Figure 2: Hz ripple riding on a Hz ac power bus, measured in the frequency domain. The PRD has a dB transducer factor, so 66 dB has to be added to measured values to get to values on the power bus. The PRD allows for monitoring and injecting ripple below the power frequency, a requirement prior to but the capability to do so was lost in when MIL-STDD prohibited use of the phase shift network method of eliminating the power frequency from the ripple measurement.
In MIL-STDD and onward, because of that prohibition, the limit for ac ripple started at the second harmonic of the power frequency, instead of at 30 Hz. The PRD facilitates monitoring down to 30 Hz on any type of bus, as shown in Figure 3, but the TSWG was not interested in reviving the 30 Hz start frequency for ac buses after over twenty years of not having done so.
The PRD as commercialized by Pearson Electronics contains an isolation transformer so that connection of the ac neutral to the PRD maintains isolation between the neutral and the grounded EMI receiver or spectrum analyzer chassis. That isolation is required by paragraph 5. CS figures are updated to show either the traditional measurement with floated oscilloscope or the new measurement with PRD and grounded receiver. Therefore, below 10 kHz when the specification limit potential cannot be developed across the test sample power input and the precalibrated power limit has been reached, it is incumbent on the tester to check that the missing signal level is not being dropped across the power source.
Stanford csL book c++.pdf | C++ | C (Programming Language)
If the missing potential is there usually due to high impedance test facility EMI filters , then steps should be taken to lower the source impedance. The PRD facilitates that measurement by having two sets of jacks for simultaneously connecting to both test sample power input and across the power source and being able to read either of these values at the flip of a switch. Electrical transients occur on all electrical distribution systems and can cause problems in circuitry which tend to be sensitive to voltage transients, such as latching circuits expecting a single trigger signal.
On submarines and surface ships, these transients can be caused by switching of inductive loads, circuit breaker or relay bounce, and load feedback onto the power distribution system. The volt peak, 5 microsecond pulse defined in Figure CS is a suitable representation of the typical transient observed on Navy platforms. Measurements of transients on Navy platforms have shown the transient durations widths are predominantly in the 1 — 10 microsecond range.
Shop by category
The underlying issue was not the response of the power supply to the transient, but crosstalk within an equipment between the transient on the power wiring and signals carried on wiring adjacent to the power wires without adequate protection. The very purpose of the requirement was to force adequate segregation between power and signal circuitry. However, CS was designed specifically to represent the coupling of transients on a power bus into cables run adjacent to it.
The very short 30 ns duration and even shorter 2 ns rise and fall times represent the leading edge of a waveform such as CS on a power bus inductively coupling into an adjacent cable. Measurements on a one foot section of ribbon cable modeling an unprotected connection between a connector and motherboard revealed that injecting CS on the simulated signal wires looked very similar to the cross-coupling from injecting CS on the simulated power wires. The limit reverts back to that of MIL-STDD, where the primary limit is the forward power recorded in the calibration fixture when the appropriate specification limit Curve 1 — 5 is induced in the fixture, with the only current limit being 6 dB higher than the current in the plateau region of the curve.
This change will make it important to tailor the breakpoint frequency of the limit nominally 1 MHz for platform or actual cable dimension, in order to avoid over-testing. In order to perform that tailoring, it is necessary to understand that the breakpoint represents the frequency at which a platform or cable is one-half wavelength long. A 1 MHz break point is a physical length of meters. So if a platform is instead about 15 meters long, the breakpoint would shift to 10 MHz.
The procedural change is that in addition to the traditional measurement of the forward power required to induce the specification limit current in the calibration fixture, the current in the fixture must be measured using the current probe that will be used to monitor current on the cable-under-test. This is an augmentation of the measurement system integrity check, because again a current probe will not require periodic calibration.
- c++ - Clion -- why do I need to type the full path? - Stack Overflow.
- Suggest Documents.
