Level gauges are meters used to determine the level of a liquid in a fixed storage or process tank. The gauge is composed of several parts including head, float, measuring tape, bottom anchored bracket, guide wires, elbows, anchors, coupling, pipe support brackets, and pipework. Liquid level gauge calibration is used to ensure proper readings are obtained when using level gauges.
Why choose us
01
Our Product
We offer a range of products, including ultrasonic liquid level meters, electromagnetic flow meters, open channel flow meters, and online water quality analyzers. Our analyzers include online pH meters, dissolved oxygen meters, conductivity meters, turbidity meters, sludge concentration meters, and sludge interface meters. Additionally, we provide pressure transmitters and input level gauges.
02
Product Application
Dongyi is a high-tech company that manufactures industrial instruments. Our products are used in many fields, such as environmental protection, chemical processing, printing and dyeing, pharmaceuticals, water treatment, municipal engineering, and tap water systems.
03
Our Certificates
We hold several certifications, including utility model patents, design patents, software works, and quality management system certifications.
04
Production Equipment
Our production facilities are equipped with advanced tools, including ultrasonic and radar testing devices, laser welding equipment, flow calibration devices, pressure debugging equipment, high and low temperature aging boxes, and circuit aging devices.
Main Advantages of Transmitters
High Accuracy and Stability
The high accuracy and stability of transmitters are among their most significant advantages. In many industrial applications, precise measurements are crucial to ensuring product quality and safety. Transmitters can maintain stable performance in extreme environments such as high temperatures and pressures, ensuring the reliability of measurement results.
Wide Applicability
Transmitters have a wide range of applications and can be used in almost all industrial sectors. Whether in the petroleum, chemical, or power industries, transmitters can adapt to various media (gas, liquid, solid) and provide customized solutions. This flexibility enables transmitters to meet the needs of different customers, enhancing their market competitiveness.
Real-time Monitoring and Data Transmission
Real-time data collection and monitoring are crucial in modern industry. Transmitters can capture various data in real-time during the production process and transmit the data to monitoring systems through advanced data transmission technologies (such as wireless transmission, cloud technology). This real-time monitoring capability not only improves production efficiency but also provides important basis for decision-making.
Reduced Maintenance Costs
The durability and reliability of transmitters significantly reduce maintenance costs. High-quality transmitters typically have a longer service life, reducing maintenance frequency. Additionally, many transmitters are equipped with fault warning systems that can promptly alert in case of issues, avoiding potential losses.
Increased Production Efficiency
The application of automation technology has significantly improved production efficiency. Transmitters play a crucial role in process optimization, allowing enterprises to adjust production parameters in real-time based on feedback from real-time data, thereby improving production efficiency. Additionally, the data provided by transmitters support decision-making, enabling enterprises to better respond to market changes.
Safety and Compliance
In many hazardous environments, the safety of transmitters is crucial. Transmitters can operate normally in harsh conditions such as high temperatures, pressures, and corrosive environments, ensuring the safety of the production process. Additionally, transmitters typically comply with industry standards and regulations, helping enterprises meet compliance requirements and reduce legal risks.
Classification of Transmitters
According to the Output Signal Type:
Transmitters can be divided into two types: Current output type and voltage output type.
(1) Voltage Output Transmitter:
This type functions as a constant voltage source. The impedance of the voltage input terminal of the PLC analog input module is very high. If the transmission distance is long, small interference signal currents can produce a higher interference voltage on the module’s input impedance. Therefore, the anti-interference capability of remotely transmitted analog voltage signals is poor. However, this type is suitable for sending the same signal to multiple instruments in parallel, and installation is straightforward. Disassembling or assembling one of the instruments will not affect the operation of the others. Additionally, the voltage withstand requirements of the output stage are reduced, improving the instrument's reliability. The voltage signal typically ranges from 1 to 5 V, 0 to 10 V, and -10 to 10 V, with 1 to 5 V and 0 to 10 V being the most common.
