SMT-51A 是一款由上海四达电子生产的袖珍型指针万用表，具有便携性和多功能性，适合职业培训、专业学生、家庭用户、业余爱好者以及专业人士使用。该万用表采用双注射工艺，外壳坚固耐用，能够有效保护内部元件，确保测量的准确性和稳定性。

SMT-51A 可以测量直流电压、交流电压、直流电流、电阻等多种参数。直流电压的量程包括 10V、50V、250V 和 500V，精度为 ±4% 满度值；交流电压的量程与直流电压相同，但精度为 ±5% 满度值。此外，该万用表还具备电池测试功能，可测试 1.5V 和 9V 的电池。

SMT-51A 的设计注重用户体验，配备了导通性测试功能，当电路导通时会发出蜂鸣声，方便用户快速判断电路连接是否正常。此外，它还支持频率响应测试，可测量 50Hz 和 60Hz 的频率。

该万用表的体积小巧，尺寸为 100×69×32mm，净重仅 116g，便于携带和操作。它使用 AA 1.5V×1 电池供电，配备测试引线、使用手册和包装卡等附件。

The SMT-51A is a pocket-sized analog multimeter produced by Shanghai Sida Electronics. It is designed for vocational training, professional students, home users, hobbyists, and professionals. With a double-injection molded case, the SMT-51A is robust and durable, ensuring accurate and stable measurements.

The SMT-51A can measure a variety of parameters, including DC voltage, AC voltage, DC current, and resistance. The DC voltage ranges are 10V, 50V, 250V, and 500V, with an accuracy of ±4% of full scale. The AC voltage ranges are the same as those for DC voltage but with an accuracy of ±5% of full scale. Additionally, the multimeter features a battery test function for 1.5V and 9V batteries.

Designed with user experience in mind, the SMT-51A includes a continuity test function that emits an audible beep when the circuit is complete, allowing users to quickly determine if the circuit connections are intact. It also supports frequency response testing for 50Hz and 60Hz.

The compact design of the SMT-51A, with dimensions of 100×69×32mm and a net weight of 116g, makes it easy to carry and operate. It is powered by a single AA 1.5V battery and comes with test leads, a user manual, and a blister card.