Patent Description:
The invention relates generally to a liquid chromatography system incorporating a pressure transducer. Methods of reducing thermal effects on pressure transducers are also disclosed.

A typical strain gage pressure transducer includes a full Wheatstone bridge foil strain gage mounted directly above a pressurized cavity having a suitable web thickness to allow for measurable deflection of intermediate housing material located between the pressurized cavity and the strain gage. The strain gage will typically have two active grids to measure deflection, and two less reactive grids to complete the Wheatstone bridge. To provide an accurate reading, a strain gage must typically be situated in an iso-thermal condition.

However, during periods of rapid compression and decompression, adiabatic heating and cooling of the medium within the pressurized cavity often imparts a thermal disturbance to the housing and onto the strain gage. This thermal disturbance may prevent the pressure transducer from accurately measuring pressure until the thermal disturbance has settled and the four transducer grids have returned to an iso-thermal state. There could be a significant delay in waiting for the grids of the strain gage to return to an iso-thermal state. This delay can be problematic and particularly undesirable in industries, such as high performance liquid chromatography (HPLC), where accurate readings are necessary very quickly after rapid compression and decompression occurs of solvent found in a pressurized cavity. For example, chromatographic solvent pumps operating with pressures larger than <NUM>,<NUM> psi require accurate pressure readings immediately after large pressure changes.

Thus, a strain gage pressure transducer configured to reduce thermal effects, and methods of reducing thermal effects on a strain gage pressure transducer, would be well received in the art.

<CIT> discloses a pressure sensor. <CIT> discloses a Pressure Sensor, and Mass Flow Meter and Mass Flow Controller Using the Same. <CIT> discloses a pressure sensor. <CIT> discloses a pressure sensing and flow control in diffusion-bonded planar devices for fluid chromatography. <CIT> discloses a pressure sensor, mass flow meter and mass flow controller using the same. <CIT> discloses a pressure sensing transducer employing piezoresistive elements on sapphire. <CIT> discloses a temperature coefficient compensated pressure transducer.

The present invention provides a liquid chromatography system as claimed.

In one embodiment, the resistive element further includes: a first resistor in operable contact with the body; a second resistor in operable contact with the body; a third resistor in operable contact with the body; and a fourth resistor in operable contact with the body.

In one embodiment, the first, second, third, and fourth resistors are operably connected to form a Wheatstone bridge, and the first and second resistors are active grids and the third and fourth resistors are balance grids.

In one embodiment, the first, second, third, and fourth resistors are each made of the material having the second coefficient of thermal expansion.

The second coefficient of thermal expansion is greater than the first coefficient of thermal expansion.

In one embodiment, the active grids are positioned proximate the fluidic cavity relative to the balance grids and wherein the balance grids are positioned distal to the fluidic cavity relative to the active grids.

In one embodiment, the balance grids are positioned in line with the active grids and wherein the balance grids are orthogonally oriented relative to the active grids.

In one embodiment, the first and second resistors are made of the material having the second coefficient of thermal expansions and wherein the third and the fourth resistors are made of the material having a third coefficient of thermal expansion that is different than both the first coefficient of thermal expansion and the second coefficient of thermal expansion.

In one embodiment, the first resistor is directly connected in series to a first active grid of the strain gauge, the second resistors is directly connected in series to a second active grid of the strain gauge, the third resistor is directly connected in series to a first balance grid of the strain gauge, and the fourth resistor is directly connected in series to a second balance grid of the strain gauge.

In one embodiment, the first resistor is connected in parallel to a first active grid of the strain gauge, the second resistors is connected in parallel to a second active grid of the strain gauge, the third resistor is connected in parallel to a first balance grid of the strain gauge, and the fourth resistor is connected in parallel to a second balance grid of the strain gauge.

Also disclosed, but not claimed, is a method of detecting pressure.

In one aspect of the method, the detecting pressure further comprises detecting pressure with the first pressure transducer during an adiabatic thermal pulse.

In one aspect of the unclaimed method, the method includes outputting a positive output voltage during an adiabatic thermal pulse.

Also disclosed, but not claimed, is a pressure transducer comprising: a transducer body having a fluidic inlet, and a fluidic cavity in fluidic communication with the fluidic inlet and enclosed by the transducer body; a strain gauge attached to the transducer body; and a filler body located in the fluidic cavity configured to reduce adiabatic thermal effects on the transducer body.

Additionally or alternatively, the filler body reduces the cross sectional area of the fluidic cavity to a reduced cross sectional area that is greater than or equal to an inlet cross sectional area at the fluidic inlet.

Additionally or alternatively, the filler body comprises the same material as the transducer body.

Additionally or alternatively, the filler body comprises a material that is different from a material of the transducer body.

The pressure transducer is a flow through pressure transducer.

Additionally or alternatively, the filler body is a cylindrical body having a diameter less than a diameter of the fluidic cavity and located in the fluidic cavity distal to the strain gauge.

Additionally or alternatively, the filler body is a tubular body having a diameter less than a diameter of the fluidic cavity and located in the middle of the fluidic cavity.

Additionally or alternatively, the filler body extends a substantial length of the fluidic cavity.

Additionally or alternatively, the pressure transducer is a diaphragm pressure transducer.

