In modern fuel dispensers, measurement accuracy is one of the core indicators for measuring equipment performance. Whether it is a self-priming pump or a submersible fuel pump, the core of its metering system cannot be separated from two key components: an encoder and a sensor. They are like the "eyes" and "nerves" of a fuel dispenser, monitoring the flow of fuel in real time, converting mechanical movements into electrical signals, ensuring that every transaction is fair, transparent, and reliable.
This article will systematically introduce the basic principles of encoders and sensors, their specific roles and types in fuel dispensers, and their applications in anti cheating, environmental protection, and other aspects.
1. What are encoders and sensors?
(1) Encoder
An encoder is a device that converts mechanical rotation or displacement signals into electrical signals. In fuel dispensers, it is usually installed on the output shaft of the flow meter to detect the rotation angle or number of turns of the flow meter, and then calculate the volume of oil flowing through it.
When the oil flows through the flowmeter, it drives the digital encoder to generate a counting digital signal. The computer device, namely the control motherboard, collects and counts the signal, and compares it with the monitoring microprocessor in real time to ensure accurate measurement
The signal output by the encoder is usually a pulse signal, with each pulse representing a certain unit of oil quantity (such as 0.01 liters). By counting the number of pulses, the system can accurately calculate the amount of fuel added.
(2) Sensors
A sensor is a device that can sense physical quantities such as position, pressure, temperature, flow rate, etc. and convert them into usable electrical signals. In addition to the encoder, there are multiple sensors working together in the fuel dispenser, such as:
Gun lifting switch sensor: detects whether the oil gun has been lifted;
Pressure sensor: used for monitoring pipeline pressure in oil and gas recovery systems;
Gas flow sensor: monitors the return gas volume and is used for gas-liquid ratio calculation;
Temperature sensor: monitors oil temperature and assists in correcting volume.
2. The working principle of encoder in fuel dispenser
(1) Signal generation and acquisition
When the oil flows through the flowmeter, it drives the internal piston or turbine to rotate, and the encoder rotates accordingly, generating a series of electrical pulses. These pulses are transmitted to the control board for counting and processing by the metering microprocessor.
(2) Real time comparison and anti cheating measures
In order to improve the reliability of metering, fuel dispensers are usually equipped with monitoring microprocessors that operate independently of the metering microprocessor, while also collecting and calculating encoder signals. The two compare refueling data in real-time. Once a deviation is found beyond the allowable range, the refueling machine will immediately shut down and prompt an error to prevent cheating behavior.
(3) Types of encoders
According to the type of output signal, encoders can be divided into:
Incremental encoder: outputting pulse signals, displacement needs to be calculated by counting;
Absolute encoder: outputs a unique position code without the need for repeated calibration.
In fuel dispensers, high-precision incremental encoders are commonly used due to their simple structure, low cost, and high reliability.
3. Diversified applications of sensors in fuel dispensers
(1) Sensors in the oil and gas recovery system
To meet environmental requirements, the fuel dispenser is equipped with an online monitoring system for oil and gas recovery, which uses various sensors:
Gas flow sensor: monitoring the volume of recovered oil and gas;
Pressure sensor: monitors the pressure of oil and gas recovery pipelines;
Encoder signal input: receives refueling pulses and calculates the amount of refueling.
These data are processed by the gas-liquid ratio control board to achieve automatic adjustment of the gas-liquid ratio, ensuring compliance with national environmental standards (usually requiring a gas-liquid ratio between 0.9 and 1.3).
(2) Gun lifting switch sensor
Used to detect whether the oil gun has been lifted, triggering the system to prepare for refueling. If no gun lifting signal is detected, the system will not initiate the refueling process to avoid misoperation.
(3) Temperature sensor
Although not elaborated in detail in the textbook, temperature has a significant impact on the volume of oil products. Some high-end fuel dispensers are equipped with temperature sensors for temperature compensation, further improving measurement accuracy.
4. Malfunctions and maintenance of encoders and sensors
(1) Common faults
Encoder communication error: If the error code "-62" is displayed, it indicates abnormal communication between the encoder and the motherboard;
Encoder authentication failed: if "-61" is displayed, it indicates that the encoder does not match the motherboard;
Abnormal sensor signals, such as abnormal gas-liquid ratio or zero return air volume, are often caused by wiring errors or device damage;
Pulse loss: causing inaccurate measurement, usually due to loose signal lines or damaged encoders.
(2) Maintenance suggestions
Regularly check if the encoder wiring is secure;
Clean the sensor probe to avoid oil contamination;
Use specialized instruments to calibrate the gas-liquid ratio system;
When replacing components, pay attention to matching the model and jumper settings.
5. The importance of encoders and sensors in the "new national standard"
According to GB/T9081-2023 and JJG443-2023, the new national standard for fuel dispensers emphasizes three major characteristics: anti cheating, traceability, and online verification. Encoders and sensors are the foundation for achieving these functions:
Anti cheating: Real time comparison of encoder data through dual CPUs to prevent data tampering;
Traceability: Key components such as encoders and motherboards have unique IDs, making the entire process traceable;
Online verification: The system can verify the status of components such as encoders and sensors in real time, ensuring the reliability of data.
6. Conclusion
Although encoders and sensors are small, they are indispensable "nerve endings" and "perception organs" in fuel dispensers. They convert mechanical motion into digital signals, realizing the intelligence, precision, and anti cheating of fuel dispensers. With the implementation of the new national standard and the increasing requirements for oil and gas recovery, their role will become increasingly important.
In the future, with the development of the Internet of Things and AI technology, encoders and sensors will further integrate more functions, such as self diagnosis, remote calibration, intelligent warning, etc., bringing more convenience and security guarantees to gas station operation and management.
