Choosing an Oscilloscope

[Musicmanager]

Hi Guys

Firstly, a reminder, I'm a complete novice !

Now....... I want to learn how and when to use an oscilloscope but in order to do that I need to acquire one. On the back of that thought, I'm getting some flack from my senior manager about the money I've spent so far in pursuit of my new hobby, so I'm going to struggle to justify the spending for even a basic new bench model. The problem with buying secondhand is that I don't know enough about what I need/don't need; condition/wear & tear etc to make a good judgement about a good deal.
Given that what I really need to do at the moment is to learn how to and when to, I'm tempted by the price ( under £100 ) of a new PC based unit which seem to have some reasonable reviews. I understand that they have limitations, but at this stage they not too important to me as they are issues that I will need to discover when I have mastered the basics which will probably take some time.

I'd be grateful for any advice anyone may have to offer.
Thanks
S

 

[canadaelk]

To get started you could use the sound card in your computer and one of the many free programs, like the Virtual Analyzer. This would allow you to view audio signals and learn how to use a scope. Also go to www.banggood.com and look for the Hantek 6022BE. At about BP50, a good starter unit. The limitation with most digital scopes is the 8-bit resolution, limiting the display detail. E

 

[JimB]

My opinion is that you should stay well away from PC sound card and some software type "oscilloscopes. You will be very limited in what you can display - just audio waveforms - rather limiting in the wider field of general electronics.

As suggested by canadaelk, the Hantek 6022BE looks interesting at the price. I have no experience of it, so I cannot give any real advice.

From a learning point of view, there may be advantage in getting a conventional CRT type oscilloscope, there are lots of them about for less than £100.
I just had a quick look on ebay, there are lots of older mid range industrial scopes and not so old bottom of the range industrial or education establishment type scopes.
Being a crust old dinosaur, that is the sort of thing which I would have suggested.
The downside to these of course is that they are old and often well used and abused. Not the ideal thing for a beginner on his own if they need TLC.

JimB

 

[Colin]

You also want to consider 2-Channel facility so you can compare two signals. This is very handy when you inject the same signal into a stereo system and look at the outputs.

 

[tvtech]

Scopes........I am also a Dinosaur when it comes to them. Rarely use a Scope for day to day repairs. No need unless I am looking for missing Line or Frame drive from the Jungle IC...

Rarely used in my game with CRT....but essential to sort crap problems out. Cheapest 20MHZ is more than enough to handle the job.

My 2c

Regards,
tv

 

[blueroomelectronics]

I'm getting some flack from my senior manager about the money I've spent so far in pursuit of my new hobby

Why does your senior manager care what you spend on a hobby?

What do you plan to use the scope for? Are you doing analog or digital design?

Tip: stay away from PC scopes. Watch some EEVBlog episodes for scope reviews including why not to buy a PC scope.

As for me I've got a DS1054z on order, and if your going on the cheap consider a used DS1052 as they were an excellent starter DSO.

 

[Musicmanager]

Why does your senior manager care what you spend on a hobby?

Probably because I married her some 20 odd years ago and you know that bit about ' All my worldly goods .. .. .. .. '
I'm not designing anything yet, I'm very new to the concept - I've found a new hobby ! I need to learn how and when to use a 'scope and when I've done that I'll maybe be able to decide on analog or digital or some other religion !

 

[blueroomelectronics]

Ahh boss = wife

Seems you're interested in PIC microcontrollers, one of my favourite tools is the discontinued PICkit2. If you're programming older PICs it's still an excellent programmer but the real bonus is the 3 channel logic tool and UART tool.

A used Rigol DS1052e can be found for ~$150US according to some posts on this site. There should be some going up for sale as the DS1054z has replaced it. It's also upgradable!
https://www.righto.com/2013/07/tips-for-using-rigol-ds1052e.html

Watch David Jones EEVBlog on setting up an electronics lab. (he also reviews many test tools).

 

[KeepItSimpleStupid]

OK, why do you need one? Protocal analysis? Audio? How much bandwidth do you need?

Analog/Digital/MSO? MSO=Mixed Signal Oscilloscope.

This one is an interesting unit:

**broken link removed**

 

[Musicmanager]

specifically for JimB .. .. ..

You may remember in reply to a post I raised about flyback diodes you kindly showed me the effect of them with the use of an oscilloscope involving a voltage spike up to 300vdc. If you fast forward to my more recent post about choosing an oscilloscope, I'm also a crusty old dinosaur and agree that a CRT is the way to go to learn the right way. However, I've been looking at spec's and they all seem to have a quoted voltage range way below such a voltage spike.
Is this a problem or am I looking at the voltage range out of context ? I'd appreciate your advice.
Thanks
S

 

[KeepItSimpleStupid]

Scopes can me 50 ohms and 1 M ohms or switchable. 50 ohm is used in transmission line measurements and would severely load "normal" things.

The 1 M ohm input Z is also specified with a capacitance value, often 1 M ohm || 22 pf

The scope probe can be x1, x10, x100, x500 etc. x1 is used at low frequencies.

