【人體脂肪測量儀】脂肪電子體重稱靠譜嗎 如何自制脂肪測量儀
脂肪電子體重稱靠譜嗎
僅僅體重并不代表健康,人們越來越擔心自己體內的脂肪,因而各種人體脂肪測量儀產品出現在商場。
人體(ti)(ti)脂肪的(de)含量,即脂肪率(lv)(lv)的(de)正確檢測方法(fa)是將人體(ti)(ti)全(quan)部沒入水中,測出排水率(lv)(lv)(體(ti)(ti)積),再根據體(ti)(ti)重求出人體(ti)(ti)的(de)比重,由此推(tui)斷出人體(ti)(ti)的(de)脂肪率(lv)(lv)。但在日常情(qing)況下這種方法(fa)不太現實(shi)。
人(ren)的身體(ti)(ti)含(han)水(shui)(shui)量約為70%,這(zhe)些水(shui)(shui)份絕大部分存在于(yu)血液、瘦肉及內(nei)臟中,而(er)脂肪中含(han)水(shui)(shui)量極低。體(ti)(ti)內(nei)水(shui)(shui)份由(you)于(yu)溶解有各(ge)種(zhong)成(cheng)(cheng)分而(er)呈現低電阻,脂肪卻(que)呈現高(gao)電阻,因而(er)人(ren)體(ti)(ti)中脂肪和(he)水(shui)(shui)的比例影響到人(ren)體(ti)(ti)的電阻,如(ru)果考慮脂肪和(he)水(shui)(shui)份的合(he)成(cheng)(cheng)電阻,則脂肪多的人(ren)體(ti)(ti)電阻值就高(gao)。目前市售的各(ge)種(zhong)人(ren)體(ti)(ti)脂肪測量儀幾(ji)乎(hu)都是以測量體(ti)(ti)電阻的方(fang)法來推測脂肪量,圖1為某產品的檢測方(fang)法。
如何自制脂肪測量儀
下面介紹一款可自制的簡易人體脂肪測量儀。
考慮到簡單(dan)(dan)易制,信號源(yuan)采用了5kHz的正弦波,且不用單(dan)(dan)片機、數字(zi)顯示等,同(tong)時考慮到同(tong)一個(ge)人(ren)使用,只要了解自身體脂肪的變化情況就可以(yi)了,因而也(ye)未考慮人(ren)的的身高、體重對檢測的影響。
由T1、T2構(gou)成文氏電(dian)(dian)(dian)橋振蕩(dang)器,產生5KHz的正(zheng)弦波,經(jing)C5送到一(yi)(yi)(yi)只腳(jiao)(jiao)電(dian)(dian)(dian)極(ji)(ji)(ji)上(shang),另一(yi)(yi)(yi)只腳(jiao)(jiao)電(dian)(dian)(dian)極(ji)(ji)(ji)與(yu)(yu)電(dian)(dian)(dian)源的負極(ji)(ji)(ji)相連,即人體兩支腳(jiao)(jiao)掌間的電(dian)(dian)(dian)阻與(yu)(yu)信(xin)號源并聯。由于(yu)人體兩腳(jiao)(jiao)間電(dian)(dian)(dian)阻一(yi)(yi)(yi)般在(zai)數百kΩ以(yi)上(shang),故(gu)(gu)其后的檢測(ce)電(dian)(dian)(dian)路(lu)(lu)(lu)輸(shu)入采用(yong)了高輸(shu)入阻抗的射極(ji)(ji)(ji)跟隨(sui)器T3;把T3輸(shu)出(chu)的信(xin)號經(jing)二極(ji)(ji)(ji)管整(zheng)(zheng)(zheng)流取出(chu)與(yu)(yu)體脂肪率相關的直流電(dian)(dian)(dian)壓(ya)(ya)(ya),再經(jing)一(yi)(yi)(yi)級射極(ji)(ji)(ji)跟隨(sui)器T4輸(shu)出(chu)到電(dian)(dian)(dian)壓(ya)(ya)(ya)表。由于(yu)輸(shu)入到檢測(ce)電(dian)(dian)(dian)路(lu)(lu)(lu)的信(xin)號很小(xiao),而常規的二極(ji)(ji)(ji)管整(zheng)(zheng)(zheng)流電(dian)(dian)(dian)路(lu)(lu)(lu)不(bu)適用(yong)于(yu)小(xiao)信(xin)號,故(gu)(gu)利用(yong)電(dian)(dian)(dian)阻R12給(gei)二極(ji)(ji)(ji)管加(jia)一(yi)(yi)(yi)偏置電(dian)(dian)(dian)壓(ya)(ya)(ya),使二極(ji)(ji)(ji)管在(zai)無信(xin)號時仍有電(dian)(dian)(dian)流通過,就可以(yi)增(zeng)加(jia)對(dui)小(xiao)信(xin)號的反應(ying)能力;與(yu)(yu)此(ci)對(dui)應(ying),在(zai)電(dian)(dian)(dian)路(lu)(lu)(lu)中增(zeng)加(jia)了由R15和VR2的調零(ling)電(dian)(dian)(dian)路(lu)(lu)(lu),以(yi)抵消前述偏置電(dian)(dian)(dian)壓(ya)(ya)(ya)對(dui)測(ce)量結果的影響。