ESCO Technologies ETS-Lindgren 7405 Скачать руководство пользователя страница 35 | Manualshive

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ESCO Technologies ETS-Lindgren 7405 Скачать руководство пользователя страница 35

www.ets-lindgren.com

Common Diagnostic Techniques

35

C

OMMON AND

D

IFFERENTIAL

M

ODE

C

URRENT

F

LOW

From the local perspective of the unit, this is a common mode situation;
EMC/EMI problems may be classified principally as current-related or
voltage-related. Current-related problems are normally associated with
differential mode situations. Likewise, voltage problems are normally associated
with common mode circuit situations. Too often solutions are attempted before
the radiating parameter is understood. Unfortunately, solutions effective for
differential mode are seldom effective against a common mode problem.

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Содержание ETS-Lindgren 7405

Страница 1: ...Model 7405 Near Field Probe Set User Manual...

Страница 2: ...ii www ets lindgren com...

Страница 3: ...ight 1996 2022 by ETS Lindgren Inc All Rights Reserved No part of this document may be copied by any means without written permission from ETS Lindgren Inc Trademarks used in this document The ETS Lin...

Страница 4: ...ormation Bulletin 10 2 0 Maintenance 11 Service Procedures 11 3 0 Specifications 13 Model 7405 13 Preamplifier 13 4 0 Operation 15 Typical Configuration 15 Probe Selection 16 Preamplifier Use 17 5 0 T...

Страница 5: ...niffer Probes 32 Diagnosing Radiation Causes 33 Common and Differential Mode Current Flow 35 Differential Mode Techniques 40 Common Mode Techniques 42 Pre Screening Alternate Solutions 43 Evaluating A...

Страница 6: ...amage Included text gives proper procedures Warning Denotes a hazard Failure to follow instructions could result in SEVERE personal injury and or property damage Included text gives proper procedures...

Страница 7: ...ht weight and compact The probes provide a fast and easy means of detecting and identifying signal sources that could prevent a product from meeting federal regulatory requirements This set is a conve...

Страница 8: ...ch creates a balanced E field shield of the coax shield The loops reject E field signals due to the balanced shield Electric E Field Probes The Model 7405 includes two E field probes the stub probe mo...

Страница 9: ...ich serves as an E field pick up The absence of a closed loop prevents current flow allowing the ball probe to reject the H field STUB PROBE The model 905 stub probe is made of a single piece of 50 oh...

Страница 10: ...Lindgren Product Information Bulletin See the ETS Lindgren Product Information Bulletin included with your shipment for the following Warranty information Safety regulatory and other product marking...

Страница 11: ...with your shipment Maintenance of the Model 7405 is limited to external components such as cables or connectors If you have any questions concerning maintenance contact ETS Lindgren Customer Service...

Страница 12: ...12 Maintenance www ets lindgren com This page intentionally left blank...

Страница 13: ...5 GHz 903 1 cm loop H Field 11 dB 2 3 GHz 904 3 6 cm ball E Field 30 dB 1 GHz 905 6 mm stub tip E Field 30 dB 3 GHz Preamplifier Absolute Maximum Ratings Input Voltage DC 12 VDC Input Voltage AC 20 d...

Страница 14: ...14 Specifications www ets lindgren com Environmental Storage and Operating Temperature 0 C to 45 C 32 F to 113 F...

Страница 15: ...shipment Typical Configuration 1 Choose the appropriate probe from the Model 7405 Near Field Probe Set See Probe Selection on page 16 2 Connect a coaxial cable from the probe to the signal analyzing d...

Страница 16: ...are the most sensitive of the E field and H field probes The stub probe and the 1 cm loop are the least sensitive The frequency of the signal If the signal is above 790 MHz the probe may go into reso...

Страница 17: ...ing This kind of refinement provides the ability to stop the radiation at the source rather than shielding an entire unit Preamplifier Use The optional preamplifier increases the sensitivity of your t...

Страница 18: ...18 Operation www ets lindgren com This page intentionally left blank...

Страница 19: ...e probe the field amplitude may be obtained All probes in the Model 7405 Near Field Probe Set were characterized in a transverse electromagnetic mode TEM cell which presented a 377 ohm field The H fie...

Страница 20: ...20 Typical Performance Factors www ets lindgren com Magnetic H Field Probes 901 6 CM LOOP...

