A1340，A1341和A1343传感器温度补偿
A1340，A1341和A1343传感器温度补偿
By Nevenka Kozomora and Jesse Lapomardo,
一种llegro MicroSystems, LLC
介绍
Sensor output can change over temperature due to sensor imperfections or temperature-dependent properties of the magnetic system. The purpose of applying temperature compensation inside the sensor is to keep the sensor output value independent of the temperature and only dependent on the input magnetic field strength.
Implementation
Allegro传感器允许客户改变传感器如何通过使用传感器温度补偿系数来响应温度偏差。这些系数是在图1所示的温度补偿块中实现的传感器温度算法的一部分。
这transfer function of the temperature compensation block is given as the following equation:
V.OUT（v）= sens（Δt一种）×V.在（v）+ OFFSET(ΔT一种）（1）
其中T.一种是环境温度，Δt一种= T.一种- 25°C。
这Sensitivity Temperature Compensation, labeled as SENS(ΔTA), is used to manipulate the effect of temperature on the gain that the sensor applies on the input magnetic signal.The Sensitivity Temperature Compensation is described as a polynomial function of second order:
SENS(ΔT一种）=
[TC1_SENS (m%/°C) × ΔT一种(°C) +
TC2_Sens（M％/°C2）×（ΔT一种）2(°C) + 1 ]（2）
在哪里感觉（Δt一种）在一些温度下，实际计算为：
（25°C）/（录制SENS @ T°C）（3）
这user-programmable parameters are described in the following table:
表1：敏感性补偿的输入变量| 范围 | Definition | 单元 |
| tc1_sens. | 一阶增益温度系数。系数适用于 灵敏度的第一阶项在温度上变化。 |
m%/°C |
| TC2_SENS | 二阶增益温度系数。系数施加 to the second order term of the sensitivity change over temperature. |
m%/°C2 |
一种pplying Compensation Coefficients, TC1_SENS and TC2_SENS, as calculated will result in a temperature-independent gain applied to the sensor’s input signal. It is important to keep in mind that there two sets of these parameters—one to compensate for temperatures below 25°C and one for temperatures above 25°C.
这抵消Temperature CompensatioN，标记为偏移（ΔTA），用于改变传感器应用于输入磁信号的偏移的温度行为。偏移量（ΔTa）的等式被描述为线性一阶函数：
偏移（ΔTa）=
TC1_OFFSET (mG/°C)× ΔT一种(°C) ×
div_sens_coarse.(mV/G)（4）
其中偏移（Δt一种）在一些温度下，实际计算为：
OFFSET(ΔT一种）=（偏移@ 25°C） -
（录制偏移@ T°C）（5）
应用系数Tc1_offset如计算出会导致温度无关的偏移行为。
在A1343设备的情况下，由于温度补偿算法未计算此参数，因此不适用参数div_sens_coarse。
表2：偏移补偿的输入变量
| 范围 | Definition | 单元 |
| TC1_OFFSET | First-order offset temperature coefficient. Coefficient applied to the first-order term of the offset change over temperature. | Mg /°C |
| div_sens_coarse. | 抵消Compensation coefficient for different magnetic ranges. It changes respectively to the change of magnetic field. It is equal to 1 for value of ±500 G. For example if field range changed to ±300 G, coefficient value will be 3/5. | MV / G. |
Calculating Sensitivity Compensation
一种llegro sensors are often used with permanent magnets of unknown field strength at the specific operating positions. Therefore exact calculation of the system Sensitivity per gauss is impossible. However, Sensitivity can be calculated with respect to device position.
In the example below, the user collects device output at two different points in the movement range. Position 1 is at –10 degrees and Position 2 is at +10 degrees.
表3：设备输出示例
| Temperature (°C) |
Sensor with Analog Output | 具有PWM输出的传感器 | Sensor with SENT Output | |||
| Sensor Output @位置1 （v） |
Sensor Output @位置2 （v） |
Sensor Output @位置1 (%D) |
Sensor Output @位置2 (%D) |
Sensor Output @位置1 (LSB) |
Sensor Output @位置2 (LSB) |
|
| -40 | 0..354 | 4..548 | 8.0 | 91.9 | 139 | 3955 |
| –20 | 0.394 | 4..532 | 8.6 | 91.3 | 165 | 3929 |
| 0. | 0.435 | 4..514 | 9.2 | 90.8 | 191 | 3902 |
| 25 | 0.500 | 4..501 | 10 | 90 | 227 | 3867 |
| 50 | 0.546 | 4..481 | 10.7 | 89.4 | 257 | 3837 |
| 75 | 0.614 | 4..459 | 11.6 | 88.5 | 298 | 3796 |
| 100 | 0.693 | 4..427 | 12.7 | 87.4 | 349 | 3746 |
| 125 | 0.790 | 4..393 | 14.1 | 86.1. | 408. | 3686. |
| 150 | 0.883 | 4..342 | 15.5 | 84.7 | 4.74 | 3621 |
这Sensitivity throughout the temperature range can be calculated as:
