Another noob wants to buy a multimeter

[vk6zgo]

For what you're doing,it probably isn't a major drama,as most of these old beasts maintain their calibration fairly well.

Most Analog Oscilloscopes don't have voltage & time readouts,so you have to learn how to read the display

If you are using DC coupling,you can usually check the volts/div against an AA cell(check the batt voltage with a DMM first),

(Australian practice is to call an Analog Oscilloscope a CRO,from Cathode Ray Oscilloscope,so I will use the term for convenience.)

Set the CRO triggering to "AUTO".This should give you a straight line across the screen.
 
If the volts/div is set to 0.5volts, an AA Ceil should cause the line to deflect verticallyapprox 1.5 divisions.

Your timebase (time/div) can be checked against a 50Hz signal as 1 cycle at that frequency should appear on the CRO display as

20mS duration.DON'T ram your probe into a mains socket!!.You can pick up enough 50Hz out of the air.

A PAL TV  line sync pulse is 4.7uS  duration.

If you look up w2aew's thread on Oscilloscopes in this forum,you will learn a lot about these wondrous devices.
 
You may have to experiment when it comes to measuring ignition timing & suchlike,but you should be able to see the control

pulses into the ECU ,& the pulses out of the various sensors OK.

VK6ZGO

[nk7]

Cheers for the info - yeh I had already started watching the mammoth video. had to take a break. I will definitely consider the analogue against digital - reminds of good ol' film cameras. I still have em and love them. When converted to digital they outperform a lot of expensive digital cameras if you do it right.

But can analogues still do audio work as well - like checking for noise and sound levels etc? anyone know what sort of max frequencies I can expect in automotive...Will 2Mhz be enough? Noticed a special on Velleman HPS10SE on tequipment.net for $150 - not sure what 2nd hand analogues will set me back but not a seemingly bad price. Btw what brand and specs for analogues should i look out for? Will they offer diverse capabilities for these older models?

[vk6zgo]

Analogue CROs are real-time devices,so you can't hit "STOP" & save the display like a DSO.
Well,actually, my Tektronix 7613 can store a waveform on the screen,but you can't manipulate the stored waveform like  you can with a DSO.
When you are looking at a real-time display,however,many CROs enable you to pick a particular point an the display & "zoom in " to it--they don't call it that,but it is a similar effect to "zooming in "with a DSO.

Analogue units don't offer Fast Fourier Transforms(FFT) like DSOs,so you do not have the (fairly limited)ability to do spectral analysis that they offer.

For Audio work,an Analogue CRO will enable you to look at wideband noise,power supply ripple,
hum ,etc  down to a few mV p-p.

I doubt whether Automotive work requires very wide bandwidth,but it is unusual for even the cheapest
Analogue CRO to have less than 10MHz  bandwidth.

Brands? Well, you can do good work with even the most basic CRO,which in this context would probably be the single channel 10MHz units that Jaycar & Dick Smith were selling for around $150 new.
You could probably pick up an old BWD quite cheaply,with similar specs to the above,but 35MHz
bandwidth & a very nice display,but they are valve units,& also have a common fault
which causes the sync circuit to fail.

More sophisticated units will have multiple channels & in many cases,delayed timebases,which allow the
"zooming" effect referred to above.

Tektronix would be my first choice,particularly the 400 series,as they are reasonably cheap ,& are fairly small.
Some of the later types are very nice,such as the 24xxx series ( I can't remember actual numbers offhand,but look through the threads here on EEVblog).
I like the (old) 7000 series,but they are very large.(Tek for some unknown reason,saw fit to recycle the "7000" numbers).

HP made some very nice CROs,but they don't have quite the same reputation for reliability as Tektronix.
There are quite a few Philips units around,of varying capabilities,again not as "bullet proof" as Tek.
BWD made a whole range of CROs,from the single channel ones referred to above,up to multi channel devices of similar performance to the Tektronix units.BWD tubes almost always have a bright display,not
seeming to be so prone to loss of tube emission as other brands----but remember the sync problem on some models!
Hameg are rugged units,& will probably be a bit pricey.
There are a number of Trios,Telequipment Serviscopes,JVCs around,which may be OK,but are getting a bit long in the tooth & may not be worthwhile.

Where to get them? eBay,the Equipment thread on this forum,Newspaper For Sales columns,Hamfests,word of mouth.

As Analogue CROs don't "spoon-feed" you like DSOs,I'd recommend you sit down with your Oscilloscope & "have a bit of a play"  to get used to interpreting the display.
A Scientific Calculator will also help to check the relationships between time & frequency,etc.

