【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。
人體脂肪的(de)(de)含量,即(ji)脂肪率的(de)(de)正(zheng)確(que)檢測方(fang)(fang)法(fa)是(shi)將人體全部(bu)沒入水中(zhong),測出排水率(體積),再根據(ju)體重求出人體的(de)(de)比重,由此推斷出人體的(de)(de)脂肪率。但(dan)在日常情況下這種方(fang)(fang)法(fa)不太現(xian)實。
人(ren)(ren)的(de)(de)(de)(de)身體(ti)(ti)(ti)含水(shui)量約為70%,這些水(shui)份(fen)絕(jue)大部分(fen)存在(zai)于(yu)(yu)血(xue)液(ye)、瘦肉及內(nei)臟中(zhong)(zhong),而脂(zhi)肪(fang)(fang)中(zhong)(zhong)含水(shui)量極低(di)。體(ti)(ti)(ti)內(nei)水(shui)份(fen)由于(yu)(yu)溶解有各種(zhong)成分(fen)而呈(cheng)(cheng)現(xian)低(di)電阻(zu),脂(zhi)肪(fang)(fang)卻呈(cheng)(cheng)現(xian)高(gao)電阻(zu),因而人(ren)(ren)體(ti)(ti)(ti)中(zhong)(zhong)脂(zhi)肪(fang)(fang)和(he)水(shui)的(de)(de)(de)(de)比例影(ying)響到人(ren)(ren)體(ti)(ti)(ti)的(de)(de)(de)(de)電阻(zu),如果考慮脂(zhi)肪(fang)(fang)和(he)水(shui)份(fen)的(de)(de)(de)(de)合成電阻(zu),則(ze)脂(zhi)肪(fang)(fang)多(duo)的(de)(de)(de)(de)人(ren)(ren)體(ti)(ti)(ti)電阻(zu)值(zhi)就高(gao)。目前市售的(de)(de)(de)(de)各種(zhong)人(ren)(ren)體(ti)(ti)(ti)脂(zhi)肪(fang)(fang)測(ce)(ce)量儀幾(ji)乎都是以測(ce)(ce)量體(ti)(ti)(ti)電阻(zu)的(de)(de)(de)(de)方(fang)(fang)法(fa)來推(tui)測(ce)(ce)脂(zhi)肪(fang)(fang)量,圖1為某產品的(de)(de)(de)(de)檢測(ce)(ce)方(fang)(fang)法(fa)。
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(kao)慮(lv)到簡單(dan)易制,信號源采(cai)用(yong)(yong)了5kHz的(de)正弦波,且不(bu)用(yong)(yong)單(dan)片(pian)機、數字顯示(shi)等,同時考(kao)慮(lv)到同一個人(ren)使用(yong)(yong),只要了解自身體(ti)(ti)脂肪的(de)變化(hua)情(qing)況(kuang)就可以(yi)了,因而也未考(kao)慮(lv)人(ren)的(de)的(de)身高、體(ti)(ti)重對檢測的(de)影響。
由T1、T2構(gou)成文氏電(dian)(dian)(dian)(dian)橋振蕩器(qi),產生5KHz的(de)(de)(de)正(zheng)弦波,經(jing)C5送(song)到一(yi)只腳(jiao)電(dian)(dian)(dian)(dian)極上(shang),另一(yi)只腳(jiao)電(dian)(dian)(dian)(dian)極與電(dian)(dian)(dian)(dian)源的(de)(de)(de)負極相(xiang)(xiang)連,即(ji)人(ren)體兩(liang)支腳(jiao)掌(zhang)間的(de)(de)(de)電(dian)(dian)(dian)(dian)阻與信號(hao)源并聯。由于(yu)(yu)人(ren)體兩(liang)腳(jiao)間電(dian)(dian)(dian)(dian)阻一(yi)般在數百kΩ以(yi)上(shang),故其后(hou)(hou)的(de)(de)(de)檢測電(dian)(dian)(dian)(dian)路輸(shu)入采用(yong)了高(gao)輸(shu)入阻抗的(de)(de)(de)射(she)極跟隨器(qi)T3;把(ba)T3輸(shu)出(chu)的(de)(de)(de)信號(hao)經(jing)二(er)極管(guan)(guan)整流取出(chu)與體脂肪率相(xiang)(xiang)關(guan)的(de)(de)(de)直流電(dian)(dian)(dian)(dian)壓,再經(jing)一(yi)級射(she)極跟隨器(qi)T4輸(shu)出(chu)到電(dian)(dian)(dian)(dian)壓表(biao)。