單軸-雙軸磁敏傳感器外文翻譯@中英文翻譯@外文文獻翻譯

英文翻譯 單軸 雙軸磁敏傳感器 HMC1001/1002 HMC1021/1022 應(yīng)用 :指南技術(shù) 航海 ,航天系統(tǒng) 姿態(tài)測試 交通定位 醫(yī)療器械 非接觸旋鈕開關(guān) 此傳感器是由 4 部分惠斯通電橋組成的永磁發(fā)電且具有抵抗沖擊的傳感器 ,將磁轉(zhuǎn)換成電壓的形式 .它可以檢測到 30高斯的磁場 ,這些 MR使檢測低磁場具有了小體積 ,低成本 ,高靈敏度 ,高可靠性等功能 . 特性與功能 :較寬的場范圍 ,場范圍 6 高斯 小體積 : 1.此設(shè)計由單軸 ,雙軸共同工作組成了主軸 (x,y,z)測試 . 2.單軸部分由一個 8pin soic 或一個瓷制 8-pin Dip 結(jié)合而成 . 3.雙軸部分由一個 16pin 或 20pin soic 組裝而成 . 堅固性 : 這種小的器械使集成變的更為簡單 ,與機械波門相比提高了可靠性和堅固性 . On-chip coils.采用其專利的芯片內(nèi)設(shè)置 /重置捆綁技術(shù)以減小高溫傾向的影響 ,無線性誤差 ,并由于磁場的存在使干擾信號得以排除 . 顯著成效 :該傳感器經(jīng)特殊工序設(shè)計成 OEM,且被應(yīng)用時可提供大的容量 . 線性磁場傳感器 基本裝置運行 : Honeywen 永磁抗沖擊傳感器是一種簡單的抗沖 擊器件 ,它采用了電橋 ,只需要提供電壓便可測量磁場 ,所供電壓在 0-10V 范圍內(nèi)時與電橋相連 ,傳感器便開始測量或者可以量測所提供的敏感軸線圈內(nèi)的磁場 .除橋電路以外 ,傳感器有 2 個在芯片上的磁組帶 .一個觸發(fā)帶和另一個調(diào)整帶 ,這些帶賦予 Honeywen 專利 ,并取消了對環(huán)繞裝置的外置線圈的需求 . 永磁抗沖擊傳感器由鎳鐵薄片貼于硅制的薄片上 ,并安裝上抗沖擊抵抗性帶 ,當(dāng)橋上的電阻變化時 ,即外界磁場變化 ,將引起輸出電壓的變化 . 膠片邊上所提供平均化的外置磁場會導(dǎo)致磁性向量旋轉(zhuǎn)并改變角度 ,這種改變將引起電阻比較值的改變 ,并使惠斯通電橋上產(chǎn)生變化的電壓 ,這種在鎳鐵電阻值上的變化稱為磁阻效應(yīng) ,電流方向與磁向量間角度直接相關(guān) . 在實驗中 ,這種簡單的軸線 (關(guān)系到磁場方向 )被設(shè)成沿薄片長度的一個方向 ,鎳鐵薄片場中 ,這就允許了一個最大電阻比值變化在鎳鐵薄片上 ,然而 ,(對于大于10g 高斯 )沿著此軸線的強磁場的影響可能被擾亂或丟棄 .膠條磁性兩極也會因此改變了傳感器的表現(xiàn)特征 .對于這種被干擾的場 ,需要提供一種強恢復(fù)性磁場 ,才能使其瞬間恢復(fù)或設(shè)置傳感器所表現(xiàn)的特征 ,這種效應(yīng)將被作為脈沖和調(diào)整脈沖所提及 ,橋兩極所產(chǎn)生的信號依靠這種內(nèi)置薄 片磁向 ,同時與零磁場所輸出的相對稱 . 當(dāng) DC 電流作用時 ,觸發(fā)帶所允許的幾種操作方式 : 1. 可消除非預(yù)期磁場 2. 橋觸發(fā)可設(shè)置為 0 3. 橋產(chǎn)物可供觸發(fā)帶去除在封閉線組成中測量的磁場 4. 電橋值的增加可在系統(tǒng)內(nèi)按要求自動劃分設(shè)置調(diào)整帶可以采用高電流脈沖傳遞信號 5. 傳感器動力系統(tǒng)以高靈敏方式運行 6. 輸出兩極的動態(tài)曲線 7. 在正常運行中循環(huán)往復(fù)以提高線圈的線性度和減小通過軸線的影響與溫度的影響 . 輸出曲線反映了圖 2中所示 s/r脈沖的影響 .當(dāng)一個啟動脈沖傳送信號時 ,就會成為RR+pin.輸出，其符合傾斜曲線 .當(dāng)重起電流以脈沖發(fā)送信號時就成為 SR-pin,輸出遵循負傾向曲線 ,這此電流除 2 個觸發(fā)效應(yīng)外都是端口的鏡像 . 在垂直方向上 ,由圖 2所示可以到橋觸發(fā)在大約 25mv.這是由于產(chǎn)生傳感器時需電阻的搭配 .通過此技術(shù)可以出發(fā)減小到 0.這種促使技術(shù)被運用在平行電阻上 ,通過橋的一個阻值使二者達到同一電壓 .DC 電流在出發(fā)帶中可調(diào)節(jié)出發(fā)至 0.其它方法例如保護非預(yù)制磁場也可以使外置觸發(fā)為 0,輸出反應(yīng)電流由于啟動和重起脈沖而反應(yīng)這兩種現(xiàn)象 . 干擾性 典型 MR 傳感器的干擾密度曲線如圖 3 所示 .1/f 斜面有一個角頻率大約 10hz,在 3.8nv/vhz 轉(zhuǎn)化為 平行 .這大約相當(dāng)于 Johnson 干擾的 850 電阻 典型橋阻 . 在圖 3 中磁場干擾形式如下表述 : 什么是觸發(fā)帶 : 周圍磁場可通過觸發(fā)帶限制電流從而去除原先的磁場 .這對削弱流失 ,硬鐵 ,反常的地磁場的影響很有作用 .例如 :減弱在地磁場中對自身的影響在使用自動指南針之后 .如果 MR傳感器在汽車上安裝在固定位置上 ,地磁場對車的影響大致認(rèn)為是一種在這種場內(nèi)的轉(zhuǎn)換或者是觸發(fā) .如果在地磁場內(nèi)的轉(zhuǎn)換可以決定 ,則可用觸發(fā)帶提供一個相同或相反的場來消除 .觸發(fā)帶的另一個用途是可以使電流通過帶 一準(zhǔn)確消除測量場 ,這稱為封閉線裝置 ,在這里電流反饋回來的喜好被提供場直接測量 . 場觸發(fā)帶將與被控測場相同方向的磁場中產(chǎn)生一個磁場 ,在 HMC1001/2 和10e/5mA以及在 HMC1021/2 時通過的每 50mA電流將為帶提供 10e 場 .例如 ,如果從觸發(fā) +pin中有 25mA電流在 HMC1001/2 時流向觸發(fā) -pin,0.5 高斯的場可以加到被測任何周圍場 .同樣 ,25mA 的電流從周圍場中減 0.5 高斯 ,觸發(fā)帶看似普通的在觸發(fā) +pin 和觸發(fā) -pin 間的電阻 . 觸發(fā)帶使用起來就像是封閉電路中的信息反饋裝置 ,在電流反饋中使用 觸發(fā)可提供測量磁場的理想結(jié)果 .為得到這種效果 ,把橋放大器輸出連接到控制觸發(fā)帶的電流源上 .在線圈使用高效率和負反饋 ,這將使 MR 橋在這行中保持電橋平衡 ,因此 ,無論被測磁場如何 ,通過觸發(fā)帶的電流將被去除 ,橋始終出現(xiàn)零磁場情形 ,最終用于去除場的電流可被直接測量并可以轉(zhuǎn)化為場值 . 觸發(fā)帶也可以在正常操作應(yīng)用過程中可自動劃分 ,這時偶然性檢測的橋為軸獲的輸出物或者對于溫度的明顯轉(zhuǎn)變做調(diào)整是非常有用的 ,這可在向上時或正常運行中任何時刻完成 .內(nèi)容簡單 ,用一條直線上的兩點決定線圈中的那條線 ,即輸出物 .在橋測量穩(wěn)定磁場時 ,值為恒 量 ,記錄穩(wěn)定場讀書 ,記作 H1,現(xiàn)在通過觸發(fā)帶測量已知的電流 ,記作 H2.