Strain Gauge: Modh Oibre & Léaráid

Cad é an Strain Gauge

Is reisistéar é an strain gauge a úsáidtear chun an strain ar ábhar a mheas. Nuair a chuirtear fórsa seachtrach ar ábhar, tar éis sin is féidir go mbeidh athrú i gcruth na n-ábhar. Is é an t-athrú seo sa ghruaig, a bhíonn bithchomhracach nó teannach, atá a luaitear mar strain, agus is é an strain gauge a mheastar é. Nuair a dhéanann ábhar athrú taobh istigh den teorainn éascacht, d'fhéadfadh sé a bheith níos boichte agus níos faide, nó d'fhéadfadh sé a bheith níos giorra agus níos leata. Mar thoradh air, is féidir go mbeidh athrú i resistance ó thaobh go taobh.

Tá an strain gauge éadrom don chuid beag de na hathruithe a tharlaíonn i gcoibhneas leis an geoiméadracht. Ag mheas an athrú resistance, is féidir an méid stress a chur in iúl a ríomh.

Is beag an luach atá ar an athrú resistance go minic, agus chun an cainte beag sin a mheas, tá striap meánach gearr ar an strain gauge suite in a patrún zigzag ar ábhar gan condae a dtugtar an carrier, mar atá léirithe thíos, iontaofa go mór an caint beag sin i bpacáiste líneanna párlálacha agus d'fhéadfadh é a mheas le haghaidh mhór. Glúitear an gauge go réaltach ar an t-ábhar trí adhbhaid.

Nuair a léiríonn ábhar déformation fisiciúil, tagann athrú ar a resistance deipeach agus mheastar an athrú sin ag an ggage.

Strain Gauge Bridge Circuit

Strain gauge bridge circuit léiríonn an stress meartha trí shiombalachas, agus úsáideann voltmeter i lár an brídge chun tomhais cruinn a dhéanamh ar an neamhiondúil:

Sa chiorcal, R1 agus R3 is iad na braigh ar a chéile, agus R2 is é an rheostat arm a bhfuil luach cothrom leis an strain gage resistance. Nuair nach bhfuil an gauge straithe, is balance an brídge, agus tá an voltmeter ag léiríodh luach zero. Nuair a bhíonn athrú i resistance an strain gauge, the bridge gets unbalanced and producing an indication at the voltmeter. The output voltage from the bridge can be amplified further by a differential amplifier.

Variation of Temperature of Strain Gauge

Is é an téarma eile a bhíonn tionchar ar an resistance an teocht. Má tá an teocht níos mó, beidh an resistance níos mó agus má tá an teocht níos ísle, beidh an resistance níos ísle. Is é seo cuid den phróiseacht ginearálta do gach an conductors. Is féidir linn an fhadhb seo a dhéanamh trí strain gauges a úsáid a bhfuil siad féin temperature-compensated nó trí an dummy strain gauge technique.

Tá formhór na strain gauges déanta as constantan alloy a chancels out the effect of temperature on the resistance. Ach tá roinnt strain gauges nach ndéantar as isoelastic alloy. Sa chás seo, úsáideann an dummy gauge in the place of R2 in the quarter bridge strain gauge circuit which acts as a temperature compensation device.

Cé acu cad a tharlaíonn, the resistance will change in the same proportion in the both arms of the rheostat, and the bridge remains in the state of balance. Effect of temperature get nullifies. It is good to keep voltage low so that the self-heating of strain gauge could be evaded. Self-heating of gauge depends upon its mechanical behavior.

This arrangement is considered as quarter-bridge. There are two more arrangements half-bridge and full-bridge configurations which give greater sensitivity over the quarter-bridge circuit. Still the quarter-bridge circuit is widely used in strain measurement systems.

Use of Strain Gauge

• In the field of mechanical engineering development.

• To measure the stress generated by machinery.

• In the field of component testing of aircraft like; linkages, structural damage etc.

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