1、操作向?qū)?ICP 脈沖力錘086B系列1.0 介紹脈沖錘的方法適合用FFT分析儀來分析測試機(jī)械構(gòu)造。用脈沖力錘儀器敲擊目標(biāo)進(jìn)行測試從而分析機(jī)械結(jié)構(gòu)的動態(tài)特性，通過加速度傳感器測量所發(fā)生的情況。結(jié)構(gòu)一般為：(1)剛性或彈性體(2)被混在一起的恒定的模型和有限元素(3) 引導(dǎo)了應(yīng)力-應(yīng)變聲音波形的分布式的叁數(shù)模型。 一個機(jī)械結(jié)構(gòu)的動態(tài)特性功能測試包括在一個重要的位置安放加速度計(jì)和在那一點(diǎn)或其它的一些點(diǎn)上用脈沖錘敲擊物體來進(jìn)行測試。涉及各種分析模型,在一個固定的地點(diǎn),加速結(jié)構(gòu)影響其他點(diǎn),反之亦然:結(jié)構(gòu)的影響,一度將加速對其他問題的興趣。 信號產(chǎn)生速度將加快, 傳統(tǒng)的計(jì)算遷移數(shù)據(jù)轉(zhuǎn)移等特點(diǎn)慣性、服從、

2、阻抗和流動性。.脈沖錘幾乎是一種力量較廣泛的頻率范圍,因此能夠刺激在那個范圍的所有的共振。 鐵錘大小、時間、物質(zhì)和速度的影響幅度和頻率,確定內(nèi)容(波浪形狀)的推動力量. 影響上限頻率決定一般物質(zhì)的含量,用質(zhì)量和速度的影響, 在確定能量含量的影響。 大型重型機(jī)車像框式支架的機(jī)車、坦克、橋梁、儀器需要一個更大的鐵錘，象壓縮機(jī)刀片的小結(jié)構(gòu)經(jīng)常要求小鐵錘。一些非常大的結(jié)構(gòu)可能要求裝有力傳感器沖擊頭的一個巨大的撞擊系統(tǒng)。本系統(tǒng)所有傳感器都列為ICP、低阻抗、電壓傳感器模式。微電子學(xué)固定放大器標(biāo)準(zhǔn)化敏感性在是充分為多數(shù)動態(tài)應(yīng)用面額的幾百分之之內(nèi)。2.0描述 整個脈沖包括ICP和安裝在鐵錘頭部用來撞擊的石英

3、力傳感器。錘傳感局部職能轉(zhuǎn)移的影響力量變?yōu)殡娦盘栠M(jìn)行分析和展示，這是石英晶體結(jié)構(gòu)僵化、固定收益微電子團(tuán)結(jié)、放大器隔離，電纜被連接到為了方便處理的末端,如果擊錯得話，可以防止出現(xiàn)接口損壞。一個普通雙電纜ICP傳感器是從一個PCB動力單元出發(fā)的，出于平安的原因,可以修補(bǔ)電線電纜彩帶擬用大設(shè)計(jì)的薄弱環(huán)節(jié)。ICP動力單元提供目前的鼓勵傳感器的信號，導(dǎo)致產(chǎn)生薄弱信號，比方許多FFT 動態(tài)分析儀/電腦系統(tǒng)有ICP供電內(nèi)置。脈沖錘是一個不可分割的整體的單元。電子束焊接可以密封不利的環(huán)境里的結(jié)構(gòu)。機(jī)械裝配是用環(huán)氧樹脂粘合劑鎖在一起的，在工廠以外不應(yīng)該被分開，錘子的敲擊末端有一個穿線的孔為各種各樣的沖擊要訣。對

