This has worked Thanks to "Diving the World" First
adjust tank water to 35ppm with a device you know is accurate like a calibrated refractometer or float device you trust.
1 Let probe
dry in air for 24 hours
2. Begin calibration sequence with probe
fully dry. Don't get it wet at all.
3 When apex says place in 53,000 solution which is 35ppm (or very close) put
it in the tank or sump and gently agitate it to
remove air bubbles. they should
come out the small holes at the side of the probe. Move it to the holder
without taking it out of the water, and secure it in place.
4. Click next in the sequence to finish the calibration.
5.
Up-Load to the apex (not sure if this is needed but can't hurt)
6. Fusion should now read 35ppm or very close to it
Let me know if this works