I can see your point, exactly. I've often heard the factual argument that the equipment we use, regardless of accuracy, is no good when it comes to ghost hunting. Despite how much you calibrate, despite how accurate these devices are they simply are not created for paranormal investigation. Even your so-called "professionally" calibrated EMF detectors are utterly worthless when it comes to detecting truly paranormal activity.
So I ask you, why bother waving these things around? I mean you're own devices, despite the calibration, are worthless, or are you telling me that the lengths you took to get them calibrated allowed you to detect ghosts? It seems to me that there are no devices at all that detect ghosts, only environmental factors. So if I take a baseline reading (not paranormal) of say, .1 to .3 milli-Gauss, and later on get a fluctuation of upwards of 3 to 7 milli-Gauss, we tend to take notice of that. What would cause that? Radar emission? An errant EMF 'cloud' drifting through the area? Someone turning on a radio or a walkie-talkie? A cellphone hit? Calibration or not, since it's not picking up paranormal activity, what, exactly, is it picking up? Is the device failing and suddenly registering false positives,randomly, that fluctuate from readings taken less than an hour ago? What causes that? Clearly there is a plausible explanation and I'm not convinced that calibration is it? And how exactly do I calibrate a device to detect paranormal activity? If I can't, then you're right, I shouldn't be utilizing such devices, but what about an ion detector? an infrasound detector? an ambient temperature detector? any such electronic devices?
In short, what are the lines of demarcation?