TriField Natural EM Meter Modification

The TriField Natural EM Meter is a popular meter in the area of paranormal research as it detects changes in extremely weak static (DC or "natural") electric and magnetic fields while ignoring AC fields.

The meter is best used in a static position due to it's high sensitivity. The unit includes a handy adjustable tone which signals an alarm when a pre-determined level is reached. Some sources of additions to the base unit including an AC power pack and input port, as well as an output jack. See

The TriField uses an analogue meter to indicate levels, when reading magnetic fields the meter reads true for microteslas, multiply by 10 for milligauss. When reading electric fields you multiply readings by 10 to get volts/meter.

The first thing we wanted to add was a digital display which could easily be recorded on a nearby DVR camera. Our meter did not come with an output jack so we soon added one, enabling readings up to 620mV to be sent from the unit via a 3.5 mono plug. This feed could easily be sent to a AD Convertor for computer logging or interfaced to a stand alone logger such as the MultiLog PRO.
TriField meter modification
We sourced a meter resolving down to 0.001V, taking 5 readings per second and drawing from a separate power supply for the display. It was a relatively quick project to put it all together in a box with 9volt battery, switch, meter and 3.5mm mono input plug. In testing the unit we found the meter required no calibration to match the analogue display of the TriField.

Ideas for expansion would be to add a trimpot/variable resistor for easy calibration to various instruments, and a rotary switch to shift the decimal point to reflect what is being measured eg. microteslas, milligauss or volts/meter.

This of course can be done manually -
Reading magnetic fields: Multiply digital readout by 100 to give microteslas or 1000 for milligauss. Eg. .200 = 20 microteslas = 200 milligauss. Reading electric fields: Multiply digital readout by 1000 to gets volts/meter. Eg .100 = 100 v/m.

Further information/discussion may be found in the Tech Bench board of the GRI Forum.

K-II meter modificationThe same project could be done to allow use with the K-II meter however this would require adding an output jack and calibrating the display to actual mG readings from another meter. Alternatively this could be fed to an AD Convertor for computer logging.
Further details on adding an output jack to the K-II and use of a meter can be found in the tech bench thread on the GRI Forum.