Abstract:
A pressure transmitter apparatus includes a unitary body with two, normally vertical pressure passageways communicating respectively between opposed pressure openings extending normally horizontally through the body portion. A transducer for generating a differential pressure signal mounts on a transducer mounting element, coupled to the body portion and located above the pressure passageways. A pair of diaphragm elements can form first and second process diaphragms, closing first and second pressure openings. Flange elements overlie the diaphragm elements and are removably and replaceably secured to the body portion, having liquid drainage and gas purging passageways. A flame retardation element can be disposed within at least one of the pressure passageways. An overrange protection element can be integrally arranged with the unitary body portion to protect the transducer from overrange pressure fluctuations. Extensions on the flange elements afford a variety of mounting options, including mounting to industry standard pipe mountings.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims priority to, and incorporates by reference, the entire disclosure of U.S. Provisional Patent Application No. 60/494,494, filed on Aug. 12, 2003. 
     
    
     FIELD  
       [0002]     This application relates to process control devices, and, more particularly, to differential pressure transmitters.  
       BACKGROUND  
       [0003]     Differential pressure transmitters measure the difference between two pressures and produce an output signal, typically with a display, responsive to the measurement. Differential pressure transmitters are commonly used in process control systems that require pressure measurements, or measurements of other variables associated with gases and liquids, e.g., flow rates. A typical differential pressure transmitter has two process diaphragms, each exposed to one of two fluid pressures that are to be compared, and has a transducer. An inert fill fluid is provided in a closed chamber between each process diaphragm and the transducer, to transmit pressures from the process fluids to the transducer. Each process diaphragm deflects in response to the pressure of one fluid, as applied from an input process line. The transducer responds to the difference between the two pressures of the process fluid, and produces electrical output signals for indication or control. Pressure transmitters that produce electrical output signals often include electronic circuitry to process the transducer signal and to display it by way of a read-out meter, and/or to apply the processed signal to a computer or other electronic device.  
         [0004]     Two conventional structural types of pressure transmitters are known: planar designs in which the process diaphragms share the same plane, and bi-planar designs in which the process diaphragms are in different planes and are disposed back-to-back. Conventional planar transmitters generally have an electronics housing that extends horizontally when the transmitter is oriented so that the plane of the process diaphragms is vertical. This configuration can require special hardware to mount the transmitter. Additionally, the electronics housing is displaced from the diaphragm plane in such a way that a read-out meter on the housing is often difficult to see.  
         [0005]     Another drawback of conventional planar transmitters is that the electronic circuitry is located close to hot process lines. Specifically, in one prior configuration, the differential pressure transmitter is close to the high pressure and low pressure input process lines. These process lines can radiate heat to the transmitter electronics, thereby creating a hot operating environment. Thus, the transmitter is more susceptible to electrical malfunctions. Additionally, exposing the electronics to unnecessary elevated temperatures reduces the life of the electrical components.  
         [0006]     A further drawback of prior transmitters is that the conventional transmitter housing assembly limits the size of the process diaphragms. A large diaphragm diameter is advantageous because it has a correspondingly low spring rate and hence aids high measuring sensitivity. The diaphragm volumetric spring rate is inversely proportional to the sixth power of the diameter of the diaphragm. However, prior pressure transmitter structures restrict the diameter of the process diaphragms to avoid undue size, which leads to a relatively large diaphragm spring rate.  
         [0007]     Prior pressure transmitters accordingly resort to thin diaphragms, to achieve a usable spring rate. This, in turn, presents a risk of diaphragm leakage, which is a serious problem.  
         [0008]     Conventional planar pressure transmitters endeavor to circumvent the foregoing mounting problems by using a flange adapter, in conjunction with the existing assembly that mounts the pressure transmitter. However, this solution adds weight and cost to the system.  
         [0009]     Conventional bi-planar transmitters are relatively heavy and relatively costly. The additional weight stems at least in part from large dual process covers that mount over the process diaphragms, and from the weight of the associated cover mounting hardware.  
         [0010]     Another drawback of both the conventional designs is that the electronic circuitry is susceptible to fluid noise, such as mechanical shocks, pipe vibrations and like mechanical disturbances. Consequently, the pressure transmitters are susceptible to producing measurement errors when mechanical disturbances occur.  
       SUMMARY  
       [0011]     The present disclosure provides a robust differential pressure transmitter that is comparatively light in weight and relatively low in cost, has a read-out indicator that is comparatively easy to view, includes a transmitter housing of comparatively small size that mounts process diaphragms of a comparatively large diameter, includes a transmitter housing that is comparatively easy to install and easy to mount, shields electronic components therein from the elevated temperatures of hot process lines and hence maintains the components in a relatively cool environment, and, operates with a reduced loss of performance when measuring fluids subjected to vibration and other mechanical noise.  
         [0012]     The disclosed differential pressure transmitter attains the foregoing and other objects with a pressure transmitter having a body portion, first and second normally vertical pressure passageways disposed therein and communicating respectively between first and second opposed pressure openings extending normally horizontally through the body portion, and a transducer mounting element, coupled to the body portion and located above the pressure passageways. A transducer mounts on the transducer mounting element and generates a differential pressure signal. A pair of diaphragm elements is configured to form first and second process diaphragms, closing first and second pressure openings. Flange elements overlie the diaphragm elements and are removably and replaceably secured to the body portion, having liquid drainage and gas purging passageways. The pressure transmitter also can include a flame retardation element that is disposed within at least one of the pressure passageways, and an overrange protection element, integrally arranged with the unitary body portion, that protects the transducer from overrange pressure fluctuations. Extensions on the flange elements afford a variety of mounting options, including mounting to industry standard pipe mountings.  