4、傳感器來說，頂端的作用是轉(zhuǎn)移沖擊力和保護(hù)傳感器以免被損壞，不同硬度的頂端可以允許你改變脈沖的寬度和頻率的有效范圍。PCB脈沖錘的八個不同型號的小型動力錘(型號086B80)121B是可用的，脈沖錘(型號086b50)。看到4頁的小冊子,包括本手冊,以獲得更多的資料。 鐵錘是在工廠里用結(jié)構(gòu)粘合劑組裝和鎖緊在一起的。頂端和增量劑通過10-32 個穿線的螺柱(見4.1用測試頭/混合劑挑選)。在系統(tǒng)的圖解里電纜連接被舉例說明和一般做10-32臺同軸連接器。 位移傳感器安裝和系統(tǒng)連接如圖、按程序詳細(xì)描述在特定變頻器手冊。 一些比擬常見的方法包括安裝柱頭螺栓的裝配、石油蠟像、粘合劑和磁鐵。試驗(yàn)使用的方法取

5、決于環(huán)境和用戶意見。一般,連接傳感器ICP動力單元在"XDCR"上，顯示器的裝置(比方分析儀/電腦)。商議ICP動力單元的操作說明,來適應(yīng)安裝和操作程序。 用電纜把鐵錘與動力單元連接在一起，然后你的分析及動力單元的操作指南在系統(tǒng)上顯示。繃緊的電纜被用來確保良好的通信質(zhì)量，如果在潮濕的環(huán)境或戶外里操作，用石蠟涂在連接的地方。轉(zhuǎn)換電源和等一、兩分鐘的擴(kuò)音傳感器里的耦合電容器將充滿電荷，為了正常運(yùn)作而檢查動力單元的儀表。如果儀表亮紅燈的哈話，找短的電纜連接。如果儀表亮黃燈的話，尋找開放電纜連接。連接加速度計(jì)談到有關(guān)以類似方式運(yùn)作指南(加速度計(jì)、電力單位)。當(dāng)所有的動力單元正常運(yùn)轉(zhuǎn)

6、 (綠燈亮)、測試?yán)^續(xù)進(jìn)行下去，接著是傳感器，動力單元、操作指令分析儀。 沖擊力的頻率帶寬適合你的結(jié)構(gòu)測試實(shí)驗(yàn)。1)用錘子打擊物體和測試過程的結(jié)果，總會得到好幾個平均數(shù)來減少偽造的聲音效果。警告：用傳感器安裝在適當(dāng)?shù)牡胤接肋h(yuǎn)不影響末端。 2)檢查信號質(zhì)量測量結(jié)果(適當(dāng)信號-噪音)及無負(fù)擔(dān)(超載或整平燈的歷史頂峰時間)。3)頻率分析成果驗(yàn)收內(nèi)容,以確保合理的范圍內(nèi)局部勢力已足以讓現(xiàn)有的利益結(jié)構(gòu)反響加速頻譜，信號能量經(jīng)常足以激起反響結(jié)構(gòu)，初步選在20dB以下的低頻脈沖。4)如有必要，可以改變鐵錘頂端或者修改它的行為。 a)高頻率響應(yīng),用一個高硬度的頂端而且不要添加任何東西。b)為更好低頻響應(yīng),用一

7、個軟的頂端而且添加?xùn)|西。 c)信號能量越大，沖擊速度越高。5)重復(fù)步驟1至4直到獲得充分的結(jié)果。一般而言，影響到脈沖錘撞擊的頻率信號，及影響信號的能量大小。用不同結(jié)構(gòu)鐵錘，頻率和能量水平都將受到影響， 鐵錘的撞擊速度也會影響到。一般來說，低硬度而體積大的結(jié)構(gòu)也有的好處，柔軟的末端用來敲擊也足夠引起低頻共振。在試驗(yàn)中，加強(qiáng)檢查機(jī)電連接。他們屢次到趨于寬松，可能造成無噪音的信號。雖然各種調(diào)整大大消除這些，當(dāng)在一個輕的物體上施加很重的鐵錘時，(多重影響)仍可能發(fā)生滲透或過重。在你的頻譜數(shù)據(jù)里，也將會出現(xiàn)有條理的成分。拋開這些數(shù)據(jù)，測試更輕一些的無題時需要一些技巧和實(shí)踐經(jīng)驗(yàn)。 PCB的新的ICP動力單

