Adjustable spacer assembly for electromagnetic compatibility testing

A novel spacer assembly includes a body defining a bottom surface and a top surface opposite the bottom surface, a guide coupled to the top surface and extending along an axis, and a plurality of spacer elements movably coupled to the guide along the axis and being configured to receive a plurality of electrical leads therebetween. Each of the spacer elements extends above the top surface of the body and defines a predetermined width along the axis. When the leads are placed between the spacer elements, a spacing between adjacent ones of the leads corresponds to the predetermined width of the interposing spacer element. The predetermined width corresponds to a predefined electromagnetic compatibility (EMC) testing criteria. The spacer assembly facilitates rapid placement and accurate spacing of leads during initial EMC test setup or reconfiguration.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to spacers and, more particularly, to an adjustable spacer assembly for spacing electrically-conductive elements. Even more particularly, the present invention relates to an adjustable spacer assembly for spacing adjacent conductors for electromagnetic compatibility testing.

Description of the Background Art

FIG. 1is a perspective view showing a prior art electromagnetic compatibility (EMC) testing setup100. EMC testing is performed on electronics equipment and electrical wiring, for example, to determine how the equipment and wiring interacts electromagnetically with its environment and to ensure that emitted EM radiation is within specifications.

EMC testing setup100includes a test bench102installed in an electromagnetic (EM) anechoic chamber enclosed by a floor104and plurality of walls. Only the rear wall106of the chamber is shown inFIG. 1so as not to obscure the other elements. Test bench102includes a ground plane108(e.g., a copper surface, etc.) on which components associated with EMC testing are arranged. Such components include equipment under test (EUT)110, line impedance stabilization network (LISN) equipment112,114, and a plurality of electrical leads116(1-n) temporarily affixed on a non-conductive sheet of material118via a plurality of pieces of tape120. EUT110represents any electronic component undergoing EMC testing. LISN equipment112and114condition the impedance of source and return direct current (DC) power, respectively, between EUT110and a power source122over a frequency range. Some of leads116carry electrical power between EUT110and power source122whereas others of leads116communicate electrical signals between EUT110and a signal terminal124, which provides relevant control signals and/or data to EUT110to operate EUT110for EMC testing. Non-conductive sheet118elevates leads elements116(1-n) above ground plane108, and tape120is used to secure leads116(1-n) to non-conductive sheet118in a desired configuration for EMC testing. A plurality of bond straps126electrically couple ground plane108to the EMC test chamber via rear wall106. It is desirable that the testing materials (e.g., tape, sheet118, etc.) not change the electromagnetic environment in the test chamber so the EMC evaluation of EUT110and leads116(1-n) is as accurate as possible.

EMC testing criteria often specify how the leads116(1-n) are to be arranged during EMC testing. For example, Section 4.3.8.6.1 of MIL-STD-461G (11 Dec. 2015) specifies that “[a]ll cables shall be supported 5 cm above the ground plane . . . ” (e.g., ground plane108) and “ . . . individual cables shall be separated by 2 cm measured from their outer circumference . . . ” for EMC testing. Similarly, Section 4.3.8.6.2 provides that “[a]ll power leads shall be supported 5 cm above the ground plane . . . ”. Such rigid EMC testing criteria are difficult to comply with due to variabilities in testing setup.

As shown inFIG. 1, pieces of tape120are used to secure leads116(1-n) at the spacing required by the above EMC testing standard, but do a poor job. For example, it is difficult to maintain leads116in parallel at the proper separation because leads116have a shape “memory” and prefer to restore themselves to their prior shapes. Because leads116are prone to movement on their own, leads116will either pull the tape120up or require placement of a lot of tape120to keep them in position. Lead placement is, therefore, a very time consuming process for the EMC test engineer or technician. Accordingly, it is often the case that leads116(1-n) are out of parallel and do not maintain the 2 cm spacing therebetween for testing.

The taping method also provides other disadvantages. For example, changing any of the wiring setup on sheet118requires the tape to be removed and reinstalled, which is a slow process especially for EUTs110involving many leads116. This wastes time and labor resources. Moreover, because the spacing of leads116will be slightly different each time a testing is set up, the repeatability of a series of EMC tests is low.