         [0013]     In one embodiment, a pressure transmitter apparatus can include a unitary body having, in a first orientation, (1) vertical surface extending along a first vertical axis and apertured with first and second pressure openings disposed at substantially the same vertical location along a first horizontal axis on opposed faces of the vertical surface, and (2) transducer mounting coupled to the body and located, in the first orientation, vertically above the pressure openings. A diaphragm can form first and second process diaphragms respectively closing the first and second pressure openings. First and second flange can be removably and replaceably secured to the body overlying the diaphragm. The first and second flanges can be apertured to form respective first and second pressure chambers adjacent the diaphragm. The first and second flanges can form respective first and second pressure ports extending vertically within the first and second flanges to intersect with the first and second pressure chambers for coupling first and second pressure inputs to the first and second process diaphragms, respectively. First and second pressure passages can extend vertically at least partly within the body for communicating respectively between the first and second pressure openings and the transducer mounting. Each of the first and second flanges can include a selectively closed first passageway extending horizontally within the first and second flanges to intersect with the first and second pressure chambers, and being offset vertically and horizontally from the first horizontal axis. Each of the first and second flanges can include a selectively closed second passageway extending horizontally within the first and second flanges to intersect with the first and second pressure chambers, and being offset horizontally from the first horizontal axis opposite from the first passageway. The first passageway can be disposed for purging gas and the first and second pressure ports can be disposed for draining liquid when the transmitter apparatus is mounted in the first orientation. The first passageway can be disposed for draining liquid and the first and second pressure ports can be disposed for purging gas when the transmitter apparatus is mounted in a second orientation rotated 180 degrees about the horizontal axis from the first orientation. The first passageway can be disposed for purging gas and the second passageway can be disposed for draining liquid when the transmitter apparatus is mounted in a third orientation rotated ninety degrees about the horizontal axis from the first orientation. The first passageway can be disposed for draining liquid and the second passageway can be disposed for purging gas when the transmitter apparatus is mounted in a fourth orientation rotated one hundred eighty degrees about the horizontal axis from the second orientation. Those of ordinary skill will understand that the use and/or labels of first, second, third, and fourth orientations, as provided herein, is merely for reference purposes relative to a given description/embodiment, and accordingly, in a description of one embodiment, an orientation may be referred to as a “first” orientation, while in a description of another embodiment, such same orientation may be referred to, for example, the “third” orientation.  
         [0014]     The pressure transmitter apparatus can include a flame retardant disposed within at least one of the vertically extending first and second pressure passages and located above the pressure openings which extend generally horizontally, and at least partly within the unitary body, for introducing a flame barrier between the transducer mounting and the pressure openings. The unitary body can have a neck interconnecting the transducer element mounting with the vertical surface for providing thermal isolation therebetween.  
         [0015]     The transducer mounting can include a sensor and a mounting for the sensor. The sensor can be located, in the first orientation, above the pressure openings and in fluid communication with the first and second passages. A circuit can connect with the sensor and can be selectively operable for electronically designating which of the first and second pressure inputs is a high pressure input. The sensor can include a housing having opposed and substantially parallel first and second faces that are transverse to the first axis and that are axially spaced apart along the first axis, in the first orientation, and a transducer, located at least partly between the first and second faces, for generating a signal in response to the difference in pressure between the first and second pressure inputs applied to the first and second pressure ports. The sensor can also include an overrange protection overlying the second face of the housing and arranged in fluid communication with the first and second pressure passages, for protecting the transducer from an overrange pressure condition, the overrange protection overlying at least the first pressure passage and integrally arranged with the housing of the sensor.  
         [0016]     The transducer mounting can include an annular support structure for mounting a sensor assembly and which extends, in the first orientation, along the first vertical axis. The transducer mounting can further include a flat face disposed substantially orthogonal to the first vertical axis in the first orientation, and from which the annular support extends, wherein one of the first and second pressure passages opens onto the face and within the annular support structure and wherein the other of the first and second pressure passages opens onto the flat face external of the annular support structure. A pressure sensor assembly can couple to the transducer mounting, disposed in fluid communication with at least one of the first and second pressure passages, and having overrange protection for protecting against an overrange pressure condition coupled to at least one of the pressure passages, the pressure sensor assembly being adapted for mounting within the annular support structure such that the overrange protection overlies the pressure passage opening onto the flat face within the annular support structure.  
         [0017]     The transducer mounting can include a horizontal annular surface coupled to the unitary body and located, in the first orientation, vertically above the pressure openings. The horizontal annular surface can include a transducer element seating, and a connection mounting an electronics housing to the horizontal surface. The connection can include a stepped annular surface for seating the electronics housing. The seating can include an annular transducer mount integrally formed on the horizontal annular surface and extending outwardly from the seating.  
         [0018]     A pressure sensor assembly can couple to the transducer mounting, disposed in fluid communication with at least one of the first and second pressure passages, and having an overrange protection for protecting against an overrange pressure condition coupled to at least one of the pressure passages. The pressure sensor assembly can include a housing having opposed and substantially parallel first and second faces that are transverse to the first axis and that are axially spaced apart along the first axis, in the first orientation, and a pressure sensing element, located at least partly between the first and second faces, for generating a signal in response to the difference in pressure between the first and second pressure inputs applied to the first and second pressure ports. The overrange protection can overlie the second face of the housing and is arranged in fluid communication with the first and second pressure passages, for protecting the pressure sensing element from an overrange pressure condition.  
         [0019]     The pressure transmitter can include an overrange-protected sensor for producing an electrical signal responsive to first and second pressure conditions applied thereto. The sensor can seat with the mounting in fluid communication with at least one of the pressure passages. First and second fastener apertures can each extend horizontally, when in the first orientation, through the body and the first and second flanges. The apertures can be horizontally spaced apart and disposed below the transducer mounting and below the sensor. First and second threaded fasteners can each pass within the same-numbered fastener aperture for securing the body and the first and second flanges when assembled together.  
         [0020]     The pressure transmitter apparatus can include apertures in both the body and the first and second flanges for mounting a plurality of fasteners, with the apertures in the first and second flanges being disposed in registration with the apertures in the body when mounted together to facilitate seating of the fasteners. The fastener shrouding on the body and the first and second flanges can shroudingly enclose the fasteners in the aperture thereof throughout engagement with the first and second flanges and with the body. A seal engaged between the diaphragm and the first and second flanges can seal each pressure port with respect to one process diaphragm, and first and second weld connections can each sealingly secure the same-numbered process diaphragm to the body at the same-numbered pressure opening, each weld connection being isolated from contact with fluids at the pressure inputs by the seal. First and second flame arrestors, vertically disposed respectively in the first and second pressure passages, can introduce flame barriers between the transducer mounting and the pressure openings.  
