16-08-2021, 07:43 PM
In my experience, just about every RMS multimeter I've come across is AC coupled by default, so measures the AC component of the signal. Which is usually what you want IME. You can measure the DC component in DC mode, and sum them together as appropriate.
A handful of multimeters - usually quite posh ones - have separate AC+DC modes that do the maths for you. This is reserved for the more expensive models in a range for obvious marketing reasons.
That said, some of the very cheap Chinese multimeters that I've reviewed are not AC coupled when in AC modes. As a result, they get confused by DC offsets on the signal - something I noted in my reviews.
I think that if a multimeter does anything other than AC coupling in its AC modes, it should (a) make that very clear, and (b) give you the option of measuring just the AC component, and at the upper end of the price end, that's exactly what they do. If no such provisos exist, then assume AC coupling is present. That stood me well until those cheap Chinese multimeters arrived on the scene...
In my experience, if you approach Fluke, you'll be lucky to get a sensible answer at first, though if you persist, you might eventually get to speak to someone more technical. If they really don't want to answer the question, they eventually send you free stuff to make you shut up and go away. I got a baseball cap, a notebook and a memory stick, all with Fluke branding. I should probably put them on eBay one day...
A handful of multimeters - usually quite posh ones - have separate AC+DC modes that do the maths for you. This is reserved for the more expensive models in a range for obvious marketing reasons.
That said, some of the very cheap Chinese multimeters that I've reviewed are not AC coupled when in AC modes. As a result, they get confused by DC offsets on the signal - something I noted in my reviews.
I think that if a multimeter does anything other than AC coupling in its AC modes, it should (a) make that very clear, and (b) give you the option of measuring just the AC component, and at the upper end of the price end, that's exactly what they do. If no such provisos exist, then assume AC coupling is present. That stood me well until those cheap Chinese multimeters arrived on the scene...
In my experience, if you approach Fluke, you'll be lucky to get a sensible answer at first, though if you persist, you might eventually get to speak to someone more technical. If they really don't want to answer the question, they eventually send you free stuff to make you shut up and go away. I got a baseball cap, a notebook and a memory stick, all with Fluke branding. I should probably put them on eBay one day...
