Oscilloscope Question

[donvan]

I'm in the market for an oscilloscope. I see that there are many lower cost options these days. Currently I am trying to decide between a used old school scope or a modern, low cost digital one.
Now I may be missing something but one difference that I seem to be seeing with digital scopes is that there is no AC coupling feature like there is on old schools scopes. I seems like that is important. I am thinking that with AC coupling and a x10 probe I should be able to probe anywhere along the signal path without damaging the scope whereas with a digital scope I might need to add a capacitor between the scope and test point and that just does not appeal to me.

Am I making something out of nothing? Is AC coupling important?

Thanks,
Don

[xtian]

If you are talking about the $200-300 digital scopes like OWON, hantek or Rigol— they DO have AC coupling. If you have three bills to spend, this is the way to go.

[pompeiisneaks]

If you are talking about the $200-300 digital scopes like OWON, hantek or Rigol— they DO have AC coupling. If you have three bills to spend, this is the way to go.

Yup my Rigol, that I love, has AC or DC coupling for sure.

~Phil

[donvan]

If you are talking about the $200-300 digital scopes like OWON, hantek or Rigol— they DO have AC coupling. If you have three bills to spend, this is the way to go.

Those are definitely in my budget. I will check them out. Thanks!

[donvan]

One more thing. Am I right in thinking that with these scopes that have been mentioned, in AC mode, with a X10 probe I should be able to probe anywhere along the signal path without doing damage to the scope?

I just want to double check.

[xtian]

With AC coupling, DC is blocked, up to 600 volts. If you need higher voltage protection, you can add a 1kV capacitor between your probe and the voltage.

[pompeiisneaks]

With AC coupling, DC is blocked, up to 600 volts. If you need higher voltage protection, you can add a 1kV capacitor between your probe and the voltage.

or you can buy a X100 probe which provides the same level of protection. Either one works. I have some cheap 100X ones but they kinda suck so I stick to AC coupled and have been good so far.

~Phil

[Tone Snob Geezer]

I've had three O' scopes over the years, Ohio, Heathkit and finally a Tektronix 2225 50 Mhz which I just love. Older CRT scopes are pretty cheap, and in my opinion you get a better feel for what you have your hands on, plus if you are that guy that is always messing around with things, calibrating one of these older ones will go a long way in correcting that curiosity!

Honestly, I've never used the digital scopes but when I was checking them out I wasn't over impressed with the displays, they were sharp and bright, but seemed to lag. Another thought, if you do something completely off the chart and damage an old one, you've only damaged an old one that you might be able to repair, or part out.

Good luck!

[donvan]

Thanks for all of the good tips and information everyone! This has been very helpful.

[romberg]

I have a Rigol and am happy enough with it for use with audio circuits like guitar amps. The *auto* button is GOD if you have ever spent any time trying to get an old CRT scope to display anything useful. I will never get the time back I wasted turning the vertical, time and trigger controls in a vain attempt to see the signal I know is there. Press AUTO and boom there ya go! Of course these digital scopes do have a manual mode if you care to go there. And the auto measure features and snapshot captures are things an old analog scope just won't do.

The thing I was not sure about (and am still not 100% sure about) is the probes themselves. The probes that come with these affordable digital scopes are usually ratted for around 300V. Of course there are voltages inside guitar amps that can be double this. Probes rated for 1KV can run you much more than the price of the scope itself!

Now there are 10x and 100x probes. These contain a voltage divider which will knock down the signal by that amount before it hits the scope. But I'm unsure that it is safe or sane to use a 300V rated 10x probe on 650V. Yes the scope may see 65V but the probe itself may not have components rated to deal with 650. I would love to be wrong about this. In the end I bought a 1kv rated 10x probe for my own piece of mind.

I wish I could remember where I found the probes I bought. Named brand 1kv probes can run 1000 bucks or something silly. And there are some really cheap looking chinese probes that say they are good for 1kv but you just know it is not true. I think I spent around 100 bucks on my pair. You will want ones you are comfortable applying high voltage to. And even then be mindful that any probe connected to high voltage could potentially be at that high voltage in a fault condition.

Mike

[xtian]

The *auto* button is GOD

+1. All hail. And the automatic measurements. Sweet baby Jesus.

[Bombacaototal]

What about the portable mini oscilloscopes being sold now-a-days. Are any of them worthed?

[TUBEDUDE]

+1 on the DSO. I bought a Rigol 1054 last year, and did the 100mHz upgrade. Best $349 i ever spent. The Measure All button, if not god, is a demigod of the first rank. Highly recommended. If you'd like, i'll ship you my old analog 30mHz scope. Just PM me your address.

[SoulFetish]

compI would say this as I have both a rigol and old Tek 465. The resolution on my rigol sucks compared to the CRT scope, and the Rigol encoders are complete garbage. Which seems odd, because they use some very quality parts in some other parts of the scope. But, the some of the auto feature, digital storage, ability to "hack" the early models for upgrades, etc are really nice. If the encoders start to go, forget it. They need to be replaced immediately, or its basically useless. I still like the resolution of analog scopes

[donvan]

compI would say this as I have both a rigol and old Tek 465. The resolution on my rigol sucks compared to the CRT scope, and the Rigol encoders are complete garbage. Which seems odd, because they use some very quality parts in some other parts of the scope. But, the some of the auto feature, digital storage, ability to "hack" the early models for upgrades, etc are really nice. If the encoders start to go, forget it. They need to be replaced immediately, or its basically useless. I still like the resolution of analog scopes

Thanks for that update. Due to lack of time I'm moving slow on my build but it is going well so far. I'd say I'm 85% complete. I haven't bought a scope yet but I need to do so soon.

What model Rigol do you have?