LVDT、半橋和數(shù)字變換理論

感應(yīng)技術(shù)
Inductive Technology

工作原理
LVDT 位移傳感器通過將核心移動(dòng)穿過主體來工作。鐵芯在體內(nèi)的位置由繞在骨架上的線圈檢測(cè)。向線圈提供交流信號(hào)，然后返回交流信號(hào)。然后通過調(diào)節(jié)電子設(shè)備處理該信號(hào)，以提供核心位置的測(cè)量值。主體通常安裝在元件的靜態(tài)部分上，而核心連接在運(yùn)動(dòng)部分上。圖中顯示了簡(jiǎn)化的電氣原理圖。

Principle of Operation
A LVDT Displacement Sensor works by moving the core through the body. The positions of the core within the body is detected by coils wound on the bobbin. The coils are supplied with an AC signal and then returned an AC signal. The signal is then processed by conditioning electronics to provide a measure of the core positions. The body is normally mounted on the static part of an element and the core attached to the moving part. A simplified electrical schematic is shown in the figure.

次級(jí)線圈 A 和 B 反向串聯(lián)，使兩個(gè)電壓 VA 和 VB 相位相反，換能器輸出為 VA-VB。如果鐵芯位于中心位置，則每個(gè)次級(jí)將感應(yīng)出大小相等但相位相反的電壓，凈輸出為零。當(dāng)鐵芯沿一個(gè)方向移動(dòng)時(shí)，相應(yīng)次級(jí)線圈中的電壓會(huì)增加，而另一個(gè)線圈會(huì)經(jīng)歷互補(bǔ)的電壓降低。凈效應(yīng)是與位移成正比的傳感器電壓輸出。了解輸出相對(duì)于激勵(lì)信號(hào)的幅度和相位允許人們從零位推導(dǎo)出芯運(yùn)動(dòng)的位置和方向。

The secondary coils A and B are connected in series opposition so that the two voltages VA and VB have opposite phase and the transducer output is VA-VB. If the core is in the centre positions then voltages of equal magnitude but opposite phase will be induced in each secondary and the net output is zero. As the core is moved in one direction, the voltage in the corresponding secondary coil increases while the other coil experiences a complementary voltage reduction. The net effect is a transducer voltage output that is proportional to displacement. Knowledge of the magnitude and the phase of the output with respect to the excitation signal allows one to deduce the positions and direction of the core motion from the null positions.

LVDT 的輸出是其校準(zhǔn)測(cè)量范圍內(nèi)位移的線性函數(shù)。超出這個(gè)范圍，輸出變得越來越非線性。測(cè)量范圍定義為距傳感器零位的 ± 距離。

The output of an LVDT is a linear function of displacement over its calibrated measurement range. Beyond this range the output becomes increasingly non-linear. Measurement range is defined as ± distance from the transducer null positions.

半橋、LVDT 和數(shù)字傳感器
Half Bridge, LVDT and digital transducers

線性可變差動(dòng)變壓器 (LVDT) 和半橋是線圈格式的兩種替代方法，將在本節(jié)中進(jìn)行介紹。LVDT 和半橋傳感器將磁芯在通電線圈產(chǎn)生的磁場(chǎng)中的運(yùn)動(dòng)轉(zhuǎn)換為可檢測(cè)的電信號(hào)。

The linear Variable Differential Transformer (LVDT) and Half-Bridge are two alternative approaches to the coil format and are described in this section. LVDT and Half-Bridge transducers convert the movement of a core within the magnetic field produced by an energised coil into a detectable electrical signal.

傳統(tǒng)半橋
Conventional Half Bridge

半橋傳感器構(gòu)成惠斯通電橋電路的一半，可以輕松確定從零開始的變化。電橋的另一半內(nèi)置于放大器中。當(dāng)磁芯處于中心位置時(shí)，兩個(gè)信號(hào) VA 和 VB 相等。隨著鐵芯移位，兩個(gè)繞組的相對(duì)電感發(fā)生變化，從而產(chǎn)生 VA 和 VB 的互補(bǔ)變化。

The Half Bridge transducer forms half of a Wheatstone bridge circuit, which enables change from null to be readily determined. The other half of the bridge is built into the amplifier. When the core is in a central positions, the two signals VA and VB are equal. As the core is displaced, the relative inductance of the two windings changes producing a complimentary change in VA and VB.

傳統(tǒng)的 LVDT
Conventional LVDT

當(dāng)磁芯處于中心位置時(shí)，從初級(jí) (VEXC) 到每個(gè)次級(jí)的耦合相等，因此 VA=VB 且輸出 Vout=0。隨著磁芯的位移，VA 與 VB 不同，輸出 VOUT 的幅度和相位與運(yùn)動(dòng)成比例變化。

When the core is in a central positions, the coupling from the primary (VEXC) to each secondary is equal, so VA=VB and the output Vout=0. As the core is displaced VA differs from VB, and the output VOUT changes in magnitude and phase in proportion to the movement.

Solartron LVDT
Solartron LVDT

Solartron Metrology 不斷開發(fā)精密線軸模具和多腔線圈繞組，確保在整個(gè)范圍內(nèi)具有出色的線性度和熱穩(wěn)定性。

Solartron Metrology's continuous development of precision bobbin mouldings and multi-chambered coil windings ensure excellent linearity and thermal stability throughout the range.

Solartron Orbit® 3 數(shù)字傳感器
Solartron Orbit® 3 digital sensors

Solartron 計(jì)量數(shù)字傳感器使用可溯源干涉儀進(jìn)行校準(zhǔn)，并頒發(fā)校準(zhǔn)證書。所有數(shù)字傳感器都配有集成電子設(shè)備，可存儲(chǔ)探頭 ID、范圍、校準(zhǔn)誤差等信息。與傳統(tǒng)模擬傳感器相比，數(shù)字傳感器具有卓越的性能。本目錄中引用的性能數(shù)據(jù)包括探頭內(nèi)的所有機(jī)械錯(cuò)誤以及電子接口模塊中的任何錯(cuò)誤。

Solartron Metrology Digital Sensors are calibrated using a traceable interferometer and are issued with a calibration certificate. All digital transducers are fitted with integrated electronics, which store information such as probe ID, range, calibration error, etc. Digital sensors provide superior performance compared to traditional analogue sensors. Performance figures quoted in this catalogue include all mechanical errors within the probe head together with any errors in the electronics interface modules.

本文翻譯自AMETEK SOLARTRON