- The One True Ocean;
- Cs 107 stanford syllabus!
- 转载自stanford cs106L course reader Generic Programming demo!
These are that cable-related tests are performed at the bulk cable level, no pin injection, and second that platform installations are divided into two categories, internal and external relative to a metallic platform. CS is adopted as a BCI requirement only, eschewing the pin injection requirements in section This greatly simplifies the test campaign on the types of equipment to which CS applies, such as flight and engine controls that have multiple cables with lots of pins.
Pin injection is important with shielded cables where the installed length is greater than the ten meters required in MIL-STD For this small subset of cables, some thought will need to be given to possibly boosting the injected current to make up for the lower shield transfer impedance of the set-up vs. CS has six waveforms borrowed from section 22, but only two levels, internal and external. In addition to that simplification vs. Level 3 maps to internal, and level 4 maps to external. This means that the same waveform applied in a CS set-up will apply less potential to the load than if the test were performed to section 22, because the power source impedance is higher with CS Before getting into requirement and test details, some background is in order.
Such damage would most likely occur during remove-and-replace operations, not during powered up use, else the failures would be much more dramatic and noticeable i.
The section 25 set-up was chosen over IEC because of the obvious similarities in a metal vehicle application, with the test sample enclosure directly grounded to structure, as opposed to the approach with a nonconductive table top 80 cm removed from ground, with at most a green wire ground connection. Likewise CS requires an electrostatic assessment of the gun potential prior to the discharge. The generator setting required to produce this output shall be recorded. Limits are 8 kV for contact, 15 kV for air discharge.
Contact discharge is the preferred method unless the test item has nonconductive surfaces requiring an air discharge approach. This is because air discharge current waveforms can have higher amplitudes at lower potentials, due to smaller arc distances and hence lower arc resistance. It was deemed that the time saved not testing to 18 GHz was insignificant. But there is another much more subtle change, and it is important in the same way that the tip of an iceberg is important to a ship at sea.
- The Presidents House: 1800 to the Present The Secrets and History of the Worlds Most Famous Home?
- Subscribe to RSS;
- Dimensions of Japanese Society: Gender, Margins and Mainstream.
The purpose of that change was to detune an observed resonance that occurs between 20 — 30 MHz. Part of the change included clamping a ferrite sleeve around the coaxial transmission line between rod antenna base and EMI receiver. But this subtle change of moving a recommendation from the appendix to the main body is just the tip of the rod antenna configuration iceberg.
This work is now described. The recommended technique was the insertion of an isolation transformer in the coaxial cable connection between the rod antenna base and the EMI receiver. Another separate suggestion from another researcher recommended a fiber optic link. Both these suggestions were evaluated during the MIL-STDG revision process, but both came up short for reasons described presently.
Also, a test equipment vendor introduced a rod antenna that was inherently floated using a fiber-optic link to a laptop computer controller. Inserting a fiber optic link in the connection to a conventional rod antenna failed due to what appeared to be parasitic capacity between the green wire ground in the laboratory power and the bias potentials fed to the opto-electronic converters.
The plan was to replace the power supply with batteries to see if that eliminated the problem, but time ran out. The problem with isolation transformers is there is always some degree of inter-winding capacitance between winding banks, and at these frequencies it cannot be ignored. While the original problem dealt with by MIL-STDF was a parallel L-C trap with capacitance between the counterpoise and floor and the inductance supplied by the coaxial shield connection, when an isolation transformer is inserted a new series L-C trap is formed from the inter-winding capacitance and the coaxial shield inductance.
The combination of capacitance and inductance have to be limited such that the resultant resonance which cannot be eliminated, only moved around is above 30 MHz. Given that different models of transformers have different and unspecified inter-winding capacitance, it would have to be measured by the test facility and then a maximum length cable would need to be specified to work with it to keep the resonance above 30 MHz. This is difficult to write into a standard. MIL-STD cannot specify test equipment by manufacturer and model, so a generic description that nevertheless conveys the desired characteristics is required.
