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Hall Sensors for Fuel Level Sensing

Fuel Level Sensor Using Hall-Effect Sensor ICs - Allegro MicroSystems

由Shashank Wekhande和Ranjit Farakate，
AvantGarde Solutions Pvt. Ltd.,
Allegro Micros亚博棋牌游戏ystems的顾问，LLC

Abstract

开发了基于霍尔的燃油电平传感器IC，为汽车应用提供了高可靠性和准确的燃油电平传感。亚博尊贵会员在本应用中提出了用于基于线圈和数字集群指示器的线性和角度传感器IC的应用。亚博尊贵会员

Introduction

A fuel level sensor (FLS) is used in all automobiles to indicate fuel level. Various methods are used to measure fuel level such as resistive film, discrete resistors, capacitive, and ultrasonic. Resistive-based sensors are most commonly used for this application. These sensors are mechanically connected to a float which moves up or down depending on the fuel level. As the float moves, the resistance of the sensor changes. This sensor is part of a current balance circuit of the fuel gauge display circuit which typically consists of coils for actuation of the display needle. As the resistance of the fuel sensor changes, the position of the needle changes proportional to the current flowing in the coil. A typical resistor-based FLS is shown in Figure 1.

电阻接触的传感器的缺点是由于传感器元件内的滑动触点导致传感器的磨损和撕裂。磨损导致传感器寿命的减少。

**Figure 1: Typical Fuel Level Sensing Arrangement**

This paper describes methods to use Hall-based sensor ICs for non-contact sensing for FLS applications.

非联系霍尔传感器基础

Hall sensor ICs typically sense the magnetic field passing through the IC. For a fuel sensing application, a diametric magnet must be installed such that its rotary movement is proportional to the float movement. Also the sensor needs to be installed in close proximity to the magnet. This is simpler to adopt for retrofitting compared to other non-contact sensor technologies. The magnet could be sealed to protect it from degradation inside the fuel. Even if the fuel is contaminated, the sensing operation will not be affected.

Hall Sensor IC Options for FLS

Allegro offers various options for FLS applications to suit accuracy, linearity, output interface, and cost.

线性大厅-Effect Sensor
线性霍尔效应传感器IC具有与绝对磁场成比例的输出信号。基于磁场的IC输出电压改变。

PWM输出：PWM output offers advantages such as better noise immunity. These type of sensors are suitable for cross-coil-based clusters.
Analog Voltage:In digital clusters, often a microcontroller is used to interface with the LCD and sensor output. An analog input voltage from the sensor is given to the ADC input of the microcontroller. These ICs operate from either a 3.3 V or a 5 V supply and ratiometric to the supply.

两点编程为磁铁和空气间隙变化提供补偿。Allegro还提供多点编程，以适应非均匀罐几何。

Angle Hall Sensor
角度传感器基于磁场的绝对角度的测量。这消除了由于磁体和空气间隙变化而导致的错误。
1. PWM输出：PWM output ICs offer advantages such as better noise immunity and direct connection to the vehicle battery.
2. Analog Voltage:IC提供与角度成比例的模拟输出电压。

表1：Allegro Microsystems的传感器产品亚博棋牌游戏用于燃料传感目的

传感器	输出	Technology	可编程性	Accuracy	Cost
A1356	PWM	线性大厅	Sensitivity + QVO Offset	更好的	Low
A1377	Analog Voltage	线性大厅	Sensitivity + QVO Offset	更好的	中等的
A1330	Analog + PWM	Angular Hall (CVH)	Gain + Short Stroke + Zero Offset + Clamp + Averaging + Rotation	最好的	Low
A1338	PWM	Angular Hall (CVH)	零偏移+平均+旋转	最好的	High

Fuel Tank Construction

燃油罐结构因汽车模型而异。一些具有常规几何形状的坦克导致线性体积浮动角度。对于这样的坦克，只有两点编程就足够了。图2中示出了均匀燃料箱及其特性的一个例子。

**Figure 2: Uniform Fuel Tank and Characteristics**

然而，大多数燃料箱在体积方面是不均匀的，以浮动角度。典型的非均匀罐及其特性如图3所示。对于这些类型的罐，多点
programming in the IC is required for output signal linearization.

**Figure 3: Non-Uniform Fuel Tank and Characteristics**

Linear PWM Hall Sensor for Analog FLS with Coil-Based Cluster

这是用于低成本应用的最常用的FSU。亚博尊贵会员十字线圈布置如图4所示。线圈的一侧直接连接在电池上，另一侧通过串联传感器连接连接到电池。当两个线圈中的电流相同时，线圈将重置为其正常位置。当传感器电流变化时，针从正常位置偏转。这种布置提供了对电池电压变化的取消。由于热效应，传感器电流不是线性的。

这A1356 ICoffers a system-level ratiometric (output which adjusts according to the supply voltage) output solution with minimal components. The A1356 works with internal reverse battery protection. This IC offers two-point magnetic field programming to adjust offset and sensitivity. This allows 4 to 18 V to compensate for magnet, coil, and manufacturing air gap tolerances.