         [0021]     The opposed faces of the vertical surface can include a pair of parallel surface elements spaced apart in a direction orthogonal to the first axis, and the first and second pressure openings can be oppositely arranged and substantially parallel to each other and the pressure passages are formed within the body between the surface elements. The first and second flanges can include a cover forming first and second process covers overlying the first and second process diaphragms, respectively, with each process cover being apertured with at least one fastener-receiving opening. The diaphragm can include a pair of diaphragm sheets forming first and second process isolation diaphragms respectively closing the first and second pressure openings formed, and a pair of weld plates, each having an aperture dimensioned and sized to define the first and second process diaphragms. Each weld plate can be configured to overlie each diaphragm sheet and configured for mounting between the vertical surface and one of the first and second flanges when the pressure transmitter is assembled.  
         [0022]     The pressure transmitter apparatus can include plural bolt-type fastener for removably and replaceably securing the first and second flanges to the body. A first shroud formed on the body can shroudingly enclose at least a selected length of each the bolt-type fastener, and second shroud formed on each of the first and second flanges can shroudingly enclose at least a selected length of each bolt-type fastener. The first and second shroud, in combination, can shroud nearly the entire length of the fastener. The fastener for removably and replaceably securing the first and second flanges to the body can include two threaded fasteners, each extending through the first and second flanges and the body. The pressure transmitter apparatus can include overrange-protected sensor for producing an electrical signal responsive to first and second pressure conditions applied thereto, the sensor being seated with the mounting in fluid communication with at least one of the pressure passages.  
         [0023]     The pressure transmitter apparatus can include an upwardly extending neck portion of relatively low thermal conductivity. The transducer mounting can be integrally formed with the neck portion to be relatively thermally isolated from and located above the pressure openings. The first and second diaphragms can respectively seal the pressure openings on the vertical surface, and a differential pressure sensor can be secured on the transducer mounting and disposed, in the first orientation, above the pressure openings. The first and second passages can communicate respectively between the first and second pressure openings and the differential pressure sensor, for separately communicating to the sensor first and second pressures responsive to pressures applied to the first and second pressure ports.  
         [0024]     The first and second flanges can be interchangeable. A flange mounting can extend from each of the first and second flanges for mounting the pressure transmitter apparatus to at least one mounting bracket. The flange mounting can include two threaded bores to receive mounting bolts of the at least one mounting bracket. The bores can extend horizontally and perpendicularly to the first horizontal axis into opposite faces of each of the first and second flanges. The first and second flanges can include process connections connecting the first and second pressure inputs to the first and second flanges. The first passageway can include a flared termination at the respective first and second pressure chambers. The flared termination can extend radially about the first horizontal axis such that the flared termination in the first orientation extends vertically from the first horizontal axis opposite the respective first and second pressure ports, and extends horizontally from the first horizontal axis opposite the second passageway.  
         [0025]     In one embodiment, a pressure transmitter apparatus can include unitary body having, in a first orientation, first and second pressure openings disposed at substantially the same vertical location along a first horizontal axis on opposed vertical faces of the body; transducer mounting coupled to the body and located, in the first orientation, vertically above the pressure openings; first and second pressure passages vertically extending at least partly within the body for communicating respectively between the first and second pressure openings and the transducer mounting; diaphragm forming first and second process diaphragms respectively closing the first and second pressure openings; first and second flanges removably and replaceably secured, respectively, to the opposed vertical faces of the body, and overlying the diaphragm, the first and second flanges apertured to form respective first and second pressure chambers adjacent the diaphragm, the first and second flanges forming respective first and second pressure ports extending vertically within the first and second flanges to intersect with the first and second pressure chambers for coupling first and second pressure inputs to the first and second process diaphragms, respectively, wherein, in the first orientation, each of the first and second flanges includes a selectively closed first passageway extending horizontally within the first and second flanges to intersect with the first and second pressure chambers, respectively, and being offset vertically and horizontally from the first horizontal axis, the first passageway having a flared termination at the respective first and second pressure chambers, the flared termination extending radially about the first horizontal axis such that the flared termination in the first orientation extends vertically from the first horizontal axis opposite the respective first and second pressure ports, and extends horizontally from the first horizontal axis opposite the second passageway, wherein, in the first orientation, each of the first and second flanges includes a selectively closed second passageway extending horizontally within the first and second flanges to intersect with the first and second pressure chambers, respectively, and being offset horizontally from the first horizontal axis opposite from the first passageway, the first and second passageways in combination with the first and second pressure ports disposed for purging gas and draining liquid when in one of the first orientation and a second orientation, rotated 180 degrees about the first horizontal axis from the first orientation, the first and second passageways alternately disposed for purging gas and draining liquid when the transmitter apparatus is mounted in one of a third orientation rotated 90 degrees about the first horizontal axis from the first orientation and a fourth orientation rotated 180 degrees about the first horizontal axis from the third orientation.  
         [0026]     The pressure transmitter apparatus can include at least first and second fastener apertures, each extending horizontally, when in the first orientation, through the body and the first and second flanges, the apertures being horizontally spaced apart and disposed below the transducer mounting; at least first and second threaded fasteners, each passing within the respective fastener aperture for securing the body and the first and second flanges when assembled together; and fastener shrouding on the body and the first and second flanges and shroudingly enclosing the fasteners in the aperture thereof throughout engagement with the first and second flanges and with the body. A flame retardant and/or means for providing the same can be disposed within at least one of the vertically extending first and second pressure passages and located above the pressure openings which extend generally horizontally, and at least partly within the unitary body, for introducing a flame barrier between the transducer mounting and the pressure openings.  
         [0027]     A pressure sensor assembly can couple to the transducer mounting and be disposed in fluid communication with at least one of the first and second pressure passages. The pressure sensor assembly can include an overrange protection for protecting against an overrange pressure condition coupled to at least one of the pressure passages. The first and second flanges can include at least first and second threaded bores extending horizontally and perpendicularly to the first horizontal axis into opposed faces of each of the first and second flanges. The threaded bores can receive mounting bolts of at least one mounting bracket for mounting the pressure transmitter apparatus to the at least one mounting bracket. The first and second flanges can also include a process connection connecting the first and second pressure inputs to the first and second flanges.  
