What should I look for in a used Oscilloscope

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comrade904
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Re: What should I look for in a used Oscilloscope

Post by comrade904 »

You guys think one of these will hold its value for the next few years?

http://www.saelig.com/miva/merchant.mvc ... gory_Code=
toalan
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Re: What should I look for in a used Oscilloscope

Post by toalan »

I have looked into the owon scope quite a bit, I was almost tempted enough to buy it but I think I will pay 2x more for a rigol scope. There is nothing wrong with the owon scope from what I know, it is worth the money, but the memory depth is a tad low and the 25mhz bandwidth is somewhat limiting.

Rigol is supposed to be an OEM for Agilent and the scopes they sell are rebranded Agilent scopes, that is what my research has told me. Rigol has a 1M sample memory depth. I am have my sights set on a 100mhz Rigol scope for ~1k USD.

For automotive, I would perfer 4 channels, it would be nice to capture the injection/ignition signals of all 4 cylinders in a 4 cyl engine at once, but 4 channel scopes are just too costly.

Right now I am surviving with a half broken tek analog scope and my usb POSCOPE. Every once in a while I check ebay for a good deal on scopes, but it is hard to find a good deal and shipping to Canada is brutal.

Anyways, for $325 the Owon scope is a good buy, it is the cheapest you can find for a standalone digital scope regardless of brand. Even ebay sells the same Owon scope for more than $325. No one else has products in the $325 range, so unless Owon releases it's successor I think the value will be protected for a long time.

If you buy it, please post up your impressions.

Regards,

Alan To
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Re: What should I look for in a used Oscilloscope

Post by MotoFab »

comrade904 wrote:You guys think one of these will hold its value for the next few years?

http://www.saelig.com/miva/merchant.mvc ... gory_Code=
I read the user manual for that scope. It's hard to believe the features for 325 dollars. Even has automatic wave form measurement. (It looks like for 75 dollars more there's a rechargeable battery version.) Based on your usage, I'd be all over that. I have 100MHz and 500MHz digital scopes for work. I don't use 1/3 of their capabilities.

If you're worried about the tool's value over time, I think you'll still be using it a decade from now. Here's something for comparison. For banging around in the garage I have an OLD 60MHz analog. (It's got dual time base and delayed sweep so it's not a complete relic. It usually sits on top of the welder, measuring arc voltage.) The only reasons I can see for buying a new low-priced digital is portability, and getting waveform data into a PC.

As far as performance need, I don't recall ever setting a timebase dial faster than 1µs/div for any signal happening in a car or motorcycle. What's that cam wheel with 360 slots? Nissan? At 8000RPM say, the period for one slot is 1/((8000/2/60)*360)=0.0000417s or 41.7µs. That's 24KHz, an audio frequency range.

That 25Meg scope you're looking at is going to own any signal in a car. I mean dominate. It'll barely be ticking over even when looking at ignition coil flyback.

- Jim
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jbelanger
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Re: What should I look for in a used Oscilloscope

Post by jbelanger »

While I agree that 25MHz is more than enough for any automotive signal. I would also think about other potential uses for someone thinking of embarking in a DIY project. If you want to see some signals between chips on the ECU such as SPI, then 25MHz becomes the bare minimal that you would want to consider. And even then, if faster CPUs are used and/or different peripherals it may not be enough to really see what is happening.

This may not be necessary and you may never have to look at such signals (e.g., there is no need to look at such signals on a Megasquirt) but it's good to keep in mind if you want to think about optimizing your purchase for any potential future uses. Having said that, I'd be glad to have this scope because it's better than what I currently have and it would have ended up cheaper than the second hand thing I got that had to be replaced. And the portability and the ability to connect to a PC without having to do so is great.

Jean
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Re: What should I look for in a used Oscilloscope

Post by MotoFab »

jbelanger wrote:While I agree that 25MHz is more than enough for any automotive signal. I would also think about other potential uses for someone thinking of embarking in a DIY project. If you want to see some signals between chips on the ECU such as SPI, then 25MHz becomes the bare minimal that you would want to consider. And even then, if faster CPUs are used and/or different peripherals it may not be enough to really see what is happening.
Hey Jean, how's it going?

Chip-to-chip serial data and logic uses on the PCB are sure worth considering. Not saying it would capture the timing of a 20MHz SPI signal very well, but this scope has a sampling rates of 100MS/s for each channel and will certainly reveal the serial 0s and 1s. Though, when sampling serial data at that speed, more memory depth is required to catch a whole byte. More memory depth usually comes with more speed, and maybe the budget is blown.

I love to spend money on test equipment, but it just seems that in practice I usually never use the extra features. And in my experience that is true across the industry. I've worked in military labs that buy test equipment with cubic money. More LeCroys per square meter than anywhere. But the capabilities are seldom if ever used. It's similar to buying an F350 to satisfy the owner's perceived need, that actually carried that big load once. An F150 would make a couple of trips, sort of like how you make do with a scope.

Anyway, here's something nifty I saw the other day. Quite a deal for $149. Decodes SPI, I2C, RS232. I bet they will add a CAN decoder soon enough. (Connected after the CAN interface chip of course.)
http://www.saleae.com/logic/

If I were going to spend a few more dollars above the $325 cost of the scope, I'd be hard pressed to choose between the $75 rechargeable battery for the scope, and the $149 logic analyzer.

But wait, this just in. Nevermind, screw the budget. This Owon scope/logic analyzer is $564 including shipping on eBay http://www.owon.com.cn/eng/msoSeries.asp The specs say it comes with a 7.4V, 8000mAh battery for portable use.

eBay link: http://cgi.ebay.com/New-portable-DIGITA ... dZViewItem

- Jim
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Re: What should I look for in a used Oscilloscope

Post by toalan »

I just got my Rigol DS1052E today, I paid $475 USD + $40 USD shipping to Canada. It is brand new, 50mhz bandwidth, 1Gs sample rate, 2 channels.

The last time I used a digital scope was 10yrs ago in school, so I am out of touch with what the standard expectations are for a digital scope. With that said, I really like the Rigol scope. Right now I am only using the Rigol like I would my tek analog scope, so I have not touched any advanced features yet.

The strongest impression that the Rigol made on me is the great user interface. A scope is a fairly complex tool, but Rigol manages to organize everything very logically and it is very intuitive to use. Almost every function is a few button pushes away, and there was minimal consulting of the manual required. The user interface is not riddled with bugs like you would expect from a chinese made budget scope, I have yet to encounter a bug in the user interface.

The scope looks to be very well made, hardware and software wise, nothing about it gives it away as a budget scope.

So far my only dislike is that the ADCs are only 8 bit.

There is PC software for the scope, you can control the scope from PC and fetch waveforms from the scope. The PC software is ok, it is a bit lacking considering how well made the scope is itself.

Regards,

Alan To
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jharvey
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Re: What should I look for in a used Oscilloscope

Post by jharvey »

toalan wrote:So far my only dislike is that the ADCs are only 8 bit.
I believe if you compare a signal captured from your analog tek, and your rigol, you'll discover your tek is 8 bit. Scopes and DVM's aren't really known for accuracy. They are typically +/-5%.

Glad to hear you like it. Sounds like my only biff with it would be the 2 channels. I'd probably go for the DS1064B to get that 4 channel. Keep us posted on your experience as time goes on. I'd be interested in hearing how it performs against the test of time.
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