氣體質量(liang)流(liu)量(liang)計測(ce)量(liang)電(dian)(dian)(dian)(dian)路(lu)的(de)(de)總體框圖，其中A/D轉(zhuan)換器、查(cha)表(biao)計算(suan)和顯示(shi)(或(huo)傳輸)由單片(pian)機實現。橋(qiao)式(shi)電(dian)(dian)(dian)(dian)路(lu)實現了保(bao)持ΔT/RH為定值的(de)(de)目的(de)(de)，當流(liu)體的(de)(de)質量(liang)流(liu)量(liang)發生變(bian)化時，電(dian)(dian)(dian)(dian)橋(qiao)失去(qu)平(ping)衡(heng)，控(kong)制電(dian)(dian)(dian)(dian)路(lu)測(ce)量(liang)出(chu)不平(ping)衡(heng)電(dian)(dian)(dian)(dian)壓，通(tong)過改變(bian)加熱電(dian)(dian)(dian)(dian)流(liu)，使電(dian)(dian)(dian)(dian)橋(qiao)重(zhong)新處(chu)于(yu)平(ping)衡(heng)狀態，加熱電(dian)(dian)(dian)(dian)流(liu)通(tong)過電(dian)(dian)(dian)(dian)流(liu)測(ce)量(liang)電(dian)(dian)(dian)(dian)路(lu)轉(zhuan)化成電(dian)(dian)(dian)(dian)壓信號(hao)，送入A/D轉(zhuan)換器，轉(zhuan)換后的(de)(de)數(shu)據經查(cha)表(biao)、計算(suan)，求出(chu)對(dui)應的(de)(de)質量(liang)流(liu)量(liang)，再顯示(shi)(或(huo)傳輸)給其他設(she)備。

氣體質量流(liu)量計(ji)橋(qiao)式電(dian)(dian)(dian)(dian)路(lu)包括運(yun)算放大(da)(da)(da)器OP07-1、三極管9014、測(ce)(ce)(ce)溫(wen)(wen)鉑(bo)電(dian)(dian)(dian)(dian)阻RT、測(ce)(ce)(ce)速(su)鉑(bo)電(dian)(dian)(dian)(dian)阻RH和精密電(dian)(dian)(dian)(dian)阻R1，R2，R3，R4，R5.測(ce)(ce)(ce)速(su)鉑(bo)電(dian)(dian)(dian)(dian)阻RH位(wei)于橋(qiao)式電(dian)(dian)(dian)(dian)路(lu)的(de)一(yi)(yi)臂，其通(tong)(tong)以較大(da)(da)(da)的(de)電(dian)(dian)(dian)(dian)流(liu)，使之加熱。測(ce)(ce)(ce)溫(wen)(wen)鉑(bo)電(dian)(dian)(dian)(dian)阻RT位(wei)于橋(qiao)式電(dian)(dian)(dian)(dian)路(lu)的(de)另一(yi)(yi)側，為了使它自(zi)身不產生(sheng)熱量，以保證測(ce)(ce)(ce)量溫(wen)(wen)度(du)與流(liu)體溫(wen)(wen)度(du)相(xiang)等，通(tong)(tong)過它的(de)電(dian)(dian)(dian)(dian)流(liu)必須很小(xiao)，因此(ci)RT的(de)電(dian)(dian)(dian)(dian)阻值應較大(da)(da)(da)，但如果RT值過大(da)(da)(da)，則測(ce)(ce)(ce)量的(de)熱慣性也增大(da)(da)(da)，儀(yi)表的(de)響應速(su)度(du)減慢。為了解決此(ci)問題，在(zai)電(dian)(dian)(dian)(dian)路(lu)中采(cai)用了副電(dian)(dian)(dian)(dian)橋(qiao)(副電(dian)(dian)(dian)(dian)橋(qiao)由(you)OP07-1，9014，RT，R3，R4，R5組成)，副電(dian)(dian)(dian)(dian)橋(qiao)相(xiang)當于一(yi)(yi)個等效大(da)(da)(da)電(dian)(dian)(dian)(dian)阻。

由儀表的工作原理可知，比值ΔT/RH應保持恒定。這一點可以通過以下計算來證明：設在工作狀態1的情況下，流體溫度為t1，測速鉑電阻溫度為T1，熱式質量流量計測速鉑電阻的阻值為RH1，測溫鉑電阻的阻值為RT1;在工作狀態2的情況下，流體溫度為t2，測速鉑電阻溫度為T2，測速鉑電阻的阻值為RH2，測溫鉑電阻的阻值為RT2。氣體質量(liang)(liang)流量(liang)(liang)計選(xuan)擇RT0=100Ω，RH0=20Ω，經過實驗驗證，測速(su)鉑電(dian)阻(zu)的溫度(du)與(yu)環境溫度(du)相差(cha)70~80℃，測量(liang)(liang)效(xiao)果較好(hao)，一(yi)般環境溫度(du)在20℃左(zuo)右，若測速(su)鉑電(dian)阻(zu)工作選(xuan)為100℃。