What device is used to measure the properties of the electromagnetic spectrum?

Answer 1

Several actually,

There is no one single device used to measure the entire electromagnetic spectrum since it runs from gamma rays through visible light, down through microwaves an radar, to radio and TV waves and finally to long waves.

Signal detectors like radio direction finders are used to detect the lower bands of the spectrum, everything from radio waves on up. Specialized ones are used to detect wi-fi hot spots. A radio it self can be used to detect signals simply by tuning it. There are detectors that look for television signals and electronic bug detectors. Then you move on up to microwaves where special detectors are designed to operate.

Once you get into the microwave and infra red spectrum then you get a detectable temperature change. Electronic probes using a simple transistor can be used to detect radiation at this level, as well as normal thermometers and laser thermometers. Our eyes and cameras can detect visible light waves. We also know that since elements burn with a specific set of colors on the visual spectrum it is possible to analyze elements and compounds by burning them and studying the colors given off. This is most often done in spectrograph machines, but you can also hook one up to a telescope to see what kind of elements are in stars and hot gases.

Up in the higher band of the ultraviolet spectrum we can no longer see the light, but we can design detectors that can and with a little computer processing we can convert that radiation down to the visible light spectrum. A plastic model of a structure put under stress will show the lines of force and areas of stress under an ultraviolet lamp, making it useful in architecture and engineering.

Then we move up into the x-ray and gamma ray spectrum where we use geiger counters to detect the radiation.

In most of these machines we use a transistor as the actual detector. A transistor tuned to a specific wavelength can detect that wavelength when exposed to it by electronically closing a switch and allowing the circuit that sounds an alert to be activated. The strength of that circuit can be used to measure the amount of this radiation.

Long wave detectors are rarely used because it takes so long between each wavelength and there was little use for it. Then the US Navy discovered that these signals were one of the very few radiations that could piece water and so contact submarines. It takes a long time to send a signal so usually the only signal sent is “call home.” Use of this is safe since it is broadcast and doesn’t betray the location of the submarine. The message could be received and even decoded by an enemy, but a simple “call home” message has little value. The Navy knows that the signals can be received world wide so they don’t send sensitive or classified material over this band width. Instead they tell the submarine to send up an antenna and contact their home base for a detailed message. The submarine commander does this at his own discretion and location to keep the location of the submarine secret.

The primary detection system for the electromagnetic spectrum is the transistor and it is used in many devices, but it is not the only item used and the transistor has to be set to a specific band, there is no universal detector.

These websites list some examples of radiation detectors.
http://www.medcom.com/
http://hps.org/publicinformation/ate/faqs/radiationdetection.html
Some EM detectors:
http://www.google.com/products?hl=en&rlz=1T4WZPA_enUS224US224&q=electromagnetic+detector&um=1&ie=UTF-8
http://scientificsonline.com/product.asp?pn=3082080&bhcd2=1192996992
Here is a do-it-yourself circuit:
http://www.electronics-lab.com/projects/science/006/index.html
The symbol that is a circle with three wires running into it and an arrow inside is the symbol for a transistor.

The website lists four electrical tools to measure electromagnetism: capacitor, magnetic, piezo, and resistive: http://www3.alps.co.jp/sensor/index-e.html?gclid=CJi_1trloI8CFTyKOAodNhdmVg

Answer 2

A spectrometer which is used to classify materials based on their electromagnetic characteristics.