         [0028]     These and other aspects of the disclosed differential pressure transmitter are evident in the drawings and in the description which follows.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The foregoing and other objects, features and advantages of the disclosed differential pressure transmitter will be apparent from the following description and apparent from the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings illustrate principles of the disclosed differential pressure transmitter and, although not to scale, show relative dimensions.  
         [0030]      FIG. 1  is a perspective view of a bi-planar pressure transmitter;  
         [0031]      FIG. 2  is a perspective view of the pressure transmitter of  FIG. 1  according to one embodiment of the disclosed differential pressure transmitter with associated mounting hardware;  
         [0032]      FIG. 3A  is a perspective view of the pressure transmitter of  FIG. 1  with an associated manifold and mounting hardware;  
         [0033]      FIG. 3B  is a perspective view of the pressure transmitter of  FIG. 2  with an associated manifold;  
         [0034]      FIG. 4  is an exploded partial view of an embodiment of a bi-planar pressure transmitter;  
         [0035]      FIG. 5  is a perspective view of a flange element of the pressure transmitter of  FIG. 4 ;  
         [0036]      FIGS. 6 and 7  are elevation views of opposite faces of the flange element of  FIG. 5 ;  
         [0037]      FIG. 8  is a perspective view of a body element of the pressure transmitter of  FIG. 4 ;  
         [0038]      FIG. 9  is an elevation view of the body element of  FIG. 8 ;  
         [0039]      FIG. 10  is a diagrammatic elevation view, in section, of the pressure transmitter of  FIG. 4 , as assembled and with elements diagrammatically relocated;  
         [0040]      FIG. 11A  is a perspective view of a pressure transmitter according to one embodiment of the disclosed differential pressure transmitter, with associated mounting hardware; and  
         [0041]      FIG. 11B  is a perspective view of a pressure transmitter of  FIG. 11A  from a reverse direction.  
         [0042]      FIG. 12  is a cross-sectional view of a flange element having vertically aligned passageways. 
     
    
     DESCRIPTION  
       [0043]     To provide an overall understanding, certain illustrative embodiments will now be described; however, it will be understood by one of ordinary skill in the art that the systems and methods described herein can be adapted and modified to provide systems and methods for other suitable applications and that other additions and modifications can be made without departing from the scope of the systems and methods described herein.  
         [0044]     Unless otherwise specified, the illustrated embodiments can be understood as providing exemplary features of varying detail of certain embodiments, and therefore, unless otherwise specified, features, components, modules, and/or aspects of the illustrations can be otherwise combined, separated, interchanged, and/or rearranged without departing from the disclosed systems or methods. Additionally, the shapes and sizes of components are also exemplary and unless otherwise specified, can be altered without affecting the scope of the disclosed and exemplary systems or methods of the present disclosure.  
         [0045]     The pressure transmitter of a first embodiment of the disclosed differential pressure transmitter determines the pressure difference between two input process lines. The transmitter includes a sensor body having flange portions and a web portion and a pair of opposed planar openings each closed by an isolation diaphragm. The diaphragms are in pressure communication with a sensor element by way of an inert fill fluid. The pressure inputs apply a pressure to the diaphragms, which is transmitted to a sensor element by the fill fluid. The sensor element generates a signal, in response to the applied pressures, indicative of the pressure difference between the two pressure inputs. The sensor body employs a horizontal bolt-hole configuration that accommodates correspondingly large diaphragms. The larger diaphragms have a correspondingly lower spring rate, and thus have a higher measuring sensitivity.  
         [0046]     The pressure transmitter also mounts a sensor assembly uppermost on the sensor body that includes an integrally mounted overrange diaphragm. The overrange diaphragm protects the sensor element mounted within the sensor assembly from overrange pressure conditions. The sensor body also presents high thermal resistance between the input process lines and the sensor assembly, shielding the sensor and associated electronics from undesirable elevated temperatures.  
         [0047]     The bolt-holes of the transmitter further mount fasteners that are enclosed or shrouded along the fastener length by the sensor body. The shrouded bolts help prevent the leakage of process fluid applied to the pressure ports by maintaining the temperature along the length of the bolt at or near the temperature of the sensor body.  
         [0048]      FIGS. 1-3  show a bi-planar differential pressure transmitter  100  that measures the difference in pressure between two pressure inputs, i.e. between two different fluid pressures, coupled to two input process connections, e.g., process lines  5 ,  5 . The pressure transmitter  100  has a unitary body element  102  that assembles with flanges  104 ,  106  to either side of body  102 . Flanges  104 ,  106  respectively receive the two input process connections,  5 ,  5 . In this arrangement, the unitary body element  102  conveys pressures, which are responsive to pressure inputs from the input connections  5 ,  5 , to a transducer mounted with the body element  102 , and further described with respect to a sensing assembly in  FIG. 4 . In response, the transducer produces a signal indicative of the difference in pressure between the two inputs. Electronic circuitry within an electronic housing  108  processes the transducer signal, and typically includes an output display (not shown). The housing  108  mounts on the body element  102 .  
         [0049]     In  FIG. 2 , transmitter  100  is illustrated rotated 90° about a vertical axis from the orientation of  FIG. 1 . Transmitter  100  can be mounted to a mounting bracket  15  by bolts  17  that can thread into blind bolt holes  104 D,  106 D, of flanges  104 ,  106 . Flanges  104 ,  106  can each include a pair of knobbed extensions,  104 J,  106 J to accommodate bolt holes  104 D,  106 D on opposite faces of flanges  104 ,  106 .  
         [0050]     Referring back to  FIG. 1 , the assembled flanges  104 ,  106  and body element  102  of the transmitter  100  form a sensor assembly  100 A that, as shown in  FIG. 10 , has first and second pressure ports  110 ,  112  extending up into the flanges  104 ,  106  into chambers  104 A,  106 A of flanges  104 ,  106 , respectively. The housing is usually installed in the upright orientation shown, where the pressure ports are at the bottom of the transmitter, conforming to standard industry mountings for such transmitters. In addition to the mounting bracket  15  shown in  FIG. 2 , transmitter  100  can mount on a manifold, such as manifold  19 , as indicated in  FIGS. 3A and 3B . Manifold  19  can be one of a number of manifolds known and standard in the industry for providing process connections. The pressure ports,  110 ,  112  can connect to the process connections of the manifold  19  (not shown in  FIGS. 3A and 3B ). Thus, it can be seen that transmitter  100 , with its upright orientation and with pressure ports  110 ,  112  at the bottom of the transmitter, together with the horizontally spaced bolt holes  104 D,  106 D, can provide a generally universal replacement for standard industry transmitters. It can be understood that other bracket configurations, such as bracket  21  in  FIG. 3A , and bracket  15  in  FIG. 3B , and other orientations of transmitter  100  can be used, as described in more detail below.  