But in the end it was decided that would be too complicated because we would have physical apertures for all other antennas, but performance characteristics of the new one, and no one wanted to change to performance characteristics for all antennas. There are several advantages to a reverb RE test method, and none of the drawbacks of RS reverb, namely the schedule hit. Reverb RE testing captures all test sample emissions, rather than those emanating from the front face.
A reverb technique removes test chamber resonance issues due to the partial absorber liming coverage allowed by MIL-STD The test chamber is much less expensive.
Cs106b fall 2018
There is the potential for making more sensitive measurements than in an absorber-lined chamber because we are capturing constructive interference of all the emanations at once. It was felt that this might not be the optimal approach, and an investigation based on the work of Norm Wehling, retired chief engineer at Elite Electronic Engineering Company as published in the issue of ITEM is underway. The basic idea is to use biconical antennas all the way from 30 — MHz and position them close to the normal placement for RE measurements, but put a paddle behind the antenna.
In an unlined chamber and the paddle stopped, this would be equivalent to the MIL-STD test method prior to , where unlined test chambers were the norm, and any RE measurement was in fact a mode-tuned measurement, except a single mode. This means that a single frequency domain sweep over in milliseconds represents a single mode because the paddle is nearly motionless in that time period. If an unlined chamber were the basis of RE measurements, as they were prior to , there would be nothing to add to the method, because basically the paddle just captured the peaks of the constructive interferences instead of recording peaks and valleys destructive interference , as in Figures 7 from Wehling.
- Predicting storm surges : chaos, computational intelligence, data assimilation, ensembles.
- Spons architects and builders price book 2011?
- Visual Inspection Technology in the Hard Disc Drive Industry?
- Standard C++ Programming;
- Refuge Recovery: A Buddhist Path to Recovering from Addiction;
- The Imjin War: Japans Sixteenth-Century Invasion of Korea and Attempt to Conquer China.
- Intelligent Transport Systems: Technologies and Applications!
In addition to the RS changes already cited, there is a subtle change in the applicability of the requirement at the tuned frequency of a radio receiver. A little historical background. The reason for this is that the radio electronics are less exposed to the external electromagnetic environment EME than the antenna, and the radio receiver is tested with antenna port dummy loaded, so that it was clear that the antenna would conduct much more signal into the electronics than through the platform and through the radio enclosure.
One radio was tuned to the local oscillator LO of the other radio, and the LO leaked enough to couple into the victim radio. This case resulted in a change where the RS requirement at the tuned frequency of a radio was the appropriate RE limit relaxed by 20 dB. The limit basis was that the culprit would meet RE, but the intensity a few centimeters away would be higher than the limit at one meter. Under MIL-STDF, this interaction was de-emphasized, but NAVSEA surface ships had a concern for radio receivers mounted below decks far from their topside antennas but exposed to wireless networks and adjacent used handheld radio transmitters.
So there was no exception whatsoever at the tuned frequency of a radio for this Service and application. For Navy equipment, RS is applicable at the tuned frequency unless the antenna is permanently attached to the equipment being tested. The reason for this is that on Navy installations, the antenna may be situated a far distance from the receiver, so these services want the test to apply to a receiver. Since the exemption at the tuned frequency is installation dependent, it may be extended to other systems as tailoring to this standard with procuring activity approval.
Therefore, during the test, responses when RS is at the tuned frequency are allowed.
And the oscilloscope single-event bandwidth is updated to MHz from the previous MHz, even though the limit itself is unchanged. ITEM , p16ff. Javor has worked in the EMC industry for over 30 years. He is a consultant to government and industry, runs a pre-compliance EMI testing facility, and curates the Museum of EMC Antiquities, a collection of radios and instruments that were important in the development of the discipline, as well as a library of important documentation. Your email address will not be published.