Mil-std-461g pdf download

Figure 6. The testing phase applies the test current to each of the interface cables and to the power cable, including and excluding the power return and ground. Polyphase power leads are classified for test as a group. A monitor current probe is placed 5-cm from the interface connector and the injection current probe is 5-cm from the monitor probe.

The positioning prevents the induced current from being returned by the parasitic elements without flowing in the equipment circuitry.

Prior to test, a calibration sweep is accomplished to record the forward power required to produce a calibration current defined by the applicable curve. Figure 7 shows the calibration configuration with the interfering signal source drives the injection current probe to induce current in the calibration fixture with a measurement receiver used to measure the induced current.

The coaxial load closes the loop to allow induced current to flow. The signal source is tuned over the test frequency range and the forward power is recorded to be used as the maximum power to be applied during test.

After the calibration, the configuration is changed to attach the measurement receiver to the monitor probe and the load is placed at the measurement receiver location to maintain a closed loop. The forward power recorded during the calibration is now used as the level to inject the calibration current again and now the monitor probe should measure the calibration current. This step verifies that the monitor current probe is operating correctly recall that periodic probe calibration is not required by MIL-STDG, so this step provides a thorough check of the monitor probe.

After the calibration process, the probes are placed on the cable selected for test. The signal source is adjusted to the start frequency and the amplitude to the lesser of the test current or calibration setting for that frequency. Modulation is applied and the test frequency range is scanned with frequency steps and dwell times meeting the standard with consideration for EUT parameters requiring longer dwell times.

If susceptibility is observed, the threshold of susceptibility should be determined to quantify the non-compliance. It is instinctive to attack problem resolution through filter connectors, filter inserts or cable shielding to reduce current in the wiring. However, before applying cable control measures, verify that the issue is not from radiation. Since the test is simulating radiated interference inducing current, it is logical that inducing a current would create radiation from the cables.

To eliminate radiation from the cables as the culprit, placing a temporary shield over the EUT and if the threshold of susceptibility sees a significant change consider that a chassis aperture may be the path for the susceptibility signal. CS testing applies to most installations except ships and submarines, unless that applicability is specified in the procurement contract. Transients normally have a broad spectral energy content and parts of the spectrum capacitively and inductively couple to adjacent cables, inducing transient current in the victim cable.

Once the waveform calibration is complete, the injection probe is placed 5 cm from the monitor probe, which is 5 cm from the EUT connector. The pulse generator is enabled, and the amplitude is set to the calibration level.

The impulses are applied at a 30 Hz rate for 1-minute while the EUT is monitored for susceptibility. The applied current is recorded, and photographs of the applied waveform are captured for the report. Note that the waveform appearance may differ from the calibration because of the cable effects. If the waveform appears to be upside down, turning the injection probe over will tend to present a positive going pulse to be more like the expected pulse. Susceptibility issues often use filter connectors or filter inserts as the primary means to mitigate the problem.

Transient suppressor inserts can be beneficial in reducing the energy applied to the affected circuitry. CS is applicable to all services and equipment with electrical cables egressing the chassis exiting the pressure hull for submarines.

The dampening results from cable resonances or to other voltage or current resonances coupled to the cable. Various test frequencies are used to simulate a wide range of potential resonances, and if a known resonant frequency is critical to the platform, that frequency is added to the list of test frequencies.

Testing can be accomplished with a sine or cosine waveform as indicated in Figure 9 with the peak current Ip meeting the test level. The dampening factor Q is set to be 15 with the calibration configuration. The calibration process involves applying the test signal to the injection probe and adjusting the peak amplitude to the calibration current. The frequency and Q are verified, the waveform generator settings are recorded, and the waveform photos taken for the report.

This process is repeated for each test frequency. The waveform generator is enabled, and the amplitude adjusted to produce the test current without exceeding the calibration level. The damped sine transients are applied at a 0. The standard indicates that the calibration setting be applied at the start of testing and then lower if the current is excessive. If the characteristic impedance of the circuit is low or unknown, the application of the calibration setting could damage the EUT so use caution to prevent over-stressing the EUT.

If susceptibility is observed, resolution typically uses transient suppressor or suppressor inserts to limit the high voltage or current applied to the sensitive circuitry. If susceptibility is noted only after the test has been running for several seconds or minutes, consider that the suppression device may be over-heated and is not limiting the voltage or current properly.

This could indicate that the suppressor rating may be inadequate. It has limited applicability, usually related to safety-critical equipment cables or non-safety critical equipment connected to safety-critical equipment.

