直讀OCA介電損耗測試儀工作原理

1．“Q"的定義

Q表是根據串聯諧振原理(li)設計，以諧振電壓的比值來(lai)定位Q值。

“Q"表(biao)示元件(jian)或(huo)系統的(de)“品質因數(shu)"，其物理含義(yi)是在一個(ge)振蕩周(zhou)期內貯存的(de)能量(liang)與(yu)損耗的(de)能量(liang)之(zhi)比。對于(yu)電(dian)抗(kang)元件(jian)(電(dian)感(gan)或(huo)電(dian)容)來說，即在測試頻率上呈現的(de)電(dian)抗(kang)與(yu)電(dian)阻之(zhi)比。

電容器容量的測量

A. 在測量范圍(wei)內的小于(yu)主調電容量的電容器(qi)的測量

a．選一個適當(dang)的諧(xie)振電(dian)感接到“Lx"的兩端(duan)；

b．將調(diao)諧(xie)電(dian)(dian)容器調(diao)到最大值(zhi)(zhi)附近，令這個電(dian)(dian)容是(shi)C1，如(ru)未知電(dian)(dian)容是(shi)小(xiao)(xiao)數值(zhi)(zhi)的，C1應調(diao)到較小(xiao)(xiao)電(dian)(dian)容值(zhi)(zhi)附近，以便達到盡可(ke)能高的分辨率；

c．調訊號(hao)源的頻率，使測(ce)試回路(lu)諧振(zhen)，令(ling)諧振(zhen)器Q的讀數為(wei)Q1；

d．將被測電(dian)(dian)(dian)容(rong)接在“Cx"兩端(duan)，調(diao)節調(diao)諧(xie)電(dian)(dian)(dian)容(rong)器(qi)，使測試電(dian)(dian)(dian)路再諧(xie)振，令(ling)新的調(diao)諧(xie)電(dian)(dian)(dian)容(rong)值為C2和(he)指示Q值為Q2。

被測(ce)電容(rong)的有效電容(rong)為：Cx= C1－C2

電(dian)容器損(sun)耗角(jiao)正(zheng)切為：

電(dian)容(rong)器的有效并(bing)聯電(dian)阻(zu)為：

C0為回路諧振(zhen)電(dian)感(gan)的自(zi)身電(dian)容(rong)。

B．大(da)于調諧(xie)電容量的(de)電容器用(yong)可替代法測量

a. 取一只適當容(rong)(rong)量(liang)的標準(zhun)電容(rong)(rong)量(liang)，其(qi)容(rong)(rong)量(liang)為(wei)C3，將它接(jie)(jie)在“Cx"接(jie)(jie)線柱上(shang)；

b．按5A／a-c各測試步驟；

c．取下標準電(dian)(dian)容(rong)器(qi)，將(jiang)被測電(dian)(dian)容(rong)接到“Cx"接線(xian)柱(zhu)，調節(jie)調諧(xie)(xie)電(dian)(dian)容(rong)器(qi)到諧(xie)(xie)振(zhen)，此(ci)時主調電(dian)(dian)容(rong)量讀(du)數(shu)為C2，則(ze)Cx可由下式(shi)得到：

固體：白云石：8； 鹽：6； 醋酸纖維素：3.7-7.5； 瓷器：5-7； 纖維素：3.9； 米及谷類：3-5； 砂：3-5；砂糖：3； 玻璃：3.7； 硫磺：3.4； 瀝青：2.7； 聚四氟乙烯塑料：1.8-2.2； 紙：2； 云母：6-8

氣態：空(kong)氣及其他氣體：1-1.2介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)是相對(dui)(dui)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)與真空(kong)中絕對(dui)(dui)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)乘積。如果有(you)(you)(you)高介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)的(de)材(cai)料(liao)放(fang)在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)場中，電(dian)(dian)(dian)(dian)(dian)(dian)場的(de)強(qiang)度(du)會在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)質(zhi)內(nei)有(you)(you)(you)可觀的(de)下降。理想(xiang)導(dao)體的(de)相對(dui)(dui)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)為(wei)(wei)(wei)無窮大(da)。一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)板(ban)中充入介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)為(wei)(wei)(wei)ε的(de)物(wu)(wu)質(zhi)后電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)變(bian)大(da)εr倍。電(dian)(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)質(zhi)有(you)(you)(you)使(shi)空(kong)間比起實際尺(chi)寸變(bian)得更(geng)大(da)或更(geng)小的(de)屬性。例如，當一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)質(zhi)材(cai)料(liao)放(fang)在(zai)兩個(ge)電(dian)(dian)(dian)(dian)(dian)(dian)荷之間，它會減(jian)(jian)少作(zuo)用在(zai)它們之間的(de)力，就(jiu)像它們被(bei)移遠了一(yi)樣(yang)。當電(dian)(dian)(dian)(dian)(dian)(dian)磁波穿(chuan)過電(dian)(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)質(zhi)，波的(de)速(su)度(du)被(bei)減(jian)(jian)小，有(you)(you)(you)更(geng)短的(de)波長(chang)。根據物(wu)(wu)質(zhi)的(de)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)可以判別高分子材(cai)料(liao)的(de)極性大(da)小。通常(chang)(chang)(chang)(chang)，相對(dui)(dui)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)大(da)于3.6的(de)物(wu)(wu)質(zhi)為(wei)(wei)(wei)極性物(wu)(wu)質(zhi);相對(dui)(dui)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)在(zai)2.8~3.6范圍內(nei)的(de)物(wu)(wu)質(zhi)為(wei)(wei)(wei)弱極性物(wu)(wu)質(zhi);相對(dui)(dui)介(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)(chang)數(shu)(shu)(shu)小于2.8為(wei)(wei)(wei)非極性物(wu)(wu)質(zhi)。

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直讀OCA介電損耗測試儀操作：