EM-7530 | Meter, Magnetic Field Strength
Specifications
Electrical
Frequency Coverage: 20 Hz-50 kHz
Bandpass-Determining Filters:
20, 100, 200, 500 Hz
1, 2, 5, 10, 20 kHz
Special Features
•
•
•
•
•
•
Full operation from either front-panel
controls or from computer via GPIB for
maximum versatility.
Special compact highly-sensitive magnetic
sensors sharing EM-7530 front-end circuits
for measurements previously not feasible.
LCD readout of magnetic field strength
directly in dB (pT) for optimum accuracy,
plus analog meter for monitoring amplitude
response.
Push-button LED-indicated choice of nine
lower-limit and nine upper-limit bandpass
cutoff frequencies for enhanced analytical
capability.
Lower Limit (High-pass @ -3 dB):
100, 200, 500 Hz
1, 2, 5, 10, 20, 50 kHz
Upper Limit (Low-pass @ -3 dB):
60 and 180 Hz
50 and 150 Hz, optional
Selectable Notch Filter:
40 dB minimum rejection at each frequency
with MF-01
Sensor Probe: 13 dB (pT/ Hz)
Sensitivity: 20 Hz-50 kHz: 60 dB (pT)
Amplitude Accuracy: Within ± 2dB
Amplitude Indicators:
Digital: 3-digit LCD showing magnetic field
strength in dB (pT)
Analog: 1-inch uncalibrated, for relative
response
Push-button LCD-indicated selection of
notch filtering at fundamental and third
harmonic of power line frequency to
eliminate power frequency problems.
Internal rechargeable battery for
independence from external power
sources and enhanced application to site
surveys.
Ref: 100517
Specifications subject to change without notice.
Unless otherwise specified, product is manufactured in
Johnstown, NY USA.
ELECTRO-METRICS | 231 Enterprise Road, Johnstown, New York 12095
tel: 518-762-2600 | fax: 518-762-2812 | email: info@emihq.com | www.electro-metrics.com
EM-7530 | Meter, Magnetic Field Strength
Specifications
Continued
Analog Output: Type BNC, with output corresponding to frequency and amplitude of probed
magnetic field
Rear-Panel Connectors:
IEEE-488: 24-pin, for GPIB connection
External DC Input: 3-pin, for connection of 40 VDC power
AC: 3-prong, for connection of AC power
Power Requirements:
AC: 105-130 VAC, 50-60 Hz
210-260 VAC, 50-60 Hz
DC: Internal rechargeable battery pack operating for approximately six hours before recharge Or
External DC supply of 40 VDC @ 800 mA
Mechanical
Physical Characteristics:
Height: 133 mm (5.25”)
Width: 222 mm (8.75”)
Depth: 368 mm (14.5”) less handles
Weight: 9 kg (20 lbs.)
Environmental Capabilities: Designed to meet MIL-T-28800C Type III, Class 5 Style E
environmental requirements
Temperature:
Non-operating: -40°C to +75°C
Operating: 0°C to +50°C
Relative Humidity:
95% from 10°C to 30°C
75% from 30°C to 40°C
45% from 40°C to 50°C
ELECTRO-METRICS | 231 Enterprise Road, Johnstown, New York 12095
tel: 518-762-2600 | fax: 518-762-2812 | email: info@emihq.com | www.electro-metrics.com
Specifications
Continued
Altitude:
Non-operating: 12,000 m (40,000 ft.)
Operating: 3,050 m (10,000 ft)
Vibration: 2 g
Shock: 30 g
Sensor Probes:
Furnished:
MF-01: Maximum sensitivity; calibrated for fields 60-120 dB (pT)
Optional:
MF-02: Calibrated for fields 100-160 dB(pT)
MF-04: Uncalibrated for localizing sources
MFEF-01: Active Calibrated E-Field Sensor
ELECTRO-METRICS | 231 Enterprise Road, Johnstown, New York 12095
tel: 518-762-2600 | fax: 518-762-2812 | email: info@emihq.com | www.electro-metrics.com
EM-7530| Meter, Magnetic Field Strength
Continued
Description
The EM-7530 Magnetic Field Meter is designed specifically to measure low-level magnetic fields at
frequencies from 20 Hz to 50 kHz, in accordance with procedures and limits mandated by MIL-STD461, MIL-STD-462, and other EMI-compliance documents, both military and commercial.
The EM-7530 differs from the EM-2110A and other interference analyzers covering the same
frequency range in that, in lieu of continuous selective tuning, it provides broadband operation with
bandpass characteristics controlled by selection of low-pass and high-pass cutoff frequencies. Also,
the EM-7530 is designed for operation with special magnetic field sensors which incorporate frontend elements to provide superior sensitivity and directional characteristics despite their small size.