The test approach is similar to CS, with a variety of waveforms selected by the coupling method allowed by the installation and includes multiple stroke and multiple burst lightning events. The test levels are significantly higher than CS The test waveforms are based on current or voltage with one being the test target value and the other providing a limiting function.

In the calibration configuration see Figure 11 , adjust the WF1 to the designated test current IT with the shorted loop setting and verify the waveform parameters.

Using the open loop setting, adjust the WF2 to the designated test voltage VT and verify the waveform parameters. It is not required that the current or voltage limit IL or VL be verified, but if the generator can attain those levels, record and verify the waveforms. After the waveform levels and parameters are verified, configure the EUT cable under test through the current monitor probe and injection transformer and adjust the generator output to the test level or until the limit level is attained.

If the limit is reached before the test level, the acceptability is evaluated as follows:. Multiple stroke and multiple burst testing are applied to the testing for each of the defined waveforms. Transient suppressors are the primary means to protect sensitive circuity from the effects of the induced lightning.

Cable shields and installation wire routing to prevent the coupling are potential solutions, but many applications do not support these approaches. Two methods of discharges are used for the evaluation.

Contact discharges are applied to conductive surfaces and air discharges is required only if the contact discharge cannot be applied. Prior to test the signal integrity checks refer to Figure 12 are accomplished to verity the ESD simulator performance.

After the signal integrity checks are complete, EUT testing can proceed while maintaining the standard test configuration Test points are selected based on accessibility with a minimum of each face being a test point. At conductive test points, use the contact discharge method at 8 kV by placing the simulator tip in contact with the test point then firing the discharge while monitoring the EUT for susceptibility.

Apply five positive and five negative discharges to each test point. If the simulator fails to discharge, use air discharge testing for that test point.

Air discharges are applied with a charged tip moved perpendicular toward the test point no faster than 0. Between discharges, remove the residual charge by grounding the point through a resistor or waiting until the charge dissipates. Testing is to be accomplished at each of the defined voltages with five positive and five negative discharges at each test level.

ESD issues typically are managed through positioning of sensitive circuits in a manner that separates the circuit from the discharge path, including the radiated field associated with the discharge. Filtered connectors or filter inserts reduce the potential for cable coupled discharges. RE has limited applicability with the focus on systems that have devices sensitive to magnetic fields that operate at low frequencies.

The purpose is to measure magnetic fields for compliance with the applicable limit reducing the risk of interference to other devices. Two limits are included in the standard, but as with any emissions limit the system compatibility requirements could prompt tailoring the limit.

In this case a known signal level is applied to the antenna cable planned for use during test and that signal is measured to confirm proper measurements. Note that the antenna is not present for the injected signal testing, but the measurement receiver should apply the antenna conversion factors, so the injected signal level should be 6 dB below the limit and less the antenna factor. The measurement system software will add the antenna factors so the resultant measurement should be 6 dB below the limit.

A second step of the signal integrity check involves measuring the antenna DC resistance to confirm that the coils of the loop antenna are not open or shorted. Testing involves placing the loop antenna 7-cm from the EUT face and measuring the field with the antenna oriented parallel to the EUT face and perpendicular to the ground plane base.

At the location of maximum emissions, the plane of the antenna is varied to obtain the maximum reading. The standard prompts the test engineer to measure at least two frequencies per octave below Hz and three frequencies per octave above Hz.

If over-limit emissions are presented, the antenna is moved away from the EUT to determine the distance where the limit is met. This information may support acceptance of the over-limit condition for applications that do not have magnetically sensitive components near the EUT.

Resolving magnetic field emission issues may use filter connectors or filter inserts if the cable current is the source of the emissions. Reducing the current may aid in emission reduction, but in many cases the current is necessary to perform the function. However, if the switching speed can be slowed, the transient current will help reduce emissions.

Shielding is another means of containing the emissions and the use of ferrous metals as the shield material may divert the flux lines through the shield and reduce the distance of the field. RE is applicable to all services and applications with various limits covering the frequency range of 10 kHz to 18 GHz based on the application. The test purpose is to measure the electric field for compliance to the applicable limit, reducing the risk of interference to other devices.

The test begins with the usual signal integrity check. In this case a known signal level is applied to the antenna cable planned for use during test though any amplifiers, filters or attenuators and that signal is measured to confirm proper measurements. Note that the antenna is not present for the injected signal testing, but the measurement receiver should apply the antenna conversion factors so the injected signal level should be 6 dB below the limit and less the antenna factor.

