because the current is not sensitive to noise.

The 4-20mA current loop uses 4mA to represent the zero signal. Use 20mA to represent the full scale of the signal. The signals lower than 4mA and higher than 20mA are used for various fault alarms.

Why Choose 4-20mA Instead of 0-20mA for the Flowmeter?

Many people will certainly ask: Why choose 4-20mA instead of 0-20mA?
Very simple, if 0 is the smallest, then the open circuit fault will not be detected!

So, why is it 4mA?
During normal operation, the current signal will not be lower than 4mA.
When the transmission cable is broken due to a fault, the loop current drops to zero. 2mA is often used as the disconnection alarm value.
There are two reasons. One reason is to avoid interference. Another reason is that a two-wire system is used at 4-20mA. That is, the two wires are the signal wires. It is also a power cord. And 4mA is to provide the static working current of the circuit to the sensor.

Extended Reading: Mechanical flow meter for diesel

How Does This 4-20mA Control Loop Work?

4-20mA constitutes the basic elements:

• 24V power supply
• The transmitter controls the 4-20mA signal to change in proportion to the process variable
• The indicator converts the 4-20mA signal into the corresponding process variable
• Indicator or controller I/O input resistance 250Ω shunt generates 1-5V input signal (Ohm’s law: voltage = current * resistance, 4-20 mA X 250 ohms = 1-5V)

Usually:

1. They convert the temperature signal of the thermocouple or thermal resistance sensor into a 4-20mA signal and then output;
2. The controller then translates 4-20mA into a specific temperature value;
3. Based on this temperature value. The control loop realizes the control of the process terminal control element.

Similarly, the pressure transmitter is in the control loop. Usually used to measure the pressure value of the process medium:

1) The sensor senses pressure. The transmitter converts the signal into 4-20mA signal;
2) The controller then reversely translates the 4-20mA signal into a pressure value;
3) The controller is based on the pressure value. Send instructions to the valve. Control valve opening to realize safety valve control. Ensure that the container does not generate dangerous pressure.

Extended reading: Orifice Plate Flow Meter

Water Flow Meter 4-20ma Output

A Digital Water flow meter is a flow meter that can display the water flow rate, and have the output for the flow rate. Like 4-20mA output, HART, RS 485, and so on. Digital Water Flow Meter is also called Electronic Water Flow Meter. Digital Water Flow Meter is widely used in industrial water and household water measurement. Most of the Sino-Inst flow meters are digital water flow meters. Like the electromagnetic flowmeter, Portable ultrasonic flow meter, Turbine flow meter…..

No matter which WaterFlow Meters you choose. The signal output by WaterFlow Meters, such as 4-20mA. The flow signal can be connected to a paperless recorder. Carry out multi-channel flow signal monitoring.

Read More About: Paperless Recorder Working Principle

Flow Meter with Analog Output

The analog flow meter is a flowmeter with the analog output signal. Analog output is a common function of flow meters. The analog signal is mainly used to output the flow signal to the next control system.

The analog signal refers to the continuous signal of the information parameter in a given range. The characteristic quantity of the information of the analog signal can be transformed into an arbitrary numerical signal in an instant. In the process of transmitting analog signals, the information signals need to be converted into electric wave signals, which are then transmitted through wired or wireless methods.

Analog signal: poor confidentiality, weak anti-interference ability.

Digital signal: strong anti-interference ability and good communication confidentiality.

Read more about Analog Flow Meters.

Turbine Digital Flow Meter

Turbine flow meters are velocity flow meters, also called impeller flow meters. Can be used to measure the instantaneous flow and cumulative flow of liquids and gases.

Turbine flowmeters are widely used in flow measurement: petroleum, organic liquids, inorganic liquids, liquefied gas, natural gas, coal gas, and cryogenic fluids. Turbine flowmeter signals can be divided into pulse signals or current signals (4-20mA). It is suitable for use with secondary display, PLC, DCS, and other computer control systems.

Turbine Flow Meter reference price: USD 200-1700/pc.

4-20ma Air Flow Meter

A digital air flow meter refers to a flow meter that can accurately measure air or compressed air inline. Industrial Digital air flow meters can be divided into mass flow meters or volume flow meters.