通過出觸發(fā)帶的電流引起 MR 傳感器在場中測量的變化H .MR 傳感器值計算如下 ,MR 值 = HHH /)( 12 除去所述外觸發(fā)帶還有許多其它的用途 ,主要內(nèi)容是場周圍與觸發(fā)場同另外的場簡單相加與作為獨立場 MR 傳感器的測量之用 . 什么是啟動帶和重置帶 ? 許多弱磁場傳感器在強磁（ 420 高斯）不會受到干擾，這、種干擾可能導(dǎo)致信號惡毒降解。為了減弱該影響，使信號值最大，雌轉(zhuǎn)化技術(shù)可以 被應(yīng)用到 MR 橋，它可以減弱先前磁的影響，裝置和重組帶的目的就是要使 MR 傳感器恢復(fù)高靈敏度條件來測量磁場，通過脈沖傳感大量電流通過裝置，重組帶便可實現(xiàn)次目的。這種裝置 S/R 帶看的 SRT 和 SR-pin 間的電阻。但它的觸發(fā)帶不同之處是磁性安裝到 MR 傳感器的通軸線上，或者靈敏的，有向的。一旦傳感器啟動（或重置），低干擾和高精度場測量產(chǎn)生了。在以下的討論中，關(guān)鍵詞“啟動”在“啟動或重置”將被涉及到。 當(dāng) MR 傳感器放置于被干擾后的磁場中，傳感器組成部分將分解為隨即定位磁場導(dǎo)致精確度降解的磁場（如圖 4A），電流脈沖以高于 最小電流的蜂值通過啟動 /重置帶時，將產(chǎn)生強大的磁場，這個磁場將在一個方向上重新合成嚴(yán)格磁場（見圖 4B）這就保證了高精確度和重復(fù)讀取，負脈沖（重置）將使磁場在反方向上定位旋轉(zhuǎn)（見圖 4C），并且改變傳感器的正負極，只要不出現(xiàn)干擾場這種磁場狀態(tài)可以維持?jǐn)?shù)年之久。 啟動 /重置芯片可以通過電流脈沖傳以重組，或“拋擲”，在傳感器內(nèi)的磁感應(yīng)域，這種脈沖可以和兩個微秒一樣短，在脈沖持續(xù)時，平均消耗少于 1mAdc 規(guī)則循環(huán)可以以每 50 毫秒至 2 微秒脈沖或更長時間中選擇，用以保存磁能。唯一的要求是每個脈沖只有一個方向，也就是說，如 果 a+3.5amp 脈沖用于啟動傳感器，那么脈沖衰退不能低于 0 電流，任何低于電流脈沖的出現(xiàn)都將導(dǎo)致“未啟動”傳感器同時精確讀不再是最合適的了。 使用啟動 /重置帶，很多影響可被避免或減弱，包括：溫漂，無線性誤差，跨軸效應(yīng)和由于強磁場出現(xiàn)而導(dǎo)致的信號值的丟失，同時這可以通過以下程序完成： 1 啟動電流脈沖，可以通過驅(qū)動從啟動 /重置 s/r-pin 來實現(xiàn)啟動，橋值可以電壓輸出來測量并儲存。另一種相同或相反的電流脈沖可以驅(qū)使通過 s/r-pin 來實現(xiàn)“重置”值的電壓輸出來測量，并加以儲存。由橋值輸出值，電壓輸出值 ，可以這樣表達： 2/)()( r e s e tvs e tvv outoutout 這種技術(shù)避免了觸發(fā)和由電產(chǎn)生的高溫效，同時避免了橋的溫漂。 盡管有很多種設(shè)計啟動 /重置脈沖電流的方向，但是預(yù)算和極限場革命將決定哪種最適合實際運用，簡易啟動 /重置電路如圖 5 所示： 啟動 /重置 電流脈沖的重要性依賴于磁干擾精確度，如果最小的調(diào)整場給定為大致在 Hmc1001/2 中的 500 高基介，那么 300amp 脈沖就足夠了，若最小調(diào)整場小于 100 高基介，則要求 4amp 的脈沖，以用產(chǎn)生啟動 /重置的電路。應(yīng)安置在靠 MR 傳感器的地方，并有強磁，還應(yīng)接地。 在 Honeywell磁傳感器上的啟動和重置帶標(biāo)志著 s/r+和 s/r-由于這只是簡易的金屬電阻而它卻不包含兩極。 單時鐘電路，一些時鐘需要激發(fā)啟動與重置脈沖，（圖 6）來產(chǎn)生轉(zhuǎn)換信號。在圖 8 所示電路中可以用以產(chǎn)生強（ 4Amp）的脈沖， diodes 電阻，電容和反轉(zhuǎn)器基本上產(chǎn)生 TRS 和 TSR 延遲，現(xiàn)在單個信號可以激勵啟動和重置脈沖，在時鐘升降沿的最小時間上由 25K 和 1nF 來決定時間常數(shù)，也就是讀時鐘最高峰和最低峰的時間是 25 s。 微處理器 -見圖 9電路中產(chǎn)生了在微處理器控制下一種強啟動 /重置脈沖（ 4Amp）。啟動和重置信號在微處理器中形成，控制 P 和 n 溝道， HEXFET 在另一個打開時關(guān)閉，基本上讀一個事前關(guān)閉組成一個開關(guān)系統(tǒng)。電流脈沖從 4.7 F的電容中讀出，如圖 7 若使用 5-20V 的轉(zhuǎn)換器。則在 16-20V 的前提下。結(jié)果產(chǎn)生了干擾和下滑，但如果在系統(tǒng)其他方面提供 16-20V 的前提下，則一系列電阻（ 500 ）則應(yīng)安裝 4.7 F 的電容和電壓供電之間。 低場測量儀 -當(dāng)測量分辨率為 100 高其介或更低時 permulloy 芯片必須完全啟動或重置。以確保低于干擾和重復(fù)測量。大于等于 4Amps 時的電流脈沖只需幾微秒，就可以實現(xiàn)在圖 8.9 中的電流低干擾和高靈敏度的識別磁技術(shù)，應(yīng)用于 Hmc1001/2 上。 1- and 2-Axis Magnetic Sensors HMC1001 / 1002 HMCI021 / 1022 Configured as a 4-element Wheatstone bridge, these magneto resistive sensors convert magnetic fields to a differential output voltage, capable of sensing magnetic fields as low as 30 gauss. These Mrs. offer a small, low cost, high sensitivity and high reliability solution for low field magnetic sensing. FEATURES AND BENEFITS Wide Field Range Field range up to +6 gauss, (earths field = 0.5 gauss) Small Package Designed for 1- and 2-axis to work together to provide 3-axis (x, y, z) sensing l-axis part in an 8-pin SIP or an 8-pin SOIC or a ceramic 8-pin DIP package 2-axis part in a 16-pin or 20-pin SOIC package Solid State These small devices reduce board assembly costs, improve