VK6ZGO

[cs.dk]

A Scientific Calculator will also help to check the relationships between time & frequency,etc.

VK6ZGO

I've got my first CRO, an old 20 MHz dual channel Aaron BS-601. Borrowed a signal generator from a friend, and I'm beginning to figure out how to adjust the trigger, sweep time, etc.
My question is, whats the formula for time/frequency calculations?

Btw: There is a good post about older Tek scopes here: https://www.eevblog.com/forum/index.php?topic=3506.msg46786

[vk6zgo]

t in seconds= 1/f,where f is in Hz

f in Hz=1/t,where t is in seconds.

For instance, the duration of 1 cycle at 50Hz=1/50 second,or 20 milliseconds(mS),&

the duration of 1 cycle at 1MHz =1/1000000 second,or 1 microsecond.(uS)

VK6ZGO

[cs.dk]

t in seconds= 1/f,where f is in Hz

f in Hz=1/t,where t is in seconds.

For instance, the duration of 1 cycle at 50Hz=1/50 second,or 20 milliseconds(mS),&

the duration of 1 cycle at 1MHz =1/1000000 second,or 1 microsecond.(uS)

VK6ZGO

Thanks 

[nk7]

So you vk6zgo you mentioned the Picoscope - I am assuming this is similar: http://www.ebay.com.au/itm/Hantek-Digital-USB-Osciliscope-DSO-2150-150MHz-/320725056618?pt=AU_B_I_Electrical_Test_Equipment&hash=item4aacb3fc6a . What are limitations compared to analogue - is the measurable frequency crap? Is this popular or does analogue still win? Just that when I consider older oscilloscopes - i don't really know how to fix them just in case they get sent as faulty and if there are expensive parts then...handheld DSO like velleman hps10 seems a better candidate. But you do say you can do a lot more with the analogues in comparison which is something I like. So many toys to choose from? Can I buy them all?!

[Zero999]

That so-called 150MHz 'scope only has 60MHz of analogue bandwidth which is presumably only any use for repetitive signals with only one channel enabled, use two and it'll drop to 30MHz.  In one shot mode, the usable bandwidth is probably something like 15MHz, again with two channels, it's probably 7.5MHz. The maximum peak input voltage is only 35V and that's at frequencies under 10kHz.

I've never used a USB 'scope before but everyone on the Internet seems to say they're shyte.

[nk7]

hmm okay. That's also prob why I can't find support articles for those items less than 4/5 years old. So if a cheap analogue can do everything a decent or perhaps an expensive handheld DSO can do apart from FFT analysis then maybe that's the way to go...?

And if I do get faulty equipment, fixing that shouldn't be too bad since I can see that there is a lot of support for analogues here and on net it seems. Any ideas on what sorta costs involved in procuring a second hand analogue? Or some sort of aim - given the hps10 is only a $150 on tequpiment.net?

[vk6zgo]

Well,the Tektronix 7613 100MHz mainframe with 2 vertical plugins (it can display 4 channels)& a delayed timebase plugins cost me $135 at a Hamfest,so this gives a fair idea of the likely cost of something similar.

A 7613 is a bit too large for convenience in your application.
If you are only going to use an oscilloscope around a car engine,the USB things may do the job,but they lack versatility compared to an analogue Cathode Ray Oscilloscope.

VK6ZGO

[Zero999]

How about buying a low end 25MHz 'scope, then hack it to 100MHz, when you've got more experience and the warranty has expired?

[nk7]

Heck if I can get something that high spec for only $135 with no issues I'd be very happy! I would work around the size and weight for that great a price.

[saturation]

For auto work, portability and some robustness is key, given your equipment will be taken to garages and such. 

http://autospeed.com/cms/title_Using-Oscilloscopes-on-Cars-Part-3/A_109873/article.html

And if I do get faulty equipment, fixing that shouldn't be too bad since I can see that there is a lot of support for analogues here and on net it seems. Any ideas on what sorta costs involved in procuring a second hand analogue? Or some sort of aim - given the hps10 is only a $150 on tequpiment.net?

[nk7]

For auto work, portability and some robustness is key, given your equipment will be taken to garages and such. ..

Even if most, if not all, work would be done in my own place??


Also, what do you guys think of this analogue from jaycar - 10Mhz one. So my understanding is effective frequency that can be measured is essentially 10Mz/10 = 1Mhz effectively. Is that right? Btw it was mentioned that analogue can be hacked or "overclocked" - is this by substituting hardware or getting like a 100:1 probe?

