Hello
I’ve gone through the performance data for the T200 thrusters.
More particularly the RPM vs PWM data, which i tested and got different values of RPM when i measured them using a laser tachometer. How accurate is the give performance data? Is there something else i need to take into account rather than simply correlating PWM and RPM ?
Edit: I tested the T200 thrusters @14V where i gave a PWM of 1680, which should correlate to a RPM of 1817 But my Tachometer measures ~3000 RPM.
Hi @Ruthless,
It sounds like you are measuring the RPM at no load in air. The RPM in our testing data in measured at load underwater at bollard (static) thrust conditions.
Note the warning regarding running the thrusters dry on the T200 product page:
Do not operate the thruster for extended periods out of water. The bearings are lubricated by the water and vibration and noise will be greater when dry.
Our thrusters should not be run dry in air for more than a second or two.
Please read the testing notes in the Excel document with the full data, in particular the final note is relevant here:
• RPM is a resultant of the given the load on the thruster by the propeller/input voltage at static conditions; the Basic ESC is an open loop control system. There is no direct relationship between ESC PWM input and RPM.
-Adam
Yes i did run the thrusters in air. I feel terrible for not reading that warning.
Thank you for clarifying the open loop control.
However is it safe to assume that given a particular PWM input, i would get uniform RPMs when the same signal is given to multiple thrusters?
No problem, happy to help.
If the thrusters are experiencing the exact same conditions in terms of water flow, supply voltage drop, etc., then yes, the resultant average RPM should be roughly the same.
-Adam