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Real Time Dynamic Compensation for Satic Pressure Effects

Yokogawa Electric Corporation is dedicated to developing the most advanced control and instrumentation products, (and systems), in the world. With their establishment in the United States in 1957, Yokogawa Corporation of America has become a leading manufacturer and supplier for the North American market in the fields of automation, measurement, and control. As a major industrial automation and test and measurement company, Yokogawa anticipates the needs of the times, continually tackling new challenges and exploring new markets in order to provide the customer-centric solutions.

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Real Time Dynamic Compensation for Satic Pressure Effects

  1. 1. Real-Time Dynamic Compensation for Static Pressure Effects Performance under pressure - DP Transmitter Static pressure (SP) is applied equally to both the high-pressure side and the low-pressure side of a DP transmitter and can vary the linear Accurate measurement is vital to efficient plant operation and plant characteristics of the DP signal output. The effect is called Static safety. When selecting a transmitter, a lot of attention is paid to the Pressure Effect . This characteristic has both Zero Effect and Reference Accuracy noted in supplier's specification documents. Span Effect components. Reference Accuracy gets its name because the accuracy is based on a set of reference conditions. The reference conditions dictate a certain temperature, humidity, and static pressure for the Reference Accuracy to be measured in a laboratory setting. In the real world, DP Transmitters are rarely installed in a laboratory and never under the rigid confines of those reference conditions; therefore, Real-world Performance (RWP) is always worse than the Reference Accuracy. To improve RWP, all smart transmitters on the market SP Effect compensate for variations in temperature; but, Yokogawa's sensor used in the EJA-A series, EJX-A series, and EJX-B series is unique in the market place because it can compensate for effects in static pressure change as well. This ability is referred to 0% 100% Real-time Dynamic Compensation . Static Pressure Effects SP = 100 Using differential transmitters to measure flow and tank level are examples of applications where variations in static pressure can effect 100 100 100 200 the differential pressure readings of a transmitter. 0% SP = 0 0 0 0 100 0% PTN1011.003a To quantify the impact, Real-world Performance (RWP) can be calculated per published specifications and process conditions. RWP is a combined error of Reference Accuracy (E1), Temperature Effect (E2), Static Pressure Zero Effect (E3) and Static Pressure Span Effect (E4). Competitors state that the static pressure zero effect (E3) can be PTN1011.001a zeroed at line static pressure during the setup of the transmitter. In many flow measurements or process level applications, static pressure is not maintained at a constant value. As operational conditions change, the static pressure exerted on the DP transmitter varies. Hence, the static pressure zero effect (E3) cannot always be cancelled by zeroing at line static pressure during setup. This effect cannot be neglected when evaluating the real-world performance. Yokogawa's Full Dynamic Compensation Yokogawa's silicon resonant sensor is a true multi-sensing platform. It can measure differential pressure, static pressure, and temperature in one compact sensor chip. This multi-sensing sensor allows the transmitter to use correction coefficients stored in the sensor's ROM to compensate for fluctuations in static pressure and temperature to reduce the static pressure and temperature effects. The correction coefficients are unique to each sensor and are PTN1011.002a generated at the factory through rigorous testing (See Figure 1). LH.091412.01a FGP-290 2nd Edition 09/2012 LH.012711.a Static Pressure Zero and Span Effect Input (DP) ERROR(%) Flow Measurement ΔP ≈ Flow² Level Measurement ΔP ≈ Process Level E3: SP Zero Effect E4: SP Span Effect 100% 100% Field Instruments
  2. 2. Alternate Sensor Technology Capacitive sensor technology used in the marketplace is not capable of multi-sensing. It can only measure differential pressure. The DP transmitters using this type of technology incorporate a resistive temperature sensor near the capacitive sensor to compensate for temperature fluctuations; but, they do not add a separate sensor to measure static pressure for static pressure fluctuations. Therefore, these transmitters are not capable of minimizing the static pressure effect (See Figure 2). Figure 1 Yokogawa's Multi-sensing Resonant Sensor Technology Transmitter Silicon Resonant Sensor Figure 2 Capacitive Sensor Technology PTN1011.003a Transmitter Capacitive Sensor RTD Not measured Static Pressure is not measured; therefore it is not compensated for. PTN1011.004a Figure 3 Comparison of Real-world Performance Conclusion Even in high static pressure applications, Yokogawa's EJA-A / EJX-A / EJX-B series dramatically reduces the static pressure effects and provides superior total performance. Using the published specifications, the Real- world Performance can be calculated for comparative estimates (See Figure 3). Note that the Reference Accuracy is the smallest component of the calculations. E1: Reference Accuracy Calibrated Span: 0 to 1500 inH ₂O E2: Temperature Effect Static Pressure: 1,200 psig E3: Static Pressure Zero Effect PTN1011.005a E4: Static Pressure Span Effect LH.091412.01a FGP-290 1st Edition 09/2012 Process Process Field Instruments Correction Coefficients Dynamic Compensation Temperature Effect & Static Pressure Effect Primary Variable: Dynamic Compensated DP Signal (4 to 20 mA) Differential Pressure Differential Pressure Temperature Temperature Static Pressure Static Pressure Differential Pressure Temperature Static Pressure Differential Pressure Temperature Temperature Correction Coefficients Temperature Effect Compensation Digital /Analog Conversion Secondary Variable: Static Pressure (Digital Protocol) Third Variable: Capsule Temperature (Digital Protocol) Digital /Analog Conversion Analog /Digital Conversion Primary Variable: Temperature Compensated DP Signal (4 to 20 mA) Secondary Variable: Temperature (Digital Protocol) EJX110A EJA110A Capacitive Sensor Transmitter RWP = E1+E2+E3+E4 0.0% 0.5% 1.0% 1.5% 2.0% 2.5%