My first oscilloscope

[aargee]

I imagine poor Mike_mike has no idea where his thread went.

[Mike60]

Hi
What you are think about :
DSO-201
http://www.sainsmart.com/sainsmart-arm-nano-dso201-oscilloscope-mini-storage-digital-pocket-sized-portable-kit.html
I need for low frequency, DC/AC. I am sure i will not work with RF or audio signal.
I need to test output voltage from OLD plating rectifiers who are working on 3phase.
It is very nice for my work - build in battery ( portable ).

Thank you in advance
Mike 

[tautech]

Expected voltages? 

I'd be worried about YOUR safety.


What do you need a scope to display?
Won't a DMM do what you need?

[Fungus]

What do you need a scope to display?
Won't a DMM do what you need?

^^ What he said - why do you need a 'scope for that?

A true RMS multimeter would be the correct tool for the job.

[JPortici]

Meanwhile, on april 1st the OP grabbed a sack of popcorn 

[Mike60]

I have TRMS meter but it is better & easier to show to my boss if one of this 3 phase are bad. 3phase on low voltage.
rectifiers for plating are no more like 20V/2000A. We have some new rectifiers but are switched electronically. So I don't need for them.
The are filled with plenty of diod and 3phase secondary transformater. To test if one low voltage phase are bad it is easier with graph.
Old factory 
So - please.
It is better DSO201 or DSO202 for what I am asking or NO ? I suppose I can save the graph and show him.
Best Regards
Mike

[Fungus]

If you want to look at phases then you really need two channels.

There's no way I'd recommend one for general EE work. The user interface on those things is awful, but... if you only want to use it with one type of signal you can set it up once and leave it.

The inputs are rated for 80V so in theory you'll be OK on a 20V tri-phase supply. OTOH I assume there might be something wrong with your supplies otherwise you wouldn't be looking at them. Anything with windings and inductors can produce big voltage spikes. I'd hack together a 10x resistor divider and connect the probes to that instead of connecting them directly to the power supply. Maybe even add a 10V Zener diode to clamp the voltage to 10V after division.

It's not perfect, but for your application, and for something the boss can look at, then ... why not? 

[Mike60]

Every time he told me power  / voltage are not correct.
BUT - all the time he see chemicals are wrong. Who make chemicals every time he makes mistake and I want to be OUT from this circuit 
If i show him i have all 3phase then he stay calm 

I will post some pictures with our OLD rectifiers 
I spoke with him to buy new but ....
I found on Aliexpress for 1000$ with delivery. He can buy from here with ~ 8000£ 
He don't have trust in China but all ours rectifiers are made in China 

Regards
Mike

PS. This oscilloscope i will buy with my £ so ar my property 
I play with oscilloscopes plenty of years ago ..... LONG TIME AGO. I am not so young. So this new are like gadget for me 

[oldway]

I also worked on these old rectifiers for electrolysis.
It was a 20V rectifier 12.000A I changed into 2 units of 20V 6000A by adding a new control.
Primaries were controlled by thyristors. (There were 2 transformers)
The secondaries and the diodes were watercooled.

What you need is an ac/dc current clamp.
This allows to check the current balance in the phases and in the diodes.

I would choose an analog scope as Tektronix 2235.
It is relatively light weight and easy to carry.

[Mike60]

We have clamp-meters but i don't like and I can not see if one phase are down.
No space rear and on both sides to open and measure inside.   
If I have final voltage on buss bars like attachment I am sure all 3 phases are working properly.
All rectifiers are only with diode air-cooling. Only one smaller has water-cooling. There are manual with mechanical control. Maximum amperage for this are 2000A / 15V.
I make many electrical changes from old non-working analog meters to digital to be accurate and better visible.
So I don't need some more expensive device to buy for this job.
What I invest in this oscilloscope are from my pocket.
Regards
Mike

[Fungus]

So I don't need some more expensive device to buy for this job.

You have very clear requirements and this will do the job. I say go for it.

[oldway]

Old rectifier, but I did not mean that old 

[Mike60]

Your rectifier are build LAST YEAR   
My, 40 years old or more   
Mike

[oldway]

Your rectifier are build LAST YEAR   
My, 40 years old or more   
Mike

I made this change in 1993 on a rectifier which already dates back more than a decade
I split the 12.000 A rectifier in two 6.000A rectifiers.
On picture rectifier1, you can see lefthand the old control and righthand the new one.

From top to bottom:
(new primary phase control)
3 x ultra fast fuses for thyristor's protection and 3 fuses of the transient filter
3 x 100/1A current transformers and transients filter
Full controlled bridge (6 SCR's) 120A
3 x auxiliary transformers and fuses
new three-phase control circuit.
watercooled diodes

[IconicPCB]

Mike get three CTs and monitor rectifier input currents.

Use lamps in parallel with CT load resistors for immediate visual comparison.

Inexpensive and self powered.

I made my own hot and cold press with three phase heating cal-rods and settled on a current transformer bi-color LEDS for ON OFF indication

[Mike60]

Hi
I need to write about this on another topic with different testing devices not here on " Oscilloscope " ?
Moderator can move what are not for Oscilloscopes ?

" oldway"
You have plenty of amperage with this rectifiers. We don't have and don't need.
But Yours are new comparing with mine.
Like I write above.
I don't have space to take down lateral or rear wall and work inside rectifier.
So I can not install nothing inside. I need only outside to do something. If i see output DC-graph i am sure are ok.
I have some cheap and perfect working displays from Ali... but are for AC. I have and for DC but i need to install shunt.
What I install are with very low cost. China but working.
Another picture with one new rectifier on top on older ( not working anymore - input primary transformer short ) rectifier. Same capacity & power.
If I will buy one small oscilloscope i will play with him and home when i have free time from my wife 
Regards
Mike