Digikey is saying this current sensor "CS0305B" from CUI Devices can measure AC and not DC. But in datasheet there is no reference or note mentioning this current sensor will not measure DC.

I have noted the same in Arrow electronics for the particular current sensor part.

How can we verify this with the datasheet because this info was not clearly mentioned in the manufacturer product page too.

Is there any hidden note in datasheet from that we can get this detail?

Or I misunderstood the whole thing from Digikey and Arrow electronics?

I am adding the reference urls,

Datasheet: https://www.cuidevices.com/product/resource/csxx05b.pdf

Digikey parametric listing: https://www.digikey.in/en/products/detail/cui-devices/CS0305B/10463370

Arrow electronics parametric listing: https://www.arrow.com/en/products/cs0305b/cui-devices?q=cs0305b

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    \$\begingroup\$ The Digikey listing says DC-40kHz. The device will measure DC and AC current. \$\endgroup\$
    – Kartman
    Commented Feb 20, 2023 at 12:37

3 Answers 3


because this info was not clearly mentioned in the manufacturer product page too.

The manufacturers product page clearly states 0-40kHz as the operating range:


That implies it should work fine for DC. As to why this is not in the datasheet is anybodies guess.

Simple solution would be to contact the manufacturer and ask for clarification.

  • \$\begingroup\$ Yes, the word "coil" in the datasheet is confusing people. A precision device will have a ferrite ring that can be interpreted as a coil. To measure low currents more accurately, the sense wire can be put through the core more than once. en.wikipedia.org/wiki/Hall_effect#/media/File:RAZC-GENARRv1.jpg \$\endgroup\$
    – Mattman944
    Commented Feb 20, 2023 at 13:11
  • \$\begingroup\$ In addition to this, with which I agree, it’s also worth noticing that the Output Voltage vs. Input Current curve reported on page 3 of the data sheet is clearly a DC transfer characteristic. \$\endgroup\$ Commented Feb 20, 2023 at 22:12

The only clue would appear to be on page 3 of the datasheet, where the frequency vs output attenuation is given all the way down to 1Hz, but not beyond. It may very well be AC coupled and this is reflected in the frequency response. If this is the case one would expect a somewhat high-pass response at the very low frequency end, but this is not the case - it appears to continue flat. You may just be lucky and have a true DC repsonse that was not well documented for some reason. Otherwise there is no other mention of DC response etc... You may need to measure it to confirm it for sure ...


The datasheet specifications mention that there is a coil, and that there is isolation between the primary and the measurement circuit.

From this, you can conclude that this device contains a current transformer; and transformers work only with AC. (This is also shown in the "Input Current Frequency vs. Output Attenuation" graph.)

There are current-sense amplifiers (e.g., INA180) that have no isolation. But CUI makes only coil sensors, so it appears they do not bother to mention it explicitly.

  • \$\begingroup\$ cuidevices.com/catalog/sensors/current-sensors CUI devices have mentioned as their current sensors are ideal for monitoring both AC and DC current in the general description. \$\endgroup\$ Commented Feb 20, 2023 at 12:49
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    \$\begingroup\$ Those devices aren't current transformers but Hall effect sensors. As opposed to transformers, they measure the magnetic field strength rather than its time-derivative and thus work for DC. \$\endgroup\$
    – user107063
    Commented Feb 20, 2023 at 13:01

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