(2) Current Output Transmitter:
This type acts as a constant current source, with a very high internal resistance. When the PLC analog input module receives a current input, the input impedance is low. As a result, the interference voltage generated by noise on the line is minimal, making the analog current signal suitable for remote transmission. It can effectively transmit over distances of hundreds of meters when using shielded cables. Standard current signals include 0 to 10 mA, 0 to 20 mA, and 4 to 20 mA, with 4 to 20 mA being the preferred choice. A current of 0 mA typically indicates circuit failure or power loss.
Current signal transmission and voltage signal transmission each have their own characteristics. Current signals are suited for long-distance transmission, while voltage signals allow meters to connect in a "parallel system." Thus, in a control meter system, the transmission signal in and out of the control room typically uses current signals, while communication between instruments within the control room uses voltage signals. In other words, the connection method employs current transmission and parallel reception of voltage signals.
Transmitters can also be categorized as two-wire systems or four-wire systems. A four-wire transmitter has two power lines and two signal lines, with no strict requirement on the power consumption of the current signal's fractional component. Two-wire transmitters have only two external wires that serve both as power and signal lines. However, the lower limit of the current signal cannot be zero. Two-wire transmitters are favored for their fewer wiring requirements and longer transmission distances, making them the most widely used in industry.
According to the Energy Used:
Transmitters can be classified into two types: Pneumatic transmitters and electric transmitters.
(1) Pneumatic Transmitter:
A pneumatic transmitter uses dry and clean compressed air as its energy source. It can convert various measured parameters (such as temperature, pressure, flow rate, and liquid level) into a pressure signal of 0.02 to 0.1 MPa for transmission to regulators, displays, and other combined instruments for indication, recording, or adjustment. The structure of pneumatic transmitters is relatively simple, and they have strong resistance to electromagnetic interference, radiation, temperature, humidity, and other environmental factors. They can be fireproof and explosion-proof, and they are relatively inexpensive. However, their response speed is slow, and their transmission distance is limited. Additionally, it can be challenging to connect them to a computer.
(2) Electric Transmitter:
An electric transmitter uses electricity as its energy source, facilitating convenient signal connections and allowing for long-distance transmission. They are also easy to connect to electronic computers and can be explosion-proof for safe use. The main disadvantage is that the initial investment is typically high, and they are significantly affected by temperature, humidity, electromagnetic interference, and radiation. Electric transmitters can convert various measured parameters into standard signals of 0 to 10 V or 4 to 20 mA for transmission to other units in an automatic control system.
Transmitter Components
Power Supply
The power supply is straightforward; it provides power to the transmitter, supplying the energy needed to broadcast the signal.
It can also transform electrical power from the input into higher voltages if required for the output. The power supply takes the electrical current and converts it into the appropriate current, voltage, and frequency needed for operation.
Electronic Oscillator
The electronic oscillator generates a wave, known as a sine wave, which carries data through the air.
Essentially, it is an electronic circuit that produces this periodic wave by converting direct current from the power supply into alternating current. The electronic oscillator helps stabilize the frequency in transmitters.
The waves it creates are often referred to as carrier waves because they carry information. Modern transmitters typically use a crystal oscillator, controlled by the vibrations of a quartz crystal.
Modulator
The modulator adds information to the carrier waves being transmitted. It is a circuit that varies aspects of the carrier wave.
The modulator provides information to the transmitter via a modulation signal, which is an electrical signal. This signal is typically either an audio signal or a video signal.
Modulation is well-known in radio transmission, with the most common types being amplitude modulation (AM) and frequency modulation (FM).
In amplitude modulation, the amplitude or strength of the carrier wave varies proportionally to the modulation signal. In frequency modulation, it is the frequency of the carrier wave that is varied by the modulation signal.
RF Amplifier
An RF amplifier, or radio frequency amplifier, is used to amplify the power of the actual signal, thereby increasing the range of the radio waves.
An RF amplifier is typically used to drive the transmitter's antenna.
Antenna Tuner
The antenna tuner matches the impedance of the transmitter to the antenna, facilitating efficient power transfer.
