A spectrum analyzer is a graphic representation of the levels (amplitude) of the frequencies of an audio signal. In the graph, the horizontal axis refers to the frequencies, while the vertical axis refers to the amplitude and is read from left to right. We are having a reading of low, medium and high frequencies. For the same, if in the graph we see a dip in the part of the bass means that the sound has more energy at low frequencies.
Usually, the spectrum analyzers show all the frequencies that are within 20Hz to 20kHz (the audible range of the human). This tool is usually very easy to understand and its use will help you a lot when it comes to mixing since it can help you identify some problematic frequencies within your mix or simply give you more information about a specific sound. Something that is highly recommended is to use the spectrum analyzer to compare your songs with more professional ones; this will help you to be able to graphically identify what is missing or what is left over from your productions. It is essential that you keep in mind that your best ally will be your ear.
How to use a spectrum analyzer
It is controlled by pressing the FREQUENCY button and attributes such as:
Central frequency, Start frequency, Stop frequency.
- START FREQ: indicates the lowest frequency that can be shown on the screen (bottom left of the screen).
- STOP FREQ: indicates the highest frequency that can be shown on the screen (bottom right of the screen).
- CENTER FREQ: indicates the frequency located in the center of the screen, i.e., between START FREQ and STOP FREQ
- CF STEP SIZE: indicates the value by which the center frequency can be altered, once the keys are pressed
- STEP (Arrows).
- FREQ OFFSET: this value will be added to all previously mentioned frequency values.
How to control them
o Press FREQUENCY, a menu will appear on the right side of the screen.
o Choose the desired attribute with the corresponding key.
o Finally enter the new value with the numeric keys, always remembering the units.
It will allow controlling the frequency range shown on the screen that will be symmetrically “distributed” around the center frequency.
The process for its modification is simpler than the frequency since with just pressing SPAN, this value will appear on the screen and can be changed with the numeric keypad, as well as the rate.
CONTROL OF AMPLITUDE
It allows handling the values of certain attributes such as:
attenuation of the entrance, vertical scale, reference value, etc.
- REF LEVEL: is activated when you press AMPLITUDE, and it will be the highest amplitude value that can be displayed on the screen.
- ATTEN: allows you to set the value of the input attenuation between 0 and 60 dB, in 10 dB increments. This function reduces the power level of the input signal.
- LOG dB /DIV: allows establishing the vertical scale in logarithmic units, between 1 and 20 dB per division.
- LINEAR: changes the units of the vertical scale from dBm to Volts, setting the reference value to the top of the
screen and the bottom of it on 0 Volts.
- REF LVL OFFSET: allows adding an offset voltage to the reference value.
Modification of Amplitude Attributes
o Press AMPLITUDE, a menu with the attributes will appear on the right side of the screen.
o Select the desired attribute using the corresponding button; the attribute will appear on the screen.
o Enter the new value through the numeric keypad, remembering the units.
(Note: the REF LEVEL attribute will not appear in the menu, but will appear on the screen, and will be active when AMPLITUDE is pressed.)
Pressing MKR will have access to a menu, which will appear on the right side of the screen, from which you can control the properties of the markers (Markers):
- NORMAL MARKER: activates a marker in the center of the screen and on the active signal. The marker can be moved with the rotary knob, the STEP (Arrows) keys.
- MARKER DELTA: activates a second marker, in the same position as the first marker. The second activated marker is the only one that can move.
- MARKER AMPED: The marker will always remain at the desired amplitude, regardless of changes in the input.
- MARKER PAUSE: Stops the scan of the analyzer at the marker position. To reactivate the sweep enter zero sec.
- MARKERS OFF: Deactivates, delete all active markers from the screen.
(Note: Amplitude and frequency values will appear in the upper right corner of the screen
corresponding to the position of the marker.)
In the example of the photograph we can see the receiver ER55, of modular type and with several ranges of frequencies between which it can be used:
or ER55C: 9KHz-30MHz (used for conducted disturbances)
or ER55R: 39MHz-1000MHz (used for radiated disturbances)
or ER55CR / 2.8: 9KHz-2800MHz (used for conducted and radiated disturbances up to 2800MHz)
We see that it will be better to take the greater frequency range, since we expand the spectrum area where we can use it, and we can use them to measure both conducted and radiated disturbances.
