以下是上海四达电子SDT-21C数字万用表的产品中英文介绍：

上海四达电子SDT-21C数字万用表是一款功能丰富、性能可靠的测量工具，广泛应用于电子电气维修、工业检测、实验室测量等多种领域。它采用2000计数的LCD显示屏，能够清晰地显示测量数据。该万用表具备双注入测试功能，可精准测量直流/交流电压、直流电流、电阻、温度以及进行二极管测试和连续性测试。其直流电压测量范围可达600V，精度为±(0.5%+5)；交流电压测量范围同样为600V，精度为±(1%+5)。在电流测量方面，直流电流和交流电流的测量范围均为200μA/200mA，直流电流精度为±(1.5%+2)，交流电流精度为±(1.8%+2)。电阻测量范围为20MΩ，其中小于1MΩ时精度为±(0.8%+5)，大于等于1MΩ时精度为±(2%+5)。温度测量范围为-40-752℉/-40-400℃，不同温度区间精度略有不同。

此外，SDT-21C还具备低电量指示功能，方便用户及时更换电池，确保测量工作的顺利进行。自动量程设计让操作更加便捷，背光功能则在光线较暗的环境中也能保证清晰读数。该万用表的电源为两节AAA 1.5V电池，LCD尺寸为61.6x26.2mm，产品尺寸为140x85x34mm，净重仅180g，便于携带和操作。其安全等级为CATⅢ 600V，能够为使用者提供可靠的安全保障。标准配件包括电池、测试笔、说明书、吸塑卡以及K型热电偶。

The SDT-21C digital multimeter from Shanghai Sida Electronic Instrument Co., Ltd. is a versatile and reliable measuring tool, widely used in electronic and electrical repair, industrial inspection, laboratory measurement, and other fields. It features a 2000-count LCD display that clearly shows measurement data. This multimeter is equipped with a dual-injection testing function, capable of accurately measuring direct/alternating current voltage, direct current, resistance, temperature, as well as performing diode testing and continuity testing. The measurement range for direct current voltage reaches 600V with an accuracy of ±(0.5%+5), and for alternating current voltage, the range is also 600V with an accuracy of ±(1%+5). In terms of current measurement, both direct and alternating current have a range of 200μA/200mA, with direct current accuracy at ±(1.5%+2) and alternating current accuracy at ±(1.8%+2). The resistance measurement range is 20MΩ, with an accuracy of ±(0.8%+5) for values less than 1MΩ and ±(2%+5) for values greater than or equal to 1MΩ. The temperature measurement range is -40-752℉/-40-400℃, with varying accuracy levels depending on the temperature range.

Moreover, the SDT-21C has a low battery indicator, which allows users to replace the batteries in time to ensure the smooth progress of measurement work. The auto-ranging design makes operation more convenient, and the backlight function ensures clear readings even in low-light environments. Powered by two AAA 1.5V batteries, this multimeter has an LCD size of 61.6x26.2mm, product dimensions of 140x85x34mm, and a net weight of only 180g, making it easy to carry and operate. With a safety rating of CATⅢ 600V, it provides reliable safety protection for users. Standard accessories include batteries, test leads, a manual, a blister card, and a K-type thermocouple.