Some solutions to improve wire spacing in EMC testing have been proposed, but fall short. For example, trays that have pre-formed grooves have been developed. Unfortunately, such trays do not easily accommodate leads of varying diameters, manually twisted leads, wiring harnesses, etc. Accordingly, such trays are unsuitable for use with strict EMC testing standards, such as MIL-STD-461G discussed above.

SUMMARY OF THE INVENTION

The present invention overcomes the problems associated with the prior art by providing an adjustable spacer assembly for EMC testing that facilitates rapid placement and spacing of leads of equipment under test according to predefined EMC testing criteria. The invention advantageously reduces EMC testing setup time and improves repeatability of EMC testing by enabling a technician to quickly and accurate set lead spacing and/or lead height.

A spacer assembly according to an exemplary embodiment includes a body defining a bottom surface and a top surface opposite the bottom surface, a guide coupled to the top surface and extending along an axis, and a plurality of spacer elements movably coupled to the guide along the axis and being configured to receive a plurality of elongated, electrically-conductive elements therebetween. Each of the spacer elements extends above the top surface of the body and defines a predetermined width along the axis. Additionally, when the plurality of electrically-conductive elements are placed in parallel between and in contact with the spacer elements, a spacing between adjacent ones of the electrically-conductive elements corresponds to the predetermined width of an interposing one of the spacer elements. The predetermined width corresponds to a first electromagnetic compatibility (EMC) testing criteria.

In one particular embodiment, the top surface of the body is disposed at a predetermined height above the bottom surface, where the predetermined height corresponds to a second EMC testing criteria different from the first EMC testing criteria. Accordingly, when the plurality of electrically-conductive elements are placed between the spacer elements, the electrically-conductive elements are further disposed at the predetermined height. In a more particular embodiment, each of the predetermined width and the predetermined height varies by no more than 5%.

In another particular embodiment, the predetermined width of a spacer element varies by no more than 5%.

In still another particular embodiment, the body, the guide, and the plurality of spacer elements are formed from a material having relative permittivity of no more than 5.

In yet another particular embodiment, at least one of the plurality of spacer elements includes a fixing mechanism configured to selectively secure the at least one spacer element in position along the axis. In a more particular embodiment, the fixing mechanism is configured to increase interference between the spacer element and the guide. In an even more particular embodiment, the fixing mechanism includes a threaded member configured to move the spacer element into engagement with the guide.

In still another particular example, each of the plurality of spacer elements comprises a cylindrical portion disposed above the top surface, where the cylindrical portion has a diameter corresponding to the predetermined width. In one more particular example, the cylindrical portion of each of the plurality of spacer elements has the same diameter. In another more particular example, each of the spacer elements comprises an adapter portion configured to movably engage the guide such that the each of the spacer elements can be adjustably positioned along the axis defined by the guide. Optionally, the adapter portion permits rotation of the each of the spacer elements within the guide.

In yet another particular example embodiment, the guide is formed in the body. More particularly, the guide can include a channel formed through the body along the axis, where the channel defines a slot through the top surface. Even more particularly, the body defines one or more sidewalls between the top and the bottom surfaces, the channel is formed through at least one of the sidewalls, and the channel comprises an inverted-T channel.

An exemplary method for spacing electrically-conductive elements coupled to equipment undergoing EMC testing is also disclosed. The method includes the steps of providing at least one spacer assembly, providing a plurality of elongated, electrically-conductive elements, and positioning the at least one spacer assembly on a test bench configured for EMC testing. Each spacer assembly includes a body, a guide coupled to the body, and a plurality of spacer elements movably coupled to the guide along an axis defined by the guide. Each of the spacer elements has a predetermined width along the axis, and the spacer assembly is positioned on the test bench such that the spacer elements are upright. Additionally, the method includes the steps of placing a first one of the electrically-conductive elements over the body and in contact with a first one of the spacer elements, moving a second one of the spacer elements into contact with the first electrically-conductive element, and placing a second one of the electrically-conductive elements over the body and in contact with the second spacer element such that the first and the second electrically-conductive elements are separated by a predetermined width of the second spacer element. The predetermined width corresponds to a first electromagnetic compatibility (EMC) testing criteria.