Страница 21: ...www ets lindgren com Typical Performance Factors 21 902 3 CM LOOP...

Страница 22: ...22 Typical Performance Factors www ets lindgren com 903 1 CM LOOP...

Страница 23: ...www ets lindgren com Typical Performance Factors 23 Electric E Field Probes 904 BALL PROBE...

Страница 24: ...24 Typical Performance Factors www ets lindgren com 905 STUB PROBE...

Страница 25: ...www ets lindgren com Typical Performance Factors 25 Preamplifier Gain 0 01 MHZ 3 GHZ...

Страница 26: ...26 Typical Performance Factors www ets lindgren com This page intentionally left blank...

Страница 27: ...ielded room Final qualification must be performed in the required test environment of a screen room or an open field site However a great deal of preliminary EMI testing can be done with a sniffer pro...

Страница 28: ...MHz The challenge is to find the EUT function that created the emissions You may be able to connect the probe to a spectrum analyzer and locate the source locating the source of an emanating signal be...

Страница 29: ...tune to the signal of interest This essentially changes the spectrum analyzer into a tuned receiver and makes the display a frequency filtered oscilloscope 2 Take the video output off the spectrum ana...

Страница 30: ...produce the observed event and also allows greater facility in recognizing the original signal from the altered and often distorted modulated representation Frequently the demodulated picture will co...

Страница 31: ...rather roll off the offending components What you have done is mentally transform a frequency domain failure to a time domain picture that you can work on After identifying what the signal of interes...

Страница 32: ...signal source Finding both the point of escape from the unit and the actual source provides choice in engineering the solution you may decide to improve the shielding or to suppress the source The mo...

Страница 33: ...This section addresses using sniffer probes for a rough estimate of field impedance which is used to diagnose the radiation physics of a given situation Knowing the field impedance can help find solu...

Страница 34: ...mode Electric fields require high impedance sources Because the changing potential is isolated by substantial impedance on all lines into the circuit all lines will carry just the forward current The...

Страница 35: ...incipally as current related or voltage related Current related problems are normally associated with differential mode situations Likewise voltage problems are normally associated with common mode ci...

Страница 36: ...hrough an H field probe Low impedance sources also will give a higher reading in the near field on an H field probe than on an E field probe Alternately high impedance sources will display a rapid fal...

Страница 37: ...ation would record two points at 0 5 meters and 1 5 meters from the source along two radials from the source The signal is measured at each point with a probe which is highly selective of the H field...

Страница 38: ...behaved Often the best indicator is the relative amplitude The E field probe will have a much higher reading than the H field probe The drop off rate will be faster when measured with the E field pro...

Страница 39: ...is predominately electrical or E field In this case the field impedance is relatively high A high field impedance means there is a potential build up across some impedance and this high potential regi...

Страница 40: ...common mode situations When differential mode solutions are applied to a common mode problem many of the techniques will prove ineffective For example Reducing circuit loop area The radiating signal...

Страница 41: ...umber of gates Therefore suppression of any one of these gates in isolation will not yield much signal reduction Shielding the entire loop A problem arises when deciding where to ground the shield The...

Страница 42: ...not work in differential mode situations Once a common mode problem is determined use techniques which have a good potential for success Start by analyzing the ground and power distribution system Und...

Страница 43: ...eduction technique has been correctly applied and indicates when you have properly analyzed the problem to the point of designing an effective solution Testing alternate solutions can save time when t...

Страница 44: ...f the distance from the source 1 R However the reactive component will fall off proportionate with the reciprocal of multiple powers of the distance from the source 1 RN Typically the reactive field w...

Страница 45: ...iate the received field altering the field being measured However technical imprecision does not necessarily eliminate a method Sometimes an attenuation of the field strength in the near field will tr...

Страница 46: ...e what the far field results will be most of the points should be one to four meters away Also choose one or two points close to the source If a solution results in a dramatic reduction this point may...

Страница 47: ...afety margin For example suppose a signal fails the required limit by 3 dB Once that signal is found in the lab it can be measured in the near field The goal is then to reduce in this near field the 3...

Страница 48: ...s involved such as a second source radiating at the same frequency Example A solution that worked in the lab and on the range before 10 00 AM failed later in the day Analysis revealed that the rise in...

Страница 49: ...www ets lindgren com EC Declaration of Conformity 49 Appendix A EC Declaration of Conformity...

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