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Products - Frequently Asked Questions

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General - Radman - EFA 200 - ELT 400 - SRM 3000

 

General Questions & Answers

 

Q) Is it possible to use the EMR with a GPIB-interface?

A) Yes. We could recommend the RS232 GPIB converter from National: National Type GPIB-232CV-A or National Type GPIB-232CT-A. National offers different options with intern power pack (120 V, 220 V, ...) with power supply connector or DC-execution with extern power pack. Experiments to use the EMR-20 at a HP-Basic-IEC-Controller with a former model of the National converter GPIB-232CT have been successful.

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Q) I bought 4 versions of EFC-400. Do I also have to buy 4 updates for the software?

A) No, one update is enough. You may use it for all your versions of EFC-400.

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Q) I'm interested in the EFC-400 software but I would like the software in the English version and the handbook in the German version. Is this possible?

A) Yes. If you buy the CD EFC-400, you can select either the English or German handbook version. Both languages are stored on the CD. You can also order the handbook in the other language or print out the other language by yourself.

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Q) Do you have devices for measurements according to MPR II?

A) Our solutions for measurements according to MPR II are our third-party products FD1 and FD2 from Combinova.

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Q) In Spatial Averaging Function, EMR-300 can calculate 6-minute average. Can we setup the sample number? Or can we setup the sample number via PC Transfer Set?

A) Spatial and standard averaging are different things from serie P on. For standard averaging you can change the sample time between 4 sec. and 15 minutes by keyboard. The sample rate is constant 400 ms and every 4 sec, the display is freshed up.

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Q) What is the 'Test Generator (27MHz)' for?

A) Checking, if the probe/instrument is still running. The instrument does a self check when you switch it on. But this selfcheck doesn't include the sensor. So you need a source for a field which is the test generator.

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Q) How long is the operation time of dry batteries used for EMR-300? I don't know the exact time of the cells since on the datasheet displays '>15hr' of dry batteries, but I request at least 20hr operation time of dry batteries. Similarly, may I replace the cells myself in my country?

A) 30 hours are possible with dry cells. You can replace them by yourself.

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Q) On the datasheet displays 'typ. 8 h' of rechargeable batteries, but I request at least 16 hr operation time. Could you please send me rechargeable cells w/16hr when delivery? Or can I replace 8hr cells with 16hr cells myself?

A) No problem to change it, here or in your country. If it should be done here, please write it on your order. With NiMH cells it is no problem. But you also have to tell the instrument to enlarge the charging time. The necessary software (EMR-conf) is delivered with the instrument. EMR-conf is delivered with EMR free of charge. It is for the configuration of probes and cell capacity of EMR products.

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Q) Which kind of operating system is supported by programs for retrieving data from the instruments with ETS-1: DOS, Windows 3.1, Windows 95, Windows 98, Windows NT?

A) Here are the requirements for ETS-1

MS DOS version 3.1 or later

Microsoft Windows operating system, version 3.1 or later (includes 95, NT, ...)

Personal computer using at least a 50 MHz 80386 or higher microprocessor

VGA resolution (or higher) video adapter

Math co-processor or one of the following co-processor emulation programs

WEMM387.386 from WATCOM

Q387 from Quickware

Minimum of 8 MB of memory

5 MB free hard disk space

(Microsoft-compatiblemouse)

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RadMan Questions & Answers

Q) What kind of response will the electric and magnetic fields generated by electrical power lines have on the RadMan (both when worn on the body and when held out)?

A) Alarm-threshold 50 % of standard will be reached at 3 kV/m (50/60 Hz) RadMan is mounted on a tripod; oriented parallel to E-field vector = RadMan is mounted to the tripod in upright position (yellow cap at the bottom of the instrument). We tried also other positions but this was as expected the worst case condition. E-field from 50/60 Hz will be very much attenuated by carrying the RadMan at the body. So we think that it could be possible to use the RadMan also on towers of power transmission lines. We recommend in this case also the slower version of the RadMan (WTC-version) because the RadMan will react not so nervously in case of a distance between RadMan and body. Extending the RadMan to arm's length as recommended in RF sites has the opposite effect in ELF-fields. This position would lead to a field overexposure at the Radman and the alarm will go off earlier. The field overexposure is due to the reaction of ELF-fields on the geometry. The ELF-fields like points or peaks.