reliability and ruggedness com-pared to mechanical fluxgates. On-Chip Coils Patented on-chip set/reset straps to reduce effects of temperature drift, non-linearity errors and Loss of signal output due to the presence of high magnetic fields Patented on-chip offset straps for elimination of the effects of hard iron distortion Cost Effective The sensors were specifically designed to be affordable for high volume OEM applications. BASIC DEVICE OPERATION Honeywell magneto resistive sensors are simple resistive bridge devices (Figure 1) that only require a supply voltage to measure magnetic fields. When a voltage from 0 to 10 volts is connected to Vbridge, the sensor begins measuring any ambient, or applied, magnetic field in the sensitive axis. In addition to the bridge circuit, the sensor has two on-chip magnetically coupled straps-the OFFSET strap and the Set/Reset strap. These straps are patented by Honeywell and eliminate the need for external coils around the devices. Magnetoresistive sensors are made of a nickel-iron (Permalloy) thin film deposited on a silicon wafer and patterned as a resistive strip. In the presence of an applied magnetic field, a change in the bridge resistance causes a corresponding change in voltage output. An external magnetic field applied normal to the side of the film causes the magnetization vector to rotate and change angle. This in turn will cause the resistance value to vary (AR/R) and produce a voltage output change in the Wheatstone bridge. This change in the Permalloy resistance is termed the magneto resistive effect and is directly related to the angle of the current flow and the magnetization vector. During manufacture, the easy axis (preferred direction of magnetic field) is set to one direction along the length of the film. This allows the maximum change in resistance for an applied field within the perm alloy film. However, the influence of a strong magnetic field (more than 10 gauss) along the easy axis could upset, or flip, the polarity of film magnetization, thus changing the sensor characteristics. Following such an upset field, a strong restoring magnetic field must be applied momentarily to restore, or set, the sensor characteristics. This effect will be referred to as applying a set pulse or reset pulse. Polarity of the bridge output signal depends upon the direction of this internal film magnetization and is symmetric about the zero field output. The OFFSET strap allows for several modes of operation when a dc current is driven through it. An unwanted magnetic field can be subtracted out The bridge offset can be set to zero The bridge output can drive the OFFSET strap to cancel out the field being measured in a closed loop configuration The bridge gain can be auto-calibrated in the system on command. The Set/Reset (S/R) strap can be pulsed with a high current to: Force the sensor to operate in the high sensitivity mode Flip the polarity of the output response curve Be cycled during normal operation to improve linearity and reduce cross-axis effects