直讀OCA介電測試儀工作原理

1．“Q"的定義

Q表是根據串聯諧(xie)振(zhen)原理設計，以諧(xie)振(zhen)電壓的比值來定位(wei)Q值。

“Q"表示元件或系統的(de)“品(pin)質因數"，其物理含義是在(zai)(zai)一個振蕩周期內貯(zhu)存的(de)能量與(yu)損耗的(de)能量之比。對于電抗(kang)元件(電感或電容)來(lai)說(shuo)，即在(zai)(zai)測試頻率上呈現的(de)電抗(kang)與(yu)電阻之比。

電容器容量的測量

A. 在測量范(fan)圍內(nei)的(de)(de)小于(yu)主調電(dian)容(rong)(rong)量的(de)(de)電(dian)容(rong)(rong)器的(de)(de)測量

a．選一個(ge)適當的(de)諧振電感接到“Lx"的(de)兩(liang)端；

b．將調諧電容器調到(dao)(dao)最(zui)大值(zhi)(zhi)附(fu)近(jin)，令這個(ge)電容是C1，如未知(zhi)電容是小數值(zhi)(zhi)的，C1應(ying)調到(dao)(dao)較小電容值(zhi)(zhi)附(fu)近(jin)，以便達到(dao)(dao)盡可(ke)能高的分辨率(lv)；

c．調訊號源(yuan)的頻率，使(shi)測(ce)試回路(lu)諧振，令諧振器Q的讀數為Q1；

d．將被測電(dian)容接在“Cx"兩端，調(diao)節(jie)調(diao)諧(xie)電(dian)容器(qi)，使(shi)測試電(dian)路(lu)再諧(xie)振，令新(xin)的調(diao)諧(xie)電(dian)容值(zhi)為C2和指示Q值(zhi)為Q2。

被測電容(rong)的有效電容(rong)為：Cx= C1－C2

電(dian)容(rong)器損耗(hao)角正切為：

電容器(qi)的有效并聯電阻為：

C0為回路諧(xie)振電(dian)(dian)感(gan)的自身電(dian)(dian)容。

B．大于調諧電容量的電容器用可替代法測量

a. 取一只(zhi)適當容量(liang)的標準電(dian)容量(liang)，其容量(liang)為C3，將(jiang)它接(jie)在“Cx"接(jie)線柱上；

b．按5A／a-c各測試步驟；

c．取下標準電容器，將被測電容接(jie)到“Cx"接(jie)線(xian)柱，調節(jie)調諧電容器到諧振，此時(shi)主調電容量讀數為(wei)C2，則(ze)Cx可由(you)下式得到：

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

直讀OCA介電測試儀氣(qi)態：空(kong)氣(qi)及(ji)其他氣(qi)體(ti)(ti)：1-1.2介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)是(shi)相(xiang)(xiang)對(dui)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)與真空(kong)中(zhong)(zhong)絕對(dui)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)乘(cheng)積。如(ru)果有(you)高介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)的(de)(de)(de)材料放在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)場中(zhong)(zhong)，電(dian)(dian)(dian)(dian)(dian)場的(de)(de)(de)強度(du)(du)會在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)質(zhi)(zhi)內(nei)有(you)可觀(guan)的(de)(de)(de)下(xia)降。理(li)想導(dao)體(ti)(ti)的(de)(de)(de)相(xiang)(xiang)對(dui)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)為(wei)(wei)無窮大(da)(da)。一個電(dian)(dian)(dian)(dian)(dian)容(rong)板中(zhong)(zhong)充入(ru)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)為(wei)(wei)ε的(de)(de)(de)物(wu)(wu)質(zhi)(zhi)后電(dian)(dian)(dian)(dian)(dian)容(rong)變(bian)大(da)(da)εr倍。電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)質(zhi)(zhi)有(you)使空(kong)間比起實際尺寸(cun)變(bian)得(de)更(geng)大(da)(da)或(huo)更(geng)小(xiao)的(de)(de)(de)屬(shu)性(xing)。例(li)如(ru)，當一個電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)質(zhi)(zhi)材料放在(zai)(zai)(zai)兩個電(dian)(dian)(dian)(dian)(dian)荷之間，它會減(jian)少作用在(zai)(zai)(zai)它們之間的(de)(de)(de)力，就像它們被(bei)移遠了(le)一樣。當電(dian)(dian)(dian)(dian)(dian)磁波(bo)穿過電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)質(zhi)(zhi)，波(bo)的(de)(de)(de)速度(du)(du)被(bei)減(jian)小(xiao)，有(you)更(geng)短的(de)(de)(de)波(bo)長(chang)。根據(ju)物(wu)(wu)質(zhi)(zhi)的(de)(de)(de)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)可以判(pan)別高分子材料的(de)(de)(de)極性(xing)大(da)(da)小(xiao)。通常(chang)(chang)(chang)，相(xiang)(xiang)對(dui)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)大(da)(da)于3.6的(de)(de)(de)物(wu)(wu)質(zhi)(zhi)為(wei)(wei)極性(xing)物(wu)(wu)質(zhi)(zhi);相(xiang)(xiang)對(dui)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)在(zai)(zai)(zai)2.8~3.6范圍內(nei)的(de)(de)(de)物(wu)(wu)質(zhi)(zhi)為(wei)(wei)弱極性(xing)物(wu)(wu)質(zhi)(zhi);相(xiang)(xiang)對(dui)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)(chang)(chang)數(shu)(shu)小(xiao)于2.8為(wei)(wei)非(fei)極性(xing)物(wu)(wu)質(zhi)(zhi)。

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