由于(yu)是采用(yong)數字電(dian)(dian)(dian)壓(ya)(ya)(ya)表來測(ce)量檢測(ce)結果,故(gu)(gu)檢測(ce)電(dian)(dian)(dian)路(lu)(lu)(lu)之后未設計放(fang)大(da)電(dian)(dian)(dian)路(lu)(lu)(lu)。兩腳(jiao)(jiao)電(dian)(dian)(dian)極(ji)(ji)(ji)可用(yong)食品包(bao)裝鋁(lv)箔剪(jian)成四塊(kuai)園片(pian),每腳(jiao)(jiao)兩塊(kuai);取絕緣板(ban)一(yi)(yi)(yi)塊(kuai),大(da)小(xiao)與(yu)(yu)市售人體秤相當(dang),在(zai)板(ban)上(shang)兩腳(jiao)(jiao)位(wei)置貼上(shang)與(yu)(yu)電(dian)(dian)(dian)極(ji)(ji)(ji)片(pian)大(da)小(xiao)相同的雙(shuang)面(mian)膠(jiao),從板(ban)下穿孔經(jing)過雙(shuang)面(mian)膠(jiao)穿入多股導線(xian)(xian),并將線(xian)(xian)頭(tou)分杈攤開在(zai)雙(shuang)面(mian)膠(jiao)表面(mian),然后將電(dian)(dian)(dian)極(ji)(ji)(ji)片(pian)壓(ya)(ya)(ya)緊在(zai)雙(shuang)面(mian)膠(jiao)上(shang)與(yu)(yu)導線(xian)(xian)緊密接觸,構(gou)成測(ce)量踏板(ban)。整(zheng)(zheng)(zheng)機電(dian)(dian)(dian)路(lu)(lu)(lu)用(yong)3V電(dian)(dian)(dian)池供電(dian)(dian)(dian)。
調整:
先(xian)確認振蕩器(qi)(qi)工作正常(chang)。用音(yin)頻信(xin)號傳輸線從(cong)將C1輸出端及(ji)地(di)端連接(jie)至(zhi)立體聲放大器(qi)(qi),若振蕩正常(chang),可從(cong)喇叭聽到音(yin)頻聲;調整VR1可聽出頻率的變化。
檢測電(dian)(dian)路應(ying)先調零,在(zai)(zai)(zai)檢測器輸出端接(jie)入數字(zi)萬用表的(de)mV檔,在(zai)(zai)(zai)兩(liang)(liang)(liang)腳電(dian)(dian)極懸空的(de)情(qing)況下調整VR2,使電(dian)(dian)壓(ya)表指示(shi)為0V。在(zai)(zai)(zai)上(shang)方兩(liang)(liang)(liang)電(dian)(dian)極片間串聯1M電(dian)(dian)阻,再將兩(liang)(liang)(liang)手掌(zhang)分(fen)別壓(ya)緊在(zai)(zai)(zai)上(shang)下兩(liang)(liang)(liang)電(dian)(dian)極板(ban)上(shang),電(dian)(dian)壓(ya)表上(shang)應(ying)有10~20mV的(de)電(dian)(dian)壓(ya)指示(shi)。
脂肪測量儀實(shi)際使用時(shi),雙腳赤腳站在(zai)兩腳電(dian)極(ji)片位置(zhi),電(dian)壓表應(ying)有一(yi)電(dian)壓值(zhi)(zhi)(zhi),如9mV,此值(zhi)(zhi)(zhi)可(ke)作為日后測量脂(zhi)肪率的(de)參(can)考值(zhi)(zhi)(zhi)。一(yi)般,脂(zhi)肪多的(de)人電(dian)壓值(zhi)(zhi)(zhi)高,瘦人電(dian)壓值(zhi)(zhi)(zhi)低。