The speed of motor

Build
1

when placing the thrusters in the air ，I usual use a Manual Photoelectric Digital Speed Meter to test the speed of thrusters，but when placing under the water，the machine cant work ，so，how can I test the speed for the working thruster

2

Hi wdodo,

There are other types of brushless motor RPM sensors including some that connect to a motor wire and count the pulses going to the thruster.

Here’s one from HobbyKing:

-Rusty

3

Hi wdodo,

There are other types of brushless motor RPM sensors including some that connect to a motor wire and count the pulses going to the thruster.

Here’s one from HobbyKing:

-Rusty

4

hi Rusty
Yes， I brought a similar one to test the speed，but the result is wrong 。for exemple，pwm from 1500-2000，when in 1700，there has 4000RPM，but when in 2000rpm，there has 3500RPM，when i use a manual Photoelectric Digita Speed Meter，3500RPM is true answer。In other word，the machine is effective in full scale。。
Please forgive me my poor English

5

Hi wdodo,

Okay, I’m not sure what might be wrong. We don’t have too much experience with either of these devices, unfortunately.

-Rusty

6

Hi wdodo,

Maybe the readings of your speed meter are showing multiples of the real speed. What type of speed meter are you using? I have seen this behavior when using stroboscopic lamps.