Additionally or alternatively, the filler body does not contact a sensing region of an inner surface of the fluidic cavity, the sensing region located directly below the strain gauge within the filler cavity.

In another aspect, a method comprises: providing a pressure transducer having a fluidic inlet, and a fluidic cavity in fluidic communication with the fluidic inlet and enclosed by the transducer body; attaching a strain gauge to the transducer body; integrating a filler body within the fluidic cavity; and reducing a volume of the fluidic cavity with the filler body.

Additionally or alternatively, the method includes reducing adiabatic thermal effects on the transducer body with the filler body relative to a second pressure transducer having the same properties as the pressure transducer other than the second pressure transducer fabricated without the filler body.

Additionally or alternatively, the pressure transducer is a flow through pressure transducer and wherein the filler body extends along a length of the fluidic cavity having a cavity cross sectional area, the method further comprising: reducing the cavity cross sectional area to a reduced cross sectional area along the length with the filler body, wherein the reduced cross sectional area is greater than or equal to an inlet cross sectional area at the fluidic inlet.

Additionally or alternatively, the integrating the filler body within the fluid cavity further comprises not contacting a sensing region of an inner surface of the fluidic cavity with the filler body, the sensing region located directly below the strain gauge within the filler cavity.

The present teaching will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present teaching is described in conjunction with various embodiments and examples, it is not intended that the present teaching be limited to such embodiments. On the contrary, the present teaching encompasses various alternatives, modifications and equivalents, as will be appreciated by those of skill in the art.

Referring to <FIG>, a top view of an in-line pressure transducer <NUM> is shown. Similarly, <FIG> shows a side view of the pressure transducer <NUM> and <FIG> shows a cross sectional view of the pressure transducer <NUM> taken at arrows A-A. The pressure transducer <NUM> includes a body <NUM>, a fluidic inlet <NUM>, a fluidic outlet <NUM>, and a fluidic cavity <NUM> extending between the fluidic inlet <NUM> and the fluidic outlet <NUM>. The fluidic cavity <NUM> is enclosed by the body <NUM>. In this embodiment, the single fluidic inlet may be considered a fluidic interface port.

A strain gauge <NUM> is disposed on a surface <NUM> located on the outside of the body <NUM>. The surface <NUM> is a flat surface as shown. The strain gauge <NUM> includes a Wheatstone bridge having a first active grid <NUM> and a second active grid <NUM> located directly above the fluidic cavity <NUM> on the surface <NUM>, along with a first balance grid <NUM> disposed above the fluidic cavity <NUM> on the surface <NUM> and a second balance grid <NUM> disposed below the fluidic cavity <NUM> on the surface <NUM>.

The active grids <NUM>, <NUM> and the balance grids <NUM>, <NUM> may each include one or more resistive elements <NUM> or resistors patterned onto a thin carrier backing <NUM> attached directly to the surface <NUM>. The thin carrier backing <NUM> may include an adhesive layer configured to attach the grids <NUM>, <NUM>, <NUM>, <NUM> to the surface <NUM>. The resistive elements <NUM> may each be thin metallic wires of foil having a particular electrical resistance that changes with the strain on the resistive elements <NUM>. The resistive elements <NUM> may each be in operable contact with the body <NUM> through the thin carrier backing <NUM>. "Operable contact" herein shall mean a state where the strain experienced by the body <NUM> is transferred to the resistive elements <NUM> to change the electrical resistance of the resistive elements <NUM>. In other words, the thin carrier backing <NUM> may be located between the resistive elements <NUM> and the body <NUM> despite the resistive elements <NUM> being operably contacting the body <NUM> for the purposes of measuring strain.

The body <NUM> is made of a material having a first coefficient of thermal expansion. For example, the body <NUM> may be made from titanium, for example, and may include a coefficient of thermal expansion at or around <NUM> x <NUM>-<NUM>. In other embodiments, the body <NUM> may be made from steel or stainless steel having a coefficient of thermal expansion between around <NUM> and <NUM> x <NUM>-<NUM>.

The resistive elements <NUM> are made of a metallic material having a coefficient of thermal expansion that is different than the coefficient of thermal expansion of the body <NUM>. The resistive elements <NUM> are made of aluminum, having a coefficient of thermal expansion at or around <NUM> × <NUM>-<NUM>.

The level of mismatch between coefficients of thermal expansion of the body <NUM> and the resistive elements <NUM> may be dependent on the thickness of body material between the fluid path <NUM> or path and the surface <NUM> upon which the strain gauge <NUM> is located, or in other words the web thickness. In the case where the body <NUM> is made of titanium, and the web thickness is <NUM> (<NUM> inches) a mismatch between coefficients of thermal expansion of the body <NUM> and the resistive elements <NUM> may be approximately <NUM> × <NUM>-<NUM>. In other words, the resistive elements <NUM> may have coefficients of thermal expansion <NUM> × <NUM>-<NUM> higher than the coefficient of thermal expansion of the body <NUM>. This amount has been found to correct the thermally induced transients of chromatographic solvents, for example, in liquid chromatography systems. Various other degrees of mismatch may correct pressure transducers having various web thicknesses and subject to various forms of adiabatic thermal events.

