Skeptics Stack Exchange is a question and answer site for scientific skepticism. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

There are a couple of Android apps to detect EMF (for ghost hunting and for hazard-protection). I tried a free one which did not work. Some I can't seem to download. Has anyone tested them (against a fan, microwave or magnet, etc.) and see if it really works and is accurate at all?

Here are the ones that claim to be work.

Ghost Hunter (EMF, EVP, SCAN) $0.99

Entity Sensor Pro $9.99

I know it might be dependent on phones, too, but it is acceptable if it works on any phone.

Edit: Please do not be distracted by the mention of ghosts in this question. The question is about EMF only, not ghosts. Since these apps are mostly used for ghost-hunting, I have listed them. My question is these apps can detect EMF and, if so, how accurately?

share|improve this question
Three problems I have with this question (and so I voted to close as "not constructive): 1. What proof is there that ghosts emit/cause EMF effects? 2. What proof is there that ghosts are real? 3. How can others verify what "seems to be working" (e.g., which brands and models of phones did you use in your tests, as jwenting just commented about more generally)? – Randolf Richardson Nov 15 '11 at 7:55
@Randolf, I think 1 and 2 are not relevant. If Android phones cannot detect EMF in the first place (and these apps are just generating random answers), they don't matter. Note the OP asks about testing them against known EMF sources, not ghosts. – Oddthinking Nov 15 '11 at 9:09
ghost hunting is just use, which ok is another topic. The question is can it detect EMF from Microwave etc. I have stated in the question I know it might be dependent on phones so I know it is hardware dependent. But the question is, are these software scams or not. – Believer Nov 15 '11 at 14:24
As I understand it the EMF sensor in all android gets overload by known sources as it is meant only to detect trace amounts. So these apps really work but only on real ghosts. So if you see a ghost but it does not show up on the emf sensor its just a hoax. – Chad Nov 15 '11 at 22:04
@jwenting: the fact that ghost do not create EMFs ( (electromagnetic fields), as they do not exist, does not mean EMF do not exist either. – nico May 19 '12 at 9:10
up vote 23 down vote accepted

Yes, but not in a way that is likely to detect Ghosts if they exist

Mobile phones are, by definition, devices that can detect EMF (which is electro magnetic field see wikpedia) since their ability to communicate depends on radiofrequency fluctuations in EMFs. So apps on a smartphone can, at least in a trivial sense, detect EMF and alter it when they send a signal. Unfortunately, mobile phones are designed to detect only specific frequencies from about 800 to 2.2 GHz which are the frequencies of 2G and 3G cellular phone systems (see wikipedia again). It seems unlikely that software can turn them into devices that can detect general fluctuation in EMFs.

Some apps claim to use the magenetometers to detect EMF. And stand alone EMF detectors seem to be calibrated in units like milliGauss (see here for an example) which is a measure of magnetic field strength (wiki definition). This suggests that the sort of EMFs sought are low frequency changes in magnetic fields. So perhaps this is more likely to work as that is just what magnetometers can do. However, there are many many sources of interference that alter the background magnetic field of the earth (which is what magnetometers detect) as anyone who walks around a built up area while using the compass app on their phone will know. Large steel-framed buildings, cars, iron lamp-posts all cause major field changes that overwhelm the background field. As one useful site on sensors reports:

The magnetometer is commonly found on mobile devices such as smart phones and tablets, but it is one of the most difficult sensors to interpret. It is commonly called a compass since it measures the strength of the magnetic field in three dimensions, but does not necessarily point north. In fact magnetic interference can cause it to behave unpredictably, as often seen in augmented reality apps.

Even the believers don't seem to take the idea of detecting ghosts via phones seriously. This app claims it is is "just for fun". This discussion (I think fairly characterised as taking place on a believer site) dismisses the idea that phones can be reliable ghost detectors.

So, yes phones can detect EMF. But ghost detection apps are likely just reporting random background noise.

share|improve this answer
I think testing such an App against a real magnetometer placed next to a fan will clarify if these Apps are scams or just for fun. – Believer Nov 15 '11 at 14:29
not completely, Believer. That would show whether they can detect EMF or not (at least of a very specific field type), not whether they can detect ghosts (which they claim to do). – jwenting Nov 16 '11 at 11:02
@Believer: There's a huge scale between spam and a device that uses very low quality measurements that make it unsuitable. – Christian Nov 16 '11 at 18:05
Actually ghost is out of question. That is just my own curiosity. The question it, can it detect EMF and how accurately if it can? I have tried the EMF Hazard App on a fan. It did not work. – Believer Nov 16 '11 at 20:06
+1 for "Mobile phones are, by definition, devices that can detect EMF". There's even a tongue-in-cheek "Tricorder" app for Android that shows various wireless signal strengths under "EM Spectrum". – Simon Nov 16 '11 at 22:45

They can detect magnetic fields, or are at least designed to.

If your phone doesn't have the hardware for it, you shouldn't be able to see it on the App Store (assuming it was programmed properly).

A little off topic, but they can detect humidity, pressure, temperature too, which I didn't know before this :)

share|improve this answer

protected by Community Jul 19 '12 at 14:18

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.