8、元積極信號幅度大于10伏特(3節(jié)電池)，在動力單元里防止超載。失真，負(fù)脈沖信號，脈沖的時域振動在展覽期間所造成的分析的反混淆過濾器是正常的行為。正確看待波形擺動，用高頻寬的分析它。 校正功能測試是將行為(敏感性)傳感器控制結(jié)構(gòu)和環(huán)境。行為目標(biāo)是直線，因?yàn)槔硐胫委熋姹壤齻鞲衅鳌㈩l率相同的利益，而不是拖延信號(無階段轉(zhuǎn)移)。用不同結(jié)構(gòu)具有不同的敏感性，因?yàn)榭荚嚱?jīng)驗(yàn)結(jié)構(gòu)的力量大于晶體傳感內(nèi)容。影響力量的整體質(zhì)量，用武力的結(jié)晶，是一個功能只有群眾背后(沖擊得末端是水晶傳感局部)。他們的分歧,取決于對群眾舉報(bào)的比例頭部重量，當(dāng)用自動補(bǔ)償適當(dāng)調(diào)整。每一個具體的結(jié)構(gòu)可以輕易地用最精確的數(shù)據(jù)，確保調(diào)整。鐵錘打

9、了一個可自由調(diào)整，取消了大量儀器石英加速度計(jì)參考。根據(jù)牛頓第二定律，立即在任何時候，遇到群眾的力量只是衡量質(zhì)量乘以加快。在儲存示波器，產(chǎn)量頂峰將信號的富群眾(mV)加快頂峰時間(G's),那么直接用敏感性mV/了lb。校正的取樣分析結(jié)果產(chǎn)生相同頻率的函數(shù)，由于群眾轉(zhuǎn)移功能好似是身體僵硬不變(1/m)的力量,力和加速度信號的比率產(chǎn)生不斷校正(最好1/M)每個不同的頻率。一錘調(diào)整的影響將是顯而易見的,要把這項(xiàng)校正。巨大的下垂暫停或乳膠放在一塊,做一個剛性的身體，用這種儀器撞擊也是一種很好的方式。 好方法檢測出的正常運(yùn)作和錘子之前測試工具，這個程序的數(shù)據(jù)結(jié)果是比擬成功的。 在密封的傳感建設(shè)單

10、位和建設(shè)保稅排除用外地維修。應(yīng)需效勞，以廠為單位回報(bào)說明上的問題。首先,將電纜,通常的根源,并再次運(yùn)行測試。 雖然鐵錘很上下不平，濫用可能造成它的損害。當(dāng)看到以下措施確保數(shù)據(jù)的準(zhǔn)確。1)不要試圖撤除在鐵錘上的傳感器局部結(jié)構(gòu)，這些工作都應(yīng)在工廠做。2)不會有產(chǎn)生超過100伏特的任何鐵錘，一般來說產(chǎn)出率為5伏，或與PCB新發(fā)電機(jī)組,產(chǎn)量10伏特，一百伏特將會破壞微型電子設(shè)備。3)不影響攻擊對象不正確安裝前場的力量增強(qiáng)因素，損壞精密傳感器可以用外表的印象影響其行為。4)測試期間,定期檢查,加強(qiáng)舉報(bào)和電纜連接,以確保繼續(xù)正常運(yùn)行，機(jī)械單位的搬遷，并注意加強(qiáng)與方便。5)不適用電壓為單位，目前固定保護(hù)。6

11、)當(dāng)前不會提供超過20mA。7)不超過30伏電壓。8)不受到250F溫度以上。脈沖錘的測試實(shí)驗(yàn)附件A 注：照片是在人數(shù)方面全面、微伏電網(wǎng)線路。 測試內(nèi)容是從PCB鐵錘撞擊，K291A示范，校正各面的質(zhì)量下降的固定用固定基地。在質(zhì)量、本錢增高的信號衰減力(x0.89)，比例計(jì)算敏感性。有良好的比例比1.23、1.25根據(jù)實(shí)驗(yàn)廠。最高的力是276lb，最高的加速度是300g。 沖擊不同的結(jié)構(gòu)與錘子登上力量變換裝置和過載信號器(在末端對面) 顯示那碰撞的不同的類型結(jié)構(gòu)和材料有一點(diǎn)點(diǎn)或沒有作用在變換裝置敏感性或在他們的比率。固定變換裝置放大器的低電子噪聲促進(jìn)處理數(shù)據(jù)在計(jì)算機(jī)里。不同的沖擊蓋帽在錘子碰撞