In other embodiments, only the active grids <NUM>, <NUM> may have a mismatched coefficient of thermal expansion relative to the body <NUM>, but not the balance grids <NUM>, <NUM>. In other embodiments, the balance grids <NUM>, <NUM> may include a mismatched coefficient thermal expansion relative to the body <NUM>, but not the active grids <NUM>, <NUM>. In other embodiments, all of the grids <NUM>, <NUM>, <NUM>, <NUM> include a mismatched coefficient thermal expansion relative to the body <NUM>. In still further embodiments, the body <NUM> may be made of a first material having a first coefficient of thermal expansion, the active grids <NUM>, <NUM> may be made of a second material having a second coefficient of thermal expansion, and the balance grids <NUM>, <NUM> may be made of a third material having a third coefficient of thermal expansion.

The coefficient of thermal expansions of the grids <NUM>, <NUM>, <NUM>, <NUM> may be mismatched with the coefficient of thermal expansion of the body <NUM> such that the difference between the coefficients of thermal expansion may be large enough that an output voltage during an adiabatic thermal pulse becomes positive. In other embodiments, the difference between the coefficients of thermal expansion between the grids <NUM>, <NUM>, <NUM>, <NUM> and the body <NUM> may be configured to reduce settling time after an adiabatic thermal pulse relative to a second pressure transducer having the same properties as the pressure transducer <NUM> other than the second pressure transducer having well-matched coefficients of thermal expansion between the grids and the body of the second pressure transducer. For example, configured the difference between the coefficients of thermal expansion between the grids <NUM>, <NUM>, <NUM>, <NUM> and the body <NUM> may be configured to reduce settling time by at least <NUM> percent relative to the second pressure transducer. In other embodiments, the settling time may be reduced by at least <NUM> by using mismatched coefficients of thermal expansion between the grids and body compared to well-matched coefficients of thermal expansion. In this manner, the difference in the coefficients of thermal expansion in the grids <NUM>, <NUM>, <NUM>, <NUM> and the body <NUM> may be configured to compensate for an adiabatic pulse caused by, for example, fast increases or decreases in pressure by actuating a valve or from a pump actuation cycle where fluid is rapidly compressed and decompressed in a liquid chromatography system (such as the system shown in <FIG> and described herein below). In other embodiments, it is contemplated that the settling time may intentionally be increased instead of being intentionally reduced through the mismatched coefficients of thermal expansion.

The fluidic cavity <NUM> is considered a fluidic path configured to receive pressurized fluid. The strain gauge <NUM> is configured to detect the pressure in the fluidic cavity <NUM> or cavity by measuring the strain caused by the pressurized fluid on the body <NUM>. The surface <NUM> may be a removed portion that is removed from the body <NUM>. In other embodiments, the surface <NUM> may be molded or otherwise integrated into the body <NUM>. As shown in <FIG>, the surface <NUM> is located closer to the fluidic cavity <NUM> than the rest of the outer circumference of the body <NUM>.

In the embodiment shown in <FIG>, the active grids <NUM>, <NUM> are positioned proximate the fluidic cavity <NUM>, while the balance grids <NUM>, <NUM> are positioned distal to the fluidic cavity <NUM> relative to the active grids <NUM>, <NUM>. In other words, the active grids <NUM>, <NUM> are positioned directly over the fluidic cavity <NUM> while the balance grids <NUM>, <NUM> are positioned above and below, respectively, the active grids <NUM>, <NUM>. In other embodiments, shown in <FIG>, the active grids and balance grids may be positioned in line with each other. In this embodiment, the active grids and the balance grids may be oriented orthogonally relative to each other.

<FIG> show various embodiments of active and balance grids positioned in other arrangements contemplated. The grids shown in these embodiments may have a mismatched coefficient of thermal expansion to the body upon which the grids are placed, like the embodiment described hereinabove with respect to <FIG>. <FIG> show embodiments contemplated are not limited by any particular position or orientation of the grids. In the embodiment shown in <FIG>, a surface <NUM> is shown having a first active grid <NUM>, a second active grid <NUM>, a first balance grid <NUM> and a second balance grid <NUM> of a strain gauge. The active grids <NUM>, <NUM>, and the balance grids <NUM>, <NUM> may include the same features as the active grids <NUM>, <NUM> and the balance grids <NUM>, <NUM> shown in <FIG>. However, the grids <NUM>, <NUM>, <NUM>, <NUM> may be oriented in a different arrangement than the grids <NUM>, <NUM>, <NUM>, <NUM>. It should be understood that the surface <NUM> may be a surface of an in-line pressure transducer such as the surface <NUM> of pressure transducer <NUM>. However, the surface <NUM> may be a longer surface than the surface <NUM> in order to accommodate the in-line grids <NUM>, <NUM>, <NUM>, <NUM> of the strain gauge. In the embodiment shown in <FIG>, the two active grids <NUM>, <NUM> may be located between the two balance grids <NUM>, <NUM> in-line. As shown, the active grids <NUM>, <NUM> may have a grid alignment with wire lengths that extend horizontally and connecting curves extending vertically, while the balance grids <NUM>, <NUM> may have a grid alignment with wire lengths that extends vertically and connecting curves that extend horizontally. In this manner, the active grids <NUM>, <NUM> and the balance grids <NUM>, <NUM> may be oriented orthogonally relative to each other.