         [0051]     Referring now to  FIGS. 4-9 , various views of the elements of the bi-planar transmitter of  FIG. 1  are shown.  FIG. 4  shows, in disassembled and exploded form, an embodiment of a bi-planar pressure transmitter  100  (with housing  108  removed) embodying further features of the disclosed differential pressure transmitter. The pressure transmitter  100 , which receives two pressure input lines from beneath the transmitter  100  as described above, has opposed pressure diaphragms. The pressure transmitter  100  includes a body element, or web  102  that is clamped between elbow-type flanges  104  and  106 . The web can be symmetrically centered in the transmitter  100 , along a first normally horizontal axis  114 , and has a rounded periphery to reduce the number of sharp contours. Flanges  104 ,  106  form input pressure ports  110  and  112 , respectively, to which process connections typically are attached, such as may be illustrated by connections  5  in  FIG. 1 , or by manifold  19  connections in  FIG. 4 . The transmitter  100  is illustrated as having a transducer mounting portion  118  that seats a sensing assembly  80 , similar respectively to a mounting portion and a sensor assembly of the bi-planar transmitter described in U.S. Pat. No. 6,038,927 (“the &#39;927 patent”) incorporated herein by reference in its entirety.  
         [0052]     More particularly, the illustrated web  102 ,  FIGS. 4, 8  and  9 , has opposed and parallel first and second normally vertical surfaces  102 A and  102 B. Horizontally spaced bolt holes  102 C aperture the web  102  and extend, parallel to the axis  114  and transverse to a first, normally vertical axis  340 , between the two surfaces  102 A and  102 B. The normally vertical surfaces  102 A and  102 B are recessed, and can be identical, with a set of concentric convolutions  102 D. Each illustrated set of convolutions forms a sinusoidal profile.  
         [0053]     The web  102  has an integrally formed extending neck portion  124  extending vertically along axis  340  and that mountingly connects to the transducer mounting portion  118 . The neck portion sensor can present high thermal resistance between the input process lines and the sensing assembly  80 , shielding the sensor assembly  80  and associated electronics from undesirable elevated temperatures. The illustrated transducer mounting portion  118  is similar to the transducer mounting portion of the bi-planar transmitter embodiment of the &#39;927 patent, and has a first annular surface  118 A and a second stepped concentric surface  118 B. A vertically extending tubular mount  118 C is integral with the second surface  118 B, and extends axially along axis  340  therefrom to an uppermost surface  118 E (in the orientation of  FIG. 4 ). The mount  118 C can circumscribe a first pressure passageway  134  ( FIG. 10 ) and surface  118 E overlies the second pressure passageway  136  ( FIG. 10 ) and is apertured with a bore  118 H that aligns with that passageway. The surfaces  118 A and  118 B are concentric with the axis  340 , and the mount  118 C is radially offset from the axis  340 . Within tubular mount  118 C, the second surface  118 B forms a mounting surface  118 D that has an undulating contour, which can be formed by concentric convolutions.  
         [0054]     An instrument casing  108  ( FIG. 1 ) mounts on the transmitter mounting portion  118  by seating on a collar  132  that seats on the web in the annular lip formed by the first surface  118 A, and the periphery of the stepped second surface  118 B. In an embodiment, the collar  132  is welded to the transducer mounting portion  118  of the web  102  along this lip.  
         [0055]     As also shown in  FIG. 10 , first and second pressure passageways  134  and  136  open onto the second surface  118 B of the mounting portion  118 , and extend vertically within the web  102 . The first and second pressure passageways  134 ,  136  communicate with transverse, i.e. horizontally-extending, first and second pressure openings  138  and  140 , respectively, formed in the web  102 . The pressure passageways  134  and  136  and the openings  138  and  140  communicate the pressures applied to the diaphragms  200 A and  200 B mounted at the opposed web faces  102 A and  102 B, at the recesses, to the transducer mounting portion  118 . Flame arrestors  142  and  144 , similar to the flame arrestors of  FIG. 4 , seat in the first and second pressure passageways  134  and  136 , respectively. Those of ordinary skill will recognize that two flame arrestors may not always be needed, particularly when all potential flame sources are on one side only of the sensing assembly  80 .  
         [0056]     Pressures applied to the input ports  110  and  112  of the flanges  104 ,  106  are coupled to the diaphragms and thus the convoluted recesses of the web  102  with further structure, as now described with reference to  FIGS. 4-7 . Each illustrated flange  104  and  106  can be a one-piece machined metal casting and forms one input pressure port  110  and  112 , respectively. A rear face (in the orientation of  FIG. 4 ) of the flange  106  is recessed with a chamber  106 A, illustratively of substantial circular cross-section that overlies the recessed convolutions  102 D of the web surface  102 A. Likewise, a face of the flange  104  (forward facing in  FIG. 4 ) is recessed with a chamber  104 A that overlies the recessed convolutions (not shown) of the web surface  102 B. Gasket grooves, for example groove  104 B of flange  104 , are concentric with the chambers  104 A and  106 A, respectively, and seat deformable gaskets  146 . Bolt holes  104 C and  106 C extend through the flanges  104  and  106 , in alignment with the bolt-holes  102 C in the web  102 , and receive bolts  148 ,  148 . The illustrated transmitter  100  is assembled with two bolts  148 ,  148  that extend through the two flanges and through the web  102  and are secured by nuts  150 ,  150 .  