[EEVblog]

Also, what do you guys think of this analogue from jaycar - 10Mhz one.

IMO, better value can be had in a second hand 20MHz dual channel scope.
But it is only $100 or so brand new with warranty.
Single channel can be limiting.

Dave.

[Kiriakos-GR]

t in seconds= 1/f,where f is in Hz

f in Hz=1/t,where t is in seconds.

For instance, the duration of 1 cycle at 50Hz=1/50 second,or 20 milliseconds(mS),&

VK6ZGO

My Agilent U1272A it can measure mS of wave forms, and at my Mains plug ( 50Hz) I got a reading, of 9.50mS ..
If what I measured are pp , then if the 20mS if it is the total wave length, then we are both correct. 

[vk6zgo]

For auto work, portability and some robustness is key, given your equipment will be taken to garages and such. ..

Even if most, if not all, work would be done in my own place??


Also, what do you guys think of this analogue from jaycar - 10MHz one. So my understanding is effective frequency that can be measured is essentially 10MHz/10 = 1MHz effectively. Is that right? Btw it was mentioned that analogue can be hacked or "overclocked" - is this by substituting hardware or getting like a 100:1 probe?

The low end Oscilloscope Hero999 was referring to was a digital unit.
This idea sounds like a good option,after reading the link saturation posted,as the Automotive signals don't seem to require very wide frequency response in the 'scope.
As he suggests,if you want to play with general Electronics later,you can probably hack it to give better performance.

With Analogue Oscilloscopes (CROs),what you see is what you get!
A "10MHz" CRO will display amplitude  for a 1 volt peak to peak (p-p) signal of,say ,1MHz
as 1 volt p-p ,but with the same input voltage at a frequency of 10MHz,will show it as 0.707 volts p-p.

In other words,the response from DC up stays pretty much the same,until a few MHz below 10MHz,it begins to fall off,until it reaches the level referred to above.

As far as measuring frequency,you may or may not be able to show a single cycle & measure its duration,& hence calculate frequency at 10MHz with a "10MHz" CRO,depending on the timebase circuitry.
A square wave signal of up to about 2MHz will be displayed without apparent distortion,but above that point will show increased distortion due to loss of the higher frequency components.

Sine waves quite a bit higher in frequency than 10MHz can be seen with these "10MHz" CROs by simply increasing the input sensitivity,but eventually they disappear into the noise.


VK6ZGO

[Zero999]

The low end Oscilloscope Hero999 was referring to was a digital unit.

What I meant was you can buy a Rigol 'scope, use it, learn a lot then, when the warranty has expired hack it to the full bandwidth.

With many cheap digital 'scopes the only difference between the higher end and lower end of the model range is the software so if you know what you're doing, you can buy a 50MHz 'scope and modify it to 100MHz. The manufacturers obviously don't want you doing this so is invalidates the warranty.

Also, what do you guys think of this analogue from jaycar - 10Mhz one.

IMO, better value can be had in a second hand 20MHz dual channel scope.
But it is only $100 or so brand new with warranty.
Single channel can be limiting.

Yes, I'd never recommend a single channel 'scope to anyone.

[saturation]

Yes.  Its easier to take the scope to the car, than the car to scope, unless you are pulling a part out for bench top analysis.  Bench scopes generally do not float its inputs, and are tied to ground;  for overall safety for your scope its preferable to have gear with full floating inputs, like the cheap Velleman.  Automotive waveforms are not very demanding in bandwidth, but some, like spark plug outputs are in the kV relative to car ground, but to earth ground it can be far worse ... even the operating voltages within the ECU can be high, and what that is relative to earth ground I know not.



If you need a bench scope for electronics, its best to get it for that purpose and get a specific one for in-car work.

For auto work, portability and some robustness is key, given your equipment will be taken to garages and such. ..

Even if most, if not all, work would be done in my own place??


Also, what do you guys think of this analogue from jaycar - 10Mhz one. So my understanding is effective frequency that can be measured is essentially 10Mz/10 = 1Mhz effectively. Is that right? Btw it was mentioned that analogue can be hacked or "overclocked" - is this by substituting hardware or getting like a 100:1 probe?

[nk7]

Yes.  Its easier to take the scope to the car, than the car to scope, unless you are pulling a part out for bench top analysis.  Bench scopes generally do not float its inputs, and are tied to ground;  for overall safety for your scope its preferable to have gear with full floating inputs, like the cheap Velleman. 