Read more about Digital air flow meters.

Related Blogs

Looking for 4-20ma flow meters? The flow meter is a fast, accurate, and reliable permanent linear motion. In Sino-Inst, you can also find other good deals on measurement and analysis instruments and tools! Keep an eye out for promotions and deals, so you get a big saving of 4 20ma flow meters. You can shop for 4 20ma flow meters at low prices.

Extended reading: How to convert a 4-20mA to 0-10V /1-5V signal?

There is a wide variety of 4-20ma flow meter items you can buy, such as turbine water flow meters, ultrasonic flowmeters. Common materials used for 4 20ma flow meters are stainless steel and carbon steel.

Sino-Inst offers over 50 4-20ma flow meters for flow measurement. About 50% of these are differential pressure flow meters, 40% are the liquid flow sensor, and 20% are Ultrasonic Level Transmitter and mass flow meters.

A wide variety of flow meters options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of flow measurement instrumentation, located in China.

Request a Quote

Sino-Inst specializes in low flow meters for micro to low flow rates. We offer:
Ultrasonic flowmeter can measure low flow rates from 0.1m/s to 5.0m/s.
The gear flowmeter can measure the microflow rate from 0.01 to 0.83.
Coriolis mass flow meters and controllers from 10SCCM~30SLM.
Below, we also introduce a lot of flow meters. based on vortex, electromagnetic, ultrasonic, and positive displacement, etc.

Flow range of flow meters

First, let’s take a look at the low flow rate measurement range of conventional flow meters.

Flow meter	Media	DN	Flow Range (m³/h)	L/min
Electromagnetic Flowmeter	liquid	15	0.19~3.18	3.166~53
Turbine flowmeter	liquid	4	0.04~0.25	0.666~4.166
Vortex Flowmeter	Gas; liquid	15	3～15;0.3～5	50~250; 5~83.30
Precession Vortex Gas Flowmeter	gas	15	1～7	16.66~116.666
Ultrasonic Flow Meters	liquid	15	0~±12m/s	–
Differential Pressure Flow Meters	Liquid; gas	15	0.8m/s	–
Oval gear flowmeter	liquid	10	0.03-0.2	0.5~3.33
Gear flow meter	liquid	2	0.0006~0.050	0.01~0.833
Coriolis Mass Flowmeter	Liquid; gas	3	0~96~144 kg/h	–
Thermal gas mass flow meter	gas	6	0.1～120Nm/s	–
Metal rotor flowmeter	Gas; liquid	15	0.07~0.7; 2.5~25	1.166~ 11.66;41.666 ~416.66

Read more about: The Pros and Cons of Micro Motion Flow Transmitters

Low flow meters for Liquids

Extended reading: Micro flow meters for low flow liquids

Low flow meters for Gas

Read more about: Benefits Of Digital Gas Mass Flow Meters

FAQ

Related articles:

Extended reading: Gas Rotameter Tips

Sino-Inst, Manufacturer for Low Flow Meters. For example crude oil flow meter, diesel flow meter, gasoline flow meter.

Sino-Inst’s Low Flow Meters, made in China, Having good Quality, With better price. Our flow measurement instruments are widely used in China, India, Pakistan, the US, and other countries.

What is gear flow meter?

The gear flowmeter is a positive displacement flowmeter. It is a high-precision transmitter for measuring volumetric flow. It uses two or more elliptical gears to rotate at right angles to each other to form a T shape. With the flow of the medium, the gears mesh and rotate. Under the action of the fluid flow, a pressure difference is formed at both ends of the instrument inlet and outlet. No power supply is required. A pair of gears rotate freely. The cavity between the gears is filled with liquid. The liquid is discharged as it rotates. Measure the number of revolutions of the gear to know the flow rate of the liquid flowing through the instrument.

Gear flow meters are used to accurately measure the flow or instantaneous flow of liquid in the pipeline continuously or intermittently. It is especially suitable for the flow measurement of Maltose, syrup. heavy oil, polyvinyl alcohol, resin, and other high viscosity media.

There are various types of gear flow meters, mainly named after the shapes of internal components. For example, the circular gear flowmeter we will introduce in this article. There are also common oval gear flow meters, helical flow meters, etc.