         [0057]     Each illustrated flange  104  and  106  has two oppositely-disposed bolt shrouds  104 E,  104 E, and  106 E,  106 E, configured as shown, each of which encloses and thereby shrouds the portion of a bolt  148  that extends beyond the web  102 . Further, the web  102  encloses and thereby shrouds the length of each bolt  148 , which extends between the flanges. The assembly of this bolt shrouding structure of the web  102  and of the two flanges  104  and  106  forms a continuous enclosure over each bolt  148  along the passage thereof between the three assembled parts  102 ,  104  and  106 . The resultant full shrouding of each bolt  148 ,  148  enhances the operational safety of the pressure transmitter  100 , including a reduction of the potential to leak process fluids applied to the pressure ports  110  and  112 , caused by unequal thermal expansion of the bolts and assembly.  
         [0058]     Each illustrated pressure port  110  and  112  extends parallel with a second normally-vertical axis  152  that is perpendicular to the axis  114  and parallel to the axis  340 . Each illustrated pressure port  110  and  112  opens at a bottom peripheral surface of each flange  104 ,  106 , respectively, illustrated in  FIG. 4  as the surface that faces downward and illustrated in elevation in  FIG. 7 .  
         [0059]     With further reference to  FIGS. 9 and 10 , each illustrated flange  104 ,  106  has a peripheral face  104 F and  106 F, illustrated in elevation in  FIG. 6 . Two threaded passages  104 G,  104 H extend from peripheral face  104 F to the chamber  104 A. The two passages  104 G,  104 H of the flange  104  extend along axes parallel to axis  114  and perpendicular to axis  152 . For the orientation shown in  FIGS. 4 and 7 , passage  104 G intersects the chamber  104 A at the periphery of chamber  104 A at a point above and to the left of axis  114  and generally at an angle of 45° from axis  114  with respect to a horizontal diametric plane of chamber  104 A. Passage  104 H intersects the periphery of chamber  104   a  at the rightmost point of the horizontal diametric plane.  
         [0060]     In the orientation of the flange  104  shown in  FIGS. 4 and 7 , the passage  104 G enters the chamber  104 A above the middle of the chamber  104 A, e.g., above the horizontal diameter. Accordingly, the passage  104 G can operate to purge gas that can collect in chamber  104 A. Passage  104 G can be flared along the periphery upon entering chamber  104 A, such that gas can be purged from near a high point of the chamber  104 A. In this position, transmitter  100  can be self draining, with pressure port  110  serving to drain liquid including condensate from chamber  104 A. It can be seen that if the transmitter  100  is rotated counterclockwise 90°, such that pressure port  110  is horizontal and to the right, passage  104 H enters at the uppermost point of the periphery and can operate to purge gas from chamber  104 A. In the rotated orientation, passage  104 G is below a horizontal diameter, and the flaring of passage  104 G provides for draining liquid from near the lower point of chamber  104 A. A further counterclockwise rotation of 90°, can bring pressure port  110  to the top of chamber  104 A, such that transmitter  100  can be self purging. As previously, passage  104 G is below a horizontal diameter, and the flaring of passage  104 G provides for draining liquid from near the lower point of chamber  104 A. A still further counterclockwise rotation of 90° brings pressure port  110  horizontal and to the left. The passage  104 G is above a horizontal diameter and the passage  104 H is at the lower point of chamber  104 A, such that passage  104 G can purge chamber  104 A of gases and passage  104 H can drain chamber  104 A of liquids. It can be seen that flange  106  can be identical to flange  104 , and having an orientation rotated 90° about axis  152  from that of flange  104 . Thus, the flange  106  passages  106 G,  106 H, formed therein identical to passages  104 G,  104 H, respectively, of flange  104 , can operate to assist in purging and draining operations for chamber  106 A.  
         [0061]     Operation for self-draining with process gases is shown in  FIG. 10 . Liquids settle in chamber  104 A,  106 A and return to the process gas in pipe  5  through pressure port  110 ,  112 . Similarly, when inverted, the flange  104 ,  106  provides self-venting operation for liquids, and gases in chamber  104 A,  106 A and in connecting passages returns to the process stream in pipe  5 . As described above, horizontal orientations of the transmitter  100  also provide either self-draining or self-venting operation. In such cases, the appropriate passageway  104 G,  104 H,  106 G,  106 H can have a connection to the process pipe  5 .  
         [0062]     Each pressure port  110 ,  112  includes a recess for seating a mating protrusion in a process connection, such as in manifold  19  and for seating a circular seal  160 . An optional filter screen can be mounted within each flange  104 ,  106  to remove particulate matter present in the input process medium. When the flange passage  104 G,  104 H,  106 G,  106 H or the port  110 ,  112  operates as a purge for gases, as illustrated in  FIG. 10 , a vent body  162  can be threaded therein. The vent body has a ventilation throughbore. A ventilation needle  164  removably and replaceably seats in the bore for selectively closing it and, alternatively, opening it to purge fluids. The vent body allows an operator to break vacuum and allow the chamber to drain. Either a vent body or a vent plug can be used in passages  104 G,  104 H,  106 G,  106 H or ports  110 ,  112  depending on operator needs or transmitter orientation.  
         [0063]     The further structure of the flange faces  1041 ,  1061  (shown in perspective in  FIG. 5  and in edge view in  FIGS. 6 and 7 ) includes recessing each with threaded bolt holes  154  that receive bolts  166  for mounting process connectors at the pressure port  110 , such as may be provided with manifold  19 . Threaded bolt holes  154  extend into each flange parallel with the axis  152 . As indicated in  FIGS. 3A and 3B , the manifold  19  overlies the pressure ports  110 ,  112  and can have through bolt-holes at locations complementary to threaded bolt holes  154  and can have input passageways at locations complementary to the passages formed by pressure ports  110 ,  112 . It can be understood that other process connectors, including those described in the &#39;927 patent, can be used.  
         [0064]     Thus, the illustrated flange  104  can be used in the upright orientation of transmitter  100  shown in  FIG. 4  or in the inverted or horizontal orientations, as described above, so as to accommodate mounting restrictions that can be encountered. The flange  106  can be identical to and hence interchangeable with the flange  104 . The flange  106  hence has face  106 F and passages  106 G,  106 H for venting and for input porting. A process connector can be mounted by bolting at the input port  112 , and a vent body  162 , removably and replaceably seating a vent needle  164 , can be threaded into the passages  106 G,  106 H, or port  112 , as previously described.  
