Error -1074118531 in LabVIEW: Hazardous Voltage Detected at SMU Output

Updated Nov 14, 2023

Reported In


  • PXIe-4135
  • PXIe-4136
  • PXIe-4137


  • LabVIEW


  • NI-DCPower

Issue Details

  • Why am I seeing error -1074118531 when I output a voltage on my Source Measurement Unit (SMU)?
  • I am using a PXIe-4136 and LabVIEW™ is detecting a "hazardous voltage" even though I am within the safety limit.
  • My PXIe-4135 is detecting a hazardous voltage at the output. Why?
  • I am seeing the following error on my PXIe-4137. How can I resolve this?
A hazardous voltage was detected at the output while the interlock circuit was open. Fix the problem and reset the device to return to normal operation. For more information, refer to the NI-DCPower documentation


This error occurs when a hazardous voltage is detected at the output terminals of the SMU. A voltage that is greater than the maximum voltage limit is considered hazardous. This voltage limit depends on the state of the Safety Interlock of the device:
  • If the Safety Interlock is closed, the voltage limit refers to the maximum voltage of the device.
  • If the Safety Interlock is open, the voltage limit is +/- 40 VDC. A hazardous voltage is detected if the terminals exceed +/- 42 V (peak) with a tolerance of +/- 0.4 V.
Note: The status of the Safety Interlock can be checked with the Interlock Input Open Property .

This error can be fixed by resetting the device using the niDCPower Reset Device VI . However, the source of the problem should be addressed to prevent the error from reoccurring. 

If resetting the device does not fix the error, the following areas should be checked:
  1. The voltage limit of the device if the Safety Interlock is open.
    • If the voltage limit is set to a greater value than +/- 40 VDC, this error will occur.
    • Check the Overvoltage Protection (OVP) limit using the OVP Limit Property  and ensure that it is within the allowable range. This property can be written to in LabVIEW if needed.
    • Refer to the Using the Safety Interlock topic for the PXIe-4135, PXIe-4136, or PXIe-4137 for further information.
  2. Ensure that a voltage is not being applied to the Safety Interlock input terminals.
  3. Ensure that there is no oscillation created when the SMU connects to a DUT.
  4. The SMU should always be connected to the DUT to avoid overprotection errors.
    • If this is not possible, and the SMU must switch between DUTs, ensure that the SMU is always connected with a known voltage.

Additional Information

Refer to SMU Best Practices: Understanding Compliance and Device Protection Errors to better understand the possible causes of different SMU overprotection errors.