The antenna tuner is also known as the impedance matching circuit. In addition to transferring power to the antenna, the antenna tuner prevents standing waves, which occur when power is reflected from the antenna back to the transmitter.
A transmitter works by taking an input signal, which may be either analog or digital, and converting it into a format suitable for transmission. This usually involves a process known as modulation, where the input signal is combined with a carrier signal to create a new signal that can be efficiently transmitted over long distances.
● Amplitude Modulation (AM): Here, the strength (amplitude) of the carrier wave is varied in accordance with the input signal.
● Frequency Modulation (FM): In this case, the frequency of the carrier wave is altered based on the input signal.
● Phase Modulation (PM): The phase of the carrier signal is changed according to the input signal.
Maintenance of a Level Gauge
Regular maintenance is necessary to ensure that a level gauge continues to provide accurate readings. Here are some tips for maintaining a level gauge:
Clean the Gauge Regularly:
The level gauge should be cleaned regularly to remove any dirt, buildup, or debris that can affect the readings.
Check for Leaks and Repair Damaged Components:
The level gauge should be checked for leaks, and any damaged components should be repaired or replaced immediately.
Replace Worn or Damaged Seals or Gaskets:
The seals and gaskets on the level gauge should be inspected regularly and replaced if they are worn or damaged.
Check the Calibration of the Gauge Regularly:
The calibration of the level gauge should be checked regularly to ensure that it is providing accurate readings.
Variables Measured by the Transmitter
Pressure Transmitters
Pressure transmitters, also called pressure transmitters, are primarily used to measure various types of process pressures. They include:
(a) Absolute Pressure Transmitter – This transmitter measures pressure relative to a perfect vacuum, also known as a vacuum transmitter.
(b) Gauge Pressure Transmitter – This transmitter measures pressure relative to atmospheric pressure at a given location. When the pressure gauge reads 0 PSI, it means the pressure is atmospheric.
(c) Differential Pressure Transmitter – This transmitter measures the difference between two or more pressures introduced as inputs to the sensing unit. They are commonly used to measure the pressure drop across an oil filter, for example, and are also popular for measuring flow or level in pressurized vessels.
Level Transmitters
Level transmitters are used to measure the level of a liquid or solid material within a vessel or space. These transmitters can measure level continuously or at specific points:
(a) Point Level Transmitters – Provide an output when a specific level measurement is reached. This output is generally in the form of an audible alarm or an electrical signal to turn on a switch.
(b) Continuous Level Transmitters – Measure level within a specified range and provide an output as a continuous reading in proportion to the changing level of the liquid.
Various types of level transmitters are used in the process industries, including:
(a) Ultrasonic Level Transmitters – Used for non-contact level sensing of highly viscous liquids and bulk solids.
(b) Conductive Level Transmitters – Used for point level detection of a wide range of conductive liquids, such as water, and are especially well-suited for highly corrosive liquids like caustic soda and hydrochloric acid.
(c) Pneumatic Level Transmitters – Used in hazardous environments and where there is no electric power. They are ideal for applications involving heavy sludge or slurry.
(d) Capacitance Level Transmitters – Used in non-conductive liquids with a high dielectric constant and suitable for continuous level monitoring.
(e) Hydrostatic-based Level Transmitters – These transmitters use hydrostatic pressure at a point in a liquid to determine the level.
Temperature Transmitters
A temperature transmitter comprises a temperature sensor and a transmitter. The transmitter receives a signal from temperature sensors, such as a thermocouple or RTD, computes the temperature based on this signal, and then converts it to a 4-20 mA output signal meant for a receiving device, such as a controller.
Different types of temperature transmitters are used in the process industries, utilizing various temperature measurement technologies. The most common types include:
(a) Thermocouple-type Temperature Transmitter – With a thermocouple, the electromotive force generated by changes in process temperature is used to calculate temperature.
