Conversion of ppm on Oakton SaltTestr to a saturated paste equivalent

The Oakton Waterproof SaltTestr is an EC meter with a design similar to the old Oakton TDS tester 4 — it has two metal probes extending out from the end of the meter (photo comparing TDS testers and Spectrum Field Scout probes). These meters are designed for use in water but they can also be used to directly measure soil salinity. However, due to the resistance to electron flow caused by soil particles between the the electrodes, a conversion equation…