Oval gear flowmeter
The oval gear flowmeter uses two oval gears to mesh and rotate. It is suitable for flow measurement of medium with higher viscosity.

Extended reading: Positive displacement flow meter working principle

Helical flow meter
The metering part of the spiral rotor flowmeter is mainly composed of a metering box and a pair of uniquely designed spiral rotors.

Extended reading: Cylinder Gear flow meter for micro flow measurement.

Circular gear flowmeter (spur gear flowmeter)
The circular gear flowmeter uses two circular gears to mesh and rotate. Suitable for microflow measurement.

Tool: Volumetric Flow Rate & Pipe Diameter to Flow Speed Calculator

Gear flow meter

A gear flow meter is a micro digital positive displacement flow meter. Can measure very small flow rates and quantify small volumes of liquid. High and low-temperature resistance (-196℃-200℃).

The Gear flow meter for Microflow is made of stainless steel and is used for precise continuous or intermittent measurement of the flow or instantaneous flow of liquid. It is especially suitable for the flow measurement of heavy oil, polyvinyl alcohol, grease, and other high-viscosity media.

It can measure fluids with a viscosity of up to 10000 Pa.s.
The lowest flow rate can be measured at 0.6L/H. That is 0.0026 GPM.

Extended reading: Micro flow meters for low flow liquids

Helical gear flow meter

PD Flow Meter is referred to as a positive displacement flow meter. Helical Gear-PD Flow Meter is also called, spiral double rotor flowmeter, LLT, LZ double rotor flowmeter, or UF-Ⅱ spiral rotor flowmeter.

As a high-precision flow meter, PD Flow Meter has an accuracy of 0.2 level. It is especially suitable for the measurement of industrial liquids such as crude oil, refined oil, and light hydrocarbons. It is a new generation volumetric flowmeter. Because it uses a pair of spiral rotors with special teeth, it is also called “Helical Gear Flowmeter”.

Extended reading: Flat Pressure Sensor for High Viscosity Fluids

Oval gear flow meter

Oval gear flow meter is one of the typical positive displacement flow meters. Measure the flow of liquid filling the pipeline under a certain pressure.

The oval gear flow meter is a pointer display type positive displacement flowmeter. The word wheel accumulates counting and can be equipped with a zero return device. Oval gear flowmeters are widely used in liquid flow control in various industrial fields. Applicable to various types of liquid measurements, such as crude oil, diesel, gasoline, etc. Choose different manufacturing materials, such as crude oil, diesel, gasoline, etc. can be measured.

Extended reading: How to choose a high viscosity flow meter?

Explore Oil and Gas Flow Meters

Mirco flow-high viscosity fluid measurement

High-viscosity liquid means that the liquid is viscous and thick, which is different from general liquids and non-Newtonian fluids (mud, pulp). The activity is slow and it is very difficult to filter by simple methods.

What’s more, in addition to some dust, the liquid also contains colloidal particles that are not completely dissolved.

For example solutions such as rubber, paraffin, cellulose acetate, viscose, polyacrylonitrile, paint and animal glue.

Read more about Liquid Flow Meters Guide

Gear flowmeter is a new type of volumetric flow transmitter, used for precise continuous or discontinuous measurement of the flow or instantaneous flow of liquid in the pipeline. Cylindrical gear flowmeter is especially suitable for heavy oil, polyvinyl alcohol, resin and other viscosities. Flow measurement of high media.

It can measure fluids with a viscosity of up to 10000 Pa.s.
The lowest flow rate can be measured at 0.6L/H. That is 0.0026 GPM. Read more about: what is gpm;

Model	Measure Range L/H	K P/L	Pressure-Bar		Temperature	Accuracy	Interface	Installation dimensions
			Aluminum alloy	stainless steel
GF02	0.6-50	10500	150	400	-15-80℃	+/- 0.5% ( Range 1:10) +/- 1.0%    （Range 1:100）	G1/8	Φ84*55
GF04	5-250	9117	150	400	-15-80℃		G1/4	Φ84*55
GF06	10-500	3000	150	400	-15-80℃		G1/4	Φ84*67
GF10	50-1200	1280	150	400	-15-80℃		G1/2	Φ84*67
GF15	200-3000	126.75	150	400	-15-80℃		G3/4	Φ116*98*74
GF25	1000-12000	61.1	150	400	-15-80℃		G1-1/2	158*118*68
GF32	2000-20000	59.9	150	400	-15-80℃		G1-1/2	158*18*68