Since the scopes probe has an adjustable variable capacitance, (Not x1), the probe cane be made to act as an impedance divider where frequencies up to to the limiting bandwidt (scope or probe) can be measured. These adjustments can be on the probe body or the connector. Tektronix had a way for the probe to modify the volts/divion depending on the probe.

The probes are labeled x10 , but they really divide by 10. x10 is what you have to do to the normal scale. So, 0.1 V/div is now 1V /div

The act of adjusting this capacitor is done with the scope's built-in calibrator. The edges of the displayed "square wave" are adjusted square with the variable capacitor.

Not all scopes and scope probes are alike. Usually you can get 100 mHz probes with a x1. x10 and gnd switch on the probe body. In X1, the capacitor adjustment screw is usually covered.

 

[JimB]

A specific reply from JimB .. .. ..

The scope used to take that picture of the relay back EMF was an Agilent DSO3202A, a fairly new digital storage oscilloscope which is a bit beyond the price range which we are discussing here.
The vertical sensitivity ranges of that scope are switch selectable from 2mV to 5V per division.
If you look at the relay picture, you will see that there are eight major divisions on the vertical axis.
Also on that picture you will see that it is annotated CH1 50V/div at the bottom left hand corner.
In the set-up menu for the vertical axis, there is a place to manually set the division ratio of the probe which you are using, in this case I was using a X10 probe which made the 5V/div range into a 50V/div range.

Looking at my much older Telequipment D75 scope, the vertical axis scaling is from 5mV to 20V per division.
Using a X10 probe with that, you would have to look at the range switch, look at the probe and do a bit of mental arithmatic to arrive at 200V/div.

When you say:

However, I've been looking at spec's and they all seem to have a quoted voltage range way below such a voltage spike.

I guess that you are looking at the "Volts per division" and forgetting that there are probably eight or ten divisions, and that it is good practice to use a X10 divider probe for most measurements.

Why is it good practice to use a divider probe?
Expanding on what KISS says above...
The input impedance of 99.99% of all scopes is 1Meg Ohms with some value of capacitance in parallel, typically 20 to 30pF depending on the scope.
Using a length of screened cable or coax cable to connect the scope to the circuit under test will only increase the capacitance, and depending on what type of circuit you are connected to, the extra capacitance, and sometimes the 1Meg Ohm resistance can affect the circuit operation.
Using a X10 divider probe will increase the resistance to 10Meg Ohm and reduce the capacitance (theoretically) to 2 to 3pF. I practice the capacitance will be higher, but still generally less that 10pF.

JimB

 

[Musicmanager]

Thanks for the help guys. The reason I began 'specifically for JimB' is the earlier post about flyback diodes. I didn't think other members would be able to see that thread easily and I'm not sure I could reiterate JimB's explanation without misquoting it.
However, I do understand now, I didn't realise there is provision for adjustment/built in resistance on the probe. I will keep looking for a scope. there is a Lecroy scope on Ebay with a power supply problem which I have married up with a website blog from Azur Electronics about exactly the same scope with a power supply problem which is caused by a power resistor failure outlined as a most common problem with the model because of excessive heat. Risky maybe, but if I can get it cheap and successfully repair, I'd have an all singing and dancing scope which would always cope with my needs as my knowledge expands, hopefully.
Thanks again Guys

S

 

[KeepItSimpleStupid]

Here https://www.radio-electronics.com/info/t_and_m/oscilloscope/oscilloscope-probes.php is the "short" version of compensation.

A 50 ohm input is not likely to be of any use, so make sure it's switchable to 1 Megohm.

 

[Musicmanager]

Morning folks

Looks like I've got a Gould Advance OS 4000 Scope fully working, under £50
Did I do well ?

 

[JimB]

Sounds reasonable.
But we want to see pictures or it never happened!

JimB

 

[Musicmanager]

As directed : -

No probes yet and I'll have a question for you about that when you get over the shock of the staggering quality of my acquisition !

S

 

[JimB]

OK, I have recovered - ask your question.

JimB

 

[Musicmanager]

LOL
It's about the probes. This scope is labelled as 60 Mhz so I presume that means I have to match to 60 Mhz probes. Is there other operational data that I need to compare or match. I'm thinking of Rapid 85-2212 ? There seems to be a choice between expensive british made probes that I can't afford or cheap chinese that are not likely to be serviceable and I may have turned my toes up before they get here !
Thanks

S

 

[JimB]

This scope is labelled as 60 Mhz

Which means that the 3dB bandwidth of the Y amplifiers is 60Mhz.

so I presume that means I have to match to 60 Mhz probes.

No, it is not necessary to "match" the bandwidth.
A probe bandwidth of 60Mhz or greater is fine. In fact a probe with only 60Mhz bandwidth will significantly limit the system bandwidth. There is a calculation for it which I cannot remember and am too busy to look for it right now.

There seems to be a choice between expensive british made probes that I can't afford or cheap chinese that are not likely to be serviceable

Whilst the Chinese do make some crap, it is because we let them and then buy it from them.
The thing to do is to buy some mid-priced probes. They will hopefully last a long time.
The last probes which I bought were about £10, and that was 20 years ago. They still work OK.
In fact they were used in measuring the "relay back EMF".

JimB