Hello Nickfry08!
The calibration on a Dura ABS Meter is to adjust for differences in viscosity. This means variation in products as well as product temperature. I generally recommend running a cool weather and a warm weather calibration for each chemical. Since the meter can store up to 5 calibrations, you could be set for 2 chemicals per meter over the course of a season. It all depends how much accuracy you want vs how much viscosity variation you will see over your application period. For most, two times a season will get you great accuracy. Don't hesitate to reach out with any additional questions, and thanks for considering Dura Products! Check out the new FastBatch Multijet https://duraproducts.com/fastbatch-multijet/