and temperature effects. The output response curves shown in Figure 2 illustrate the effects of the S/R pulse. When a SET current pulse (Ireset) is driven into the SR+ pin, the output response follow the curve with the positive slope. When a RESET current pulse (Ireset) is driven into the SR- pin, the output response follow the curve with the negative slope. These curves are mirror images about the origin except for two offset effects. In the vertical direction, the bridge offset shown in Figure 2, is around -25mV. This is due to the resistor mismatch during the manufacture process. This offset can be trimmed to zero by one of several techniques. The most straight forward technique is to add a shunt (parallel) resistor across one leg of the bridge to force both outputs to the same voltage. This must be done in a zero magnetic field environment, usually in a zero gauss chamber. The offset of Figure 2 in the horizontal direction is referred to here as the external offset. This may be due to a nearby ferrous object or an unwanted magnetic field that is interfering with the applied field being measured. A dc current in the OFFSET strap can adjust this offset to zero. Other methods such as shielding the unwanted field can also be used to zero the external offset. The output response curves due to the SET and RESET pulses are reflected about these two offsets. NOISE CHARACTERISTICS The noise density curve for a typical MR sensor is shown in Figure 3. The 1# slope has a corner frequency near 10 Hz and flattens out to 3.8 nV/vHz. This is approximately equivalent to the Johnson noise (or white noise) for an 850 resistor-the typical bridge resistance. To relate the noise density voltage in Figure 3 to the magnetic fields, use the following expressions: For Vsupply=5V and Sensitivity=3.2mVN/gauss, Bridge output response = 16 mV/gauss or 16 nV/u gauss The noise density at 1Hz = 30nV/Hz and corresponds to 1.8 ugauss/Hz For the noise components, use the following expressions: 1/f noise(0.1-10Hz) = 30 * (In(10/.1) nV 64 nV (rms) 4 ugauss (rms) 27ugauss (p-p) white noise (BW=IKHz) = 3.8* /BW nV 120 nV (rms) 50 ugauss (p-p) WHAT IS OFFSET STRAP? Any ambient magnetic field can be canceled by driving a defined current through the OFFSET strap. This is useful for eliminating the effects of stray hard iron distortion of the earths magnetic field. For example, reducing the effects of a car body on the earths magnetic field in an automotive compass application. If the MR sensor has a fixed position within the automobile, the effect of the car on the earths magnetic field can be approximated as a shift, or offset, in this field. If this shift in the earths field can be determined, then it can be compensated for by applying an equal and opposite field using the OFFSET strap. Another use for the OFFSET strap would be to drive a current through the strap that will exactly cancel out the field being measured. This is called a closed loop configuration where the current feedback signal is a direct measure of the applied