The K-II meter was designed to find electrical wires behind walls. When electricity is flowing through wires, it generates a magnetic field. The K-II detects this magnetic field and alerts the user with LED lights.
Frequency is how many times per second the electricity cycles in the unit of Hertz (or Hz). This means that 50Hz the electricity cycles 50 times per second. Since electricity around the world operates at either 50Hz or 60Hz, the K-II is dialed in at 95% accuracy for 50Hz-60Hz. Although it can read as high as 20,000Hz the accuracy for that number of cycles is less than 5%.
The sensing antenna on the K-II meter is actually built into the circuit board. It is a square spiral located mid-way on the bottom of the device called a co-planar loop. Popular belief is that the sensor is at the tip, however this is not true.
What does this mean for ghost hunting?
When an investigator is holding the K-II meter and pointing it at something, they are holding with the antenna in the palm of their hand. This will significantly limit its range and accuracy.
Since the K-II meters antenna is located mid-way on the bottom, the proper way to hold a K-II is tip-up with the bottom of the meter facing out from your body. Imagine you're holding it against the wall looking for electrical wiring (the same way you would hold a stud finder against the wall).
The K-II is a single axis meter. This means it can only read one axis of the 3 axis available. If you are just looking for basic EMF reading, this is sufficient. If you are looking for direction or total strength, for example if a spirit is with you somewhere in the room, you would need a tri-field meter or other 3-axis meter like the PICCOLO by Ghost Gear.
A note about EMF phone apps: At least for the Apple iPhone, they do not work. Apple has blocked the access to the built in EMF detection. No developer can access it. Any EMF meter app on the market is a hoax.
Should paranormal investigators use K-II meters?
Paranormal investigators have been using the K-II for a long time now. I personally don’t use a K-II in my ghost hunting adventures. I use a tri-field meter. This 3-axis meter gives accurate readings. You can get direction and maximum strength with this kind of device.
Paranormal investigators should be aware of their surroundings and identify devices that can generate low-frequency EMF. Kitchen appliances, electric motors, or space heaters are some items to be weary off. Not every instance of the K-II going off is paranormal.