Extended Reading: Insertion Flowmeter Types

Cylindrical gear flow meters are small in size and light in weight.
During operation, the vibration and noise are small and the operation is stable.
It can also be used to measure the small flow rate of small pipe diameters.
The starting flow is small, and the range ratio is wide, suitable for measuring the liquid flow with large fluctuations.
The measurement accuracy is not affected by changes in pressure and flow, with stable performance, long life and large flow capacity.

• Resin and glue measurement
• Measurement of hydraulic oil, lubricating oil and grease
• Fuel oil measurement
• Ink and asphalt measurement
• Liquid nitrogen, freezing liquid, solvent measurement
• Filling measurement of edible oil, fish oil and food
• Chemical and anti-corrosion requirements fluid measurement
• Fluid quantitative control system

Read More about: Chemical Flow Meter Guide

Related Products:

Related Blogs:

Extended reading: Oil Level Measurement Solutions for the Oil & Gas Industry

Sino-Inst, Manufacturer for Gear flow meter for Microflow. For example crude oil flow meter, diesel flow meter, gasoline flow meter.

Sino-Inst’s Gear flow meter for Microflow, made in China, Having good Quality, With better price. Our flow measurement instruments are widely used in China, India, Pakistan, the US, and other countries.

Flow measurement in the food industry

In the food and beverage processing industry, accurate measurement and control of raw materials are very demanding. Food grade flow meters Cut costs and increase productivity. Certain processes in the food industry require sanitary conditions. Food industry: dairy products, alcohol, beverages, syrup, chocolate, edible oil, etc.

Food grade oil flow meter

Food grade flow meters can measure edible oil.

There are many steps in the processing of edible oil that require a flow meter to measure the volume and weight of how much oil flows out of the pipeline. Companies that produce and process edible oils need to use flow meters for statistics on the crude oil that is initially refined and the essential oil that is finally refined.

First of all, for oil measurement, electromagnetic flowmeters cannot be selected.

You can choose turbine flowmeters, gear flowmeters, ultrasonic flowmeters, metal rotor flowmeters to measure oil. If you need high-precision measurement. You can also consider mass flow meters.

Extended reading: Sanitary Positive Displacement Flow Meter

Flowmeter used in the beverage industry

An electromagnetic flowmeter is used to measure the volume flow of conductive liquid medium with conductivity greater than 5μs/cm. Electromagnetic flowmeters are usually used to measure the flow of large pipelines. It can be accurately measured in a large beverage production workshop. The minimum diameter of the current electromagnetic flowmeter is 0.1 inches, that is, 2.5 mm, and the maximum diameter can reach nearly 3 meters.

The beverage industry includes beer, fruit juice, etc., and electromagnetic flowmeters could not be better. Generally, the medium is conductive, and it is very good to add ions appropriately. And there is no loss. There is no differential pressure loss or something.

Originally, there are still many ways to protect the electrodes of the electromagnetic flowmeter. We should pay more attention to it in the process of use. Don’t cause the electromagnetic flowmeter to fail to operate normally in the future due to a little negligence.

Flow measurement in Breweries

What kind of flowmeter can be used to solve beer flow measurement? Beer is a conductive medium. Can use electromagnetic flowmeter to measure. When measuring beer, you only need to use stainless steel electrodes and tetrafluoroethylene lining. The electromagnetic flowmeter is a measuring instrument with high measurement accuracy and good stability. It has been widely used in beer flow measurement.

Beer flow measurement. Let’s take a look at how to select a beer electromagnetic flowmeter:

1. Medium
2. Temperature
3. Pressure

When measuring beer flow, you can select according to the above three corresponding parameters to meet the on-site measurement requirements.

Of course, except for electromagnetic flowmeters. The sanitary turbine flowmeter can also be used to measure beer or liquor.

