生产资料市场化以后，加剧激烈的竞争，真假优劣难辨，又因变送器是边缘学科，很多工程设计人员对此较陌生，有些厂家产品工业级别和民用商用级别指标混淆（工业级的价格是民用商用级的2-3倍）
After the marketization of the means of production, fierce competition has intensified, and it is difficult to distinguish between the true and the false. Because the transmitter is a marginal discipline, many engineering designers are unfamiliar with it. Some manufacturers confuse the industrial level and commercial level indicators of their products (the price of industrial level is 2-3 times that of commercial level)
以常用的0.5级精度的电流电压变送器为例，从以下方法着手来辨别真假优劣。
Taking the current and voltage transmitter with 0.5 level accuracy as an example, the following methods are used to distinguish the true and the false.
(1)基准要稳,4mA是对应的输入零位基准，基准不稳，谈何精度线性度，冷开机3分钟内4mA的零位漂移变化不超过4.000mA0.5%以内;(即3.98-4.02mA),负载250Ω上的压降为0.995-1.005V，国外IC心片多用昂贵的能隙基准，温漂系数每度变化10ppm；
(1) The benchmark should be stable. 4mA is the corresponding input zero benchmark. The benchmark is not stable. How about the accuracy linearity? The zero drift change of 4mA within 3 minutes after cold start is not more than 4.000ma 0.5%; (i.e. 3.98-4.02ma). The pressure drop on the load 250 Ω is 0.995-1.005v. Foreign IC chips mostly use expensive energy gap benchmark, and the temperature drift coefficient changes 10ppm per degree;
(2)内电路总计消耗电流<4mA,加整定后等于4.000mA,而且有源整流滤波放大恒流电路不因原边输入变化而消耗电流也随之变化，国外IC心片采用恒流供电；
(2) The total current consumption of the internal circuit is less than 4mA, which is equal to 4.000ma after setting. Moreover, the current consumption of the active rectifier filter amplification constant current circuit does not change due to the change of the original side input. The foreign IC core adopts constant current power supply;
(3)当工作电压24.000V时,满量程20.000mA时,满量程20.000mA的读数不会因负载0-700Ω变化而变化;变化不超过20.000mA0.5%以内；
(3) When the working voltage is 24.000v and the full range is 20.000ma, the reading of the full range is 20.000ma, which will not change due to the change of load 0-700 Ω; the change is not more than 20.000ma 0.5%;
(4)当满量程20.000mA时,负载250Ω时,满量程20.000mA的读数不会因工作电压15.000V-30.000V变化而变化;变化不超过20.000mA0.5%以内；
(4) When the full scale is 20.000ma and the load is 250 Ω, the reading of the full scale is 20.000ma, which will not change due to the change of the working voltage 15.000v-30.000v; the change is not more than 20.000ma 0.5%;
(5)当原边过载时，输出电流不超过25.000mA+10%以内，否则PLC/DCS内供变送器用的24V工作电源和A/D输入箝位电路因功耗过大而损坏，另外变送器内的射随输出亦因功耗过大而损坏，无A/D输入箝位电路的更遭殃；
(5) When the primary side is overloaded, the output current shall not exceed 25.000ma + 10%. Otherwise, the 24V working power supply and a / D input clamping circuit for the transmitter in PLC / DCS will be damaged due to excessive power consumption. In addition, the output of the transmitter will also be damaged due to excessive power consumption, and there will be no further damage to the A / D input clamping circuit;
(6)当工作电压24V接反时不得损坏变送器,必须有极性保护;
(6) When the working voltage is connected reversely at 24V, the transmitter shall not be damaged, and polarity protection must be provided;
(7)当两线之间因感应雷及感应浪涌电压超过24V时要箝位,不得损坏变送器；一般在两线之间并联1-2只TVS瞬态保护二极管1.5KE可抑制每20秒间隔一次的20毫秒脉宽的正反脉冲的冲击,瞬态承受冲击功率1.5KW-3KW;
(7) When the induced lightning and induced surge voltage between two lines exceed 24V, clamp them and do not damage the transmitter; generally, 1-2 TVs transient protection diodes 1.5ke in parallel between two lines can suppress the impact of positive and negative pulse with 20 millisecond pulse width every 20 seconds, and the transient withstand impact power is 1.5kw-3kw;
(8)产品标示的线性度0.5％是绝对误差还是相对误差,可以按以下方法来辨别方可一目了然:符合下述指针是真的线性度0.5％.