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Q) How does the RadMan work with peaks?Is it a mean alarm or any peak above standard limits cause a warning alarm? What about peaks which are 1/5000 of standard but high duty cycle?

A) RadMan is very fast. It is designed to detect even scanning radar signals with more or less errors. For short pulses that means it was tried to display at least 1/1000 of the peak power density in the practical range of common radar signals.

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Q) Give me information about radiation suites!I have a customer that I have been working with for some time looking at RadMan. The application that he has is for riggers that are doing maintenance such as painting on MF AM broadcast masts. He says that he has solved his problem by using 'radiation suites' that are worn by the riggers and are supposed to provide 60 dB of attenuation at 1 MHz.

1. Do these really work?

2. If they don't, is there any source of evidence that i can use to prove to the customer that he still needs the RadMan?

A) I've talked to a person who was involved in measurements on 'radiation suites'. He told me, that there are materials on the market, that could provide a high suppression of electric and/or magnetic fields as long as they are brand new and no suite is made out of them. In the moment you glue or sew a suite out of it, the technical characteristics are changing drastically!! And none of the materials can supply a reasonable suppression on magnetic fields below 50 MHz! Germany has a draft for requirements and approval of radiation suites and it looks like that the European community will take it over (DIN 32780-100). The frequency range is 80 MHz to 1 GHz. At the end of the day, also when the result of some frequencies is better, none of the suites is getting a better specification then 10 dB, in words 'ten'. For a higher specification in a German/European standard you need a lot of different requirements and test methods. The experience out of the evaluation shows, that the lower the frequency, the lower the suppression (depending on the material for the electric and/or for the magnetic fieldstrength. And a real protecting suite you need both.). So, the result of 60 dB, I don't know were it comes from. Please provide us with more information about this suites, we are very interested.Some weeks ago, there was a seminar from NSP (company who is producing radiation suites), a very big and well organized seminar. None of the user or producers of suites reported about such a high suppression.P.S.: Some time ago, suites with a high suppression were sold in the US. But they had one disadvantage: Many of them went up in flames.

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Q) Please explain in details how does the absorber cap work!

A) The absorber material in the cap compensates for body influence in the range of resonance frequency (some 100 MHz, wavelength up to 2 m). The cap is required only when wearing the RadMan close to the body. It should be removed for monitoring signals apart from the body for best isotropical response (e.g. leakage search or area monitoring). In this case the RadMan is hold in hand with the cap positioned as a handle on the bottom side of the instrument. This way the sensors are not covered by the cap. For best results the RadMan should be placed far away from the body or mounted on a tripod (the cap includes a thread for this purpose).

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Q) How are you calibrating the RadMan? Is it in close room or open field?

A) Every RadMan is calibrated in a TEM cell. Samples of RadMan are calibrated in free space to verify frequency response.

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Q) What situations could cause a false alarm?

A) Personal protection requires early alarming in case of dangerous field conditions. Therefor long averaging times (e.g. 6 minutes) are not appropriate. So the monitor will detect short peaks exceeding the limit which triggers an alarm. Also the problem of distance is important. With the personal monitor you are often much closer to a radiation source as with a measuring instrument. Because of the quadratic or cubic relationship between distance and field strength you have very close to the antenna a high field strength which is sometimes over the limits (e.g. mobile phone, TV-Sets, displays ...).

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Q) Which kind of information may be obtained by linking a computer to the optical socket of RadMan?

A) If you connect RadMan by optical link to the PC you will get ASCII values in Hex Format over the serial connector into your serial port of the PC. The ESM-TS software converts the Hex values into readable ASCII values. The software displays the measured value in % of standard, independently for the E and H field. The resolution is 0.625 % of standard from 0 % to 150 %. The rate is 25 measurements per second.

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EFA-200 Questions and Answers

Q) Give me information about measuring non-sinusoidal fields with EFAs!

A) Non-continuous, non-sinusoidal fields occur in connection with welding equipment and magnetizing equipment. Before evaluating a field measurement, knowledge of the time characteristics of the field strength and its comparison with the characteristics of the EFA is necessary.


1. Bandwidth / rise time of the measuring equipment (EFA):
The rise time of the signal under test should be larger than the settling time of the measuring instrument. For pulse envelopes of sinusoidal fields, this means that the bandwidth must be greater than the carrier frequency.