         [0065]     As also shown in the exploded view of  FIG. 4 , the pressure transmitter  100  employs two circular diaphragm plates  258 ,  258 , that overlie the web faces  102 A,  102 B, thus covering the corrugated regions, e.g. region  102 D, formed on both faces. The diaphragm plates can form first and second bi-planar process diaphragms  200 A and  200 B,  FIG. 10 . Weld plates  264 ,  264 , overlie the exposed faces of the diaphragm plates  258 . Each weld plate has a circular opening  264 A having a diameter D2 equal to or slightly smaller than the outer diameter of the convoluted regions  102 D,  102 E (the convoluted region  102 E being on face  102 B). Each weld plate  264  hermetically seals the diaphragm plate  258  to the web  102 , as by forming a laser or other penetrating weld  264 B to the web  102  at the periphery of the plate  264  and at the circumference of the opening  264 A. The deformable gaskets  146 ,  146  mount over the welds  264 B formed around the openings  264 A. The diameter of each gasket can be smaller than the diameter of the weld line at the circumference of each opening  264 A, to ensure that process fluid does not wet the weld connection.  
         [0066]     The diameter of the circular chambers  104 A,  106 A can be equal to or slightly less than the diameter D2 of the weld plate openings  264 A. In an embodiment, each chamber  104 A,  106 A allows the input process medium applied by one pressure input line to act upon the entire portion of the diaphragm plate overlying one convoluted region  102 D,  102 E, i.e. the portion that is circumscribed by the chambers  104 A,  106 A.  
         [0067]     Thus, in the assembled transmitter  100  ( FIGS. 1-3  and  10 ), the illustrated axial succession of weld plates  264 ,  264 , the diaphragm plates  258 ,  258 , and the gaskets  146 ,  146  is secured between the web  102  and the two flanges  104 ,  106 . In one embodiment, diaphragm plates  258 ,  258 , and/or weld plates  264 ,  264 , can be configured complementary to the surfaces  102 A and  102 B of the web  102 , having punched holes at locations complementary to the bolt-holes  102 C.  
         [0068]     Referring again to  FIG. 4 , a sensing assembly  80 , identical in structure and operational features to the sensor assembly of the &#39;927 patent, mounts in the annular mount  118 C. The sensing assembly  80  includes an overrange diaphragm  82 , a chip carrier  84 , an epoxy mounting sheet  86 , and a header  88 . The illustrated header  88  has a substantially circular main body  88 A having a flat top face  88 B from which a series of transducer lead-out holes  88 C and fill tube holes  88 D,  88 E, and  88 F extend into the body  88 A. Referring to  FIG. 10 , a substantially rectangular cavity  88 G recesses an opposed bottom face  88 H of the header  88 . The illustrated header  88  has a first opening  88 D and a third opening  88 F, both of which extend between the header top and bottom faces  88 B and  88 H. A second opening  88 E extends partly through the header body  88 A and communicates with a cross-bore opening  88 I, which in turn communicates with the chip carrier  84  by a substantially vertical bore  88 J.  
         [0069]     As best shown in  FIG. 10 , the illustrated chip carrier  84  has a dielectric body that mounts a pressure sensing element  89 . Similar to the planar embodiment and bi-planar embodiment as described in the &#39;927 patent, this cross-sectional view of the sensing assembly  80  includes the fill tube  92  diagrammatically relocated for clarity of discussion. A set of electrical pins  84 B,  FIG. 4 , is connected by wire bonds to the contacts of the sensing element  89  and extends upwardly from the top surface  84 C.  
         [0070]     Also as described with reference to the embodiments of the &#39;927 patent, the mounting sheet  86  seats over the chip carrier top surface  84 C, and when heated to a selected elevated temperature, hermetically seals the chip carrier  84  to the header  88 . The chip carrier  84  and the sheet  86  mount within the rectangular cavity  88 G, and the electrical pins  84 B extend upward and through the header holes  88 C that aperture the top face  88 B. The electrical insulator cap  90  can mount over the pins  84 B to center the pins within the chip carrier holes, and to electrically isolate the pins from the header  88 .  
         [0071]     The overrange diaphragm  82 , which can be formed with concentric convolutions in registration with the circular ridges or convolutions of the floor  118 D of the mounting portion  118 C, is secured, for example, by welding along the periphery, to the header bottom face  88 H. The diameter of the diaphragm  82  is closely equal to the outer diameter of the header  88 .  
         [0072]     In the illustrated embodiment of the bi-planar transmitter of  FIG. 4 , the sensing assembly  80  seats in the annular mount  118 C and the overrange diaphragm  82  overlies the first pressure passageway  134  ( FIG. 10 ). Similar to the embodiments of the &#39;927 patent, this configuration places the diaphragm proximate to both the chip carrier  84  and the housing  108 . The sensing assembly  80  is then secured and sealed to the annular mount  118 C.  
         [0073]     An electrical contact plate  328 , which assembles onto the header  88 , has a series of transducer holes  328 A and a set of peripheral notches  328 B,  328 C, and  328 D. A flexible electrical cable  330  is coupled at one end to the top plate  328  and extends upwardly therefrom. When the plate is properly positioned for assembly, the notches  328 B,  328 C and  328 D are aligned to receive the fill tubes  94 ,  96  and  92 , respectively. The transducer holes  328 A seat over the portions of the electrical pins that extend beyond the insulator cap  90 . The contact plate provides a secure electrical connection to the electrical pins  84 B and thus to the sensing element  89 . The flexible cable  330  carries the output electrical signals generated by the sensing element in response to pressure differences applied to the diaphragms  200 A and  200 B, to the associated electronic circuitry mounted within the housing  108 .  
         [0074]     Referring again to  FIGS. 4 and 10 , the fill tube  92  seats in the third opening  88 F in the header  88 , and the tube  94  seats in the second opening  88 E. The U-shaped tube  96  has one end that seats in the first opening  88 D and a second end that mounts to the protrusion  144 A of the flame arrestor  144 . The fill tubes  92  and  94 , and openings  88 F and  88 E, respectively, provide structure for filling the high and low pressure sides of the transmitter  100  with fill fluids. In addition,  FIG. 10  illustrates that a potting material  276  is cast within the sleeve  132  and embeds the sensing assembly  80  in the mount  118 C. The potting material fills the volume within the sleeve  132  and protects the sensing assembly  80  and its associated electrical leads from mechanical shock, vibrations, and like disturbances, and excludes moisture and corrosive agents.  
