Rotating or static torque sensor

[djroseman]

Hello,

I am specifying a sensor for measuring torque on an electric motor system, and have come across both static (reaction) sensors and rotational sensors which spin with the shaft.

What would be the relative advantages of choosing one type of sensor over another ?

My application has max torque requirement of 3kNm and speed of 6000rpm.

Thanks
Dave Roseman

 

[btrueblood]

Some questions to ask that might help in selection:

How do you get power to each?
How do you calibrate each?
How many of each sensor are required, and how much real estate do they take up?

 

[drawoh]

djroseman,

A sensor attached to your shaft is battery operated and communicates wirelessly, or it is electrically connected through slip-rings.

A reaction sensor is part of your motor mount, and your motor is attached such that it can rotate against the sensor.

I suggest that you select a couple of likely sensors, and crudely design them into a functioning motor and shaft. Having done this, you can do rough cost estimates. You have a picture you can examine, and you can visualize how the thing(s) will work. The picture may show off some obvious problems that were not obvious to a forum discussion. The pictures may be helpful to your co-workers.

JHG

 

[Metrics]

Typically, a reaction sensor would be your first choice for price and accuracy. You would then move to a more expensive rotary system when the application requires.

If you can provide more details on the application, maybe we can provide some guidance.

 

[djroseman]

Thanks for all your replies. After having a look at the application an driveline, I discovered that the torque flange solution was the only one (limited space), and found that there are a couple of good inductive contactless systems around

Dave

 

[DynoGuy78]

There are several good torque flange makers out there. Some use radio frequency to communicate torque information from the rotating world to the stationary world. Others use rotating LED's to that 'shine' on a stationary receiver. And there are others that use rotary transformers (but these have rolling element bearings).

Drawback of the RF variety - be careful about interfering the antenna with ferrous material (steel) such as a shaft guard. Follow the manual carefully!
Drawback of the IR variety - heat can screw up your torque signal...calibrate and operate at the same temperature.
Since you have limited space, the rotary transformer suggestion is no good.

Good luck!