Measurement bandwidth

Rise time (10% to 90%)

3dB- Bandwidth

Broadband ...2 kHz

app. 180 us

2 kHz

Broadband ...30 kHz

app. 12 us

30 kHz

Selective ...2 kHz

app. 5 / center frequency

+/- 10% * center frequency

Due to the faster settling time selecting the measurement bandwidth 30 kHz might be the best choice.


2. Sampling rate of the measuring equipment (EFA):
The sampling rate of the measuring equipment must be high enough in comparison to the duration or rate of change of the signal under test to ensure that the signal is correctly digitized.
Measurement bandwidth

Measurement bandwidth

Sampling rate

Sampling frequency

Broadband ...30 kHz

app. 31.3 us

32 kHz

Otherwise

app. 141 us

7.11 kHz

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Q) Is it possible to get the phase angle between the amplitudes with the FFT-mode of EFA-200 /300?

A) The EFA-200 / 300 performs a correct measurement taking into account the phase of the different signals through a synchronous measurement on the three channels (X, Y and Z). With the FFT-option you don't get the information about the phase (which is also not essential for safety concerns). Anyway, the internal phase information is used for the calculation of the so called vector peak value.

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Q) How are you calibrating the RadMan? Is it in close room or open field?

A) During the measurement the reading of the spectrum can be stopped and the peaks can be evaluated with a peak marker. The spectrum can also be stored and it can be read out via PC. It is then possible to get the results in a table in a 1 Hz resolution (for the 5 Hz to 2 kHz FFT) or 10 Hz resolution (for the 40 Hz to 32 kHz FFT). Additional evaluations of the spectrums are possible with the PC software EFA-TS.

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ELT 400 Questions and Answers

Q) What measurements can I make with the ELT-400?

A) You can use the ELT-400 for all measurements in the low frequency range:
- To display the safety margin relative to a limit value curve (STD Method)
- For traditional field strength measurements
- For further analysis using an oscilloscope or FFT analyzer connected to the analog output
- To demonstrate compliance with EN50366 (domestic appliance standard).

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Q) Does the ELT-400 take the corners in the limit value curves into account in the STD Method?

A) No. The latest publications, such as EN50392, EN50366 and ICNIRP specify smoothed limit value curves just like those implemented in the ELT-400 for analyzing them.

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Q) How do I differentiate the curve shapes (e.g. harmonic overshoot)?

A) Evaluation using the STD Method is valid for all possible curve shapes, so you do not need to differentiate between signal shapes or handle them differently. If you need to see the actual signal shape, this information is available from the analog output and can be displayed on an oscilloscope.

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Q) Can I use the ELT-400 to measure radiation from monitor workstations?

A) Yes. The ELT_400 is sensitive enough to measure even very small magnetic field strengths such as those found at monitor workstations for compliance with human safety standards.

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Q) Why does the frequency range start from as low as 1 Hz?

A) This makes the ELT_400 useful for applications in heavy industry (e.g. magnetic stirrers) as well as for other important applications where this low frequency range is needed.

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Q) What should I do when measuring impulses or time-variable signals?

A) Use the Max-Hold function of the ELT-400. This continuous measurement of the ambient magnetic field yields meaningful results.

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Q) Do I need an oscilloscope to measure pulsed signals?

A) No. The ELT_400 with its STD Method evaluates all signal shapes including pulses efficiently and correctly. It can also be used to detect signal shapes not mentioned in BGV B11.

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Q) How do I display the time domain signal?

A) The ELT_400 is equipped with a 3-channel analog output corresponding to the three spatial axes (x, y, and z), so you can display each time domain signal individually using an oscilloscope.

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Q) I used a spectrum analyzer to perform a comprehensive analysis for an ICNIRP evaluation. Why does this give much higher results than the ELT_400?

A) Depending on the system, the final result of an isotropic (3-axis) peak value measurement calculated from a spectrum analysis may be significantly higher than the actual value that is displayed by the ELT_400. That is because the signal phase is not taken into account in the spectrum analysis.

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Q) What is the STD Method?

A) STD stands for Shaped Time Domain: The field strength is evaluated in the time domain. The method is described in EN50366.

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SRM - 3000 Questions & Answers

Q) What effect does the coaxial extension cable have on the measurement results from the SRM_3000?

A) The Narda STS coaxial extension cable is equipped with ferrite cores at several points along its length. These ferrite cores reduce the influence of the cable on the field to a negligible amount within the specified frequency range, so the cable has no effect on the measurement result.

