How to identify the true and false voltage transmitter

1. There is a long-term short-circuit protection of the non-polarity output current: when the primary input is 100% or when the overload is greater than 125%-200%, the load is short-circuited to 250Ω, and the short-circuit protection limit is measured to be 25mA+10%;

2. Industrial level and civil commercial level identification: Industrial grade operating temperature range is -25 degrees to +70 degrees, temperature drift coefficient is 100ppm per degree change, that is, temperature change per degree 1 degree, precision change is one ten-thousandth; Civilian commercial grade operating temperature range is 0 degrees (or -10 degrees) to +70 degrees (or +50 degrees), temperature drift coefficient is 250ppm per degree, that is, temperature changes every degree 1 degree, accuracy changes to 2/10000 Point five; temperature and voltage transmitter temperature drift coefficient can be used to test the incubator or high and low temperature box to verify more cumbersome. 1) When the primary side is overloaded, the output current does not exceed 25.000mA+10%. Otherwise, the 24V power supply and A/D input clamping circuit used in the PLC/DCS for the transmitter are damaged due to excessive power consumption. The transmitter-to-output in the transmitter is also damaged due to excessive power consumption, and the A/D input clamp circuit is even more vulnerable.

3. When the working voltage is 24V reversed, the transmitter must not be damaged and must have polarity protection;

4. Clamping discrimination when induced surge voltage exceeds 24V: In the two-wire output port and an AC 50V pointer meter, use AC 50V to connect two wires to instantly touch the two-wire output port to see if there is any clamp Bit, how many volts can be clamped at a glance;

5. With or without polarity protection discrimination: use an analog multimeter by 10K positive and negative measurement of the two-wire output port, there is always an infinite resistance Ω, there is polarity protection;

6. When the voltage between the two lines is inductively induced and the induced surge voltage exceeds 24V, the transmitter must be clamped, and the transmitter must not be damaged; generally, 1-2 TVS transient protection diodes 1.5KE can be suppressed in parallel between the two lines. The pulse of positive and negative pulse of 20 millisecond pulse width of one time interval of one second, transient withstand impact power 1.5KW-3KW;

7. When the working voltage is 24.000V, when the full scale is 20.000mA, the full-scale 20.000mA reading will not change due to the load 0-700Ω; the change does not exceed 20.000mA0.5%;

8. When the full-scale range is 20.000mA, when the load is 250Ω, the full-scale 20.000mA reading will not change due to the working voltage of 15.000V-30.000V; the change does not exceed 20.000mA0.5%;

9. The reference must be stable, 4mA is the corresponding input zero reference, the reference instability, talk about the linearity of the accuracy, the zero drift of 4mA within 4 minutes of the cold boot does not change within 4.000mA0.5%; (ie 3.98- 4.02mA), the pressure drop on the load 250Ω is 0.995-1.005V, the IC core chip in foreign countries often uses the expensive energy gap reference, and the temperature drift coefficient varies by 10ppm per degree;

10. The total current consumption of the internal circuit is <4mA, equals to 4.000mA after the setting is completed, and the active rectifier filtering and amplifying constant current circuit does not change the current consumption due to the change of the primary input. The IC IC in foreign countries adopts constant current power supply;

11. The linearity of the product marking 0.5% is an absolute error or a relative error, which can be discerned in the following way: At a nominal linearity of 0.5% in accordance with the following criteria. Output 4mA plus or minus 0.5% when the primary input is zero (3.98-4.02mA), with a voltage drop of 0.995-1.005V at 250Ω load,

When the input of the primary side is 10%, the output is 5.6mA plus or minus 0.5% (5.572-5.628mA), and the load voltage at 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 load voltage at 250Ω is 1.990-2.010V.

When the input voltage is 50% at the primary input, the output voltage is 12mA plus or minus 0.5% (11.94-12.06mA), and the load voltage at 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). The load is 250mA with a voltage drop of 3.980-4.020V.

When the primary input is 100%, the output voltage is 20mA plus or minus 0.5% (19.90-20.10mA). The pressure drop across the 250Ω load is 4.975-5.025V.

12. When the primary input is overloaded, it must be current-limited: When the primary input overload is greater than 125%, the output over-current limit is 25mA+10% (25.00-27.50mA). The pressure drop on the load 250Ω is 6.250-6.875V;

The above 12 methods can also be used to distinguish between the true and false advantages and disadvantages of other transmitters.