As shown in <FIG>, a surface <NUM> is shown having a first active grid <NUM>, a second active grid <NUM>, a first balance grid <NUM> and a second balance grid <NUM> of a strain gauge. The active grids <NUM>, <NUM>, and the balance grids <NUM>, <NUM> may include the same features as the active grids <NUM>, <NUM> and the balance grids <NUM>, <NUM> shown in <FIG>. The surface <NUM> may include the same features as the surface <NUM> shown in <FIG>. In the embodiment shown in <FIG>, the first active grid <NUM> may be placed in a bottom position, followed the first balance grid <NUM>, followed next by the second active grid <NUM> and finally by the second balance grid <NUM> on top, all oriented in-line. Like the embodiment in <FIG>, the active grids <NUM>, <NUM> may be oriented orthogonally relative to the balance grids <NUM>, <NUM>.

As shown in <FIG>, a surface <NUM> is shown having a first active grid <NUM>, a second active grid <NUM>, a first balance grid <NUM> and a second balance grid <NUM> of a strain gauge. The active grids <NUM>, <NUM>, and the balance grids <NUM>, <NUM> may include the same features as the active grids <NUM>, <NUM> and the balance grids <NUM>, <NUM> shown in <FIG>. The surface <NUM> may include the same features as the surface <NUM> shown in <FIG>. In the embodiment shown in <FIG>, the first active grid <NUM> may be placed in a bottom position, followed the first balance grid <NUM>, followed next by the second balance grid <NUM> and finally by the second active grid <NUM> on top, all oriented in-line. Like the embodiment in <FIG>, the active grids <NUM>, <NUM> may be oriented orthogonally relative to the balance grids <NUM>, <NUM>.

Referring now to <FIG>, the surface <NUM> of the pressure transducer <NUM> is shown. A darkened region <NUM> on the surface <NUM> in this Figure represents the strain of the surface due to an adiabatic event such adiabatic heating or cooling caused by a rapid change in pressure within the thermal chamber or fluid path <NUM>. Thus, the active grids <NUM>, <NUM> may be placed in a compressive state as a result of the body <NUM> compressing from the adiabatic event or thermal wave. This compression has not impinged upon the balance grids <NUM>, <NUM>. Instead, the pulling to the center by the body <NUM> may actually create a state of expansion at the location of the body <NUM> located under the balance grids <NUM>, <NUM>. As the thermal wave spreads outward (not shown), the wave amplitude may dissipate and the contractive strain may be radially toward the outer edges on the left and right of the surface <NUM>. As the thermal wave dissipates, the grids begin to return to their normal, isothermal state. In the event that the coefficient of thermal expansion is greater in the grids <NUM>, <NUM>, <NUM>, <NUM> than the body <NUM>, when the body <NUM> contracts due to an adiabatic thermal event, the grids <NUM>, <NUM>, <NUM>, <NUM> would contract more. Since the grids <NUM>, <NUM>, <NUM>, <NUM> are bonded to the surface <NUM> of the body <NUM> and thereby constrained with the thin carrier backing <NUM>, the grids <NUM>, <NUM>, <NUM>, <NUM> cannot contract as much as they would in a free non-bonded state. The result is an actual strain measured by the strain gauge <NUM> increasing despite the contraction naturally caused by the adiabatic event's thermal wave. Depending on the amount of the mismatch, it is even possible to have a contracting thermal event result in a positive output voltage, despite the body <NUM> experiencing a contraction causing adiabatic event. With a smaller mismatch, the output voltage of the strain gauge <NUM> may be less negative and/or may have a smaller peak.

Referring now to <FIG>, a graph <NUM> of the pressure transducer <NUM> is shown having the strain gauge <NUM> with a mismatched coefficient of thermal expansion between the body <NUM> and the grids <NUM>, <NUM>, <NUM>, <NUM> compared to a pressure transducer having the same properties as the pressure transducer <NUM> except having well-matched coefficients of thermal expansion between the body and the grids. The graph <NUM> plots pressure output of the strain gauges along the y-axis vs. settling time on the x-axis. In particular, in the plot <NUM> of the mismatched pressure transducer <NUM>, the strain gauge pressure output returns to zero after only two seconds. In contrast, the plot <NUM> of the well-matched pressure transducer returns to zero after ten seconds. This long settling time can be undesirable in industries and applications where pressure must be detected immediately and adiabatic thermal events are common.

Referring now to <FIG>, an electrical schematic of a strain gauge <NUM> of a pressure transducer such as the pressure transducer <NUM> in accordance with one embodiment. The strain gauge <NUM> may be similar to the strain gauge <NUM> and may include two active grids <NUM>, <NUM> and two balance grids <NUM>, <NUM>. However, unlike the strain gauge <NUM>, the strain gauge <NUM> may include additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM>. Rather than the grids <NUM>, <NUM>, <NUM>, <NUM> being the resistive element having a mismatched coefficient of thermal expansion relative to the thermal expansion of the body, the additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may be the resistive element having mismatched coefficients of thermal resistance relative to the body upon which they are attached. In other embodiments, both the grids <NUM>, <NUM>, <NUM>, <NUM> and the additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may include mismatched coefficients of thermal resistance relative to the body. The additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may be low impedance and/or low resistance circuit elements. The thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may each be connected in series to respective active and balance grids <NUM>, <NUM>, <NUM>, <NUM>, as shown. In the embodiment shown, the thermal resistors <NUM>, <NUM> proximate the active grids <NUM>, <NUM> may have the same coefficient of thermal expansion as the thermal resistors <NUM>, <NUM> proximate the balance grids <NUM>, <NUM> but may have different resistances. In other embodiments, each of the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may have the same resistance and coefficients of thermal resistance. In other embodiments, each of the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may have the same resistance and different coefficients of thermal resistance. In other embodiments, each of the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may have the different resistance and different coefficients of thermal resistance.