The ER55C can be upgraded to ER55CR by adding the necessary hardware and software modules to authorized service centers. In the same way, the ER55CR model can be updated to increase its frequency of use. The modularity of the ER55 receivers represents an advantage in case of future modifications in the standards.
All EMI ER55 receivers are controlled by PC with the help of software for WINDOWS.
The software allows the operator to set all the parameters specified by the CISPR16 and even modify them according to their requirements and needs. Some examples are:
- Frequency range
- Detectors (peak, Near-Peak, Medium Value), and delay time.
- Limits according to European standards and other standards.
- Antenna correction factors.
- The positioning of the turntable
- Control of the absorbent clamp (3D graph showing the levels of disturbances concerning the frequency and position of the clamp)
The software incorporates functions to save time during the tests as data storage procedures and parameters in files (measurements, frequency tables, antenna correction tables).
The ability to memorize the system is unlimited thanks to its PC control.
Availability of customized software to communicate with turntable controllers, masts, …
- SPECTRUM ANALYZER MODE
The EMI ER55 receivers have an ultra-fast peak detector, allowing operation in analyzer mode for pre-certification evaluations. The parallel port communication protocol guarantees a fast exchange of data between the PC and the receiver.
- MANUAL MODE
Manual Mode allows you to monitor a selected frequency to capture sporadic events.
The software has specific files for each equipment that can be traced according to national and international standards, by the requirements of CISPR 16-1.
- COMPLETE RANGE OF ACCESSORIES
According to your needs, a complete range of accessories such as LISNs, Antennas, Clamps, probes … are available
- LISNs (Line Impedance Stabilization Network) for an average of conducted emissions from 9KHz to 30 MHz
- Biconical or logo periodic broadband antennas, for measurements between 30 MHz and 1000 MHz according to the standards.
- Absorption clamps for measurements of radiated interference in cables, from 30 MHz according to specifications of EN50014
- Tension probes to be used in those cases where it is impossible to use a LISN, for example in situations of high intensities.
- Loop antennas for magnetic field media from 9KHz to 30 MHz according to EN55015.
- Probes of the near field for pre-certification of radiated emission measurements. Very useful for R & D measures
The EMI receivers of the ER55 Series include Quasi-peak Detector according to the first section of the CISP16-1 and an Average detector according to clause 23, Section four of the CISPR16.
The response of the quasi-peak pulse detector (absolute calibration) is by Table 2 of clause 2.4.1 of CISPR16. The response of the quasi-peak detector to repeated pulses (relative calibration) is within limits specified in Table 3 of clause 2.4.2 of the CISPR16.
The limits ± 1.5dB or ± 2.0dB are met up to the minimum frequency of repeated disturbances from the EUT (1 Hz). The ten tuned presets guarantee more than 40dB of attenuation for intermediate frequencies and intermodulation effects.
In the following table, we have the technical specifications of the ER55C, used for conducted disturbances.
|Frequency Settings||50Hz (9KHz-150KHz)
|Setting Error||<3×10 -6|
|RF Input||BNC 50 W (9KHz-30MHz)|
|VSWR Input||<2: 1
<1.5: 1 with preamplifier
<1.2: 1 with attenuator
|Preselector 9KHz-30MHz Fixed filters||9KHz-150KHz
|Max. Input||127dB m V|
|Intermediate Frequency||153.22MHz 10.7MHz 455KHz|
|(IF 200Hz) (IF 9KHz)
<-10dB m V <0dB m V
<-13dB m V <-3dB m V
<-20dB m V <-10dB m V
|Measuring error||± 1.5dB max.|
|Demodulation||AM / FM|
|Display Measure Level||-20 to 120dB m V|
|Press Spectral Density||90db m V / MHz|
|Image Freq. Rejection||85dB Typ.|
|Intercept Point d3||| f2-f1 | ³ 100 kHz
level f1, f2: -10dBm
end <2MHz: 8dBm typ
fin> 2MHz: 15dBm typ
|Delay Time||2ms to 60s|
|Display Units||dB m V, dB m V / m, dBm, dBpW, dB m A / m|
|Interface||Bidirectional 8 bit Parallel Printer Port|
|PC Requirements||IBM compatible, Pentium 120MHz or above 16Mb RAM (min) Operating System: Win95 / 98|
|Power Supply||110/230 Vac ± 10% 50 / 60Hz|
|Operating Temperature||0 ° to 45 ° C|
|StorageTemperature||-20 ° to 70 ° C|
|Size (WxHxD)||450x135x436 mm|