Virtual cadence change with grade change

In training mode when grade increase the displayed cadence decreases even though my actual has not. Just the opposite for negative grade - displayed cadence increase with constant actual pedal. This makes cadence matching to the training plan difficult (almost impossible). Any ideas how to address this? Thanks

Set up -
Kurt kinetic Smart Control
Zwift running on pc with iPhone zml bridge
Erg mode on

How do you measure your cadence, if it is measured at the trainer then that is the reason why you see this happening. The trainer estimate your cadence based on power and wheel speed. if you want true cadence you need a cadence sensor at your crank. 

Yes. Cadence is being measured at the trainer. According to Kurt they calculate cadence based on pedal torque as felt by the resistance unit. So, I was hoping for better displayed data. Still seemed odd that the cadence would change based on grade. My understanding was in training mode with ERG that grade is not reflected in the plan - is that incorrect?
None the less, I have ordered a crank cadence sensor to see if it works better.

Yes the road grade is not simulated in workout mode, I would suspect that subconsciously you pedal harder when the road goes up. If you have a very smooth pedal stroke then the trainer will have a hard time determining what your cadence is. If you want accurate cadence then the crank sensor will be your best bet.

It is nice to know why it happens. I can’t use the workout modes as the fact that it changes resistance inversely up/downhill drives me crazy. I’ve gone old school and only use the ET timer from Zwift for my workouts. I now let my Wahoo ELEMNT take care of my power range training levels, instead of the Zwift HUD.

I bought a Wahoo crank mount sensor. Wow, what an improvement. Cadence is now actually showing what I am pedaling and no longer am I seeing the cadence being affected by grade when I’m in workout mode. Definitely a worthwhile expense!