sens =（vOUT@位置2 - VOUT@位置1）
/（位置2 - 位置1）（6）
Table 4
| Temperature (°C) |
Sensitivity （v /°C） |
Sensitivity (%D/°C) |
Sensitivity (LSB/°C) |
| -40 |
0.210 | 4..19 | 190.78 |
| – 20 | 0.207 | 4..14 | 188.23 |
| 0. | 0.204 | 4..08 | 185.55 |
| 25 | 0.200 | 4. | 182.00 |
| 50 | 0..197 | 3.93 | 179.00 |
| 75 | 0..192 | 3.84 | 174.90 |
| 100 | 0..187 | 3.73 | 169.85 |
| 125 | 0..180 | 3.60 | 163.90 |
| 150 | 0..173 | 3.46 | 157.35 |
In order to calculate the compensation function SENS(ΔT一种）versus ΔT一种值，在表4中的录制数据上应用等式3。方程有效地执行相对于25°C的反相归一化。结果数据如下表所示（注意，温度值现在显示为ΔT一种值，表示偏差25°C）：
Table 5: Normalized Inverse Sensitivity vs. Temperature
| Δta. (°C) |
归一化的逆 Sensitivity |
|
| (cold) | –65 | 0..954 |
| -45 | 0..967 | |
| –25 | 0.981 | |
| 0. | 1.000 | |
| (hot) | 25 | 1.017 |
| 50 | 1.041 |
|
| 75 | 1.072 | |
| 100 | 1.110 | |
| 125 | 1.157 |
这graphical representation of Table 5 is given in Figure 3:
因为快板传感器有不同的温度oefficient codes for compensation at hot and cold temperatures, the above curve is divided into two regions. The hot region, from ΔT一种在0°C和以上，描述了以下等式：SENT（ΔT一种）= 1.408E-06x2+ 7.994e-04x + 1.000。寒冷地区，低于Δt一种X轴上的0°C是由等式的管辖（ΔT一种）= 5.941E-06x2+ 5.094E-04x + 1.000。
这programmable coefficients can now be calculated from the above equations. Note that to convert to m%, a factor of 105 should be introduced.
Table 6: Calculated Temperature Compensation Coefficients
| Coefficients 热的 |
价值 | Coefficients Cold |
价值 |
| tc1_sens_hot. (m%/°C) |
79.94 | tc1_sens._CLD (m%/°C) |
50.94 |
| TC2_SENS_HOT (m%/°C2) |
0..1408 | TC2_SENS_CLD (m%/°C2) |
0..5941 |
编程灵敏度系数
Calculated values for the temperature adjustment can be entered in the software directly under the “Value” column, or the user can calculate the code manually and enter it under the “Code” column.
如果用户在“值”列下方进入所需的系数，则软件将在设备中提供的实际数字舍入到最接近的离散值。例如，TC2_Sens_CLD计算为0.5941 m％/°C2，但程序舍入为0.593m％/°C2。该软件根据TC2_Sens_CLD值，该寄存器的步长，以及值与代码之间的传输函数来自动计算代码。
在用户希望计算必要的代码的情况下，从数据表中提取的下表，可以用作指导。0.5941m％/°C2的所需值将分为0.00596m％/°C2, the typical step size, to get to the needed code of 99.
计算偏移补偿
In the application, linear sensors often see a magnetic field in all positions or often the customer cannot determine in which position the field will be equal to 0. However, reading the device output in two application positions can help to determine the needed sensitivity of the sensor which then helps to calculate the offset as: (VOUT @ Position 2 – Position 2 × Sensitivity). This is shown in Table 7 below:
表7：高温电压偏移
| Temperature (°C) |
抵消 （v） |
抵消 (%) |
抵消 (LSB) |
| -40 |
2.45 | 49.95. | 2047. |
| –20 | 2.46 | 49.96 | 2047. |
| 0. | 2.47 | 49.97 | 2047. |
| 25 | 2.5 | 50.00 | 2047. |
| 50 | 2.51 | 50.01 | 2047. |
| 75 | 2.53 | 50.04 | 2047. |
| 100 | 2.56 | 50.06 | 2047. |
| 125 | 2.6 | 50.09 | 2047. |
| 150 | 2.61 | 50.11 | 2047. |
一旦获得每个温度的偏移，就使用等式5计算校正曲线。
From Figure 7, it can be seen that offset over temperature can be calculated as
OFFSET(ΔT一种）= -0.0009×Δt一种+ 0.0004.
这recorded behavior is in mV/°C and represents the formula:
OFFSET(ΔT一种）= TC1_OFFSET（MG /°C）×ΔT一种(°C)
× DIV_SENS_COARSE (mV/G).
0.0004的恒定项接近零，因此可以忽略它。0.0009的功能增益是TC1_OFFSET（MG /°C）×DIV_SENS_COARSEST（MV / G）的乘积，因此有必要将增益数分成DIV_SENS_COARSEST（MV / G），这取决于所选的磁粗糙范围。如果所选择的范围为250g，则参数div_sens_coarse（mv / g）的值为0.5。
表8：偏移系数值
| 抵消Coefficient | 价值 |
| TC1_OFFSET (mG/°C) for +/-250 G range | 0..0009 / 0.5 = –0.002 |
编程灵敏度系数
Calculated values for the temperature adjustment can be entered in the software directly under the “Value” column, or the user can calculate the code manually and enter it under the “Code” column.
In the case that the user would like to calculate the necessary codes, the table below, extracted from the datasheet, can be used as a guideline