由于(yu)(yu)輸(shu)入到檢測電(dian)(dian)(dian)(dian)路的(de)(de)(de)信號(hao)很小,而常(chang)規的(de)(de)(de)二(er)極管(guan)(guan)整流電(dian)(dian)(dian)(dian)路不適(shi)用(yong)于(yu)(yu)小信號(hao),故利用(yong)電(dian)(dian)(dian)(dian)阻R12給二(er)極管(guan)(guan)加(jia)一(yi)偏(pian)置電(dian)(dian)(dian)(dian)壓,使二(er)極管(guan)(guan)在無信號(hao)時仍(reng)有(you)電(dian)(dian)(dian)(dian)流通過(guo),就可以(yi)增加(jia)對(dui)小信號(hao)的(de)(de)(de)反應能力;與此對(dui)應,在電(dian)(dian)(dian)(dian)路中(zhong)增加(jia)了由R15和VR2的(de)(de)(de)調零電(dian)(dian)(dian)(dian)路,以(yi)抵消前述(shu)偏(pian)置電(dian)(dian)(dian)(dian)壓對(dui)測量(liang)結(jie)果的(de)(de)(de)影響(xiang)。由于(yu)(yu)是采用(yong)數字電(dian)(dian)(dian)(dian)壓表(biao)來測量(liang)檢測結(jie)果,故檢測電(dian)(dian)(dian)(dian)路之后(hou)(hou)未設計放大(da)(da)電(dian)(dian)(dian)(dian)路。兩(liang)腳(jiao)電(dian)(dian)(dian)(dian)極可用(yong)食(shi)品包(bao)裝鋁箔剪成四塊(kuai)(kuai)園片(pian),每腳(jiao)兩(liang)塊(kuai)(kuai);取絕緣板(ban)(ban)一(yi)塊(kuai)(kuai),大(da)(da)小與市售人(ren)體秤(cheng)相(xiang)(xiang)當,在板(ban)(ban)上(shang)兩(liang)腳(jiao)位(wei)置貼上(shang)與電(dian)(dian)(dian)(dian)極片(pian)大(da)(da)小相(xiang)(xiang)同的(de)(de)(de)雙(shuang)面(mian)(mian)膠(jiao)(jiao),從(cong)板(ban)(ban)下穿孔(kong)經(jing)過(guo)雙(shuang)面(mian)(mian)膠(jiao)(jiao)穿入多股導(dao)線(xian),并將(jiang)線(xian)頭(tou)分杈攤(tan)開在雙(shuang)面(mian)(mian)膠(jiao)(jiao)表(biao)面(mian)(mian),然(ran)后(hou)(hou)將(jiang)電(dian)(dian)(dian)(dian)極片(pian)壓緊在雙(shuang)面(mian)(mian)膠(jiao)(jiao)上(shang)與導(dao)線(xian)緊密(mi)接觸(chu),構(gou)成測量(liang)踏板(ban)(ban)。整機電(dian)(dian)(dian)(dian)路用(yong)3V電(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)。
調整:
先確認振(zhen)蕩(dang)器工(gong)作正常。用(yong)音頻信號傳輸線從將C1輸出端及地端連(lian)接(jie)至立(li)體聲放大(da)器,若振(zhen)蕩(dang)正常,可從喇叭聽到音頻聲;調整VR1可聽出頻率的(de)變化(hua)。
檢測(ce)電(dian)(dian)路應先調零,在(zai)檢測(ce)器輸(shu)出端接入數字萬用表的(de)mV檔,在(zai)兩腳電(dian)(dian)極(ji)懸空的(de)情況下(xia)調整(zheng)VR2,使電(dian)(dian)壓表指(zhi)示為0V。在(zai)上方兩電(dian)(dian)極(ji)片間串聯(lian)1M電(dian)(dian)阻,再將兩手掌(zhang)分別壓緊在(zai)上下(xia)兩電(dian)(dian)極(ji)板上,電(dian)(dian)壓表上應有10~20mV的(de)電(dian)(dian)壓指(zhi)示。
脂肪測量儀實際使(shi)用時,雙腳(jiao)(jiao)赤腳(jiao)(jiao)站在(zai)兩腳(jiao)(jiao)電(dian)極片(pian)位(wei)置,電(dian)壓(ya)表應有一電(dian)壓(ya)值(zhi)(zhi)(zhi),如(ru)9mV,此值(zhi)(zhi)(zhi)可作為(wei)日后測量脂肪(fang)率的參(can)考(kao)值(zhi)(zhi)(zhi)。一般,脂肪(fang)多(duo)的人(ren)電(dian)壓(ya)值(zhi)(zhi)(zhi)高,瘦人(ren)電(dian)壓(ya)值(zhi)(zhi)(zhi)低。