I Don't Understand Multimeters

[Mark]

Or electronics in general.

I need to measure the AC of a circuit at 100 KHz but I don't know if there are any multimeters in my budget range (up to £200) that are capable of doing this.

[digitaldrummer]

then you may already be over your head and should seek some help from a professional! For most modern digital multimeters, 100KHz is probably at the higher edge of their capabilities. To accurately measure a 100KHz signal, you may need something that has greater capabilities, and so you might be looking at an oscilloscope (which can usually measure much higher frequencies, but possibly lower voltages). So really depends on what kind of precision you need and what kind of voltages you want to measure, etc. and if you don't know how to interpret the results, then see again my first statement.

[Scodiddly]

It all starts with "what exactly do I need to measure?" and from there it's easier. 100KHz is probably not something you're going to measure accurately with a bog-standard DMM, but at least you should be able to look at the specs. A basic oscilloscope with decent specs should be able to give you a good peak-to-peak measurement. A modern digital one would also give you the RMS voltage pretty easily as well.

What *are* you measuring or trying to fix?

[Mark]

Yes, Calum of the youtube channel Tetrakan did say that I'd be better off with an oscilloscope.

I'm trying to measure the voltages on the rec/play cards in my 388. I want to know why it's playing back but not recording or erasing.

[Scodiddly]

I'm trying to measure the voltages on the rec/play cards in my 388. I want to know why it's playing back but not recording or erasing.

That kind of work you want an oscilloscope, it'll make everything easier.

There are some affordable units that use your computer or tablet as the screen and such, I don't have one myself but probably a good starting point. I've owned a couple of garage sale old analog scopes but eventually they died and were too much bother to fix. My current scope is a Fluke 123, about $1200 when I bought it 18 years ago.

[digitaldrummer]

I'm not saying this is the one, but there are many in the same price range (and same technology) that may do the job for a lot less than $1200... only $40 here:

https://www.amazon.com/WisTek-Shell-Osc ... B07SZPY9R9

[Scodiddly]

I don't know if I'd want a $40 scope, wouldn't trust it much.

Here's an old-school style, only a couple hundred bucks:
https://www.jameco.com/z/AS101-Owon-Tec ... 26119.html

Jameco's a pretty good site for reasonable quality at hobbyist prices. I still have a meter I bought from them 2-3 decades ago.

[The Scum]

I've played with some of those import "pocket scope" options, and found them to be pretty limited, and quickly devised situations where they wouldn't resolve the signal (small AC signal riding on significant DC offset, comparatively low input impedance, bandwidth that's rather constrained (even considering 100 khz), etc).

(not to be confused with the Fluke mentioned above - it's a real scope)

The Rigol/Owon scopes aren't too bad for the money. Much, much better than the little toy scopes.

But that same money would get you a clean used Textronix 465, extremely trustworthy, and enough scope to troubleshoot any modest analog audio or simple radio situation (which is what I'll call a 100khz bias oscillator).