12、搖擺大量拿著過載信號器有非常少許作用在他們的比率。觀察, 這種力量變換裝置, 具體地被構(gòu)造為沖擊測試, 引起質(zhì)量信號沒有敲響或其它假信號在多數(shù)應(yīng)用。不同的增量劑改變錘子結(jié)構(gòu)(許多) 修改它的行為和改變錘子的明顯的力量敏感性當(dāng)觸擊測試對象。提到敏感的傳感器減少了大規(guī)模地震的比例(群眾傳播的影響和限制)的總重量為力量的變頻器用。根據(jù)配置變動是從百分之二到百分之三十，錘子結(jié)構(gòu)的這個正常行為建議校準(zhǔn)錘子配置被使用與一臺慣性大量定標(biāo)器(PCB 式樣904.A) 在測試前。變換裝置電子的超載由鋪平蹤影的頂峰部份見證，退役測驗(yàn)數(shù)據(jù)。交換對24V 恒定的供電(電池或線) 將加倍變換裝置的范圍。脈沖測試錘的結(jié)構(gòu)

13、、行為、校準(zhǔn)附錄B 結(jié)構(gòu)動力試驗(yàn)的行為是明顯的,目的是測試用儀器，測試結(jié)果正確,必須考慮到行為的結(jié)構(gòu)作用。由于慣性效應(yīng)(加載大量的晶體)的力量用在結(jié)構(gòu)上的傳感器只有局部的實(shí)際影響力量,約70至95%依靠鐵錘的結(jié)構(gòu)，用不同組合的脈沖幅度調(diào)整，以適應(yīng)寬度和上升時間的應(yīng)用。用結(jié)構(gòu)調(diào)整改變其行為。測試之前，擊中了群眾印象校正用具體的配置和使用的重要決定力量比例為加速傳感器敏感度。 數(shù)據(jù)也將產(chǎn)生負(fù)面的計(jì)算工具的階段,如果需要或難以正確信息. 從教育的觀點(diǎn)來看,這表現(xiàn)出一種慣性校準(zhǔn)計(jì)算常數(shù)、僵化的組織結(jié)構(gòu)模式。結(jié)構(gòu)：一個脈沖測試鐵錘典型的機(jī)械結(jié)構(gòu)是一個塑造模型，群眾傳播的力量和影響力形成大規(guī)模地震前的水晶

14、傳感內(nèi)容。頭的大量, 增量劑和一局部的把柄支持水晶。行為：在中低頻率，用集體的行為結(jié)構(gòu)為主,這是由牛頓定律確定的，制定有效的錘子/剎車測試對象接口全部用群眾的經(jīng)驗(yàn)，只有局部結(jié)晶，局部群眾的力量制止，它的意義并不相關(guān)的局部部隊(duì)和地震影響群眾上限。提高質(zhì)量頭部或減少的幅度可能造成的影響,但反彈或多重滲透，這支部隊(duì)的傳感器安裝測試對象不是一個好方法，因?yàn)樗苍斐闪舜笠?guī)模的地震,以及采取武力。 加速度沖擊與安裝在錘(撞擊目標(biāo)上限對面)的慣性作用,顯示出極大的鐵錘校正方法。校正：機(jī)械結(jié)構(gòu)的測試功能將取決于敏感特性的比例：力傳感器的傳送。 這個比例可以由用鐵錘敲擊帶有傳感器的巨大結(jié)構(gòu)，由重力校正或者其他方

