Information
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Patent Grant
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6218745
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Patent Number
6,218,745
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Date Filed
Friday, March 12, 199925 years ago
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Date Issued
Tuesday, April 17, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
US
- 307 104
- 318 492
- 336 30
- 336 92
- 336 98
- 361 139
- 361 816
- 361 818
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International Classifications
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Abstract
A connector has conductive pins extending from outside the device to within the device and an electrically conductive wall surrounding a portion of the pins. The conductive wall abuts a printed wiring board containing EMI protective circuitry and contacts a ground plane within the printed wiring board. A selected pin is brazed to the connector and holds the printed wiring board in compression to assure a low impedance connection to the ground plane.
Description
CROSS REFERENCE TO RELATED APPLICATIONS (IF ANY)
Not applicable.
U.S. GOVERNMENT RIGHTS (IF ANY)
Not applicable.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to the control of electromagnetic interference (EMI) and specifically to an apparatus for making electrical connection to a device containing electronics requiring EMI protection. Electromagnetic interference is said to exist when unwanted voltages or currents are present so that they adversely affect the performance of a device or system. These voltages or currents may reach the victim circuit by conduction or by radiation. Electrical filters may be designed to offer little opposition to the passage of certain frequencies or direct current (dc) while blocking the passage of other frequencies. Filters play a significant role in the reduction of conducted interference. A metal barrier may be imposed between sources of electrical noise and their victims to reduce or eliminate the electrical interference due to radiated interference.
The present invention is described in the environment of a pressure sensor or pressure transducer application. However, it is to be understood that this is only an illustrative environment and the present invention applies to other applications as well.
A transducer transforms one form of energy into another form. For example, a transducer can covert the measure or value of some physical property such as pressure or temperature into a corresponding value of an electrical parameter such as voltage. Transducers typically include extensive electronics to reliably manipulate or process very low level electrical signals. Therefore, it is necessary to take precautions in the design to minimize the effects of EMI on the transducer electronics. Transducers, for example precision pressure transducers, are applied in a wide variety of industrial and other applications in which the associated wiring or cabling is routinely exposed to EMI from many sources. In the past, electrical filtering arrangements including electrical components provided on a separate board specifically designed to reduce EMI have been employed in pressure transducers. In the past, EMI shielding of the EMI board circuitry has been provided by using additional parts for shielding. The extra parts add both piece part and labor costs. Thus, there is a need for an improved apparatus for making electrical connections to a device containing electronics requiring EMI protection.
BRIEF SUMMARY OF THE INVENTION
The present invention solves these and other needs by providing an apparatus for making electrical connections to a device requiring EMI protection. The apparatus includes a connector having conductive pins extending from outside the device to within the device and an electrically conductive wall surrounding a portion of the pins. A printed wiring board includes EMI protective circuitry and a ground plane. The conductive wall abuts the circuit board making electrical contact with the ground plane and forming a cavity of conductive material.
In another aspect of the present invention a selected pin is brazed to the connector and secured to the printed wiring board so that the printed wiring board is in compression. the compressive force holds the printed wiring board against the connector wall assuring a low impedance connection.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
shows a cross sectional perspective view of the present invention applied to a pressure sensing device with portions of the pressure sensing device also being shown.
FIG. 2
shows an enlarged cross sectional perspective view of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
An apparatus for making electrical connections to a device containing electronics requiring EMI protection is shown in the drawings and generally designated
10
.
FIG. 1
shows a pressure sensing device or pressure transducer assembly
12
including pressure interface
14
, sensor header
16
, housing
18
and apparatus
10
. Sensor header
16
includes diaphragm
20
, sensor die
22
and conductive pins
24
which provide for communication between sensor die
22
and electronics located within housing
18
. Housing
18
contains electronics such as printed wiring board
26
and connector
28
for communication between board
26
and a board that is not shown. Pressure interface
14
, sensor header
16
, housing
18
and apparatus
10
are joined together by welding. Apparatus
10
includes a connector body
40
which has an outwardly extending connector coupling arrangement
42
such as the 6 pin military connector type that is shown. Connector body
40
includes a generally planar portion
44
which has a shoulder
46
for being received on end
32
of housing
18
. Connector body
40
further includes a downwardly extending wall or shell
48
which in the preferred embodiment is shaped or beveled so that it presents a small surface or a sharp edge
50
. Conductive pins
52
are accessible outside pressure transducer
12
and extend through glass insulators
54
located in planar portion
44
. Apparatus
10
further includes an EMI board
60
. The purpose of EMI board
60
is to provide electrical filtering of the power or signals that are coming into the electronics of pressure transducer
12
and of signals coming from pressure transducer
12
. EMI board
60
has a surface
62
on which electrical filtering components (not shown) are typically mounted and a surface
64
. EMI board
60
may be referred to herein as second printed wiring board
60
. Components found on the EMI board
60
may include, for example, AVX transguards to protect against incoming transients (ESD, etc.), capacitors to filter out high frequency noise, both incoming and outgoing, and ferrite beads to act as high impedance to high frequency noise, both incoming and outgoing. EMI board
60
includes a low impedance shielding plane
66
which may also be referred to as an internal ground plane or chassis plane. Plane
66
is brought to surface
62
by equally spaced vias
68
. At surface
62
a circumferential conductive surface
70
is provided.