A second step of the signal integrity check involves measuring a radiated field from a stub radiator. The stub radiator is typically a coaxial cable with a short length of the cable shield removed so it acts like a monopole antenna. The level of the radiated signal is not defined but detection of the signal via the antenna is required. Some laboratories construct a fixed radiator and always use the same drive level to obtain consistent measurements during this part of the signal integrity check.

Once the signal integrity checks are complete, testing can begin by placing the antenna 1-meter from the test boundary at the specified elevation.

Note that the 1-meter is from the test boundary, not from the ground plane. The test boundary is the area with the EUT and the associated 2-meters of exposed cables, normally cm from the ground plane front.

With the antenna positioned, the receiver is swept over the test frequency range measuring the peak emissions in equivalent rms terms. Specific antennas are called out for various frequency ranges with positioning requirements described in the standard. Figure Multiple Antenna Position Arrangement. As mentioned earlier, several limits are provided in the standard with limit tailoring employed if system integration plans identify a need for special treatment.

Many of the limits shown have a lower frequency of 2 MHz which supports the test frequency range for that application. When working a multi-service application that calls out a 10 kHz lower frequency range, avoid the inclination to extend the limit to 10 kHz at the 2 MHz level. The 10 kHz to 2 MHz range should meet the application limit for that range, even if it is dis-continuous. If over-limit emissions are detected, resolution is usually required.

Several methods are used once the source and point of radiation are determined. If cables are the escape point, adding filtering is often the initial approach with filter inserts providing a quick answer. If the chassis is the escape point, either suppressing the signal source or improving the shielding are typical resolution approaches.

RE may be used as an alternative for CE when testing transmitters with their intended antennas or if the antenna impedance curve is non-standard. The test frequency range is based on the operating frequency range of the EUT with test start frequencies specified. The limit is suppression of 80 dB from the transmit fundamental frequency except for the 2nd and 3rd harmonics.

The 2nd and 3rd shall be suppressed to dBm or 80 dB from the fundamental whichever requires less suppression. Special applications may vary these suppression levels. If different measurement system hardware is used for various frequency ranges, signal integrity checks for those configurations are also necessary.

Testing is accomplished in the far field with the distance calculated from EUT and measurement system antenna physical parameters and the transmit frequency wavelength. The operating frequency of the EUT determines which far field formula is used to calculate the distance. Measurements start with confirmation of the transmitter effective radiated power ERP by using a power monitor, if feasible to insert a power monitor, adding the antenna gain and converting the power measurement to dBW.

With the EUT in transmit mode, tune the measurement receiver to the transmit frequency for the maximum measurement. Align the transmit and receive antenna to maximize the measurements. Record the measurements and the measurement receiver bandwidth note that the standard bandwidth setting in MIL-STDG is replaced by the optimum bandwidth to maximize the transmit signal and the signal to noise ratio.

If power monitor measurements are not feasible, then determine the ERP from other methods for the comparison. The tuning of the EUT is often the cause of ERP disagreement, so make sure that the transmitter is operating at the rated power. Make sure that the compliance limit is aligned with the ERP and adjust the limit if necessary. Data item requirements are also included. Basic Search. Text Search. Data updated: 24 Nov Document Details. Document ID:. This standard establishes interface and associated verification requirements for the control of the electromagnetic interference EMI emission and susceptibility characteristics of electronic, electrical, and electromechanical equipment and subsystems designed or procured for use by activities and agencies of the Department of Defense DoD.

The amplifier is air cooled using internal The EMC Partner MIL Military Test System is a military and avionic modular test system offering technicians their choice of couplers, which allow easy expansions to fulfill an array of requirements.

These test systems are It meets the most stringent requirements for certification measurements in line This weaponization of the EM spectrum is known as electronic warfare. This table outlines the different MIL-STD test procedures and their applicability to equipment and subsystems installed on major military platforms and installations. Conducted emissions refer to EM energy generated by a system or device and transmitted through its power cord via an electric current.

Radiated emissions, on the other hand, refer to the unintentional generation of EM energy from a system or device.

MIL-STDG CS is applicable to equipment installed on surface ships, military aircraft, space systems and launch vehicles and military ground platforms and installations. It is limited in applicability to submarines. MIL-STDG RS is applicable to equipment installed on surface ships, submarines, military aircraft, space systems and launch systems and military ground platforms and installations.

This table lists the standard's test procedures in the left-hand column and brief descriptions of each procedure in the right-hand column.