Referring to <FIG>, an electrical schematic of a strain gauge <NUM> of a pressure transducer such as the pressure transducer <NUM> in accordance with one embodiment. The strain gauge <NUM> may be similar to the strain gauge <NUM> and may include two active grids <NUM>, <NUM> and two balance grids <NUM>, <NUM>. However, unlike the strain gauge <NUM> but like the strain gauge <NUM>, the strain gauge <NUM> may include additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM>. Rather than the grids <NUM>, <NUM>, <NUM>, <NUM> being the resistive element having a mismatched coefficient of thermal expansion relative to the body, the additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may be the resistive elements having mismatched coefficients of thermal resistance relative to the body upon which they are attached. In other embodiments, both the grids <NUM>, <NUM>, <NUM>, <NUM> and the additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may include mismatched coefficients of thermal resistance relative to the body. The additional thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may be high impedance and/or resistance circuit elements, particularly compared with the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> connected in series described hereinabove with respect to the strain gauge <NUM>. The thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may each be connected in parallel to respective active and balance grids <NUM>, <NUM>, <NUM>, <NUM>, as shown. In the embodiment shown, the thermal resistors <NUM>, <NUM> connected in parallel with the active grids <NUM>, <NUM> may have the same coefficient of thermal resistance as the thermal resistors <NUM>, <NUM> connected in parallel to the balance grids <NUM>, <NUM> but may have different resistances. In other embodiments, each of the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may have the same resistance and different coefficients of thermal expansion. In other embodiments, each of the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may have the same resistance and different coefficients of thermal resistance. In other embodiments, each of the thermal resistors <NUM>, <NUM>, <NUM>, <NUM> may have the different resistance and different coefficients of thermal resistance.

While the embodiments depicted in the figures include only in-line pressure transducers, other embodiments are contemplated utilizing mismatched resistive elements on a strain gauge relative to a body for other types of pressure transducers including, for example, diaphragm style pressure transducers.

Methods of detecting pressure are also contemplated. For example, a method of detecting pressure may include providing a first pressure transducer such as the first pressure transducer <NUM> having a body such as the body <NUM> and a resistive element such as one or more of the resistive elements <NUM> attached to the body. The method may include mismatching a first coefficient of thermal expansion of the body to a second coefficient of thermal expansion of the resistive element. The method may include detecting pressure of a fluid system with the first pressure transducer. The method may include detecting pressure with the pressure transducer during an adiabatic thermal pulse. The method may further include reducing settling time after the adiabatic thermal pulse by at least <NUM> percent relative to a second pressure transducer having the same properties as the first pressure transducer other than the second pressure transducer having well-matched coefficient of thermal expansions. The second coefficient of thermal expansion may be greater than the first coefficient of thermal expansion. The method may still further include outputting a positive output voltage during an adiabatic thermal pulse. The method may include compensating, with the mismatched first and second coefficient thermal expansions, for an adiabatic thermal pulse.

Referring now to <FIG>, a top view of an in-line pressure transducer <NUM> is shown in accordance with one embodiment. Similarly, <FIG> shows a side view of the pressure transducer <NUM> and <FIG> shows a cross sectional view of the pressure transducer <NUM> taken at arrows B-B. The pressure transducer <NUM> includes a body <NUM>, a fluidic inlet <NUM>, a fluidic outlet <NUM>, and a fluidic cavity <NUM> extending between the fluidic inlet <NUM> and the fluidic outlet <NUM>. The fluidic inlet <NUM> and the fluidic outlet <NUM> may include inner threads (not shown) configured to receive a connector, port, fitting or other coupling for connecting the in-line pressure transducer <NUM> to a fluidic system, such as a liquid chromatography system. While the embodiment shown includes both the fluidic inlet <NUM> and the fluidic outlet <NUM>, other embodiments contemplated include single ended transducers including a single fluidic inlet that acts as both a fluidic inlet and a fluidic outlet. In this embodiment, the single fluidic inlet may be considered a fluidic interface port.

The fluidic cavity <NUM> is enclosed by the body <NUM>. A strain gauge <NUM> is disposed on a surface <NUM> located on the outside of the body <NUM>. The surface <NUM> is flat surface as shown. The strain gauge <NUM> includes a Wheatstone bridge having a first active grid <NUM> and a second active grid <NUM> located directly above the fluidic cavity <NUM> on the surface <NUM>, along with a first balance grid <NUM> disposed above the fluidic cavity <NUM> on the surface <NUM> and a second balance grid <NUM> disposed below the fluidic cavity <NUM> on the surface <NUM>. The orientation and position of the active and balance grids <NUM>, <NUM>, <NUM>, <NUM> shown is exemplary and various other orientations are positions are contemplated.

