DPharp INTRODUCTION Yokogawa has more than 4 years experience in the development, design and manufacture of pressure sensors and pressure transmitters. The DPharp EJA series of digital pressure transmitters represents the most revolutionary advancement in transmitter history. DPharp is the result of long time research and design providing a level of performance and reliability beyond anything available today. This totally digital transmitter features the advanced digital sensor known as harp (high accuracy resonant pressure) providing unmatched performance in the most demanding process applications. FEATURES High Tech/High Performance Sensor - DPharp s single crystal resonant silicon sensor provides unmatched accuracy, linearity and overpressure protection. Two years between Calibration - With stability of ±.1% for 24 months, DPharp EJA series eliminates drift. Compatible Construction - DPharp s standard mounting design is easily retrofitted into traditional installations while its Hastelloy C-276 process diaphragms and stainless steel cover flanges provide superior corrosion protection. CUSTOMER S BENEFIT With these features, DPharp transmitters have kept offering an accurate and reliable pressure measurement with less installation, maintenance and operation effort to the users in the various fields. PRESSURE SENSORS Smart communications and microprocessor technology are enabling manufacturers to enhance the performance of older sensor designs. But, unless the sensor itself is digital, an analog to digital (A/D) conversion must still take place. With it, come the sacrifices in resolution and accuracy. DPharp eliminates A/D conversion while further minimizing errors and allowing users to easily migrate to future fieldbus schemes. Capacitance and piezoresistive sensors developed in the late 196s and early 7s are still being used today. Both offer a relatively small output and high performance amplifiers for both types of sensors are required to correct for sensor errors. These analog signals must be converted into a digital signal before entering the CPU for correction and compensation, before being converted back to an analog output. Since the 197s transmitter manufacturers have put little effort in development of transmitter technology due to the heavy investment required. To enhance the performance of older sensor designs, improvements have been primarily electronic, such as introduction of microprocessors and communication protocols. Yokogawa is the exception completely reinventing the differential pressure transmitter...all the way from the sensor up. Resonant silicon sensor PRESSURE MEASUREMENT PRINCIPAL Yokogawa completed the development of the DPharp sensor in the late 198s. The harp sensor is fabricated from a single crystal silicon using proven 3-D semi-conductor micromaching techniques. Micro-machining from a single silicon crystal offers excellent elasticity characteristics of silicon for superior stability and repeatability while eliminating hysteresis. Magnetic Field Electric Terminal Cavity Resonator Shell Diaphragm Pressure Silicon Sensor Chip
DPharp At the heart of DPharp are two H-shaped resonators. Patterned on the sensor itself, these two bridges resonate at their natural frequency of 9 khz allowing the sensor to remain stable over long periods of time. Whenever pressure is applied, it forces the central bridge into tension and the outer bridge into compression. As a result, their resonating frequencies change - one increases, the other decreases. A microprocessor then calculates the differential change in resonant frequencies proportional to the applied pressure. SENSOR PERFORMANCE The DPharp sensor is a high performance pressure sensor capable of accuracy to.3% with hysteresis below.1%. The sensor is more accurate than other transmitter sensors available today, even more accurate than most calibration equipment. DPharp s differential frequency has many benefits. The change in output signal is double, allowing for more accurate measurement. Also, as temperature changes effect the sensor, both resonator will see a shift in the same direction. Looking at the differential frequency allows for cancellation of ambient temperature effects down to.1 % per C. H e + -- Frequency Output Because the naturally high resonant frequency of 9 khz is well above any mechanical vibrations, it is immune to vibration. It is further protected from outside interference via an electromagnetic and radio frequency isolation. The frequency, or digital, driven measurement is fundamentally different from the analog nature of capacitance or piezoresistive sensors. Unlike the analog sensors, an analog to digital (A/D) conversion is no longer necessary to get the differential pressure into the microprocessor. This totally new technology further minimizes errors induced by the conversion A unique feature of the DPharp sensor is its longterm stability. Analog technologies of the 197s (capacitance and piezoresistive) are affected by shifts in the amplitude of the sensor output signal. These shifts can be caused by changes in the drive circuity or contamination, both of which do not effect the DPharp sensor. Long-term Stability of Silicon Resonant Sensor (with compensation) @Room Temperature, Max.Span Shift +.1 Frequency (khz) 11 1 9 8 7 ft fe 5, Pressure (mmh2o) 1, -.1 1st year 2nd year 3rd year 4th year 5th year 6th year Since the frequency of the sensor is use to measure the pressure, the A/D converter used in capacitance and piezoresistive sensors are eliminated, reducing sources of errors or drift. The resonators for full scale differential pressure will see a 4, khz differential. This is a very large sensor output compared to the pf output of the capacitance sensor. At the upper range of the either sensor, high performance is easily achieved, but when the sensor is spanned lower performance can be degraded. However, The DPharp sensor, even at smaller spans, maintains high performance.