In the preferred embodiment pin
72
, is not insulated from connector body
40
, but rather is brazed to connector body
40
and is therefore at the potential of connector body
40
. In the manufacturing process, EMI board
60
is located as shown and a tool is used to apply a force to surface
64
of EMI board
60
so that it is deflected toward connector body
40
. While EMI board
60
is in this compressed position, pin
72
is soldered to EMI board
60
at
74
to take the stress of the compression once the force is removed. When the tool is removed, pin
72
will continue to hold EMI board
60
in compression so that a low impedance connection between edge
50
of wall
48
and circumferential conductive surface
70
is assured, through all environmental changes such as temperature variations. Electrical circuitry on EMI board
60
is connected through connector
76
to electronics located in housing
18
.
In the present invention, having the internal EMI ground plane
66
attached to the chassis at both the chassis pin
72
and the entire circumference of the EMI board allows the ground plane
66
to be both very low impedance and low inductance. The low impedance and low inductance ground connection at circumferential conductive surface
70
allows the capacitors to more effectively filter out the incoming (coupled into the cabling) and outgoing (generated by the electronics) high frequency signals. In addition, the ground plane and the connection at the circumference of the EMI board acts like a faraday cage, eliminating possible internally-radiated high frequency signals from going further in the housing. A significant benefit from the invention is the very low impedance and low inductance chassis connection.
The present invention has been described in the environment of a ruggedized pressure transducer where the material used for connector body
40
is stainless steel and it is of single piece construction. In other environments other materials and construction may be used. Means other than the use of pin
72
to hold printed wiring board
60
in compression may be used. For example, a threaded type of fastener could be used.
Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.
Claims
- 1. Apparatus for making electrical connections to a device containing electronics requiring EMI protection, said apparatus comprising:a connector having conductive pins extending from outside said device to within said device, said connector having an electrically conductive wall surrounding a portion of said pins within said device; a printed wiring board comprising EMI protective circuitry and having an internal ground plane; said conductive wall abutting said printed wiring board and making electrical contact with said ground plane, with selected ones of said pins connected to said EMI protective circuitry and with said wall and said ground plane forming a cavity of conductive material; and means for connecting said electronics requiring EMI protection to said printed wiring board.
- 2. Apparatus of claim 1 wherein said ground plane is electrically connected to a circumferential conductive surface on said printed wiring board and said apparatus further comprises means for forcibly maintaining said conductive surface against said wall to assure a low impedance connection.
- 3. Apparatus of claim 2 wherein said means for forcibly maintaining comprises a conductive pin having a first end embedded in said connector and a second end secured to said printed wiring board with said pin exerting compressive force to hold said circumferential conductive surface against said wall.
- 4. Apparatus of claim 3 wherein said wall terminates in an end having a shape that will bite into said conductive surface to form a low impedance connection.
- 5. Apparatus of claim 1 wherein said device is a pressure sensing device having a metal housing surrounding said electronics and having an end shaped for complementary receipt of said apparatus.
- 6. Apparatus for making electrical connections to a device containing electronics requiring EMI protection, said apparatus comprising:a connector having conductive pins extending from outside said device to within said device, said connector having an electrically conductive shell extending within said device and surrounding a portion of said pins within said device, said shell terminating in an end; a printed wiring board comprising EMI protective circuitry and having an internal ground plane; a conductive surface on said printed wiring board facing said end, said conductive surface connected to said ground plane; said conductive shell abutting said circuit board and making electrical contact with said conductive surface, with selected ones of said pins connected to said EMI protective circuitry and with said wall and said ground plane forming a cavity of conductive material; a selected one of said conductive pins having a first end embedded in said conductor and having a second end secured to said printed wiring board with said pin exerting compressive force to hold said conductive surface against said shell; and means for connecting said electronics requiring EMI protection to said printed wiring board.
- 7. Apparatus of claim 6 wherein said end of said shell is shaped to provide a low impedance connection to said conduction surface.
- 8. In a pressure sensing device having a sensor header, electronics surrounded by a metallic housing, EMI protective circuitry, and a connector for making electrical connections to said device, the improvement comprising;said connector having conductive pins extending from outside said device to within said device, said connector having an electrically conductive wall surrounding a portion of said pins within said device; a printed wiring board comprising said EMI protective circuitry and having internal ground plane; said conductive wall abutting said printed wiring board and making electrical contact with said ground plane, with selected ones of said pins connected to said EMI protective circuitry and with said wall and said ground plane forming a cavity of conductive material; and means for connecting said electronics to said printed wiring board.
- 9. The improvement of claim 8 wherein said ground plane is electrically connected to a circumferential conductive surface on said printed wiring board and said apparatus further comprises means for forcibly maintaining said conductive surface against said wall to assure a low impedance connection.
- 10. The improvement of claim 9 wherein said means for forcibly maintaining comprises a conductive pin having a first end embedded in said connector and a second end secured to said printed wiring board with said pin exerting compressive force to hold said circumferential conductive surface against said wall.
- 11. The improvement of claim 10 wherein said wall terminates in an end having a shape that will bite into said conductive surface to form a low impedance connection.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4601527 |
Lemke |
Jul 1986 |
|
5186635 |
Pechulis et al. |
Feb 1993 |
|
5842888 |
Belopolsky |
Dec 1998 |
|