A particular method further includes the steps of moving a third one of the spacer elements into contact with the second electrically-conductive element opposite the second spacer element, and placing a third one of the electrically-conductive elements over the body and in contact with the third spacer element such that the second and the third electrically-conductive elements are separated by a predetermined width of the third spacer element. The predetermined width of the third spacer element is equal to the predetermined width of the second spacer element. Optionally, the first, second, and third electrically-conductive elements can have different outer diameters/circumferences.

Another particular method includes the step of fixing the first spacer element, but not the second spacer element, in position along the axis defined by the guide.

DETAILED DESCRIPTION

FIG. 2is a perspective view showing a spacer assembly200, according to one embodiment of the present invention. The spacer assembly200is configured to support a plurality of elongated, electrically-conductive elements202(1-n) above ground plane108of test bench102during EMC testing. In this exemplary embodiment, five electrically-conductive elements202(1-5) are shown, but spacer assembly200could support more or fewer such elements202as desired. Electrically-conductive elements202(1-n) will be referred to hereinafter as leads202(1-n) for simplicity. However, it should be understood that electrically-conductive elements202(1-n) should be interpreted expansively to include any electrically-conductive elements suitable for communicating electrical power and/or signals between EUT110and power source122and/or between EUT110and signal terminal124. Electrically-conductive elements202(1-n) include, but are not limited to, wires, leads, cables or cords comprising one or more wires, etc. Additionally, an electrically-conductive element202can comprise a multi-lead wiring harnesses, a twisted plurality of leads, etc.

Spacer assembly200includes a body204, a guide206, and a plurality of spacer elements208(1-m). Body204defines a bottom surface210, a top surface212opposite bottom surface210, a first pair of opposing (long) sidewalls214,216, and a second pair of opposing (short) sidewalls218,220. Guide206is coupled to top surface212of body204and extends along (defines) an axis222. More specifically, in this embodiment, guide206defines a channel224formed through body204along axis. Channel224includes a slot226formed through top surface212.

Spacer elements208(1-m) are movably coupled within channel224such that they extend above top surface212of body204. Spacer elements208(1-m) are configured to receive the plurality leads202(1-n) therebetween and space the leads202at the leads' outer circumferences by desired amount(s). In this example, there are six spacer elements208(1-6), which receive and space five leads202(1-5). When the leads202(1-5) are placed between and in contact with the spacer elements208(1-6), a spacing between adjacent ones of the leads202corresponds to a predetermined width of the interposing spacer elements206along axis222. For example, leads202(1) and202(2) are separated at their outer circumferences by an amount corresponding to the outside diameter (D) of cylindrical spacer element208(2). Similarly, leads202(2) and202(3) are separated at their outer circumferences by an amount corresponding to the outside diameter (D) of cylindrical spacer element208(3). Because the diameters (D) of all spacer elements208interposed between adjacent pairs of leads202are the same in this example, all of leads202are equally spaced at their outer circumferences by a predetermined distance (D), regardless of the individual diameters of the adjacent leads202.

Here, the predetermined width/diameter (D) corresponds to a first EMC testing criteria. In a more particular embodiment, the outside diameter of each such spacer element208is equal to 2 cm+/−5% such that the spacing of leads202complies with MIL-STD-461G discussed above.

Spacer assembly200also stands on ground plane108via bottom surface210of body204, such that spacer elements208(1-m) are positioned generally vertically. Additionally, top surface212is generally flat and located at a predetermined height, H (FIG. 3), above bottom surface210. Accordingly, when leads202(1-n) are placed on body204, body204supports leads202(1-n) above ground plane108by an amount equal to the predetermined height, H. In a particular embodiment, the predetermined height H corresponds to a second EMC testing criteria. In a more particular embodiment, the predetermined height H is equal to 5 cm+/−5% such that the height of leads202(1-n) above ground plane108complies with MIL-STD-461G.

