Large-discharge-current-capacity moisture-resistant ammeter piezoresistor and preparation method thereof

The preparation method comprises the following steps: step 1, after welding and cleaning a zinc oxide varistor chip, dip-coating the zinc oxide varistor chip with aqueous epoxy resin at a dip-coating height not exceeding the height of subsequent epoxy encapsulation, and curing at normal temperature for 8-24 hours; and 2, racking the zinc oxide varistor chip, encapsulating the zinc oxide varistor chip with epoxy powder, taking the zinc oxide varistor chip out of an encapsulating machine, and heating and curing the zinc oxide varistor chip before the zinc oxide varistor chip is cooled thoroughly to obtain the varistor. As the oxidized piezoresistor chip is porous ceramic under a microscopic condition, when the oxidized piezoresistor chip is immersed into aqueous epoxy resin, the epoxy resin with good fluidity can permeate into the surface layer of the zinc oxide piezoresistor chip by 0.2-0.5 mm, gas in gaps is exhausted, and a protective film layer with the thickness of 0.1-0.3 mm is formed after curing; for th