         [0075]     As also shown in  FIGS. 1 and 4 , the illustrated housing  108  has a neck  108 A that seats over the sleeve  132  by threaded attachment thereto, and that, in turn, carries a housing portion  108 B. The housing portion  108 B can be divided into first and second internal compartments (not shown) and has a sealed opening that extends between the compartments. The illustrated housing portion  108 B has a removable and replaceable cover  108 H,  108 H at each end, i.e. on the left side and on the right side in  FIG. 1 , that can be sealed to the housing with a deformable gasket (not shown), to provide access to each internal compartment. The removable covers  108 H,  108 H allow a customer or maintenance personnel to connect the casing electronics to remote processing circuitry, as well as allow access to the housing electronics for testing and/or repair.  
         [0076]     The flexible electrical cable  330 , electrically connected at one end to the sensing assembly  80 , extends upwardly into the housing  108  through the neck  108 A and connects to the housing electronics. Typically, one cover has an optical window through which an output display can be viewed. In an embodiment, the resident housing electronics includes resident software code and a receiver that allows a system operator, via a remote digital logic module transmitter, to electronically switch the high and low pressure sides of the pressure transmitter  100 .  
         [0077]     With reference to  FIG. 1 , the housing, or casing  108  can further include a boss structure  108 C having a threaded throughbore  19 D that forms a dormer-like structure. The boss structure  108 C allows access to the casing interior when it may be necessary to perform field tests. The throughbore  108 D provides structure through which the casing electronics can be connected to the remote processing circuitry. A second boss structure can be present on the opposite side of the casing  108  as an alternate connection port.  
         [0078]     Referring now to  FIGS. 11A and 11B , there is shown an embodiment of a bi-planar differential pressure transmitter  100 ′, having the features as described for bi-planar differential pressure transmitter  100  of  FIGS. 1-10 , and including additional mounting extensions and bolt holes for accommodating various mounting brackets.  FIG. 11A  illustrates transmitter  100 ′ generally in the same orientation as transmitter  100  of  FIG. 1 . For ease of illustration and description, those features of transmitter  100 ′ in common with transmitter  100  are referred to by corresponding reference numerals.  
         [0079]     Flanges  104 ′ and  106 ′ include knobbed extensions  104 J′ and  106 J′, as previously described. In addition to bolt holes  104 D′ and  106 D′, knobbed extensions  104 J′ and  106 J′ have each been enlarged in a direction towards unitary body portion  102 ′ to accommodate a second set of blind bolt holes  104 M,  106 M. Alternately and/or in addition to knobbed extensions  104 J′ and  106 J′, flanges  104 ′ and  106 ′ can each include a second pair of extensions  104 N,  106 N having respective blind bolt holes  104 P,  106 P. In the illustrative embodiment of  FIG. 1A , transmitter  100 ′ is shown mounted on bracket  23 .  
         [0080]      FIG. 1B  is a view of the transmitter  100 ′ from a reverse direction, illustrating four bolts  25  passing through bracket  23  to engage with bolt holes  104 M,  104 P,  106 M,  106 P in respective flanges  104 ′,  106 ′. Bolt holes  104 M,  106 M are shown in  FIGS. 11A and 11B  as horizontally aligned with bolt holes  104 D′,  106 D′. Also, bolt holes  104 P,  106 P of extensions  104 N,  106 N are shown vertically aligned with respective bolt holes  104 M,  106 M. However, other configurations and locations of extensions  104 N,  106 N and bolt holes  104 M,  104 N,  106 M,  106 N can be provided to accommodate other mounting brackets as may be standard in the industry.  
         [0081]      FIG. 12  shows an embodiment of a flange element  104 ″ having a first threaded passageway  104 G″ and a second threaded passageway  104 H″ extending from peripheral face  104 F to the chamber  104 A. The two passages  104 G″,  104 H″ of the flange  104 ″ extend along axes parallel to axis  114  and perpendicular to axis  152  (not shown in  FIG. 12 ). For the orientation shown in  FIG. 12 , passage  104 G″ intersects the chamber  104 A at the periphery of chamber  104 A at a point above axis  114  and passage  104 H″ intersects the periphery of chamber  104   a  at a point below axis  114 . By intersecting chamber  104   a  at its periphery, passages  104 G″,  104 H″ can provide full venting and draining of chamber  104   a . Passages  106 G″,  106 H″ of a flange element  106 ″ (not shown in  FIG. 12 ) can be similarly configured, though flanges with differing passageway configurations can be provided.  
         [0082]     The structures of the illustrated embodiments attain pressure transmitters that are compact, relatively lightweight and relatively low in cost. The pressure transmitters can also mount a read-out display positioned for relatively easy viewing. Furthermore, at least one transmitter embodiment attains large process diaphragms in a compact transmitter size by employing only a pair of bolts along a horizontal axis. This configuration accommodates large process diaphragms without increasing the overall size of the transmitter.  
         [0083]     Unless otherwise stated, use of the word “substantially” can be construed to include a precise relationship, condition, arrangement, orientation, and/or other characteristic, and deviations thereof as understood by one of ordinary skill in the art, to the extent that such deviations do not materially affect the disclosed methods and systems.  
         [0084]     Throughout the entirety of the present disclosure, use of the articles “a” or “an” to modify a noun can be understood to be used for convenience and to include one, or more than one of the modified noun, unless otherwise specifically stated.  
         [0085]     It can thus be seen that the disclosed differential pressure transmitter efficiently attains the objects set forth above, among those made apparent from the preceding description. Since certain changes may be made in the above constructions without departing from the scope of the disclosed differential pressure transmitter, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.  
         [0086]     It is also to be understood that the following claims are to cover all generic and specific features of the disclosed differential pressure transmitter described herein, and all statements of the scope of the disclosed differential pressure transmitter, which, as a matter of language, might be said to fall therebetween. Many additional changes in the details, materials, and arrangement of parts, herein described and illustrated, can be made by those skilled in the art. Accordingly, it will be understood that the following claims are not to be limited to the embodiments disclosed herein, can include practices otherwise than specifically described, and are to be interpreted as broadly as allowed under the law.