strainmeter，漢語意思是應變計(應變儀；伸長計；張力計)。
strainmeter,英[streɪ'nɒmɪtə] 美[streɪ'nɒmɪtə]
A strainmeter is an instrument used by geophysicists to measure the deformation of the Earth. Linear strainmeters measure the changes in the distance between two points, using either a solid piece of material (over a short distance) or a laser interferometer (over a long distance, up to several hundred meters). The type using a solid length standard was invented by Benioff in 1932, using an iron pipe; later instruments used rods made of fused quartz. Modern instruments of this type can make measurements of length changes over very small distances, and are commonly placed in boreholes to measure small changes in the diameter of the borehole. Another type of borehole instrument detects changes in a volume filled with fluid (such as silicone oil). The most common type is the dilatometer invented by Sacks and Evertson in the USA (patent 3,635,076); a design that uses specially shaped volumes to measure the strain tensor has been developed by Sakata in Japan.
應變儀器用於測量地球的變形。線性應變儀用一個固體片的材料（測量短距離）或雷射干涉儀（測量比較長的距離，大於幾百米）測量兩點之間距離的變化。貝尼奧夫在1932年發明了堅實的長度標準套用，用一根鐵管;後來的文書用熔融石英棒。這種類型的現代儀器可以對非常小距離的長度的變化進行測量，並且通常放置在鑽孔中測量鑽孔的直徑的微小變化。鑽孔儀器的另一種類型的檢測填充有流體（例如矽油）的體積的變化。最常見的類型是膨脹計是由美國的Sacks和Evertson（專利3635076）發明的，在日本坂田已經制定了一個設計，使用特殊形狀的捲來測量應變張量。
All these types of strainmeters can measure deformation over frequencies from a few Hz to periods of days, months, and years. This allows them to measure signals at lower frequencies than can be detected with seismometers. Most strainmeter records show signals from the earth tides, and seismic waves from earthquakes. At longer periods, they can also record the gradual accumulation of stress (physics) caused by plate tectonics, the release of this stress in earthquakes, and rapid changes of stress following earthquakes.
所有這些類型的應變儀可以測量變形頻率從幾赫茲到按天，月，年。這使他們能夠在較低的頻率都可以檢測到測量信號。大多數應變儀記錄顯示從地球潮汐和地震的地震波信號。在更長的時間，他們還可以記錄逐步積累引起的板塊構造，地震，釋放這種壓力和快速變化的壓力和地震後應力（物理）。