(8) Whether the linearity of 0.5% of the product mark is absolute error or relative error can be identified at a glance by the following methods: the true linearity of 0.5% conforms to the following indicators
原边输入为零时输出4mＡ正负0.5%(3.98-4.02mA),负载250Ω上的压降为0.995-1.005V
When the primary input is zero, the output is 4mA plus or minus 0.5% (3.98-4.02ma), and the pressure drop on the load 250 Ω is 0.995-1.005v
原边输入10％时输出5.6mＡ正负0.5%(5.572-5.628mA)负载250奥姆上的压降为1.393-1.407V
Output 5.6ma plus or minus 0.5% (5.572-5.628ma) with 10% primary input, the pressure drop on the load 250 OM is 1.393-1.407v
原边输入25％时输出8mＡ正负0.5%(7.96-8.04mA)负载250Ω上的压降为1.990-2.010V
When the primary input is 25%, the output 8Ma is plus or minus 0.5% (7.96-8.04ma). The pressure drop on the load 250 Ω is 1.990-2.010v
原边输入50％时输出12mＡ正负0.5%(11.94-12.06mA)负载250Ω上的压降为2.985-3.015V
When the primary input is 50%, the output is 12mA plus or minus 0.5% (11.94-12.06ma). The pressure drop on the load 250 Ω is 2.985-3.015v
原边输入75％时输出16mＡ正负0.5%(15.92-16.08mA)负载250Ω上的压降为3.980-4.020V
When the primary input is 75%, the output 16mA is plus or minus 0.5% (15.92-16.08ma). The pressure drop on the load 250 Ω is 3.980-4.020v
原边输100％时输出20mＡ正负0.5%(19.90-20.10mA)负载250Ω上的压降为4.975-5.025V
When the primary side input is 100%, the output 20mA is plus or minus 0.5% (19.90-20.10ma), and the pressure drop on the load 250 Ω is 4.975-5.025v
(9)原边输入过载时必须限流:原边输入过载大于125%时输出过流限制25mＡ+10%(25.00-27.50mA)负载250Ω上的压降为6.250-6.875V；
(9) The current must be limited when the primary input overload is greater than 125%. When the primary input overload is greater than 125%, the output overcurrent is limited to 25mA + 10% (25.00-27.50ma). The pressure drop on the load 250 Ω is 6.250-6.875v;
(10)感应浪涌电压超过24V时有无箝位的辨别:在两线输出端口并一个交流50V指针式表头,用交流50V接两根线去瞬间碰一下两线输出端口,看有无箝位,箝位多少伏可一目了然啦;
(10) Identify whether there is clamping when the induced surge voltage is more than 24V: connect two lines of AC 50V output port with an AC 50V pointer meter, and touch the two lines of output port with two lines of AC 50V in an instant to see if there is clamping, and the clamping voltage can be seen at a glance;
(11)有无极性保护的辨别:用指针式万用表Ω乘10K档正反测量两线输出端口,总有一次Ω阻值无限大,就有极性保护；
(11) Identification of whether there is polarity protection or not: measure the two-wire output port by multiplying 10K gear with the pointer multimeter Ω, and once the Ω resistance is infinite, there is polarity protection;
(12)有无极输出电流长时间短路保护：原边输入100％时或过载大于125%-200%时，将负载250Ω短路，测量短路保护限制是否在25mＡ+10%；
(12) Long time short circuit protection with or without pole output current: when the primary side input is 100% or the overload is greater than 125% - 200%, short circuit the load 250 Ω, and measure whether the short circuit protection limit is 25mA + 10%;
(13)工业级别和民用商用级别的辨别:工业级别工作温度范围是-25度到＋７0度，温漂系数是每度变化100ppm,即温度每度变化1度,精度变化为万分之一；民用商用级别工作温度范围是0度（或-10度）到＋７0度（或+50度）,温漂系数是每度变化250ppm,即温度每度变化1度,精度变化为万分之二点五；电流电压变送器的温漂系数可以用恒温箱或高低温箱来试验验证较繁琐。
(13) Identification of industrial grade and commercial grade: the working temperature range of industrial grade is - 25 ° C to + 70 ° C, and the temperature drift coefficient is 100ppm per degree change, i.e. the temperature changes by 1 ° C, and the accuracy changes by 1 / 10000; the working temperature range of commercial grade is 0 ° C (or - 10 ° C) to + 70 ° C (or + 50 ° C), and the temperature drift coefficient is 250PPM per degree change, i.e. the temperature changes by 1 ° C, The accuracy changes to 2.5% of 10000; the temperature drift coefficient of current and voltage transmitter can be verified by constant temperature box or high and low temperature box test.
华恒仪表制造厂家凭借专业技术优势，可靠稳定的产品质量，坚持大限度的满足用户的需求是企业发展的动力源泉，以优质专业的服务为我国电力、石油、化工、冶金、水泥、矿业、市政、造纸等行业提供了高性能价格比的工业自动化仪表产品。为我国自动化仪表的发展做出了重要贡献。
Relying on the advantages of professional technology, reliable and stable product quality, Huaheng instrument manufacturer insists on meeting the needs of users to a large extent, which is the power source of enterprise development. With high-quality professional services, it provides industrial automation instrument products with high performance price ratio for China's electric power, petroleum, chemical industry, metallurgy, cement, mining, municipal administration, papermaking and other industries. It has made an important contribution to the development of automatic instruments in China.