VPD is based on LST not ambient temperature. That's important if you're using LED's because LED don't heat the grow space the way that incandescents do (for better or for worse). You can get LST using an IR thermo gun - $20 at Amazon.
If a chart works for you, go wit that but f you've got the budget, go
here and send them $$. I bought a PulseOne and, at first, was somewhat unconvinced of the value - VPD is just RH and temperature on a curve so I thought it would be fine to fiddle with the Inkbird heat sensor and the Inkbird RH sensor to dial in the right VPD. Sure, that works but how much time do you want to spend year after year after year doing something that a dumb machine will do? That's my perspective but that's because…
I've been a programmer for 30 years, including three years at Apple, and the
value of what the Pulse does is
far higher than the price. I've attached a screenshot.
The Pulse does not (yet) tie into the Inkbird controllers but it makes it a lot easier to get VPD in the ballpark. I have zero connections to Pulse other than a customer.
