Vortex Sound Research

So I’m currently trying to calibrate my BIA using a multimeter (as described in the manual). I have a 4 digit multimeter. I feel like I might need a 5 digit for this task, but they are quite a bit more expensive than what I have now. (Anyone know of a reasonably priced five-digit?)

I followed the instructions precisely and still am a number of cents off going up an octave. I ran into similar issues with my DPO, albeit a different calibration process.

The BIA manual says a better method is to use a Peterson 490 strobe tuner…. That’s probably not going to happen :/

What is the expectation for tuning across a couple octaves. Is it unreasonable to expect being fairly spot on? Any tips in general?