These differences permit applications not possible with other instrumentation and make the EM-7530
ideal for investigation of magnetic field leakage and other detailed analysis of EMI radiated magnetic
fields. In addition to the standard MF-01 probe furnished with the instrument, three optional sensor
probes, as covered on page 6, are also available for use with the EM-7530.
Microprocessor control of all operating functions and digital outputs for all responses to input signals
permits the EM-7530 to be exercised completely either from its front panel or from an external
computer, via the IEEE-488 General Purpose Interface Bus (GPIB). The numerous parameters
available for control and monitoring are illustrated and described on the following paragraphs.
Basic operating principle of the EM-7530 is that of a variable-magnetometer, with its response directly
proportional to the strength of the field being intercepted by the sensor being used. The ferrite
material in the sensor exhibits a change in permeability with any change in the strength of the
magnetic field in which it is immersed. This change in permeability is used to affect the inductance of
an element in the oscillator tank circuit located in the sensor, thus producing a shift in output
frequency corresponding to any change in the magnetic field. The FM signal thus produced by any
timer-varying magnetic field present is then demodulated and calibrated to obtain a voltage
proportional to magnetic field strength; it is then used for front-panel meter display and converted to
produce a digital output. Frequency response of the servo circuit used to feed the analog voltage
back to the sensor for stabilization is tailored to make EM-7530 operating independent of the earth’s
magnetic field.
The EM-7530 has excellent stability and front-panel/remote control for selection of passband, notch
filters, gain, and attenuation. The selected passband limits are displayed in kHz on a digital LCD
panel meter. Signal amplitude is displayed both on a three-digit LCD panel meter calibrated in dB (pt)
and as a relative level on an analog meter. Noise floor of the EM-7530 over its operating range of 20
Hz to 50 Hz is lower than 4.5 pt/ Hz, or 13 dB(Pt/ Hz).
ELECTRO-METRICS | 231 Enterprise Road, Johnstown, New York 12095
tel: 518-762-2600 | fax: 518-762-2812 | email: info@emihq.com | www.electro-metrics.com
EM-7530| Meter, Magnetic Field Strength
Description
Continued
The EM-7530 is complementary to the Electro-Metrics EM-2110A Interference Analyzer and can be
used with it as a special sensor. In this mode of operation, the EM-7530 provides its highly-sensitive
wide-band, flat frequency response (with power-frequency notch, if desired) for intercepting magnetic
fields, while the EM-2110A provides the frequency selectivity, tenability, and detector functions
appropriate for analyzing them.
Several unique advantages of the EM-7530 make it the ideal choice for a variety of
applications:
•
Near-Field Measurements
Although valuable for measurements of magnetic fields at any location, the compact size of the
probes which are an integral part of the EM-7530 makes it particularly suited for the measurement of
magnetic fields in confined spaces and within the “near-field” region of an emitter, where the electric
and magnetic components are usually neither planar nor orthogonal.
•
Narrowband and Broadband/Impulsive Measurements
Broadband measurements can be made without any auxiliary equipment, using the low- and highpass filters built into the front end of the EM-7530 to establish the passband of interest. Where
narrowband measurements of magnetic field are required, such as to establish degree of compliance
to limits of MIL-STD-461, the EM-7530 must be augmented by a selective voltmeter or EMI analyzer,
such as the EM-2110. However, the EM-7530 provides a unique advantage when used in this fashion
in that the combined response with its associated sensor probe is flat versus frequency over its entire
range of operation.
•
Advantage over Loop Sensors
The flatness of response obtained when using the EM-7530 avoids two unfortunate consequences of
using loop sensors: the drastic fall-off in sensitivity at low frequencies and the resultant differentiation
and distortion of any impulsive signals. Thus, the EM-7530 with its flat response becomes the ideal
instrument for characterizing the structure of any magnetic field, regardless of both near- or far-field
considerations and the type of emission being measured.
Use of the optional current probe applies the EM-7530 advantages to the measurement of EMI
currents. It provides high sensitivity and its flat response over the entire frequency range from 20 Hz
to 50 kHz avoids the differentiation of impulsive signals.
These inherent advantages make the EM-7530 the ideal instrument for certain specific applications
such as measurement of shielding effectiveness, especially at frequencies below 500 Hz. Its superior
sensitivity permits the use of lower power in the transmitting source for such measurements, and the
compact size of its probes permit more detailed mapping of the topology of the shielding barrier
leakage field.
ELECTRO-METRICS | 231 Enterprise Road, Johnstown, New York 12095
tel: 518-762-2600 | fax: 518-762-2812 | email: info@emihq.com | www.electro-metrics.com
ELECTRO-METRICS | 231 Enterprise Road, Johnstown, New York 12095
tel: 518-762-2600 | fax: 518-762-2812 | email: info@emihq.com | www.electro-metrics.com