The fluidic cavity <NUM> may be considered a fluidic path or other fluidic body configured to receive pressurized fluid. The strain gauge <NUM> may be configured to detect the pressure in the fluidic cavity <NUM> or cavity by measuring the strain caused by the pressurized fluid on the body <NUM>. The surface <NUM> may be a removed portion that is removed from the body <NUM>. In other embodiments, the surface <NUM> may be molded or otherwise integrated into the body <NUM>. As shown in <FIG>, the surface <NUM> is located closer to the fluidic cavity <NUM> than the rest of the outer circumference of the body <NUM>.

Within the fluidic cavity <NUM> is shown a filler body <NUM>. The filler body <NUM> may extend a substantial length of the fluidic cavity <NUM>, as shown in <FIG> and <FIG>. The filler body <NUM> may extend almost the entire length of the fluidic cavity <NUM>. In other embodiments, the filler body <NUM> may be located only at the location located directly below the strain gauge <NUM> and/or surface <NUM>.

The filler body <NUM> may be located within the fluidic cavity or fluidic cavity <NUM> and may be configured to reduce adiabatic thermal effects on the body <NUM> of the pressure transducer <NUM>. The filler body <NUM> may reduce the volume within the fluidic cavity <NUM>. As shown in <FIG>, the filler body <NUM> may further be configured to reduce the cross sectional area of the fluidic cavity or fluidic cavity <NUM> to a reduced cross sectional area <NUM>. The reduced cross sectional area <NUM> may be a greater or larger area than the smallest cross sectional area at the fluidic inlet <NUM> and/or the fluidic outlet <NUM> after the fluidic inlet <NUM> and fluidic outlet <NUM> has been connected in line to a fluidic system as described herein above. In other embodiments, the reduced cross sectional area <NUM> may be an equal cross sectional area to the smallest cross sectional area at the fluidic inlet <NUM> and/or the fluidic outlet <NUM> after the fluidic inlet <NUM> and fluidic outlet <NUM> has been connected in line to a fluidic system as described herein above. Whatever the embodiment, the reduced cross sectional area <NUM> may not be a limiting dimension for reducing the volume of fluid flow through a fluidic system.

In one embodiment, the filler body <NUM> may include the same material as the body <NUM> of the pressure transducer <NUM>. In other embodiments, the filler body <NUM> may be made of a material that is different than the material of the body <NUM>. The filler body <NUM> may be made of a metallic material such as, for example, zinc, stainless steel, titanium, Invar, or aluminum. In other embodiments, the body <NUM> may be a metallic material but the filler body <NUM> may be made of a non-metallic material such as a plastic, a composite or synthetic. The filler body <NUM> may be a separate component from the shape of the fluidic cavity <NUM> that is disposed within the fluidic cavity <NUM> during fabrication of the pressure transducer <NUM>. Disposing the filler body <NUM> within the fluidic cavity <NUM> may include welding or otherwise attaching the filler body into the fluidic cavity <NUM>. In other embodiments, the filler body <NUM> may simply be the integral shape of the fluidic cavity <NUM>.

As shown in <FIG>, the filler body <NUM> may have a cylindrical shape. The cylindrical body or shape of the filler body <NUM> may have a diameter less than the diameter of the fluidic cavity <NUM>. The filler body <NUM> is shown located at a location within the fluidic cavity or fluidic cavity <NUM> that is distal to the strain gauge <NUM>. In particular, the filler body <NUM> is located at a bottom of the fluidic cavity <NUM>. Thus, the filler body <NUM> may not contact a sensing region <NUM> of the inner surface of the fluidic cavity <NUM> that is located directly below the strain gauge <NUM>. The sensing region may include the upper half of the inner surface of the fluidic cavity <NUM>. This may allow the fluid to flow closely to the web thickness so that the pressure transducer <NUM> can more easily detect pressure within the fluidic cavity <NUM>. The filler body <NUM> may be a solid cylinder as shown. A fluid path space <NUM> is located above the filler body <NUM> between the filler body <NUM> and the circumference of the fluidic cavity <NUM>.

While the filler body <NUM> of <FIG> is a solid cylinder located within the fluidic cavity <NUM>, other shaped filler bodies are contemplated, as shown in <FIG>. While several shapes shown in <FIG>, the invention is not limited to these shapes.

<FIG> depicts a cross sectional view of an in-line pressure transducer <NUM> at a midpoint along its length. The pressure transducer <NUM> includes a strain gauge <NUM>, and a fluidic cavity or path <NUM>. The pressure transducer further includes a filler body <NUM> disposed within the fluidic cavity or path <NUM> configured to reduce the fluid volume found within the fluidic cavity or path <NUM> at any given time. A first fluid path space <NUM> may be located outside the filler body <NUM> and a second fluid path space <NUM> may be located within the filler body <NUM>. In this embodiment, the filler body <NUM> may have a hollow cylindrical shape. In other words, the filler body <NUM> may be a tubular body having a diameter less than the diameter of the fluidic cavity or path <NUM> and may be located in the middle of the fluidic cavity or path <NUM>. The filler body <NUM> may be disposed within the fluidic cavity or path <NUM> in a loose or unattached manner. In other embodiments, the filler body <NUM> may be attached to the fluidic cavity or path <NUM> with an extending portion (not shown) that extends between the filler body <NUM> and fluidic cavity <NUM> and holds the filler body <NUM> into the place shown.