Spacer assembly200will now be further described with reference toFIGS. 3 and 4.FIG. 3shows a front view of spacer assembly200, whereasFIG. 4shows a top view of spacer assembly200. As shown, leads202(1-5) are supported on top surface212of body204at a predetermined height, H, above ground plane108. Additionally, spacer elements208(1-6) facilitate equal spacing of leads202(1-5) at the leads' outer circumferences as discussed above, based on the width (diameter in this case), D, of the interposing spacer elements208. Because each of interposing spacer elements208(2-5) have the same diameter, leads202(1-5) are equally spaced.

FIGS. 3 and 4further show that each spacer element208(1-6) includes a cylindrical spacer portion302and a cylindrical adapter portion304. Cylindrical spacer portion302of each spacer element208(1-6) is disposed above top surface212, where the cylindrical spacer portion302has the diameter, D. In contrast, the adapter portion304is disposed below the cylindrical portion304within guide206and is configured to movably engage guide206, via channel224and slot226. Adapter portion304defines multiple diameters such that spacer element208can be selectively positioned laterally along said axis222, but cannot pull out of channel224vertically (FIG. 3). Adapter portion304is also sized to permit spacer element208to rotate within channel224.

FIGS. 3 and 4also illustrate how different groups of spacer elements208(1-6) can include different structural features. Spacer elements208(1-6) comprise both a securable group306and a floating group308of spacer elements208. Securable group306includes spacer elements208(1) and208(6), which are the outer-most spacer elements208. Each of spacer elements208(1) and208(6) includes a fixing mechanism310, which is configured to selectively secure the associated spacer element208in position along axis222as described in more detail below. In contrast, floating group308includes spacer elements208(2-5), which “float” between spacer elements208(1) and208(6), but are generally secured in position along axis222when each of spacer elements208(1) and208(6) are secured in position via their respective fixing mechanisms310. Accordingly, there is one more spacer element208than lead202in this embodiment.

In use, spacer assembly200can be installed during EMC testing setup as follows. If not done so already, the adapter portions304of spacer element208(1-6) are inserted in channel224of guide206such that spacer elements208(1-6) are in the positional order shown inFIGS. 3 and 4. Spacer assembly200is then placed (and optionally secured with tape, etc.) on ground plane108such that spacer elements208are standing upward. Spacer element208(1) is moved to the position shown and secured in position by actuating fixing mechanism310. Lead202(1) is then placed in contact with spacer element208(1), after which spacer element208(2) is moved along axis222until it is in contact with lead202(1). Lead202(2) is then placed in contact with spacer element208(2) opposite lead202(1). Spacer element208(3) is then moved along axis222into contact with lead202(2), and lead202(3) is placed in contact with spacer element208(3) opposite lead202(2). Thereafter, spacer element208(4) is moved along axis222into contact with lead202(3), and lead202(4) is placed in contact with spacer element208(4) opposite lead202(3). Then spacer element208(5) is moved along axis222into contact with lead202(4), and lead202(5) is placed in contact with spacer element208(5) opposite lead202(4). Thereafter, spacer element208(6) is moved along axis222into contact with lead202(5) opposite spacer element208(5). Spacer element208(6) is then secured in position by actuating its fixing mechanism310, which also secures spacer elements208(1-6) and leads202(1-5) in the contiguous arrangement shown.

Thus, spacer assembly200advantageously permits a plurality of leads202(1-n) to be oriented in parallel at a predetermined spacing (D) at the outer circumferences of the leads202(1-n) in accordance with lead spacing criteria for EMC testing. Additionally, spacer assembly200supports leads202(1-n) above ground plane108at the desired predetermined height, H, further in accordance with ground plane spacing criteria for EMC testing. Spacer assembly200advantageously speeds up lead routing and spacing during initial EMC testing setup and reconfiguration by readily spacing leads and eliminating, or at least significantly reducing, the amount of lead taping.