15、式。 例如：1英鎊出現(xiàn)大規(guī)模的頂峰加速100g遭到力100磅的比例最高，比例是敏感信號。在校準(zhǔn)系統(tǒng)的比例是感情因素減弱"N"除以群眾印象"M"。輕易放棄大規(guī)模固定在一個固定的工廠檢查用的校正器確定了其在比率左右，因?yàn)樵谶@個過程中，群眾地震集結(jié)上限并不明顯行動。PCB結(jié)構(gòu)穩(wěn)定的力量，嚴(yán)格器只有一兩個具體內(nèi)容石英擅長錘沖擊試驗(yàn)申請。其電力結(jié)構(gòu)，包括內(nèi)置組件、統(tǒng)一的擴(kuò)音機(jī)得到反應(yīng)，大大降低噪音的系統(tǒng)，精密的電腦輔助技術(shù)是有幫助的。提供資料收集方式，鐵錘和可靠的低阻抗轉(zhuǎn)換經(jīng)營領(lǐng)域，直接與計(jì)算機(jī)接口及分析人員。這里的想法是由在辛那提市布朗大學(xué)史博士在最艱苦創(chuàng)業(yè)時的

16、結(jié)構(gòu)進(jìn)行測試。OPERATING GUIDEICP IMPULSE-FORCE HAMMERSERIES 086B1.0 IntroductionThe impulse hammer adapts your FFT analyzer for structural behavior testing. Impulse testing the dynamic behavior of mechanical structures is striking the test object with the force instrumented hammer and measuring the resulta

17、nt motion with an accelerometer. Structures generally respond as (1) rigid or elastic bodies (2) finite elements, lumped constant models and (3) distributed parameter models conducting stress-strain (sound) waves. Testing the functional transfer and transactional characteristics of a mechanical stru

18、cture involves mounting the accelerometer at one location of interest and striking the test object with the hammer at that point or some other point. Modal analysis and modeling involves fixing the accelerometer at one location and impacting the structure at other points, or vice versa: impacting th

19、e structure at one point and moving the accelerometer to the other points of interest. Integration of the acceleration signal yields velocity or displacement data for use in computing classical transfer characteristics such as inertance, compliance, impedance and mobility. The hammer impulse consist

20、s of a nearly constant force over a broad frequency range and is therefore capable of exciting all resonances in that range. The hammer size, length, material and velocity at impact determine the amplitude and frequency content (wave shape) of the force impulse. The impact cap material generally det

21、ermines the frequency content and the hammer mass and velocity at impact determine energy content.Large, heavy structures like locomotive frames, tanks, and bridges require an instrumented sledge hammer; whereas, small structures like compressor blades often require minihammers. Some very large stru

22、ctures may require a special massive mechanical ram instrumented with a force-sensing impact head.All sensors in this system are classified as ICP, low impedance, voltage mode sensors. Microelectronic built-in amplifiers standardize sensitivities within a few percent of a nominal value which is adeq

23、uate for most dynamic applications. 2.0 Description The hammer consists of an integral, ICP, quartz force sensor mounted on the striking end of the hammer head. The sensing element functions to transfer impact force into an electrical signal for display and analysis. It is structured with rigid quar

24、tz crystals and a built-in microelectronic unity gain, isolation amplifier. The cable is connected at the end of the handle for convenience and to avoid connector damage should a miss hit occur.The ICP sensor operates over ordinary two-wire cable from a PCB power unit. For reasons of safety, the eas

25、ily repairable ribbon wire cable is intended to be the weak link in larger hammer design. The ICP power unit supplies constant-current excitation to the sensor over the signal lead and debiases the output signal. Many FFT analyzer/computer systems have the ICP power supply built-in.The hammer is a s

26、ingle, integral unit. Electron beam weld sealed construction of operation in adverse environments. The mechanical assemble is locked together with an epoxy structural adhesive so it should not be taken apart except at the factory.The striking end of the hammer has a threaded hole for a variety of im

27、pact tips. The tip functions to transfer the force of impact to the sensor and protects the sensor face from damage. Tips of different stiffness allow you to vary the pulse width and frequency content of the force.PCB impulse hammers are available in eight different models ranging from the mini-impu