Extended reading: Stainless steel flow meters|304-316 optional

Syrup flow measurement

Food grade flow meters can measure syrup.

High viscosity syrup flow measurement

If the viscosity of the measured syrup is relatively high. Then I recommend using a target flowmeter or an oval gear flowmeter.

The target flow meter is a speed meter. It calculates the flow rate of the medium according to the force of the medium pushing the target. Its intelligent liquid crystal meter head can clearly display the instantaneous flow and cumulative flow of the medium. And output 4-20mA signal. The installation is simple and the maintenance is small. High temperature and high-pressure resistance. Suitable for large, medium, and small pipe diameters. The application range is very wide.

The oval gear flowmeter is a positive displacement flowmeter. It is a mechanical instrument. He calculates the medium flow rate based on the measurement of the rotation of the internal gear. The general configuration is a pointer display type, which only displays the cumulative flow and does not display the instantaneous flow. Therefore, the user needs to explain to the manufacturer when displaying the instantaneous flow rate. The manufacturer will be equipped with a smart meter.

In addition, the output signal is a pulse signal. The user needs a 4-20 mA signal, and the manufacturer also needs to explain it to the manufacturer. Oval gears are relatively bulky. Therefore, it is not suitable for the measurement of large-diameter pipes. Its largest caliber is also smart to 200mm.

Why Generally Choose 4-20ma Output?

In addition to the above two types of vortex, flowmeters are also possible.

Low viscosity syrup flow measurement

If the measured viscosity of the syrup is not very high, an electromagnetic flowmeter or a liquid turbine flowmeter has been used.

Electromagnetic flowmeters are mainly used for the measurement of medicines such as glucose syrup and food syrup. Because medicine and food have higher hygiene requirements. Strict disinfection is required, so clamp-type electromagnetic flowmeters are generally used.

The liquid turbine flowmeter measures low viscosity, and the effect of relatively pure syrup is very good. Responsive, high precision, beautiful and light appearance, installation and maintenance are also very simple. It is suitable for the measurement of small and medium pipelines. Both types of flow meters are smart meters. On-site LCD displays instantaneous flow and cumulative flow. Output 4-20mA signal. The scope of application is also very wide.

Here I simply recommend several flow meters based on the viscosity of the syrup. How to choose specifically. Users need to provide relevant parameters and requirements to make the most suitable and correct choice.

Extended reading: Sludge flow meter for sewage treatment return activated sludge system

Featured Food grade flow meters

Food grade positive displacement flow meter

Positive displacement flow meters, also known as fixed displacement flow meters or PD flow meters, are the most accurate measuring instruments. The oval gear flowmeter is the most typical positive displacement flowmeter.

According to the measuring elements, the volumetric flow plan can be divided into elliptical gear flow meters, double rotor flow meters, disc flow meters, rotary piston flow meters, wet gas meters, and membrane gas meters, etc. The clamp connection oval gear flowmeter has the advantages of a lightweight and convenient connection. Especially in the chemical and pharmaceutical industries, it has a wide range of uses.

Extended reading: Mechanical flow meter types

Sino-Inst offers over 10 Food grade flow meters, with the Best Price. Food grade flow meters are Also called sanitary flowmeters.

A wide variety of Food grade flow meters options are available to you, such as free samples, paid samples.

About 13% of these are magnetic flow meter, 14% are Turbine Flow Meters, 25% are Venturi flow meter, 13% are Handheld ultrasonic flow meter, and others are Liquid mass Flow Meters.

Sino-Inst is Food grade flow meters supplier, located in China. Food grade flow meters products are most popular in North America, Mid East, and Eastern Europe. The United States, and India, which export 99%, 1%, and 1% of Food grade flow meters respectively.

Can rotameter be used for gases?

Rotameter can measure gas.

Rotameter is a variable area flow measuring instrument commonly used in industrial automation process control, which can be used to measure the flow of liquid, gas, and steam.

Rotameters are especially suitable for dry gas and steam measurement. Such as the measurement of nitrogen, air, oxygen and other gases.

It is not applicable if the liquid medium or gas medium contains impurity particles. It will affect the accuracy of the measurement.

