FT300 signal noise

jianlan_ · December 2017

Hi DoF Pros,

I have been using FT300 for a while, I am posting here to confirm what I got is reasonable.

Setup: UR5/CB3/Polyscope 3.3.4/Robotiq 85mm gripper/FT300 FT300 purchased in July, accuracy would be 1N according to Robotiq, URCap Version 1.0.1

1. The frequency I got is typically 62.5HZ, sometimes even lower than than (20HZ), please see attached picture. I tried different USB ports, never could get 125HZ, is this normal?

Image: https://us.v-cdn.net/6027406/uploads/editor/an/vz7k3tl27yvo.png

2. After calibration, and all procedures suggested by the manual, I still get a 3-5N drift on Fx, Fy or Fz even the sensor is not touching anything. And this value jumps a lot even in static. I attach a picture of sensor reading when the robot is at rest, not touching anything.

Image: https://us.v-cdn.net/6027406/uploads/editor/cl/ybyr514bk1zt.png

Is this the normal signal I would expect from FT300?

Thank you so much !

louis_bergeron · December 2017

@jianlan_

Since july, we have changed our electronic board inside the sensor to have a better signal. At that time the standard deviation of the signal noise was 1.2 Newton in Fx, Fy. With what I see, everything seems normal. Don't forget to use the command rq_set_zero() before taking measurements.

Regarding the frequency, I got the same rate as you if the thread takes too much time. UR can confirm that but what I understand is that thread are started with a clock at a fixed rate of 125 Hz. If the thread is not ready, it will be started at the next tick of this 125Hz clock which can give you this 62.5Hz.

louis_bergeron · December 2017

For your information, the new electronic board now give us a standard deviation of the signal noise as low as 0.1 Newton in Fx, Fy and Fz.

jianlan_ · December 2017

@louis_bergeron

Thanks for the reply. Just to confirm, my FT300 SN number is 2017 S/N F-30776, is this the new model with 0.1 std or old 1.2N std one?

Also, I am using CB3.0 + PolyScope3.3.4+ URCap 1.0.1. From what I learned from the forum, I can't upgrade to newer URCap because of the compatible issues. When I tried to use rq_set_zero(), it pops up a window 'rq_set_zero() is not defined', is this something to do with URCap version? Is upgrading to CB3.1 the only solution?

May I know how rq_set_zero() works? Does it zero the current sensor value, and set as a zero reference point?

Thanks!

louis_bergeron · December 2017

@jianlan_

For your information, our sensor have the new electronic board since October, you then have the previous one. To get the rq_set_zero() function on the urcap version 1.0.1, you must start your program with the template_sensor.urp. This template includes a script file "accessor_capt.script" where the function is defined. The template_sensor.urp will also give you access to the force and torques values in your program. The rq_set_sero() or rq_zero_sensor() since the latest urcap function will effectively zero the current sensor value.

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FT300 signal noise

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