field. The field offset strap (OFFSET+ and OFFSET-) will generate a magnetic field in the same direction as the applied field being measured. This strap provides a 1 Oersted (Oe) field per50 mA of current through it in HMC1001/2and 10e/5mA in HMC1021/2. (Note: I gauss=l Oersted in air). For example, if 25 mA were driven from the OFFSET+ pin to the OFFSET- pin in HMC1001/2, a field of 0.5 gauss would be added to any ambient field being measured. Also, a current of -25 mA would subtract 0.5 gauss from the ambient field. The OFFSET strap looks like as a nominal resistance between the OFFSET+ and OFFSET- pins. The OFFSET strap can be used as a feedback element in a closed loop circuit. Using the OFFSET strap in a current feedback loop can produce desirable results for measuring magnetic fields. To do this, connect the output of the bridge amplifier to a current source that drives the OFFSET strap. Using high gain and negative feedback in the loop, this will drive the MR bridge output to zero, (OUT+) = (OUT-). This method gives extremely good linearity and temperature characteristics. The idea here is to always operate the MR bridge in the balanced resistance mode. That is, no matter what magnetic field is being measured, the current through the OFFSET strap will cancel it out. The bridge always sees a zero field condition. The resultant current used to cancel the applied field is a direct measure of that field strength and can be translated into the field value. The OFFSET strap can also be used to auto-calibrate the MR bridge while in the application during normal operation. This is useful for occasionally checking the bridge gain for that axis or to make adjustments over a large temperature swing. This can be done during power-up or anytime during normal operation. The concept is simple； take two point along a line and determine the slope of that line-the gain. When the bridge is measuring a steady applied magnetic field the output will remain constant. Record the reading for the steady field and call it H1. Now apply a known current through the OFFSET strap and record that reading as H2. The current through the OFFSET strap will cause a change in the field the MR sensor measures-call that delta applied field (AHa). The MR sensor gain is then computed as: MRgain = (H2-H1) / AHa There are many other uses for the OFFSET strap than those described here. The key point is that ambient field and the OFFSET field simply add to one another and are measured by the MR sensor as a single field. WHAT IS SET/RESET STRAP? Most low field magnetic sensors will be affected by large magnetic disturbing fields (4 - 20 gauss) that may lead t$ output signal degradation. In order to reduce this effect, and maximize the signal output, a magnetic switching technique can be applied to the MR bridge that eliminates the effect of past magnetic history. The purpose of the Set/Reset (S/R)strap is to restore the MR sensor to its high sensitivity state for measuring magnetic fields. This is done by pulsing a large current through