Advantages and Disadvantages of Integrated Vibration Transmitters

# Advantages and Disadvantages of Integrated Vibration Transmitters

1. At an operating voltage of 24.000 V and a full-scale output of 20.000 mA, the reading remains unaffected by load variations ranging from 0 Ω to 700 Ω; the deviation is controlled within less than 0.5% of 20.000 mA.

2. With a full-scale output of 20.000 mA and a load resistance of 250 Ω, the full-scale reading of the transmitter stays stable when the operating voltage fluctuates between 15.000 V and 30.000 V; the deviation is kept below 0.5% of 20.000 mA.

3. In the event of primary side overload, the output current shall not exceed 25.000 mA plus 10%. Otherwise, PLC/DCS systems supply 24 V power to transmitters and are equipped with A/D input clamping circuits to prevent transmitters from burnout caused by excessive power consumption from overloaded outputs; equipment without A/D input clamping circuits is far more vulnerable to such damage.

4. Reverse connection of the 24 V operating voltage must not damage the transmitter, which shall be fitted with reverse polarity protection.

5. Identification of surge voltage clamping performance for induced voltages exceeding 24 V: Connect an AC 50 V analog meter to the two-wire output terminals, then briefly apply AC 50 V across the two output wires to directly observe whether effective voltage clamping is available and evaluate its performance.

6. Stable reference circuit: 4 mA corresponds to the zero input reference. A shaky baseline makes linear accuracy meaningless. After a 3-minute cold start, the zero drift of the 4 mA signal shall not exceed 0.5% of 4.000 mA (i.e., ranging from 3.98 mA to 4.02 mA), generating a voltage drop of 0.995 V to 1.005 V across a 250 Ω load. Imported IC chips adopt costly bandgap references with a temperature drift coefficient of 10 ppm.

7. Circuit quiescent current consumption is less than 4 mA, and the total current including trimming is exactly 4.000 mA. Unlike conventional active rectification, filtering and amplifier constant-current circuits whose current consumption varies with primary input fluctuations, imported IC solutions feature dedicated constant-current power supplies.

8. Reverse polarity protection test method: Use the 10 kΩ resistance range of an analog multimeter to measure the two-wire output terminals with reversed probes. An infinite resistance reading indicates the presence of reverse polarity protection.

9. Distinction between industrial-grade and commercial-grade products: Industrial-grade devices operate within a temperature range of -25 °C to +70 °C with a temperature drift coefficient of 100 ppm/°C, meaning accuracy drifts by one thousandth per degree Celsius of temperature change. Commercial-grade units operate from 0 °C (or -10 °C) to +70 °C (or +50 °C) with a temperature drift coefficient of 250 ppm/°C, corresponding to an accuracy drift of five thousandths per degree Celsius. The temperature drift coefficients of current and voltage transmitters can be verified via testing in incubators or high-low temperature chambers, which requires complex test procedures.

10. The two-wire transmitter shall be equipped with clamping protection to avoid damage when induced lightning surge voltages exceed 24 V. Typically, two 1.5KE TVS transient suppression diodes are connected in parallel between the two wires. They can withstand positive and negative pulses with a pulse width of 20 ms at 20-second intervals, with an instantaneous surge power tolerance of 1.5 kW to 3 kW.

11. Clarification on the marked linearity of 0.5% (absolute vs. relative error): The authenticity of the 0.5% linearity specification can be verified through the following criteria.

    - Zero primary input: Output of 4 mA ±0.5% (3.98–4.02 mA), voltage drop of 0.995–1.005 V across a 250 Ω load.

    - 10% primary input: Output of 5.6 mA ±0.5% (5.572–5.628 mA), voltage drop of 1.393–1.407 V across a 250 Ω load.

    - 25% primary input: Output of 8 mA ±0.5% (7.96–8.04 mA), voltage drop of 1.990–2.010 V across a 250 Ω load.

    - 50% primary input: Output of 12 mA ±0.5% (11.94–12.06 mA), voltage drop of 2.985–3.015 V across a 250 Ω load.

    - 75% primary input: Output of 16 mA ±0.5% (15.92–16.08 mA), voltage drop of 3.980–4.020 V across a 250 Ω load.

    - 100% primary input: Output of 20 mA ±0.5% (19.90–20.10 mA), voltage drop of 4.975–5.025 V across a 250 Ω load.

12. Primary input overload limiting function: When the primary input of the transmitter exceeds 125% of the rated value, the output overcurrent is limited to 25 mA plus 10% (25.00–27.50 mA), creating a voltage drop of 6.250–6.875 V across a 250 Ω load.