EJA A Series Transmitter INTRODUCTION The EJA is the second generation transmitter to use the DPharp (Differential Pressure high accuracy resonant) sensor. The series offers a complete line of products, including differential, draft, flange mounted level, absolute and gauge pressure transmitters. EJA A series models which have appeared as strong successors of EJA models offers greater range ability than earlier EJA models. TEPERATURE AND STATIC EFFECTS Environmental changes around the transmitter, day to night, start up to shut down, cause shifts in calibration. EJA A series sees very little effects to these types of changes Zero shift by Temperature Change.75-4 -25 23 5 8.75 C Zero shift by Static Pressure.75 -.75 5 1 14 Input Output of % Static pressure (kgf/cm 2 ) Accuracy is not the only specification to determine the performance of the transmitter. The entire performance specifications must be used. Using accuracy, total temperature effects, total static effects, over pressure effects, and stability should be used to calculate the real total performance of a transmitter. (All the graph data shown in this page are examples of typical testing data of model EJA11A-DM ) ACCURACY The reference accuracy of the transmitter at full span and at a 1:1 turndown ratio is excellent providing a wide range of operation without compromise. The graphs below show the superior performance and the negligible linearity and hysteresis errors of the transmitter. Both are testament to the capability of the DPharp sensor. Range to 1 kpa ( to 4 in H2O).75 Upward Downward 5 1.75 Input OVER PRESSURE Impulse lines, mis-sequence of the manifold or very high differential pressures cause a transmitter to be over pressured. EJA A series are not only capable to withstand a single overpressure event, but over a million over pressure cycles with negligeable effects to calibration. A capacitive sensor sees large effects with only a single over pressure event..2.1 -.1 Over Pressure Cycle Test Zero shift Point @ MAX.SPAN, P=6.9MPas -.2 1 1 1 2 3 5 17 28 6 1 Over Pressure Cycle Number STABILITY The DPharp sensor allows the transmitter to maintain high performance over long periods of time. Conventional sensors like capacitance or piezoresistive require adjustments to correct for analog drift over time. The EJA A series offers very tight stability of ±.1 % per 2 years. Range to 2 kpa ( to 8 in H2O).275.75 -.75 -.275 5 1 Input Upward Downward TRADITIONAL DESIGN The EJA mounting design is with the standard 54 mm (2.125 inch) process connector spacing, and thus replacement of the existing installation can be done with less cost and effort. Other proprietary connections, like single planes, do not allow for standard installations. This makes retrofitting existing installation difficult and costly.
UPGRADED WETTED PARTS MATERIALS The traditional style EJA includes Hastelloy C-276 process diaphragms and stainless steel cover flanges as standard. The typical transmitter offers 316 SS diaphragm with carbon steel cover flanges as a base material. Due to the corrosive nature of many processes and thin process diaphragms (less than 5 µm or 2 mils), a small amount of corrosion can cause failure of the diaphragm and sensor. In most cases Hastelloy C-276 offers more corrosion resistance than 316 SS, allowing the diaphragm to last longer. As with the diaphragm, stainless steel cover flange experience less corrosion than carbon steel. Both providing superior protection. ENHANCED SOFTWARE TODAY Microprocessor has the capability to store information in nonvolatile memory. The EJA A series transmitter has an error memory buffer to store process events. The user can diagnose the instrument problems quickly. Also, this can be used to diagnose and solving problems with the process. SETTING VIA BT2 and HART HHT Intelligent Brain Terminal BT2 and HART HHT allow users to set the necessary parameters of Transmitters very easily. IMPROVED SEAL The standard capsule gasket is a Teflon-coated stainless steel gasket. Typical transmitters use Teflon or Viton O-rings which will dry-rot over time or cold flow with temperature cycles. The metal gasket provides long term sealant characteristics, and preventing leakage of hazardous materials. LINE-UPS MODEL EJA11A.75% accuracy, range ability 1: 1 (M, H & V) Capsule. :.5 to 1 kpa (L capsule) 1 to 1 kpa (M capsule) 5 to 5 kpa (H capsule).14 to 14 MPa(V capsule) Range :-1 to 1 kpa (L capsule) -1 to 1 kpa (M capsule) -5 to 5 kpa (H capsule) -.5 to 14 MPa(V capsule) MODEL EJA12A Drift range.2% accuracy, range ability 1:1 (.1% accuracy available optionally) :.1 to 1kPa Range : -1 to 1kPa MODEL EJA13A.75% accuracy, range ability 1:1 :1 to 1 kpa (M capsule) 5 to 5kPa (H capsule) Range :-1 to 1 kpa (M capsule) -5 to 5 kpa (H capsule)
MODEL EJA21A/22A (FLOUNG MOUNTED).75% accuracy, range ability 1:1 :1 to 1 kpa (M capsule) 5 to 5kPa (H capsule) Range :-1 to 1 kpa(m capsule) -5 to 5 kpa (H capsule) MODEL EJA31A ABSOLUTE PRESSURE TRANSMITTER.15% accuracy, range ability 1:1(M & A capsule) (.75% accuracy available optionally) :.67 to 1 MPa (L capsule) 1.3 to 13 MPa (M capsule).3 to 3 MPa (H capsule) Range : to 1 MPa (L capsule) to 13 MPa (M capsule) to 3 MPa (H capsule) MODEL EJA43A GAUGE PRESSURE TRANSMITTER.75% accuracy, range ability 1:1 :.3 to 3 kpa (A capsule).14 to 14 kpa (B capsule) Range :-.1 to 3 kpa (A capsule) -.1 to 14 kpa (B capsule) MODEL EJA44A GAUGE PRESSURE TRANSMITTER.12% accuracy, range ability 1:1 (D capsule) :5 to 32 MPa (C capsule) 5 to 5MPa (D capsule) Range :-.1 to 32 MPa (C capsule) -.1 to 5 MPa (D capsule) MODEL EJA51A/53A ABSOLUTE/GAUGE PRESSURE TRANSMITTER.2% accuracy, range ability 2:1(A,B & C capsule) :1 to 2 kpa (A capsule).1 to 2 MPa (B capsule).5 to 1 MPa (C capsule) 5 to 5 MPa (D capsule) Range : to 2 kpa (A capsule) to 2 MPa (B capsule) to 1 MPa (C capsule) ` to 5 MPa (D capsule)