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Q) What is the main difference between the antennas for the SRM_3000 and the broadband probes such as those used with the EMR_300?

A) The EMR and SRM use different technologies, so they cannot really be compared with each other. The SRM_3000 is a frequency-selective field measurement system, whereas the EMR is designed for broadband measurements. The SRM receives the high frequency signals through an antenna or antenna array and analyzes the raw signal in terms of both amplitude and frequency in the instrument itself. The EMR probes also receive the high frequency signals through an antenna or antenna array initially, but then they are converted into a DC signal by means of diodes in the probe head. The EMR therefore only measures the amplitude.

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Q) Spectrum analyzers usually allow you to set a resolution bandwidth (RBW) as well as a video bandwidth (VBW). Why is there no video filter in the SRM_3000?

A) Some modern spectrum analyzers traditionally still use so-called video filters. Since selectivity in the SRM is based on fast Fourier transformation (FFT), which simultaneously analyzes different frequencies, there is no need for a video filter. If averaging is still required, the AVERAGE function provided in all SRM-300 operating modes can be used as an alternative. You can additionally set the VBW indirectly using the RBW in Safety Evaluation mode.

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Q) SRM-3000 What frequency range is covered by calibration of the SRM_3000, and how is traceability ensured?

A) The SRM is calibrated at 20 frequencies between 100 kHz and 3 GHz (see data sheet for details). Traceability back to SI unit standards is guaranteed to comply with DIN EN ISO/IEC 17025. The cables, SRM basic unit and SRM antennas are each calibrated separately.

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Q) SRM-3000 The isotropic antenna for the SRM_3000 consists of three mutually perpendicular dipoles, a three channel switch and a coaxial cable connecting to the basic unit. Could measurement errors be caused by switching from one axis to the next?

A) A complete switching cycle in Time Analysis mode takes 120 milliseconds. This means that no measurement errors can occur as a result of switching from one axis to the next if the signal is static or changes only slowly over time in relation to the cycle duration. During switching, there is a blind time of 20 milliseconds between each axis. This is several orders of magnitude less than the blind time of a classical spectrum analyzer, which can only detect one frequency at a given point in time, thus being blind to all other frequencies.

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Q) The SRM basic unit is fitted with a multi-pole socket in addition to the standard N connector. What is this used for?

A) The multi-pole antenna plug that is provided in addition to the N connector contains, among other things, an EEPROM in which the antenna data_antenna type, correction values as determined by calibration_are stored. The same is true of the hybrid coaxial extension cables supplied by Narda STS which have the calibration data stored in the multi-pole plug. When you plug this into the corresponding socket on the SRM, the device automatically detects the antenna or cable and takes the correction values into account in the result. The multi-pole antenna plug also performs the switching operations for triaxial antennas.

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Q) What is meaning of the Measurement range configuration parameter?

A) The Measurement Range parameter is similar to the reference level of conventional spectrum analyzers. Instead of setting the attenuation (51 settings between 0 and 50 dB), you enter the maximum expected level. This is called the measurement range. The attenuation is set automatically according to the measurement range. Unlike the reference level of conventional spectrum analyzers, the measurement range does not automatically correspond to the Y-axis reference (upper limit of the Y-axis). This parameter can be set independently in the display menu.

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Q) How many spectral lines are available for a spectrum in the SRM-3000?

A) The distance between two spectral lines is around one half of the currently selected resolution bandwidth. A maximum of 6 709 spectral lines (or measurement points) is available for one spectrum.

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Q) Is it possible to set the sweep time?

A) No. The parameter called _sweep time_ is actually the time required for the measurement of one spectrum and to display it. This time depends on the frequency span that is to be covered and on the resolution bandwidth selected. A minimum sweep time must be set on conventional analog spectrum analyzers because of the IF filter settling time (the minimum sweep time is then proportional to the frequency span and to the square of the inverse of the resolution bandwidth).

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Q) How do I choose the resolution bandwidth (RBW) for measuring the channel power level?

A) A RBW equal to the channel bandwidth should be chosen if possible. A RBW higher than the carrier spacing would prevent selective analysis, and a RBW less than the channel bandwidth would require channel power processing. GSM carrier spacing is equal to 200 kHz. A RBW of 300 kHz would include the entire power of the measured channel but also part of the power from adjacent channels. A RBW of 100kHz would result in a 1.5 dB underestimation of the channel power.

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