How to Distinguish True and False of Current and Voltage Transmitters

The author tries to use the commonly used 0.5-level accuracy current and voltage.TransmitterFor example, from the following methods to identify true and false pros and cons.
(1) The benchmark should be stable. 4mA is the corresponding input zero benchmark. The benchmark is unstable. Talk about accuracy linearity. The zero drift change of 4mA within 3 minutes of cold startup should not exceed 4.000mA 0.5%. (I .e. 3.98-4.02mA), the voltage drop on the load 250Ω is 0.995-1.005V, the expensive energy gap benchmark is used for overseas IC chips, and the temperature drift coefficient changes by 10ppm per degree;
(2) the total consumption current of the internal circuit is less than 4mA, which is equal to 4.000mA after setting. moreover, the consumption current of the active rectifier filter amplifier constant current circuit does not change due to the change of the primary input. the overseas IC chip adopts constant current power supply;
(3) When the working voltage is 24.000V and the full scale is 20.000mA, the reading of the full scale 20.000mA will not change due to the change of load 0-500Ω; The change shall not exceed 20.000mA 0.5%;
(4) When the full scale is 20.000mA and the load is 250Ω, the reading of the full scale 20.000mA will not change due to the change of the working voltage 15.000V-30.000V; The change shall not exceed 20.000mA 0.5%;
(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 clamp circuit for transmitter in PLC/DCS will be damaged due to excessive power consumption. In addition, the output of transmitter will also be damaged due to excessive power consumption, and those without A/D input clamp circuit will suffer even more;
(6) When the working voltage 24V is reversed, the transmitter shall not be damaged, and there must be polarity protection;
(7) When the voltage between the two lines exceeds 24V due to induced lightning and induced surge, the transmitter shall not be damaged; Generally, 1-2 TVS transient protection diodes 1.5KE connected in parallel between the two lines can suppress the impact of positive and negative pulses with a pulse width of 20 milliseconds once every 20 seconds, and the transient impact power is 1.5KW-3KW;
(8) Whether the linearity of 0.5% marked by the product is an absolute error or a relative error can be distinguished at a glance by the following methods: it is true linearity of 0.5% that meets the following indicators.
When the primary input is zero, the output is 4mA plus or minus 0.5%(3.98-4.02mA), and the voltage drop on the load 250Ω is 0.995-1.005V.
When the primary input is 10%, the output is 5.6mA plus or minus 0.5 (5.572-5.628mA). The voltage drop on the load 250 ohms is 1.393-1.407V
When the primary input is 25%, the output is 8mA plus or minus 0.5 (7.96-8.04mA) and the voltage drop on the load 250Ω is 1.990-2.010V.
When the primary input is 50%, the output is 12mA plus or minus 0.5 (11.94-12.06mA) and the voltage drop on the load 250Ω is 2.985-3.015V.
When the primary input is 75%, the output is 16mA plus or minus 0.5 (15.92-16.08mA) and the voltage drop on the load 250Ω is 3.980-4.020V.
When the primary side is 100, the output is 20mA plus or minus 0.5%(19.90-20.10mA) and the voltage drop on the load 250Ω is 4.975-5.025V
(9) Current must be limited when the primary input overload is greater than 125: when the primary input overload is greater than 25mA + 10%(25.00-27.50mA), the voltage drop on the load 250Ω is 6.250-6.875V;
(10) Discrimination of whether there is clamp when the induced surge voltage exceeds 24V: connect the two-wire output port with an AC 50V pointer type meter, connect the two wires with AC 50V to touch the two-wire output port instantly to see if there is clamp, and how many volts are clamped can be seen at a glance;
(11) Distinguish whether there is polarity protection: use a pointer multimeter Ω times 10K gear to measure the two-wire output port, there is always a polarity protection when the Ω resistance is infinite;
(12) Long-term short-circuit protection with non-polar output current: when the primary input is 100% or the overload is greater than 125-200%, short-circuit the load 250Ω, and measure whether the short-circuit protection limit is 25mA +10%;
The above 12 methods can also be used to distinguish between true and false and other transmitters.