直讀介質損耗測試儀工作原理

1．“Q"的定義

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

“Q"表示元件(jian)或系統的(de)“品(pin)質(zhi)因數"，其(qi)物理含(han)義是(shi)在(zai)一個振蕩周(zhou)期內貯存的(de)能量(liang)與(yu)損耗的(de)能量(liang)之比。對(dui)于電(dian)(dian)抗(kang)元件(jian)(電(dian)(dian)感或電(dian)(dian)容)來說，即在(zai)測試頻(pin)率上呈現的(de)電(dian)(dian)抗(kang)與(yu)電(dian)(dian)阻之比。

電容器容量的測量

A. 在(zai)測量(liang)范圍(wei)內的(de)小(xiao)于主調電(dian)容量(liang)的(de)電(dian)容器(qi)的(de)測量(liang)

a．選一個適當的諧振電感接到“Lx"的兩端；

b．將調諧電(dian)(dian)容(rong)(rong)器調到(dao)(dao)最大值附(fu)(fu)近，令這個(ge)電(dian)(dian)容(rong)(rong)是C1，如未知(zhi)電(dian)(dian)容(rong)(rong)是小數值的(de)(de)，C1應調到(dao)(dao)較小電(dian)(dian)容(rong)(rong)值附(fu)(fu)近，以便達到(dao)(dao)盡可能高的(de)(de)分辨率；

c．調訊(xun)號源的(de)頻率，使(shi)測試(shi)回(hui)路諧(xie)振，令諧(xie)振器Q的(de)讀數為Q1；

d．將(jiang)被測(ce)電(dian)容接在“Cx"兩端，調節調諧電(dian)容器，使測(ce)試電(dian)路(lu)再諧振，令(ling)新的調諧電(dian)容值為C2和(he)指(zhi)示Q值為Q2。

被測電容的有(you)效電容為：Cx= C1－C2

電(dian)容器損(sun)耗角正切為：

電(dian)容器的有(you)效并聯電(dian)阻為(wei)：

C0為回路(lu)諧振電(dian)(dian)感的自身電(dian)(dian)容。

B．大(da)于調諧電容量(liang)的(de)電容器用(yong)可替代(dai)法測量(liang)

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

b．按5A／a-c各測試步驟(zou)；

c．取下(xia)(xia)標準(zhun)電(dian)容(rong)器，將被測電(dian)容(rong)接到“Cx"接線柱，調節調諧(xie)電(dian)容(rong)器到諧(xie)振，此時主調電(dian)容(rong)量讀數為C2，則(ze)Cx可由下(xia)(xia)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

氣(qi)(qi)(qi)態：空(kong)氣(qi)(qi)(qi)及其他氣(qi)(qi)(qi)體：1-1.2介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)是相(xiang)(xiang)對(dui)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)與真空(kong)中(zhong)絕對(dui)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)乘積。如果有(you)(you)(you)高(gao)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)的(de)(de)(de)(de)材(cai)料放在(zai)電(dian)(dian)(dian)(dian)(dian)場(chang)中(zhong)，電(dian)(dian)(dian)(dian)(dian)場(chang)的(de)(de)(de)(de)強(qiang)度會(hui)在(zai)電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)(jie)(jie)質(zhi)(zhi)(zhi)(zhi)內(nei)有(you)(you)(you)可觀(guan)的(de)(de)(de)(de)下降。理想導體的(de)(de)(de)(de)相(xiang)(xiang)對(dui)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)為(wei)無窮大(da)(da)。一(yi)個電(dian)(dian)(dian)(dian)(dian)容(rong)板中(zhong)充入(ru)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)為(wei)ε的(de)(de)(de)(de)物質(zhi)(zhi)(zhi)(zhi)后(hou)電(dian)(dian)(dian)(dian)(dian)容(rong)變(bian)大(da)(da)εr倍。電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)(jie)(jie)質(zhi)(zhi)(zhi)(zhi)有(you)(you)(you)使空(kong)間比起(qi)實(shi)際尺寸變(bian)得(de)更(geng)大(da)(da)或更(geng)小(xiao)(xiao)的(de)(de)(de)(de)屬(shu)性。例如，當一(yi)個電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)(jie)(jie)質(zhi)(zhi)(zhi)(zhi)材(cai)料放在(zai)兩個電(dian)(dian)(dian)(dian)(dian)荷之(zhi)間，它(ta)會(hui)減少(shao)作用在(zai)它(ta)們之(zhi)間的(de)(de)(de)(de)力，就像它(ta)們被移遠了(le)一(yi)樣(yang)。當電(dian)(dian)(dian)(dian)(dian)磁波(bo)穿過電(dian)(dian)(dian)(dian)(dian)介(jie)(jie)(jie)(jie)(jie)質(zhi)(zhi)(zhi)(zhi)，波(bo)的(de)(de)(de)(de)速度被減小(xiao)(xiao)，有(you)(you)(you)更(geng)短的(de)(de)(de)(de)波(bo)長。根據物質(zhi)(zhi)(zhi)(zhi)的(de)(de)(de)(de)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)可以(yi)判(pan)別高(gao)分子(zi)材(cai)料的(de)(de)(de)(de)極(ji)性大(da)(da)小(xiao)(xiao)。通常(chang)，相(xiang)(xiang)對(dui)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)大(da)(da)于(yu)3.6的(de)(de)(de)(de)物質(zhi)(zhi)(zhi)(zhi)為(wei)極(ji)性物質(zhi)(zhi)(zhi)(zhi);相(xiang)(xiang)對(dui)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)在(zai)2.8~3.6范(fan)圍內(nei)的(de)(de)(de)(de)物質(zhi)(zhi)(zhi)(zhi)為(wei)弱極(ji)性物質(zhi)(zhi)(zhi)(zhi);相(xiang)(xiang)對(dui)介(jie)(jie)(jie)(jie)(jie)電(dian)(dian)(dian)(dian)(dian)常(chang)數(shu)小(xiao)(xiao)于(yu)2.8為(wei)非(fei)極(ji)性物質(zhi)(zhi)(zhi)(zhi)。

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直讀介質損耗測試儀測試注意事項

1．本儀器(qi)應(ying)水(shui)平(ping)安放。

2．如果(guo)你(ni)需要較精(jing)確地測量，請接通電源后(hou)，預熱30分鐘。

3．調節主調電容數碼開(kai)關時(shi)(shi)，當接近(jin)諧振點時(shi)(shi)請緩調。

4．被測件和(he)測試電路接(jie)(jie)線柱間的(de)(de)接(jie)(jie)線應盡量短(duan)，足夠粗，并應接(jie)(jie)觸良好、可靠，以(yi)減(jian)少因接(jie)(jie)線的(de)(de)電阻和(he)分布(bu)參(can)數所帶來的(de)(de)測量誤差。

5．被測件不(bu)要(yao)直接擱在(zai)面(mian)板(ban)頂部(bu)，離頂部(bu)一(yi)公分以上，必(bi)要(yao)時可用低損耗的絕緣(yuan)材料如聚(ju)苯(ben)乙(yi)烯等做成的襯墊(dian)物襯墊(dian)。

6．手不得靠近(jin)試件，以免人(ren)體感應影響造成測量誤(wu)差，有屏蔽(bi)的(de)試件，屏蔽(bi)罩應連接(jie)在低(di)電位(wei)端的(de)接(jie)線柱。