FIG. 5shows an end view of spacer assembly200.FIG. 5shows that guide206comprises a channel224formed through at least one of short sidewalls218,220of body204. Doing so facilitates insertion of as many spacer elements208in guide206as desired and enables spacer assembly200to be configured for different EUTs110with differing numbers of leads202. Additionally, channel224is shown to be in the shape of an inverted-T, which defines slot226through top surface212. The (cylindrical) adapter portion304of each spacer element208has a shape that is complementary to channel224such that the spacer element208can both slide axially and rotate therein.

FIG. 5also shows how fixing mechanism310is configured to increase interference between spacer element208(1) and guide224. More particularly, fixing mechanism310comprises a threaded device (in this case a screw510) that is configured to contact the bottom of channel224and move adapter portion304vertically into engagement with guide206. Here, as screw510is screwed downward through spacer element208(1), the bottom distal end of screw510protrudes through adapter portion304and selectively contacts the bottom of channel224. Once screw510contacts channel224, further advancement of screw510pushes spacer element208(1) upward until the wider cylindrical region of adapter portion304contacts the underside of channel224as shown inFIG. 5. The increased friction between adapter portion304and channel224secures spacer element208(1) in position. The fixing mechanism310of spacer element208(6) operates similarly.

FIG. 6is a partially exploded and cross-sectioned view of spacer element208(1) taken along line A-A ofFIG. 4.FIG. 6shows that spacer element208(1) defines a threaded bore602that receives screw510(not sectioned) therethrough. Screw510can be selectively advanced into contact with the bottom of channel224as discussed above.FIG. 7shows a cross sectional view of spacer element208(2) taken along lines B-B ofFIG. 4. In contrast toFIG. 6,FIG. 7shows that spacer elements208(2) (and the others of floating group308) are solid, unthreaded pieces.

With reference toFIGS. 2-7, the components of spacer assembly200discussed herein are formed from a non-hygroscopic material with low relative permittivity. Low relative permittivity is considered to be relative permittivity less than 5. However, components of spacer assembly200can be made from a non-hygroscopic material having a relative permittivity less than 4 or even less than 3. As a particular example, the components of spacer assembly200can be fabricated from a synthetic polymer, such as acetal (e.g., Delrin®), nylon, linen phenolic, etc. Forming the components of spacer assembly200from a material that is both non-hygroscopic and low relative permittivity is desirable because those material properties keep the inherent capacitance of spacer assembly200low, such that spacer assembly200does not negatively impact EMC testing.

Turning now toFIG. 8,FIG. 8shows a plurality of spacer assemblies200(1-x) (only two shown) used to equally space a plurality of leads202(1-5) to a predetermined width (D) at their outer circumferences and to further space each of the leads202(1-5) at a predetermined height, H, above ground plane108.FIG. 8further shows that a plurality of support structures800(1-y) (e.g., Styrofoam blocks, etc.; only two shown) are used in conjunction with spacer assemblies200(1-x) to prevent leads202(1-5) from sagging in the runs between adjacent spacer assemblies200(1-x). Spacer assemblies200(1-x) and support structures800(1-y) form a close configuration that supports leads202(1-5) in parallel at the predetermined height, H, across the test bench102. Support structures800(1-y) also help maintain spacer assemblies200(1-x) in a desired position on ground plane200. It should be noted that spacer assembly200can be optionally affixed to ground plane108(e.g., with tape, fasteners, etc.) if it is desirable to do so. For example, placing tape over a spacer assembly200to adhere it to ground plane108can quickly add additional, temporary, stability to spacer assembly200if desired.

The spacer assembly200of the present invention advantageously enables rapid setup of the leads202(1-5) in parallel, at the desired spacing, and at the desired height while eliminating (or significantly reducing) the taping of leads202(1-5). Spacer assembly200makes the initial EMC testing setup process faster, which saves technician time. Reconfiguration of the leads202(1-5) is also faster, because the spacer assembly200can be moved and/or the spacer elements repositioned. Moreover, because the spacer assembly200enables leads202to be equally spaced in a repeatable manner, as opposed to the prior art method, EMC testing is more repeatable across different test setups and testing occurrences.

