Some time ago I was asked on an investigation if I had equipment to detect the presence of a spirit reported to be next to a Medium, at that time I answered no, but I also realised the EMF meter, commonly used by paranormal investigators was extremely unlikely to be affected if a spirit was present.

EMF meters are designed to detect the presence of an alternating, electrically generated, magnetic field from domestic mains wiring, no connection with the spirit world.

It did Encourage me to think how would you detect the presence of a spirit with little energy of its own?
My answer is to monitor and measure changes in a weak, self generated energy field.
What type of energy field to monitor? After research and experiment I settled on four-

Electric, Magnetic, Sound/vibration and Laser light

The Energy Change Detection System (ECDS) generates the four energy fields and
indicates any detectable changes of those energy fields on LED displays and through an audio tone indicating any change of an individual energy field.

I will also use this on future psychokinesis tests.