Fan Speed Control

The PWM frequency is something like 20 kHz and the Victron is reporting at 1Hz, but may sampling a little higher than that and averaging in software. The BMV-712 current measurement doesn't jump all over the place, so it safe to assume that there is a fair amount of capacitative integration on the ADC which should provide a decent average measurement. There is also no chance of aliasing when the response rate of the sensor is several orders of magnitude lower than the PWM frequency. For the type of measurements we are talking about here it is certainly good enough.

2112 wrote:

FWC wrote:
For reference the 'classic' Fantastic Fan model 4000R draws ~ 3A on high, 2.3A on medium and 1.9A on low. Using a PWM controller, dialed in for what appears/sounds to be about the same speeds medium and low I am seeing 1.6 and 0.9A

The PWM measurements are deceiving. The fan still draws 3A during the duty cycle period. Your digital current meter is trying to average the ON periods but its sample rate is too slow to be accurate. This is called aliasing. The true average over time will be higher. No fault of your meter. It wasn't designed to accurately measure high speed pulses.

The first measurements using the "heating elements" should be accurate because this will be a steady analog signal. The "heating elements" are there to reduce current. The higher the "heating element" resistance, the lower the current.