An application circuit for an A1356-based FSU is shown in Figure 5.

这RC filter of R2 and C2 converts PWM output of the A1356 to a proportional analog voltage. MOSFET Q1 converts this voltage to a current output suitable to drive the coil.

Magnet selection is not very critical for this application. NdFeB or ferrite magnets are suitable for this application. For better repeatability, magnets with tighter tolerances should be used.

这magnet used for this application is a diametric type of magnet (round) shown in Figure 7 and it is fitted on the pivot of the float and the sensor is placed on the magnet surface with 2 mm of air gap, as shown in Figure 6. Magnet orientation and linear Hall sensor positioning are shown in Figure 8.

**Figure 8: Positioning of Diametric Magnet (attached to float) and Sensor**

实验结果

Figure 9 shows linear coil current with respect to float angle. Coil current changes with supply voltage and is inherently non-linear due to self-heating thermal effects.

**Figure 9: Float Angle vs. Coil Current**

基于微控制器的簇的数字FLS线性模拟霍尔效应传感器

这A1377是一个可编程线性采用霍尔传感器哪个provides an analog output voltage proportional to magnetic field. The A1377 provides a ratiometric output between 4.5 and 5.5 V input supply voltage. Use the 5 V supply from the cluster used by the interfacing ADC to power the A1377. A linear analog Halleffect sensor-based digital FLS is shown in Figure 10.

这A1377 provides two-point magnetic field programming to adjust offset and sensitivity. This allows users to compensate for magnet, coil, and manufacturing air gap tolerances.

**Figure 10: Linear Analog Hall-Effect Sensor-Based Digital FLS Using A1377**

实验结果

Figure 11 shows linear output voltage with respect to float angle.Output voltage is linear over 50 degrees of float angle displacement.

**Figure 11: Float Angle vs. Output Voltage**

Figure 12 shows the A1377 linear sensor and magnet placement on the fuel sensor assembly.

用于数字杂志的角度厅传感器与基于微控制器的簇

线性传感器由于气隙或磁铁漂移而遭受误差。线角传感器也适用于60度角位移。角度传感器提供宽角位移测量，其输出电压无关，与气隙和绝对磁场无关。A1330是360°角传感器IC，可提供基于磁圆形垂直厅（CVH）技术的非接触角位置。基于角度霍尔传感器的数字FLS如图13所示。该应用使用直径磁体。

Programmable parameters include zero offset to provide flexible magnet placement and short angular displacement for full dynamic range.

**Figure 13: Angle Hall Sensor-Based Digital FLS Using A1330**

实验结果

A1330output voltage with float angle is shown in Figure 14 with 6 mm × 3 mm diametric magnet. Results show a linear output voltage over 75 degrees of displacement which is independent of air gap.

图15示出了燃料传感器组件上的A1330角度传感器IC和磁体放置。

**Figure 15: Arrangement of A1330 Angle Sensor and Magnet on the Fuel Sensor Assembly**

对于电池供电，使用A1330的非比率版本，并在燃料传感器组件中提供本地LDO。

A1330的PWM输出版本可用于数字液体以获得更好的抗噪性。

表2：各种可编程霍尔传感器选项的比较

传感器	Application	Pros	Cons
A1356线性传感器 (PWM)	Coil-Based Analog FLS	更好的noise immunity, ratiometric output with battery voltage, offset and sensitivity programming compensate magnet and air gap tolerances during manufacturing.	Magnet orientation is critical 在大会期间。输出错误 magnetic field drift.
A1377 Linear Sensor (Analog)	Digital FLS	Offset and sensitivity programming compensate magnet and air gap tolerances during manufacturing.	Magnet orientation is critical during assembly, Output error with magnetic field drift. Needs 5 V 供应。
A1330Angle Sensor (Analog + Ratiometric)	Digital FLS	输出voltage independent of air gap and absolute magnetic field, flexible magnet placement, short angular displacement for full dynamic range, SMD package.	Need 5 V from cluster.
A1330Angle Sensor (Analog + Non- 比率）	Analog FLS	输出voltage independent of air gap and absolute magnetic field, Flexible magnet placement, short angular displacement for full dynamic range, SMD package.	Needs LDO for 5 V supply.
A1330Angle Sensor (PWM)	Digital FLS	输出voltage independent of air gap and absolute magnetic field. Flexible magnet placement, short angular displacement for full 动态范围，更好的抗噪声，SMD封装。	需要5 v来自群集或 LDO.

Conclusion

Hall-based fuel level sensing offers reliable non-contact fuel measurement for automotive applications. Allegro offers a wide range of Hall sensors suitable for different FLS systems. All the sensors use simple diametric magnet and offers programming to achieve a linear output signal, even with asymmetric fuel tank shapes.

这information contained in this document does not constitute any representation, warranty, assurance, guaranty, or inducement by Allegro to the
customer with respect to the subject matter of this document. The information being provided does not guarantee that a process based on this information
will be reliable, or that Allegro has explored all of the possible failure modes. It is the customer’s responsibility to do sufficient qualification
testing of the final product to insure that it is reliable and meets all design requirements.