(b) RTD-type Temperature Transmitter – When an RTD is used, changes in process temperature result in changes in the electrical resistance of the RTD sensor. This relationship between process temperature and electrical resistance is then used to calculate temperature by the transmitter.
Flow Transmitters
A flow transmitter is used to measure and indicate flow. It combines a flow sensor and transmitter in one unit. The flow signal from the flow sensor is used by the transmitter to generate a 4-20 mA output that represents changes in flow in the actual process.
Power Output or Input
Power output may be tested into the antenna only if the channel is not busy; otherwise, a dummy load is used. An RF wattmeter, or SWR meter, is added between the transmitter and the dummy load. When the transmitter is switched on, the wattmeter indicates the power output. The output power may also be determined by:
Po=Ia2RaP_o = I_a^2 R_aPo=Ia2Ra
Where IaI_aIa is the value read on a thermocouple antenna ammeter calibrated for VHF or UHF, and RRR is the resistance of the dummy load or the impedance of the antenna at the measured point. When a dummy load is used, the SWR should be nearly 1:1. If connected to an antenna, it may be higher. If the SWR is above 1.3:1, there may be something wrong with the antenna system. Power input is determined by:
Pin=VdcIdcP_{in} = V_{dc} I_{dc}Pin=VdcIdc
of the final RF amplifier, where IdcI_{dc}Idc is the output circuit DC current and VdcV_{dc}Vdc is the output circuit's DC power supply voltage. Power output may also be determined by:
Pin×efficiency of the final stageP_{in} \times \text{efficiency of the final stage}Pin×efficiency of the final stage
Transmitters should not be operated at levels greater than the manufacturer's ratings.
Modulation Deviation or Percentage
Modulation tests for an FM transmitter require a calibrated modulation monitor. A sinusoidal 1000-Hz tone (or a whistle in an emergency) should produce a maximum of about 4.5 kHz of deviation at the beginning of limiting, and it should be equal in both the positive and negative directions. Voice modulation should then be set to produce a 5-kHz deviation. If positive and negative deviations are dissimilar (non-symmetrical), the cause may be due to mistuning of one or more of the RF stages, a detuned antenna, or improper functioning of the modulator stage.
For AM transmitters, a sinusoidal 1000-Hz input should be able to produce at least 70% modulation, as shown on a modulation monitor or oscilloscope. Speech should never drive the negative peaks to zero on the scope. Distortion, whether audible or noted on a scope, can be checked by observing waveforms as the audio signal progresses from the microphone to the modulator. A distortion analyzer may be used to check for suspected audio distortion. The inability to produce the required modulation levels can often be pinpointed using an oscilloscope. A spectrum analyzer provides a measurement of the sidebands or spurious signals (“spurs”) generated by modulation. The peak envelope power (PEP) of SSB, FM, AM, or CW transmission can be determined with a calibrated oscilloscope connected across the known antenna transmission line impedance by:
P=V2ZP = \frac{V^2}{Z}P=ZV2
Frequency Checks
Frequency checks are made using special frequency monitors or a frequency counter set at a 1-second gating time. The frequency tolerance must be known to determine whether the transmitter is operating within limits. The frequency should be checked when the transmitter is cold and again after it has been turned on for at least 20 minutes to establish the direction of frequency drift. The transmitter frequency should be set so that, when warm, it is as close to the assigned frequency as possible without being out of tolerance when starting cold. No modulation—voice, tone, CTCSS, etc.—should be present on the carrier when the frequency is being checked.
Our Factory
Zhejiang Dongyi Technology Co., Ltd. was formerly known as Hangzhou Tuosheng Automation Instrument Co., Ltd. "TUOSHENG" was founded in 2010. It has been deeply involved in the industrial instrument industry for more than ten years and has profound technical accumulation. Dongyi Company was built by the original team of "Tuosheng" and its headquarters is located in the beautiful paradise on earth - Hangzhou, Zhejiang. In 2023, the company began to prepare for international cross-border business, and registered and established Hangzhou Dongyi Import and Export Co., Ltd. in 2024 to enter the international market.
FAQ
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