the S/R strap. The Set/Reset (S/R) strap looks like a resistance between the SR+ and SR- pins. This strap differs from the OFFSET strap in that it is Magnetically coupled to the MR sensor in the cross-axis, or insensitive, direction. Once the sensor is set (or reset), low noise and high sensitivity field measurement can occur. In the discussion that follows, the term set refers to either a set or reset current. When MR sensors exposed to a magnetic disturbing field； the sensor elements are broken up into randomly oriented magnetic domains (Figure 4A) that leads to sensitivity degrading. A current pulse (set) with a peak current above minimum current in spec through the Set/Reset strap will generate a strong magnetic field that realigns the magnetic domains in one direction (Figure 4B). This will ensure a high sensitivity and repeatable reading. A negative pulse (Reset) will rotate the magnetic domain orientation in the opposite direction (Figure 4C), and change the polarity of the sensor outputs. The state of these magnetic domains can retain for years as long as there is no magnetic disturbing field present. The on-chip SIR should be pulsed with a current to realign, or flip, the magnetic domains in the sensor. This pulse can be as short as two microsecond and on average consumes less than 1 mA dc when pulsing continuously. The duty cycle can be selected for a 2 usec pulse every 50 msec, or longer, to conserve power. The only requirement is that each pulse only drive in one direction. That is, if a +3.5 amp pulse is used to set the sensor, the pulse decay should not drop below zero current. Any undershoot of the current pulse will tend to un-set the sensor and the sensitivity will not be optimum. Using the S/R strap, many effects can be eliminated or reduced that include: temperature drift, non-linearity errors, cross-axis effects, and loss of signal output due to the presence of a high magnetic fields. This can be accomplished by the following process: A current pulse, Iset, can be driven from the S/R+ to the S/R- pins to perform a SET condition. The bridge output can then be measured and stored as Vout(set). Another pulse of equal and opposite current should be driven through the S/R pins to perform a RESET condition. The bridge output can then be measured and stored as Vout(reset). The bridge output, Vout, can be expressed as: Vout = Vout(set) - Vout(reset)/2. This technique cancels out offset and temperature effects introduced by the electronics as well as the bridge temperature drift. There are many ways to design the set/reset pulsing circuit, though, budgets and ultimate field resolution will determine which approach will be best for a given application. A simple set/reset circuit is shown in Figure 5. The magnitude of the set/reset current pulse depends on the magnetic noise sensitivity of the system. If the minimum detectable field for a given application is roughly 500 ugauss in HMC1001/2, then a 3 amp pulse (min) is adequate. If the minimum detectable field is less than 100 ugauss, then