Pulse measures the pore electrical conductivity of your medium which relates directly to the nutrients available to your plant.
Pore electrical conductivity is the conductivity, linked to the ionic strength, of the pore water stored in the soil. This is the water the plant can uptake and hence the ions that the plant has access to.
The other main type of conductivity is the bulk conductivity which is the conductivity of everything in the medium including the pore water, the soil, the roots, organic matter, air gaps, etc. This type of conductivity is very susceptible to change in moisture content so two media with identical conductivities would measure differently if one has a higher moisture level than the other.
Things to watch out for
- Pore conductivity does require there to be some water in the pores to measure, so if your moisture content goes below 20% the pore EC measurement becomes unreliable
- The pore conductivity is affected by very high ionic concentrations so when the conductivity goes past around 8.0 EC the accuracy does decrease slightly