I just got this combined multimeter - oscilloscope Hantek 2D72 

Link to manual: https://www.circuitspecialists.com/content/476383/HANTEK2D72_Manual.pdf&ved=2ahUKEwiQ9_K14YrzAhUDyYsKHdEHBE4QFnoECAYQAQ&usg=AOvVaw1b1eiep0FHhM_FdR878vby

In the specifications it says:

Input: Maximum Input Voltage 150VRM

My probe specs are: Max Input voltage: 1X 150V rms cat II 10X 300V rms cat II

I want to measure a DMX controlled dimmer. The output of the dimmer is 230 VAC so I will use the settings for 10x. Since I haven't used an oscilloscope before, I wonder how can I connect the probe to the outlet.

Can I simply connect the probe tip to the outlet on the dimmer channel I want to measure like on this image (not my image) and the ground tip to the metal chassis for grounding?

enter image description here

  • \$\begingroup\$ Edit to add link to the 'scope user manual. You need to be very careful with the ground clip to prevent current flowing between neutral and earth via the probe's ground clip. While you're at it, double check "150VRM". \$\endgroup\$
    – Transistor
    Sep 19, 2021 at 8:41
  • \$\begingroup\$ The probe ground clip is connected to mains earth via the scope (not handheld scopes of course). Do not connect it to anywhere except to things that are electrically connected to mains earth. You don' know if the dimmer has a direct neutral connection through it, or direct live connection through it, so never connect the ground clip to neutral. Best way to measure is differentially with two 10x probes, one probe on neutral, one probe on live, with both probe ground clips connected to earth. Set up the scope for differential measurement. Use extreme caution as mains voltage is dangerous. \$\endgroup\$
    – Justme
    Sep 19, 2021 at 9:07

1 Answer 1


The user manual file you have linked is in zip format so I didn't download it. Looking at pictures on the web it seems that the instrument is a large multimeter style device.

enter image description here

Figure 1. One of the Hantek range of instruments.

I notice that this device has a USB port. The big danger of this is that there may be no isolation between the USB ground and the COM pin on the scope. If there is no isolation then connecting the COM pin to a live circuit while the USB is plugged in may cause high current to flow through the meter's ground destroying it and the USB source. The outline specification does not mention this. With USB unplugged there may also be a shock hazard on the USB port. Check this very carefully and understand the limitations of the device before use on mains circuits.

Can I simply connect the probe tip to the outlet on the dimmer channel I want to measure like on this image (not my image) and the ground tip to the metal chassis for grounding?

Normally you would measure between the line and neutral, not ground as there may be a slight difference between the two.

The 10x probe setting reduces the voltage seen by the 'scope and 230 V is within the 300 V RMS specified. There isn't a lot of safety margin there and at the price these are sold at I'd be concerned that safety might not be quite at the top of the priorities list.

  • \$\begingroup\$ Ok. for sure. I will not have anything plugged into the usb. And not anything else either except for the probe. So can I then instead meassure it by connecting probetip to one of the pins on the socket and the groundtip on the probetip to the other pin? I have pdated the link for the manual \$\endgroup\$
    – acroscene
    Sep 19, 2021 at 9:53
  • 1
    \$\begingroup\$ That sounds OK. I would identify the L and N first and be sure to connect tbe ground clip to N. \$\endgroup\$
    – Transistor
    Sep 19, 2021 at 12:11
  • \$\begingroup\$ Ok. If it is safe I will try. \$\endgroup\$
    – acroscene
    Sep 19, 2021 at 16:40

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