While exemplary embodiments of spacer assembly200have been described above, it should be recognized that modifications can be made to spacer assembly200without departing from the spirit and scope of the invention. For example, body204can be elongated such that additional spacer elements208can be installed and utilized for spacing additional leads202. As another example, spacer elements208can have a different common predetermined width (D) and/or body204can define a different predetermined height, H, depending on the EMC testing criteria being tested against. As yet another example, spacer assembly200can employ different sets of spacer elements208having different predetermined widths/diameters such that different leads can be spaced at different predetermined distances by the same assembly200. As still another example, an alternative spacer assembly can be envisioned having spacer elements208oriented on multiple axes. However, the spacer assembly200having a single axis200provides good adjustability, because it is compact and readily relocated and oriented according to a desired test setup. As yet another example, the cross-sectional shape of channel224can be varied.

The dimensions of body204can also be adjusted as desired to meet a particular EMC testing application and/or to ensure that spacer assembly200is stable on ground plane108. Care should be taken, however, to minimize the impact of the dimensions of spacer assembly200on the EMC testing, from an electromagnetic interference standpoint or otherwise. For example, the larger the volume of spacer assembly200, the greater its inherent capacitance and ability to affect electromagnetic testing. As another example, in the case that bottom surface210and top surface212have different dimensions in a direction perpendicular to axis222, the ability to closely configure support structures800and spacer assemblies is diminished. For this reason, the inventor recommends minimizing differences between the bottom and top surfaces210and212(e.g., to less than 12.5 mm (0.5 inches) total, etc.). Indeed, the embodiment of spacer assembly200as illustrated inFIGS. 2-8provides good stability, low inherent capacitance, is readily adjustable in position on ground plane108, and facilitates the close positioning of spacer assemblies and support structures800in alternation. As yet another possible modification, an alternative body904of a spacer assembly900can be manufactured with feet930for added stability, such as shown inFIG. 9. Feet950stabilize spacer assembly900but do not interfere with the placement of support structures800under leads202.

Methods of the present invention will now be described with reference toFIG. 10. For the sake of clear explanation, these methods might be described with reference to particular elements or modules of the foregoing description. However, it should be noted that other elements or modules, whether explicitly described herein or created in view of the present disclosure, can be substituted for those referenced without departing from the scope of the present invention. Accordingly, the methods of the present invention are not limited to any particular element(s) that perform(s) any particular functions. Furthermore, the steps of the methods presented herein need not necessarily occur in the order shown and/or some steps might occur simultaneously. These and other variations of the disclosed methods will be readily apparent in view of this disclosure and are considered to be within the scope of the invention.

FIG. 10shows a flowchart summarizing a method1000for spacing electrically-conductive elements (e.g., leads, etc.) coupled to equipment undergoing EMC testing. In a first step1002, at least one spacer assembly is provided. The spacer assembly includes a body, a guide coupled to the body, and a plurality of spacer elements movably coupled to the guide along an axis defined by the guide. Each of the spacer elements has a predetermined width along the axis defined by the guide. In a second step1004, a plurality of elongated, electrically-conductive elements (e.g., leads, etc.) are provided. In a third step1006, the spacer assembly is positioned on a test bench configured for EMC testing such that the spacer elements are oriented upright. In a fourth step1008, a first one of the electrically-conductive elements is placed over the body of the spacer assembly and in contact with a first one of the spacer elements. In a fifth step1010, a second one of the spacer elements is moved into contact with the first electrically-conductive element opposite the first spacer element. In a sixth step1012, a next one of the electrically-conductive elements is placed over the body of the spacer assembly and in contact with the second/prior-positioned spacer element such that the first and second/prior-placed electrically-conductive elements are separated by a predetermined width of the second/prior-placed spacer element. The predetermined width corresponds to an electromagnetic compatibility (EMC) testing criteria. In a seventh step1014, a next one of the spacer elements is moved into contact with the second/prior-placed electrically-conductive element. In an eighth step1016, a determination is made if there are more electrically-conductive elements to place using the spacer assembly. If so, method1000returns to sixth step1012. If not, method1000ends. Method1000can be repeated for placing the electrically-conductive elements in additional spacer assemblies.