If the pressure is relatively large, you can use a metal tube float flowmeter. The metal tube float flowmeter can transmit signals remotely for total accumulation or flow control. You can also customize the remote metal rotor flowmeter according to your needs. Explosion-proof metal rotor flowmeter.

Further reading: Nitrogen(N2) Flow Meter Types

More Featured Gas meters:

Extended reading: Beginner’s Guide: Variable area flow meter

Air Rotameter

Metal tube rotameter can be used to measure air. Because the rotameter is a variable area flow measuring instrument commonly used in industrial process automation control.

Rotameter has the characteristics of small size, large detection range and convenient use. It can be used to measure the flow of liquid, gas and steam. It is especially suitable for medium flow measurement with low flow velocity and small flow. Therefore, there is no problem in measuring air. However, it should be noted that the metal tube rotor flowmeter is only suitable for the flow measurement of small-diameter and low-velocity media within DN200.

Extended Reading: Digital air flow meters

More about Types Of Air Flow Measurement Instruments.

Chlorine Gas Rotameter

Rotameters are used to measure the flow of various small-diameter media. Of course, it is also very reliable when used in the chlorine flow measurement industry.

For the measurement of chlorine gas, the metal tube rotameter can fully meet this measurement requirement. Rotameters are not only made of metal, but also made of glass.

Comparing the two, the metal tube rotor flowmeter has on-site display and intelligent remote transmission functions. The measurement accuracy is high and it is easy to use. And the whole is relatively sturdy and has a long service life.

The glass tube rotameter has a simple structure. There should be no bumps during use. It is fragile and non-explosive, and has a short service life. The metal tube rotameter is superior to the glass tube rotameter when measuring chlorine.

Extended reading: Gas Mass Flow Meter

Nitrogen Gas Rotameter

There are many types of Nitrogen gas flow meters. There are three types of flow meters commonly used to measure nitrogen. Precession vortex flowmeter, gas vortex flowmeter, thermal gas mass flowmeter. When selecting a model, it is necessary to select a suitable model and specification according to the parameters and cost that can be provided on-site.

Of course, the rotameter is also a good choice for measuring nitrogen. Because of the low cost.

Read more anout: Nitrogen Gas-Liquid Nitrogen Flowmeters

Hydrogen Gas Rotameter

There are three types of flowmeters commonly used to measure hydrogen flow: precession vortex flowmeter, gas vortex flowmeter, and thermal gas mass flowmeter. When selecting a model, it is necessary to select a suitable model and specification according to the parameters and cost that can be provided on site. You must communicate well with the sales staff to make the measurement accurate.

Of course, the rotameter is also a good choice for hydrogen measurement. Because of the low cost.

Extended reading: Featured Hydrogen flow meters

Natural Gas Rotameter

The flow measurement of natural gas is currently mainly used in trade settlement and is relatively common. my country’s natural gas trade measurement is based on the volume or energy method under the legally required quality indicators for transfer measurement. At this stage, volume measurement is basically the main method.

At present, the flowmeter products used for natural gas flow measurement generally include: gas waist wheel flowmeter, gas turbine flowmeter, precession vortex flowmeter, vortex flowmeter, ultrasonic flowmeter and orifice flowmeter.

Let’s make a simple comparison on the use of these flow meters.

Extended reading: 5 matters to pay attention to when choosing threaded Vortex Nitrogen Gas Flow Meter

Rotameter Gas Flow Conversion

When measuring gas and liquid media, are the parameters of the rotameter the same?

Metal rotor flowmeter is a variable area flow measuring instrument commonly used in industrial automation process control. When it is measuring liquid and gaseous media, because the density of the two media is different, the material of the rotor of the flowmeter will also be different due to the density of the medium.

Regardless of whether it is measuring gas or liquid, the metal rotor flowmeter is the same in appearance and structure. But because the density of a gas is lower than that of liquid, the density of gas rotor material is smaller than that of the liquid rotor.

Whether the rotameter for measuring gas or liquid, the structure is basically the same, and it is equipped with a rotor in a conical tube. The main differences are as follows:

1. The calculated density of the rotor: the density for liquid is high, and the density for gas is low.
2. Rotor shape: the cross-sectional area of ​​liquid is relatively small, and the cross-sectional area of ​​gas is relatively large
3. Damping device: It is better to use a damping device for liquids and gas, so that the measured value is stable.