What do you mean by full floating inputs? Is that floating point numbers..as in programming or something else? yeh the Velleman would be good for quick jobs even if it is only 1 channel. Yeh I will work mostly at home in the garage - but if I do take it somewhere else and need a a scope, a portable would come in handy. So are you saying that moving a CRO/analogue around isn't particularly safe for the scope? It would either be sitting inside on the car seat or on a table (that can be wheeled around) when looking under the hood.

I found some cheap analogues on ebay here in Oz if anyone would care to comment on:
1) Kenwood CS1021
http://www.ebay.com.au/itm/Kenwood-CS1021-2ch-20MHz-Oscilloscope-/370524265455?pt=AU_B_I_Electrical_Test_Equipment&hash=item5644f79bef

2) Digitec 20MHZ
http://www.ebay.com.au/itm/Oscilloscope-Digitec-20MHZ-Dual-Trace-Near-New-/220811758055?pt=AU_B_I_Electrical_Test_Equipment&hash=item33696809e7

3) BWD 530A
http://www.ebay.com.au/itm/BWD-OSCILLOSCOPE-Model-530A-made-Melbourne-LQQK-/180691538341?pt=AU_Electronics_Vintage_Electronics&hash=item2a120e11a5

4) Tektronix type 422
http://www.ebay.com.au/itm/Tektronix-type-422-oscilloscope-15-MHz-/330587200436?pt=AU_B_I_Electrical_Test_Equipment&hash=item4cf8885bb4

and 5) Tektronix 2225
http://www.ebay.com.au/itm/Tektronix-2225-50MHz-oscilloscope-/330587201570?pt=AU_B_I_Electrical_Test_Equipment&hash=item4cf8886022


I tried to look for dual trace and ones that are not being sold 'as is'.


Thanks
N

[vk6zgo]

"Automotive waveforms are not very demanding in bandwidth, but some, like spark plug outputs are in the kV relative to car ground, but to earth ground it can be far worse ... even the operating voltages within the ECU can be high, and what that is relative to earth ground I know not."

A car is normally an isolated system,with the chassis as the reference point,so the voltage at some high voltage test point with respect to mains earth could be almost anything -but it will always be lower than that at the same point with respect to the car chassis.

Normally, the only connection to the mains earth will be via capacitance between the car chassis & earth, in parallel with the quite high resistance of the car tyres.

Of course,if the Oscilloscope has an earthed connection,the car chassis goes to earth potential,so the
voltages w.r.t mains earth & chassis become the same.

Voltages "floating" w.r.t  car chassis are not at all common in Automotive equipment,so using a "floating"input is not necessary for that reason either.

nk7:- A "floating" input just means that neither side of the input is connected to
the common  side of the 'scope power supply--in the case of a mains operated unit--mains earth.

You would not attach a CRO probe to the 30kV or so of the Spark plug leads,but anything else in a car is no more than about 400 volts.
Voltages of this level are commonly observed with a X10 probe when working on CRT type monitors,or Tube type radios & Amplifiers.

Professional Auto tester units usually have special pickups that can read Spark voltages,but these
(mains operated) units are extremely expensive.

 Apart from being awkward to handle,using bench 'scopes in Auto situations does present the possibility of breaching the insulation of the mains lead in some of the mechanicals & elevating the car chassis to mains potential.


VK6ZGO

[nk7]

"Automotive waveforms are not very demanding in bandwidth, but some, like spark plug outputs are in the kV relative to car ground, but to earth ground it can be far worse ... even the operating voltages within the ECU can be high, and what that is relative to earth ground I know not."

nk7:- A "floating" input just means that neither side of the input is connected to
the common  side of the 'scope power supply--in the case of a mains operated unit--mains earth.

You would not attach a CRO probe to the 30kV or so of the Spark plug leads,but anything else in a car is no more than about 400 volts.
Voltages of this level are commonly observed with a X10 probe when working on CRT type monitors,or Tube type radios & Amplifiers.

 Apart from being awkward to handle,using bench 'scopes in Auto situations does present the possibility of breaching the insulation of the mains lead in some of the mechanicals & elevating the car chassis to mains potential.

VK6ZGO

With this then I can guess that you are saying perhaps handheld DSO like HPS10 is the way to go for automotive and if I do want to get into electronics (which I do at a later stage) look for a second hand oscilloscope to get me started. Although I was trying to think of ways for making the CRO work (in terms of portability) the handheld is prob the best option apart from being inferior in a lot of its specs.