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How to Judge Pressure Transducer Performance

With the development of mechanical automation technology, the demand for pressure transducers on the market is also growing. Therefore, there are more and more manufacturers of pressure transducers. When the user selecting the pressure transducer, it is difficult to distinguish the high performance and the inferior performance of the pressure transducer without mastering some technical expertise. This article will describe how to judge the performance of a pressure transducer.
The accuracy level of a conventional pressure transducer is 0.5. Take a pressure transducer with 0.5 accuracy, output current and voltage signal as an example. Users can try to distinguish the high performance and the inferior performance for the pressure transducer in the following ways.
  1. Benchmark of the high performance pressure transducer should be stable. 4mA is the corresponding input zero benchmark. If the benchmark is unstable, the accuracy and linearity of the pressure transducer cannot be guaranteed. Within 3 minutes after cold boot, the 4 mA zero drift variation cannot exceed 0.5% of 4.000 mA. (That is, the current range is within 3.98-4.02mA). The voltage drop across the 250Ω load is 0.995-1.005V. For the bandgap energy gap of the IC chip, the temperature drift coefficient varies by 10 ppm per degree.
  2. The internal circuit of the high performance pressure transducer consumes a total of <4mA. After the adjustment, the value is equal to 4.000mA. When the active rectification filter amplifies the constant current circuit, the current consumption does not change due to the change of the input of the primary side. The IC chip is powered by constant current.
  3. For a high performance pressure transducer, when the operating voltage is 24.000V and the full scale is 20.000mA, its full-scale 20.000mA reading will not change due to load change 0-700Ω. The varying interference signal of the pressure transducer does not exceed 0.5% of 20.000 mA.
  4. When the high performance pressure transducer has a full-scale range of 20.000 mA and a load of 250 Ω, the full-scale 20.000 mA reading will not change due to the operating voltage change of 15.000V-30.000V. The change does not exceed 0.5% of 20.000 mA.
  5. When the primary side is overloaded, the output current does not exceed 25.000mA + 10%. Otherwise, the 24V working power supply and A/D input clamp circuit for the pressure transducer in the PLC/DCS will be damaged due to excessive power consumption. In addition, the emitter follower in the transducer will also be damaged due to excessive power consumption. Pressure transducers without an A/D input clamp circuit will be damaged more seriously.
  6. When the polarity of the 24V voltage is reversed, the high performance pressure transducer must not be damaged. Therefore, there must be polarity protection.
  7. If the voltage between the two wires exceeds 24V due to inductive thunder and induced surge, clamp it to avoid damaging the pressure transducer. Generally, connect 1 to 2 TVS transient protection diodes 1.5KE in parallel between the two lines. It suppresses the impact of positive and negative pulses with 20 milliseconds pulse width every 20 seconds. The transient withstand impact power is 1.5KW-3KW.
  8. The primary side must be current limited when the input is overloaded. When the primary input overload is greater than 125%, the output overcurrent limit is 25mA+10% (25.00-27.50mA), and the voltage drop across the load of 250Ω is 6.250-6.875V.
  9. For the emitter output current, there must be long-term short-circuit protection to the high performance pressure transducer. When the primary input is 100% or the overload is greater than 125%-200%, short the load of 250Ω. Short circuit protection limits for measurement should be within 25mA + 10%.
  10. The method for discriminating whether the pressure transducer has polarity protection is as follows. Measuring the two-wire output port with the R×10kΩ file of the pointer multimeter. If at least once the Ω resistance is infinite, the pressure transducer has polarity protection.
  11. The method for discriminating whether there is clamping when the voltage of the induced surge exceeds 24V is as follows. Connect a 50V AC pointer head to the two-wire output port. Connect the two wires with 50V AC, and then instantly touch the two-wire output port of the pressure transducer. Observe that whether there are clamps at this time and how many volts are visible in the clamp.
  12. The linearity 0.5% marked at the product is absolute or relative error, which can be identified as follows. The linearity of the pressure transducer meeting the following data is 0.5%.
  • When the primary input of the differential pressure transducer is zero, the output is 4mA plus or minus 0.5% (3.98-4.02mA), and the voltage drop across the load of 250Ω is 0.995-1.005V.
  • When inputting 10% on the primary side, the output is 5.6mA plus or minus 0.5% (5.572-5.628mA), and the voltage drop across the load of 250Ω is 1.393-1.407V.
  • When inputting 25% on the primary side, the output is 8mA plus or minus 0.5% (7.96-8.04mA), and the voltage drop across the load of 250Ω is 1.990-2.010V.
  • When inputting 50% on the primary side, the output is 12mA plus or minus 0.5% (11.94-12.06mA), and the voltage drop across the load of 250Ω is 11.94-12.06mA.
  • When inputting 75% on the primary side, the output is 16mA plus or minus 0.5% (15.92-16.08mA), and the voltage drop across the load of 250Ω is 3.980-4.020V.
  • When inputting 100% on the primary side, the output is 20mA plus or minus 0.5% (19.90-20.10mA), and the voltage drop across the load of 250Ω is 4.975-5.025V.

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