Therefore, when we choose the metal rotor flowmeter, we need to clearly describe the real-time conditions of the working conditions with the manufacturer. In this way, we can formulate qualified process and technical parameter models of flowmeters according to the actual requirements of the working conditions. So as to be able to solve the measurement problem more effectively.

Extended reading: Radar level sensor for solids – Dust solid level measurement

Gas Rotameter Calibration

It is not feasible to calibrate metal tube rotameters with conventional methods. This is determined by the structural principle of the transmitter.
Because the rotameter is between the input pressure source and the generated 4-20mA current signal. Besides to machinery and circuits. There are also micro-processing chips that perform calculations on input data. Therefore, the adjustment is different from the conventional method.

In fact, the manufacturer also has instructions on the calibration of metal tube rotameters. A series of transmitters produced by our company. For calibration, there are: “Set range”, “Re-quantity range”, “Fine adjustment” points.

Extended reading: liquid nitrogen level measurement

Among them, the “set range” operation is mainly to complete the configuration work through the number of LRV and URV. The “re-quantity range” operation requires the transmitter to be connected to a standard pressure source. Guided by a series of instructions, the transmitter directly senses the actual pressure and sets the value. The initial and final settings of the range directly depend on the actual pressure input value. But it should be seen that although the analog output of the transmitter has a correct relationship with the input value used. But, the value displayed by the digital readout of the process value will be slightly different. This can be calibrated by fine-tuning items.

Because each part of the metal tube rotor flowmeter needs to be adjusted separately and must be adjusted together. Therefore, the actual calibration can be carried out according to the following steps:

Make a 4-20mA fine-tuning first. It is used to calibrate the D/A converter inside the transmitter. Because it does not involve sensing components.

No external pressure signal source is required.

Do one more full fine-tuning. Make the 4-20mA and digital readings coincide with the actual applied pressure signal. Therefore, a pressure signal source is required.

Finally, do the re-quantification process. Adjust the analog output 4-20mA to match the external pressure signal source. Its function is exactly the same as that of the zero adjustment (Z) and range adjustment (R) switches on the transmitter housing.

Some people think that the range of metal tube rotameter can be changed as long as the HART handheld communicator is used. And can adjust the zero point and span. There is no need to enter a pressure source. But this approach cannot be called calibration, but can only be called “setting range”.

The real calibration requires a standard pressure source to enter the transmitter. The range adjustment (LRV, URV) is not calibration because the standard instrument is not used. Ignore the input part (pressure of the input transmitter) to adjust the output, (transmitter conversion circuit) is not a correct calibration.

Furthermore. The relationship between pressure and differential pressure detection components. A/D conversion circuit. And current output is not equal. The purpose of calibration is to find out the relationship between the three changes.

Extended reading: Cryogenic Flow Meters | Liquid Nitrogen-Liquid Oxygen

Extended reading: How does a rotameter work

Sino-Inst offers over 30 rotameter products. About 50% of these are for liquids. 40% are for gas. At the best price.

A wide variety of Gas Rotameter options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Gas Rotameters, located in China.

The top supplying country is China (Mainland), which supply 100% of the Float Flow Meter respectively.

Sino-Inst sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. Gas Rotameter products are most popular in Domestic Market, Southeast Asia, and Mid East.

You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification.

How does a float flow meter work?

Float Flow Meter is also called rotor flow meter. It is mainly used for small and medium caliber flow measurement. It can measure liquid, gas, steam, etc. The product series have complete specifications and are widely used.

Extended reading: Gas Rotameter Tips

Float Flow Meter working principle

Float Flow Meter consists of two parts. One of the rotameter is a tapered tube that gradually expands from bottom to top. The other is a rotor that is placed in the tapered tube and can move freely up and down along the centerline of the tube.

When measuring the flow of fluid, the measured fluid flows in from the lower end of the tapered tube. The flow of fluid impacts the rotor and produces a force on it. The magnitude of this force varies with the flow rate.