28、lse hammer (model 086B80) to the 12 1b. sledge hammer (model 086B50). See the 4-page brochure included with this manual for more information.3.0 Installation The hammer is assembled and locked together with structural adhesive at the factory. Tips and extender via 10-32 threaded studs (see 4.1 testi

29、ng for hammer tip/extender selection). Cable connections are illustrated in the system drawing and are generally made via 10-32 coaxial connectors.Motion sensors install and connect as illustrated in the system drawing and according to detail procedures described in specific transducer manuals. Some

30、 more common installation methods include stud mount, Petro-wax, adhesive, and magnetic. The method used depends on test conditions and user preference. In general, sensors connect to the ICP power unit at the jack labeled “XDCR. The readout device (FFT analyzer/computer). Consult ICP power unit ope

31、rating guide for proper installation and operating procedures.4.0 Operation With cables supplied, connect the hammer to a power unit and then to your analyzer as shown in the system and power unit operation guide. Tighten the cable connectors securely by hand to insure good electrical contact. If op

32、erating outdoors or in humid environments, coat connections with Petro-wax. Switch power on and wait a minute or two for the sensor amplifier to turn on and the coupling capacitor to fully charge. Check the power unit meter for normal operation (meter pointed in green). If meter reads in the red, lo

33、ok for shorted cables or connections. If meter reads in the yellow, look for open cables or connections. Connect accelerometer(s) in similar manner referring to the appropriate operating guides (accelerometer and power unit).When all power unit meters indicate normal operation (green), proceed with

34、tests, following sensor, power unit, and analyzer operating instructions.4.1 Testing To test the behavior of your structure and to tailor the frequency bandwith of the force:1) strike the test object with the hammer and process the results. Always take several averages to reduce the effects of spuri

35、ous noise.Warning: never impact without a hammer tip properly installed on the sensor element. 2) check the measured results for signal quality (adequate signal-to-noise) and no overloads (overload lights or sharp flattening of time history peaks). 3) analyze results for frequency content and check

36、to insure that the reasonably flat portion of the force spectrum is sufficient to cover the structural resonances of interest present in the acceleration spectrum. Often signal energy is sufficient to excite structural resonances at 20 dB below initial low frequency force levels.4) change hammer tip

37、s and/or mass to modify its behavior if necessary: a) for higher frequency response, use a stiffer tip and no extender . b) for better low frequency response, use a softer tip and install the extender. c) to increase motion signal energy, increase impact velocity and/or hammer mass.5) repeat steps 1

38、 and 4 until adequate results are obtained.Generally speaking, the impact tips affect the hammer impulse frequency content and the extender affects the signal energy level. Frequency content and energy level are interrelated so both will be affected by different hammer structures. Hammer velocity at

39、 impact will also affect both. In general, massive structures with lower stiffness require the use of the extender and soft impact tip to adequately excite low frequency resonances. During testing, occasionally check and tighten the electrical and mechanical connections. Repeated impacting tends to

40、loosen them potentially causing erratic and noisy signals. Although modal-tuning has done much to eliminate this, bouncing(multiple impacts) or penetration may still occur when using too heavy a hammer on too light a structure or section of structure. This will appear as an oscillatory component sup

41、erimposed on the spectrum in your data. Reject such data. Some skill and practice may still be required to test lighter structures. PCBs newest ICP power units with greater than 10 volts positive signal range (three batteries) prevent undetected overloads in the power unit. Distortion, undershoot, a

42、nd oscillation of the impulse time history as viewed on the analyzer display is caused by ringing of the analyzers anti-aliasing filters which is their normal behavior. To view the correct impulse waveform, switch the analyzer to a high frequency range.5.0 Calibration Calibration involves testing th

43、e functional transfer behavior (sensitivity) of the sensor structure in controlled transactions and environments. Behavior objectives are straight lines, since ideal sensors treat amplitudes proportionally, frequencies of interest the same, and do not delay the signal (no phase shift). Different ham

44、mer structures have different sensitivities because the test structure experiences a force greater than the crystal-sensing elements. The force of impact on the total mass of the hammer while the force on the crystals is a function of only the mass behind them (the impact tip is in front of the crys

45、tal sensing element). Their differences, which depend on the ratio of the tip mass to the head mass, is automatically compensated for when the hammer is properly calibrated. Each particular hammer structure can be easily calibrated to insure the most accurate data. A hammer can be calibrated by hitt

46、ing a freely suspended mass instrumented with a quartz reference accelerometer. According to Newtons second law of motion, at any instant in time, the force experienced by the mass is simply the mass multiplied by the measured acceleration. On a storage oscilloscope, dividing the peak output signal

47、of the hammer (mV) by the mass (lb.) times the peak acceleration (gs), gives the hammer sensitivity directly in mV/lb. Calibration on a FFT analyzer produces the same result as a function of frequency. Since the transfer function of a mass behaving as a rigid body is a constant (1/M), ratioing the f

48、orce and acceleration signals produces a calibration constant (ideally 1/M) for each discrete frequency. The effects of a nonmodally tuned hammer will be readily apparent when performing this calibration. The mass, pendulously suspended, or placed on a piece of foam rubber, will behave as a rigid bo

49、dy. Hitting such an instrumented mass is also a good way A good way of checking out the normal operation of the hammer and instruments prior to testing. This procedure builds confidence in data results.6.0 MaintenanceThe sealed construction of the sensing element and the bonded construction of the h

50、ammer preclude field maintenance. Should service be required, return unit to factory with a note describing the problem. First, however, replace the cables, which are usually the source of trouble, and test operation again.7.0 Cautions Although hammers are very rugged in construction, damage can res

51、ult from misuse. The following precautions when observed ensure long life and accurate data. 1) Do not attempt to dismantle sensor element from hammer structure. All service should be performed at the factory.2) Never generate more than 100 volts with any hammer. Generally, observe the force rating

52、for 5 volts output or, with newer PCB power units, 10 volts output. One hundred volts will destroy the built-in miniature electronics.3) Never strike an object without an impact tip properly installed in front of the force sensing element. Damaging the precision lapped surface of the hammer sensor c

53、an affect its behavior.4) During testing, periodically check and tighten tip, extender and cable connections to ensure continued proper operation. Machined flats on the tips and extender facilitate tightening and removal.5) Do not apply voltage to unit without constant current protection.6) Do not a

54、pply more than 20mA of current.7) Do not exceed 30 volts supply voltage.8) Do not subject units to temperatures above 250 F.BEHAVIOR TESTING OF IMPULSE-FORCETEST HAMMERAPPENDIX ANote: numbers on the photographs represent full scale dimensions of the grid lines in microseconds and volts. Components t

55、ested are from the PCB hammer kit, model K291A.Calibration at various amplitudes by dropping mass on stationary hammer fixed to base. With mass of 0.92 lb. and attenuation of force signal (X0.89), measured ratio of sensitivities (force to accel.) of 1.23 compares favorably with ratio of 1.25 based o

56、n factory calibrations. Peak force is 276 lb. and peak acceleration is 300 g.Impacting different structures with hammer mounting both force transducer and accelerometer (opposite ends) shows that striking different types of structures and materials has little or no effect on the transducer sensitivi

57、ties or on their ratio. The low electronic noise of the built-in transducer amplifiers facilitates processing the data in computers.Different impact caps on a hammer striking a pendulous mass holding the accelerometer have very little effect on their ratio.Observe that this force transducer, structu

58、red specifically for impact testing, generates a quality signal without ringing or other spurious signals in most applications.Different extenders change the hammer structure (mass) modifying its behavior and changing the apparent force sensitivity of the hammer when striking a test object. The refe

59、rence sensitivity of the transducer is reduced by the ratio of the seismic mass (impact cap and distributing mass) of the force transducer to total mass of the hammer. The change is minus 2 to 30 percent depending on the configuration. This normal behavior of the hammer structure suggests calibrating the hamm