Section 100 Content Consideration
Spectrum and Field Analysers and Receivers
This section contains our active measuring devices such as spectrum and field analysers and receivers, both tunable and broadband. Some are battery powered but most are mains powered.
Within the first subsection, you will find Electromagnetic field Analysers. Decide first whether you wish to work with a spectrum analyser or a spectrum receiver. Very basically, the attributes are that Receivers are more accurate in reading level and frequency (when synthesized) especially with specific detector functions but take much longer to gather the data over a given range. They generally exhibit a good degree of pre-selection (tuning before the mixer) which prevents front-end overload and are likely to be relatively more sensitive.
On the other hand, the conventional spectrum analyser generally has little or no pre-selection, tends to be insensitive and their accuracy falls somewhat short in amplitude & sometimes frequency. However, they have one striking advantage and that is to display the complete range of interest in a single presentation. The price tag for all of this is of course resolution. What you are in fact seeing is a prescribed number of data points per sweep, generally in the region of 400 or so, regardless of how wide the frequency span is. This enables the operator to instantly see what is going on in that chosen spectrum. The spectrum can then be narrowed down to give a better resolution on the area of interest. A further expansion of this is the peak-hold facility which enables sporadic signals to be eventually caught & displayed.
However, when capturing data over a given period of time the observer is unable to deduce exactly when any given signal appeared. If during a surveillance programme the end user does wish to know the timing of random signals then running the field analyser under control of our software (which can also be hired pre-loaded on a laptop) will facilitate this. To offset the insensitivity, pre-amplifiers can be used in front of the field analyzer and can be found in section 400.
If you are fairly new to EM measurements one of our staff will be pleased to help you make the choice. In general, operating any of the spectrum analysers or spectrum receivers with a laptop is preferential and avoids the learning time in getting to grips with some complex front panels.
This deals mainly with the laptop computers that are available with our already configured software. The computers are Dell “Lattitude” C600, 14-inch screen, 1GHz processor speed devices and have their own case which comes complete with an installed PCMCIA card, IEEE interface cable and a security plug programmed with a hundred timed runs during your hire period.
On long hires we will set higher run figures or they can be reset by the end-user when provided with a code. You will have noticed that you may hire the laptop & software alone, item 125. This enables the customer who already has the equipment necessary to form a system but maybe without any form of automation. The other peripherals are a small HP 340 mains printer and couple of portable accumulator powered AC supplies which will give about 2 amps at 240vac for about four or more hours, (Equivalent to running a laptop; an Analyser & pre-amp for about two and one-half hours.
Broadband Electric & Magnetic Sensors
These deal mainly with the industry range of field analyser probes used in shielded rooms & cells to measure the volts/metre field strength for EN61000-4-3. They are all essentially extremely broadband and therefore the end user will only read the field level and not the frequency unless already aware of the transmission.
When selecting a particular system, you will need not only the field sensor probe but the interface with it so that you can discern the levels either visually or over the GPIB. Probes are found under the brand names of EMCO; AR; Holaday; Narda and Wandel & Goltamann. Check the frequency range is compatible. All probes and readouts come complete with fibre optic cables.
Health & Safety Instrumentation
This is mainly devoted to the low frequency (up to 400kHz) element of the magnetic spectrum commonly encountered in industrial environments with some measurements on the electric component. Again, these are essentially broadband. Two other “E” field walkabouts are available in this group including a microwave sensor which can be carried in the pocket. The end user must decide whether the sensor should be orthogonal or not. There are handheld devices and more sophisticated units with a better accuracy.
Nearly all require the pertinent field to be sinusoidal except item 170 which will measure DC & AC fields of relatively high values. A few devices will strictly measure only 50Hz ±5Hz and no more. We hope you find sufficient data by reading the specification under each item number.
Most of these devices are just handheld walkabouts to give the end user an idea of the EM field environment. A typical application would be monitoring the effect near power lines or industrial RF heat welders, etc. Checks on buildings being sited near some transformer sub-station or near a transmitting station or microwave link. Decide if there is a need to know the plane of polarization or if you only wish to know the overall RMS value.