<FIG> depicts a cross sectional view of an in-line pressure transducer <NUM> at a midpoint along its length. The pressure transducer <NUM> includes a strain gauge <NUM>, and a fluidic cavity or path <NUM>. The pressure transducer further includes a filler body <NUM> disposed within the fluidic cavity or path <NUM> configured to reduce the fluid volume found within the fluidic cavity or path <NUM> at any given time. A fluid path space <NUM> may be located outside the filler body <NUM>. In this embodiment, the filler body <NUM> may have a solid cylindrical shape larger than the filler body <NUM> described hereinabove. The filler body <NUM> may be disposed within the fluidic cavity or path <NUM> at the bottom of the fluidic cavity or path <NUM> in a similar manner to the filler body <NUM>.

<FIG> depicts a cross sectional view of an in-line pressure transducer <NUM> at a midpoint along its length. The pressure transducer <NUM> includes a strain gauge <NUM>, and a fluidic cavity or path <NUM>. The pressure transducer further includes a filler body <NUM> disposed within the fluidic cavity or path <NUM> configured to reduce the fluid volume found within the fluidic cavity or path <NUM> at any given time. A fluid path space <NUM> may be located above the filler body <NUM>. The filler body <NUM> may have a cylindrical shape with a flat removed portion disposed along the length of the cylinder at a circumferential location proximate the strain gauge <NUM> when the filler body <NUM> is attached to the fluidic cavity <NUM>. The filler body <NUM> may be attached to the fluidic cavity or path <NUM>. The filler body <NUM> may have a substantially similar outer circumference than the circumference of the fluidic cavity or path <NUM>, with the exception of the removed portion.

<FIG> depicts a cross sectional view of an in-line pressure transducer <NUM> at a midpoint along its length. The pressure transducer <NUM> includes a strain gauge <NUM>, and a fluidic cavity or path <NUM>. The pressure transducer further includes a filler body <NUM> disposed within the fluidic cavity or path <NUM> configured to reduce the fluid volume found within the fluidic cavity or path <NUM> at any given time. A first fluid path space <NUM> may be located above the filler body <NUM> and a second fluid path space <NUM> may be located below the filler body <NUM>. In this embodiment, the filler body <NUM> may be a flat bar extending across the cross sectional area of the fluidic cavity or path <NUM> having curved edges. The curved edges may correspond dimensionally to the circumference of the fluidic cavity or path <NUM>. The filler body <NUM> may be attached to the fluidic cavity or path <NUM> at the curved edges.

<FIG> depicts a cross sectional view of an in-line pressure transducer <NUM> at a midpoint along its length. The pressure transducer <NUM> includes a strain gauge <NUM>, and a fluidic cavity or path <NUM>. The pressure transducer further includes a filler body <NUM> disposed within the fluidic cavity or path <NUM> configured to reduce the fluid volume found within the fluidic cavity or path <NUM> at any given time. The filler body <NUM> may be "X" shaped and may be attached to the fluidic cavity or path <NUM> at the extensions of the X. A first fluid path space <NUM> may be located above the filler body <NUM>, a second fluid path space <NUM> may be located to the right side of the filler body <NUM>, a third fluid path space <NUM> may be located below the filler body <NUM> and a fourth fluid path space <NUM> may be located to the left side of the filler body <NUM>.

<FIG> depicts a cross sectional view of an in-line pressure transducer <NUM> at a midpoint along its length. The pressure transducer <NUM> includes a strain gauge <NUM>, and a fluidic cavity or path <NUM>. The pressure transducer further includes a filler body <NUM> disposed within the fluidic cavity or path <NUM> configured to reduce the fluid volume found within the fluidic cavity or path <NUM> at any given time. The filler body <NUM> may have a square shaped cross section with rounded or chamfered outer edges and may be attached to the fluidic cavity or path <NUM> at the rounded outer edges. A first fluid path space <NUM> may be located above the filler body <NUM>, a second fluid path space <NUM> may be located to the right side of the filler body <NUM>, a third fluid path space <NUM> may be located below the filler body <NUM> and a fourth fluid path space <NUM> may be located to the left side of the filler body <NUM>.

<FIG> depicts a top view of a diaphragm pressure transducer <NUM> in accordance with one embodiment while <FIG> depicts a cutaway view of the pressure transducer of <FIG> taken at arrows C-C. The diaphragm pressure transducer <NUM> includes a body <NUM>, a fluidic inlet <NUM>, a fluidic outlet <NUM>, and a fluidic cavity <NUM> located between the fluidic inlet <NUM> and the fluidic outlet <NUM> and enclosed by the body <NUM>. While the embodiment shown includes both the fluidic inlet <NUM> and the fluidic outlet <NUM>, other embodiments contemplated include single ended transducers including a single fluidic inlet that acts as both a fluidic inlet and a fluidic outlet. In this embodiment, the single fluidic inlet may be considered a fluidic interface port.