When the flow is large enough, the generated force will lift the rotor and raise it.

Extended reading: Fluid flow meter types

At the same time, the measured fluid flows through the annular section between the rotor and the tapered tube wall. At this time, there are three forces acting on the rotor. The dynamic pressure of the fluid on the rotor, the buoyancy of the rotor in the fluid, and the gravity of the rotor itself.

When the flowmeter is installed vertically, the center of gravity of the rotor coincides with the axis of the tapered tube. The three forces acting on the rotor are all along the direction parallel to the axis of the tube.

When these three forces reach a balance, the rotor floats smoothly on a certain position in the cone tube.

For a given rotameter, the size and shape of the rotor have been determined. Therefore, its buoyancy in the fluid and its own gravity is known to be constant. Only the dynamic pressure of the fluid on the float changes with the flow rate of the incoming flow.

Therefore, when the flow rate of the incoming flow becomes larger or smaller, the rotor will move up or down. The flow cross-sectional area of ​​the corresponding position also changes. Until the flow rate becomes the corresponding speed when the flow rate becomes balanced, the rotor is stable in the new position.

For a given rotameter, the position of the rotor in the cone tube is in one-to-one correspondence with the flow rate of the fluid flowing through the cone tube.

In order to prevent the rotor from touching the tube wall when moving up and down on the centerline of the tapered tube, two methods are usually used.

One is to install a guide mandrel in the center of the rotor to keep the rotor moving up and down on the centerline of the tapered tube.

The other is a chute on the edge of the rotor disc. When the fluid flows through the rotor from bottom to top, one side bypasses the rotor. At the same time, it passes through the chute to generate a reverse thrust. The rotor keeps rotating around the centerline. . It can keep the rotor from touching the pipe wall when working. The rotor material of the rotameter can be made of stainless steel, aluminum, bronze, etc.

Extended reading: Micro flow meters for low flow liquids

Types of Float Flow Meter-variable area flowmeter

Float type water flow meter

Rotameters can be used to measure the instantaneous flow of water. There are many flow meters for measuring water. Almost all flow meters that measure liquids can be used to measure water.

The original rotameter used to measure water is now used to measure the flow rate of gasoline. Is the reading correct?

Certainly not. Rotameter measuring liquid is most affected by liquid density and viscosity. It is recommended to find the manufacturer to tell them the parameters of your gasoline. It should be able to help you convert and tell you the true flow rate when the current scale is used to measure gasoline.

Rotameters measure different liquids. How to convert?

Rotameter display value correction. The fluid and state when the flowmeter is in use are generally different from the fluid and state when the flowmeter is scaled. Therefore, the value of the flow meter reading during use is not the real flow through the flow meter. The indicated value must be corrected according to the fluid and state in use. In order to get the correct flow.

The flow meter produced by Sino-Inst is calibrated with water for measuring liquid. The flowmeter for measuring gas is calibrated with air. The indicated value is scaled according to the volume flow rate of the standard state (water at 20°C; air at 20°C, 101.325KPa). Therefore, all corrections are based on the standard state index.

Extended reading: Beginner’s Guide: Variable area flow meter

More Featured Water Flow Meters:

Float air flow meter

Metal tube rotameter can be used to measure air. Because rotameter is a kind of variable area flow measuring instrument commonly used in industrial process automation control.

It has the characteristics of small size, large detection range, and convenient use.

It can be used to measure the flow of liquid, gas and steam. It is especially suitable for medium flow measurement with low flow rate and small flow, so there is no problem in measuring air.

However, it should be noted that the metal tube rotor flowmeter is only suitable for the flow measurement of small-diameter and low-velocity media within DN200.

More Featured air flow meters:

Extended reading: Integral DP Flow Meter|Gas, liquid, steam|Compact structure

Sino-Inst offers over 30 Float Flow Meter products. About 50% of these are for liquids. 40% are for gas. At the best price.

A wide variety of Float Flow Meter options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Rotameter flow meters, located in China.

The top supplying country is China (Mainland), which supply 100% of the Float Flow Meter respectively.

Sino-Inst sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. Float Flow Meter products are most popular in Domestic Market, Southeast Asia, and Mid East.

You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification.