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CS114 Analysis SettingsUsing EMI Analyst to perform method CS114Analyses for MIL-STD-461

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Use EMI Analyst to Perform CS114 AnalysesCS114 has conditional injection levels1. Inject the power drive level recorded during pre-test calibration

or…2. Inject twice the specified current limit,

…whichever is reached first

Settings for EMI Analyst are shown on the following page.For more details, read on…

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EMI Analyst Settings for CS114 Dual LimitThe CS114 current limit is entered using the Limit property form

Injected power level is defined using the Threshold property form

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CS114 Limit Curves Map Directly to EMI Analyst Limit Form Limit Form Settings MIL-STD-461 CS114 Limit Curves

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Threshold Form Settings Capture CS114 PropertiesSettings• Option

• Pretest Calibration – Closed Loop Method

• Calibration Fixture Impedance• 100 ohms

• Pretest Units• Watts or dBm

• Margin Units• Same units as Limit form (dBA)

• Margin• 6 (dBA)

Threshold Form

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CS114 Settings Explained• Limit Form• The Limit form contains information about the CS114 current limit.• Values entered on the Limit form table are vertices of the CS114 current limit.

• Threshold Form• The Threshold form contains CS114 injection power level. Power levels are

determined by driving current equal to the current limit through a test fixture whose series impedance is 100 ohms.• When the Pretest Calibration – Closed Loop Method is selected, power levels

shown on the Threshold form are injected on the cable while monitoring induced current.• For CS114, if induced current limit exceeds Limit form values by more than 6 dB,

injected power is reduced.

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What is CS114?Method CS114 is a conducted susceptibility test method specified in MIL-STD-461D, E, F, and G.

• The basic concept is to simulate currents that will be developed on platform cabling from electromagnetic fields generated by antenna transmissions both on and off the platform.• An advantage of this type of requirement is that it provides data that can be directly

related to induced current levels measured during platform-level evaluations.

(from MIL-STD-461F, paragraph A.5.13)

This type of test is often considered as a bulk current test since current is the parameter measured. However, it is important to note that the test signal is inductively coupled and that Faraday's law predicts an induced voltage in a circuit loop with the resultant current flow and voltage distribution dependent on the various impedances present.

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CS114 Requirements Can Be ConfusingWhat CS114 says:(from paragraph 5.13.2 of MIL-STD-461F)

The EUT shall not exhibit any malfunction, degradation of performance, or deviation from specified indications beyond the tolerances indicated in the individual equipment or subsystem specification, when subjected to an injection probe drive level which has been pre-calibrated to the appropriate current limit shown in Figure CS114-1 and is modulated as specified below. The appropriate limit curve in Figure CS114-1 shall be selected from Table VI. For EUTs intended to be installed on ships or submarines, an additional common mode limit of 77 dBμA is applicable from 4 kHz to 1 MHz on complete power cables (highs and returns - common mode test). Requirements are also met if the EUT is not susceptible at forward power levels sensed by the directional coupler that are below those determined during calibration provided that the actual current induced in the cable under test is 6 dB or greater than the calibration limit.

What CS114 Means:1. Record the power level needed to generate

the Limit current in a standard test fixture.2. Inject the test signal on each cable bundle

using the lesser of:A. The recorded power levelB. Two times the limit current

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Pretest Calibration(from MIL-STD-461F, pargraph 5.13.3 and 5.13.4)

1. Place the injection probe around the center conductor of the calibration fixture.

2. Terminate one end of the calibration fixture with a 50 ohm load and terminate the other end with an attenuator connected to measurement receiver A.

3. Set the signal generator to 10 kHz, unmodulated.

4. Increase the applied signal until measurement receiver A indicates the current level specified in the applicable limit is flowing in the center conductor of the calibration fixture.

5. Record the "forward power" to the injection probe indicated on measurement receiver B.

6. Scan the frequency band from 10 kHz to 200 MHz and record the forward power needed to maintain the required current amplitude.

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Test Procedure(from MIL-STD-461F, paragraph 5.13.3 and 5.13.4)

1. Place the injection and monitor probes around a cable bundle interfacing with EUT connector.

2. To minimize errors, maintain the same signal circuit that was used for calibration between the attenuator at the calibration fixture (oscilloscope, coaxial cables, bulkhead connectors, additional attenuators, etc.) and connect the circuit to the monitor probe. Additional attenuation may be used, if necessary.

3. Locate the monitor probe 5 cm from the connector. If the overall length of the connector and backshell exceeds 5 cm, position the monitor probe as close to the connector's backshell as possible.

4. Position the injection probe 5 cm from the monitor probe.

Perform the following procedures on each cable bundle interfacing with each electrical connector on the EUT including complete power cables (high sides and returns). Also perform the procedures on power cables with the power returns and chassis grounds (green wires) excluded from the cable bundle. For connectors which include both interconnecting leads and power, perform the procedures on the entire bundle, on the power leads (including returns and grounds) grouped separately, and on the power leads grouped with the returns and grounds removed.

(continued on next slide)

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Test Procedure(from MIL-STD-461F, paragraph 5.13.3 and 5.13.4)

1. Turn on the EUT and allow sufficient time for stabilization.

2. Susceptibility evaluation.a. Set the signal generator to 10 kHz with 1 kHz pulse modulation, 50% duty cycle.b. Apply the forward power level determined under 5.13.3.4b(4) to the injection probe while

monitoring the induced current.c. Scan the required frequency range in accordance with 4.3.10.4.1 and Table III while maintaining

the forward power level at the calibration level determined under 5.13.3.4b(4), or the maximum current level for the applicable limit, whichever is less stringent.

d. Monitor the EUT for degradation of performance during testing.e. Whenever susceptibility is noted, determine the threshold level in accordance with 4.3.10.4.3 and

verify that it is above the applicable requirement.f. For EUTs with redundant cabling for safety critical reasons such as multiple data buses, use

simultaneous multi-cable injection techniques.

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CS114 Test Method and Current Limit

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Calibration Fixture(from MIL-STD-461F, paragraph A.5.13)The calibration fixture with terminations is a 50 ohm transmission line. Since the injection probe is around the center conductor within the fixture, a signal is being induced in the loop formed by the center conductor, the two 50 ohm loads, and the structure of the fixture to which the 50 ohm loads are terminated. From a loop circuit standpoint, the two 50 ohm loads are in series, providing a total loop impedance of 100 ohms. Because of the transmission line configuration, inductance effects are minimized. Measurement of induced current levels is performed by measuring a corresponding voltage across one of the 50 ohm loads. Since the 50 ohm loads are in series for the induced signal, the total drive voltage is actually two times that being measured.The actual current that appears on a tested cable from the pre-calibrated drive signal depends on the loop impedance associated with the cable and the source impedance characteristics of the drive probe and amplifier. If the loop impedance is low, such as would often result with an overall shielded cable, currents greater than those in the calibration fixture will result. The maximum required current is limited to 6 dB above the pre-calibration level.

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