C740A0 - Hardware monitoring critical problem


I work with a new UR10e with an OEM DC control box and a teach pendant with polyscope 5.11 software installed. After connecting and enabling the teach pendant I am receiving a C740A0 error when trying to turn on the UR10e via the teach pendent. The robot is fed via a 24V 30 amp power supply.

did anyone encounter such a problem?

I have found a similar issue but with no real solution in the comments


ur_20225290051_2022-05-30_17-05-36.zip (2.6 MB)
Attached to this comment is the error log file.

Hi lior,

I looked at the log_history.txt
I found this: 48V voltage is outside of the allowed range: 39.89
It happens immediately after you try to power on the robot arm.

Is it possible that your power supply cannot deliver current fast enough?
Did you consider this notice?

Hello Jor

Thank you for your response. thanks to your input i have found the problem and was anble to operate the robot. The problem occured, as you have said, due to lack of ability to provide the required current to the UR system. This current limitation was created due to an inrush current limiter which was installed on the robotic arm.

here is a link to the current inrush limiter which was used: https://www.mouser.co.il/datasheet/2/600/ametherm_MM3_%201R050-DIN-1214946.pdf.

additional information to others that would adress this problem:

  • control box: OEM DC
  • Input voltage: 24VDC
  • robotic arm used: UR10e
  • inrush current limiting component: Ametherm MM35 1R050-DIN

Thank you again for you help and have a great day

How did you wire in the inrush limiter on the control box?

I solved my issue regarding the same error code. Turns out my supply was not pushing out enough voltage. I was at 24~25V and after turning it up to 27~28V it was able to engage. The controller states 19~72V so I was a bit mislead and suppose I forgot to compensate for the robot draw in of its self. Current drawn seems to be ok with in this range.

Im using a U16e by the way.

Hey Sorry for the late reply.

Regarding the wiring of the Inrush limiter I have connected it in series upstream to the control box.
My guess is that the problem for both of us was that, before the robot is started, the current running through the Inrush limiter was low and thus the temperature of the resistor (which is the Inrush limiter) was low and the resistance was close to 1 ohm, which limited the current supply to the system and caused a significant voltage drop somewhere in the system.

Although this is wierd to me i believe that that is the reason.

Jor, would you suggest creating a bypass to the Inrush limiter that will be triggered a few seconds after the robot is powered up? how would you suggest solving the voltage drop issue (beside raising the voltage or getting rid of the current lnrush limiter)?

Hi lior,

I would suggest that you use an oscilloscope to measure.

  • Does the supply deliver 24V ? Did you damage your supply during initial testing
  • What happens with the supply when you power-on the robot ? Does the supply shutdown when too much current is drawn
  • How big is the voltage drop across your thermistor ? Consider different “soft starter”
  • How big voltage drop is there across the wires from the supply to the robot ? Consider using shorter thicker wires
  • Is there a loose connection ?