A strain gauge <NUM> is disposed on a diaphragm surface <NUM> located on the outside of the body <NUM> of the diaphragm pressure transducer <NUM>. The strain gauge <NUM> includes a Wheatstone bridge having grids as described hereinabove. The strain gauge <NUM> may be configured to detect the pressure in the fluidic cavity <NUM> by measuring the strain caused by the pressurized fluid on the body <NUM> or diaphragm surface <NUM>. The diaphragm surface <NUM> may be a surface located above the fluidic cavity <NUM>.

Within the fluidic cavity <NUM> is shown a filler body <NUM>. Like the filer bodies described hereinabove, the filler body <NUM> may be located within the fluidic cavity <NUM> and may be configured to reduce adiabatic thermal effects on the body <NUM> of the pressure transducer <NUM>. The filler body <NUM> may reduce the volume within the fluidic cavity <NUM>. As shown in <FIG>, the filler body <NUM> may further be configured to reduce the cross sectional area of the fluidic cavity <NUM>. The reduced cross sectional area of the cavity <NUM> may be a greater or larger area than the smallest cross sectional area at the fluidic inlet <NUM> and/or the fluidic outlet <NUM>. In other embodiments, the reduced cross sectional area may be an equal cross sectional area to the smallest cross sectional area at the fluidic inlet <NUM> and/or the fluidic outlet <NUM>. Whatever the embodiment, the reduced cross sectional area may not be a limiting dimension for reducing the volume of fluid flow through a fluidic system.

The filler body <NUM> and the body <NUM> of the diaphragm pressure transducer <NUM> may be made of the same materials as those described hereinabove with respect to the filler body <NUM> and the body <NUM> of the in-line pressure transducer <NUM>. In creating or fabricating the diaphragm pressure transducer <NUM>, a lower body portion <NUM> of the body <NUM> and an upper body portion <NUM> of the body <NUM> may be joined, welded or otherwise attached after the filler body <NUM> has been disposed, attached, or otherwise included into the cavity <NUM>. In other embodiments, the filler body <NUM> may simply be the integral shape of the fluidic cavity <NUM>.

<FIG> depicts a graph <NUM> of the pressure transducer <NUM> is shown having the filler body <NUM> disposed or otherwise included in the fluidic cavity or path <NUM> compared to a pressure transducer having the same properties as the pressure transducer <NUM> except having no filler body located with the fluidic cavity or path. The graph <NUM> plots pressure output of the strain gauges along the y-axis vs. settling time on the x-axis. In particular, the plot <NUM> shows the pressure transducer <NUM> including the filler body <NUM>, the strain gauge pressure output returns to zero after only. <NUM> seconds. In contrast, the plot <NUM> of the pressure transducer without the filler body returns to zero after one full second. This long response time can be undesirable in industries and applications where pressure must be detected immediately and adiabatic thermal events are common.

Further methods of fabricating a pressure transducer and/or detecting pressure are also contemplated. In one embodiment, a method includes providing a pressure transducer such as one of the pressure transducers <NUM>, <NUM>, having a fluidic inlet such as one of the fluid inlets <NUM>, <NUM>, a fluidic outlet such as one of the fluid outs <NUM>, <NUM>, and a fluidic cavity located between the fluidic inlet and the fluidic outlet enclosed by the transducer body such as one of the fluidic cavities <NUM>, <NUM>. The method may include attaching a strain gauge to the transducer body such as one of the strain gauges <NUM>, <NUM>. The method may include integrating a filler body within the fluidic cavity, such as one of the filler bodies <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The method may include reducing a volume of the fluidic cavity with the filler body. Further, the method may include reducing adiabatic thermal effects on the transducer body with the filler body relative to a second pressure transducer having the same properties as the pressure transducer other than the second pressure transducer being fabricated without the filler body. The method may further include reducing the cavity cross sectional area to a reduced cross sectional area along a length of the cavity with the filler body. The reduced cross sectional area may be greater than or equal to an inlet cross sectional area at the fluidic inlet. The method may include not contacting a sensing region of an inner surface of the fluidic cavity with the filler body, the sensing region, such as the sensing region <NUM>, located directly below the strain gauge within the filler cavity.

Claim 1:
A liquid chromatography system (<NUM>) comprising:
a solvent delivery system (<NUM>);
a sample delivery system (<NUM>) in fluidic communication with solvent delivery system (<NUM>);
a liquid chromatography column (<NUM>) located downstream from the solvent delivery system (<NUM>) and the sample delivery system (<NUM>);
a detector (<NUM>) located downstream from the liquid chromatography column (<NUM>); and
a pressure transducer (<NUM>) comprising:
a body (<NUM>) made of a first material having a first coefficient of thermal expansion, the body (<NUM>) having a flat surface on the outside of the body (<NUM>), wherein the first material is titanium or stainless steel;
a fluidic inlet (<NUM>);
a fluidic outlet (<NUM>); and
a fluidic cavity (<NUM>) enclosed by the body (<NUM>) extending between the fluidic inlet (<NUM>) and the fluidic outlet (<NUM>);
further comprising a strain gauge (<NUM>) including a resistive element (<NUM>) in operable contact with the body (<NUM>) and disposed on the flat outside surface of the body (<NUM>),
characterized by at least a portion of the resistive element (<NUM>) made of a second material having a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion of the body (<NUM>), wherein the second material is aluminum.