ETS-Lindgren 94456 User Manual

Model 94456

Archived 6/1/10

Current Probe

MANUAL

© EMC TEST SYSTEMS, L.P. – MARCH 2002 REV B – PN 399265

94456-5

MODEL 94456 CURRENT PROBES

Archived 6/1/10

EMC Test Systems, L.P. reserves the right to make changes to any product described herein in order to
improve function, design or for any other reason. Nothing contained herein shall constitute EMC Test
Systems, L.P. assuming any liability whatsoever arising out of the application or use of any product or
circuit described herein. EMC Test Systems, L.P. does not convey any license under its patent rights or the
rights of others.

© Copyright 2002 by EMC Test Systems, L.P. All Rights Reserved.

No part of this document may be copied by any means

without written permission from EMC Test Systems, L.P.

E-MAIL & INTERNET

[e-mail]
http://www.ets-lindgren.com

USA

1301 Arrow Point Dr., Cedar Park, TX 78613
P.O. Box 80589, Austin, TX 78708-0589
Tel [phone] Fax [phone]

FINLAND

Euroshield OY
Mekannikontie 1
27510, Eura, Finland
Tel [phone]
Fax [phone]

SINGAPORE

Lindgren RF Enclosures Asia-Pacific
87 Beach Road
#06-02 Chye Sing Building
Singapore 189695
Tel [phone] Fax [phone]

© EMC TEST SYSTEMS, L.P. – MARCH 2002
REV B – PN 399265

MODEL 94456 CURRENT PROBES

Archived 6/1/10

Table of Contents

INTRODUCTION.........................................................................................................1

PRINCIPLES OF OPERATION..................................................................................2

CIRCUIT.......................................................................................................................2

SENSITIVITY.................................................................................................................3

CORE SATURATION AND INTERMODULATION ................................................................3

TRANSFER IMPEDANCE.................................................................................................4

INSTALLATION..........................................................................................................5

EQUIPMENT SETUP .......................................................................................................5

INSTALLATION .............................................................................................................6

TYPICAL TEST CONFIGURATION.........................................................................7

PRECAUTIONARY MEASURES...............................................................................8

OPERATION................................................................................................................9

SIGNAL MEASUREMENT ...............................................................................................9

Oscilloscope Use – In terms of RF Amperes ............................................................9

In Terms of dB Above One Microampere at Meter Input (CW Conducted

Measurements)........................................................................................................9

In Terms of dB Above One Microampere per Megahertz at Meter Input (Broadband

Interference Measurement)....................................................................................10

In Terms of Microampere in Test Sample Lead (CW Conducted Measurements)....11

In Terms of Microampere per Megahertz in Test Sample Lead (Broadband

Interference Measurement)....................................................................................12

SPECIFICATIONS.....................................................................................................13

MAINTENANCE........................................................................................................15

WARRANTY STATEMENT .....................................................................................16

© EMC TEST SYSTEMS, L.P. – MARCH 2002
REV B – PN 399265

MODEL 94456 CURRENT PROBES

Archived 6/1/10

© EMC TEST SYSTEMS, L.P. – MARCH 2002
REV B – PN 399265

MODEL 94456 CURRENT PROBES Introduction

Archived 6/1/10

INTRODUCTION

The ETS-Lindgren EMCO brand Model 94456 RF Current
Probe is a clamp-on RF current transformer designed for
use with Electromagnetic Interference (EMI) Test
Receivers/Spectrum Analyzers, or with any similar
instrument having a 50 Ohm input impedance, to determine
the intensity of RF current present in an electrical
conductor or group of conductors.

The Current Probe provides a means of accurately
measuring net (common mode) radio frequency current
flowing on a wire or bundle of wires without requiring a
direct connection to the conductor(s) of interest. The Model
94456 Current Probe is simply clamped around the test
conductor which then becomes a one turn primary winding,
with the current probe forming the core and secondary
winding of an RF transformer. Measurements can be made
on single and multi-conductor cables, grounding and
bonding straps, outer conductors of shielding conduits and
coaxial cables, etc.

© EMC TEST SYSTEMS, L.P. – MARCH 2002 1
REV B – PN 399265

Principles of Operation MODEL 94456 CURRENT PROBES

Secondary Winding

Noise Currents

Primary (Test Sample Lead)

Archived 6/1/10

PRINCIPLES OF OPERATION

The RF Current Probe, Model 94456 is an inserted-primary
type of radio frequency current transformer. When the
probe is clamped over the conductor or cable in which
current is to be measured, the conductor forms the primary
winding. The clamp-on feature of this probe enables easy
placement around any conductor or cable.

CIRCUIT

The circuit is that of a radio frequency transformer as

Electrostatic
Shield (Case)

illustrated below:

Output to Coaxial Cable
50 Ohms Impedance

Figure 1. Basic RF Transformer

Since the current probe is intended for “clamp on”
operation, the primary shown in Figure 1 is actually the
electrical conductor in which interference currents are to be
measured. This primary is considered as one turn since it is

2 © EMC TEST SYSTEMS, L.P. – MARCH 2002
REV B – PN 399265

assumed that the noise currents flow through the conductor
and return to the source via a “ground” conductor such as a
frame, common ground plane, or earth. On some current
probe models the secondary output terminals are resistively