a 4 amp pulse (min) is required. The circuit that generates the SIR pulse should be located close to the MR sensor and have good power and ground connections. The Set/reset straps on the Honeywell magnetic sensors are labeled S/R+ and S/R-. There is no polarity implied since this is simply a metal strap resistance. Single Clock Circuitry-Some form of clock is needed to trigger the set and reset pulses (Figure 6) to create the switching signal. The circuit shown in Figure 8 can be used to create a strong (4Amp) pulse. The diodes, resistors, capacitors and inverters basically create the TRS and the TSR delays. Now a single signal (Clock) can trigger a set or reset pulse. The minimum timing between the rising and falling edges of Clock are determined by the 25K and lnF time constant. That is, the minimum high and low time for Clock is =25 us Micro Processor-The circuit in Figure 9 generates a strong set/reset pulse (4 Amp) under microprocessor control. The SET and RESET signals are generated from a microprocessor and control the P and N channel HEXFET drivers (IRF7105). The purpose of creating the TRS and the TSR delays are to make sure that one HEXFET is off before the other one turns on. Basically, a break-before-make switching pattern. The current pulse is drawn from the 4.7 uF capacitor. If the 5V to 20V converter is used as shown in Figure 7, then the resultant noise and droop on the 16-20V supply is not an issue. But if the 16-20V supply is used elsewhere in the system, then a series dropping resistor (=500.Q) should be placed between the 4.71zF capacitor and the supply. Low Field Measurements-When measuring 100 ugauss resolution or less, the perm alloy film must be completely set, or reset, to insure low noise and repeat, able measurements. A current pulse of 4 amps, or more, for just a couple microseconds will ensure this. The circuits in Figures 8 and 9 are recommended for applications of HMC1001/2 that require low noise and high sensitivity magnetic readings. Low Cost-For minimum field measurements above 500 ugauss, a less elaborate pulsing circuit can be used. In both Figures 10 and 11, the pulse signal is switched using lower cost Dadington transistors and fewer components. This circuit may have a more limited temperature range depending on the quality of transistors selected. If accuracy is not an issue and cost is, then the reset only circuit in Figure 11 will work. For any magnetic sensor application, if temperature drift is not an issue, then the reset pulse need only be occasionally applied. This will save power and enable the use of digital filtering techniques as shown in Figure 12. Circumstances for a reset pulse would be 1) power on or, 2) field over/ under range condition. Any other time the sensor should perform normally. The circuit in Figure 13 generates a strong set/reset pulse under a microprocessor clock driven control. A free running 555 timer can also be used to clock the circuit. The SET current pulse is drawn from the 1 uF capacitor and a 200 ohm dropping resist