Help me pick an o-scope, $3k budget

[tautech]

All of what Andy wants can be bought quite cheaply in brands other than Pico excepting for their well priced current probe which TBH makes their package attractive.
I did a bit of an exercise yesterday and put together a package from Siglent where by a long way their 3rd party current probes were the biggest value item in the package but none are scope powered like the Pico in this price bracket.
To get it down a bit, a Dif probe like Pintek DP-25 and a Pintek current probe could pull $500 from the total price and then we'd get under the Pico cart price with a higher BW 100 MHz 4ch DSO.

Two things that nag me about the Pico (and maybe someone knows better) are the apparently low voltage rated inputs and I couldn't find accuracy specs for their current probe.

I enjoy brain teasers like this...........

[2N3055]

12/14 bit scope with 256 MS memory, 4CH and fully differential inputs.....
Advanced arbitrary math, 1M point FFT.....
Yeah, gazillion of those around...
This is scope custom made for exactly this type of work.


Low voltage what?

Input ranges (full scale)   ±10 mV, ±20 mV, ±50 mV, ±100 mV, ±200 mV, ±500 mV,
±1 V, ±2 V, ±5 V, ±10 V, ±20 V, ±50 V   ±2.5 V, ±5 V, ±12.5 V, ±25 V, ±50 V, ±125 V, ±250 V, ±500 V, ±1000 V

Input common mode range   ±5 V on ±10 mV to ±500 mV ranges
±50 V on ±1 V to ±50 V ranges   ±125 V on ±2.5 V to ±12.5 V ranges
±1000 V on ±25 V to ±1000 V ranges

As for current probe, you could or couldn't find specs?

Accuracy (0 to 200/1500 A)±1% of reading ± 100 mA, ± 500 mA
Accuracy (1500 to 1800 A)   ±3% of reading
Accuracy (1800 to 2000 A)   ±6% of reading

[tautech]

12/14 bit scope with 256 MS memory, 4CH and fully differential inputs.....
Advanced arbitrary math, 1M point FFT.....
Yeah, gazillion of those around...
This is scope custom made for exactly this type of work.


Low voltage what?

Scope input spec:
±100 V DC + AC peak (any differential input to ground)
±100 V DC + AC peak (between differential inputs)

As for current probe, you could or couldn't find specs?

Accuracy (0 to 200/1500 A)±1% of reading ± 100 mA, ± 500 mA
Accuracy (1500 to 1800 A)   ±3% of reading
Accuracy (1800 to 2000 A)   ±6% of reading

Thanks, didn't find that. 

[mzzj]

OP wanted to measure current transients (20khz current clamp was also mentioned)

Normal 60mV 200Amp shunt is borderline useless at 10khz because of the self-inductance.

Won't it be background noise compared to the inductance of the motor?

Umm..no.
Electronics 101: Your AC current measurement results go haywire if the shunt impedance is 0.25 milliohms instead of assumed 0.1milliohm. 
It doesn't take much inductance even at "low" frequency like 10khz if the shunt resistance is very small (like high current shunts are)
For example 0.3mOhm shunt resistor with 10nH series inductance has 10% error at around 2 khz.
(and if you are measuring watts/power thing get 10 times worse because phase shift error starts to show at about 200hz with the aforementioned shunt values)
(there is also another added error from skin depth )

[2N3055]

±100 V DC + AC peak (any differential input to ground)
±100 V DC + AC peak (between differential inputs)

Yes, you are right about that. They are not as robust in that regard. That is their weakness.

Not a problem with high voltage probe (±1000 V DC + AC peak in that case), which is something you would use for it anyways...

[tautech]

±100 V DC + AC peak (any differential input to ground)
±100 V DC + AC peak (between differential inputs)

Yes, you are right about that. They are not as robust in that regard. That is their weakness.

Not a problem with high voltage probe (±1000 V DC + AC peak in that case), which is something you would use for it anyways...

Which is not ideal when a 1:1 connection for greater sensitivity is required.

SHS1000 isolated ch HH spec:
CATII1000V and CATIII600V between two channels references，between channels reference and earth ground
CATII600V and CATIII300V between channels reference and Multimeter input reference
CATII300V and CATIII150V input direct
CATII1000V and CATIII600V input with 10:1 probe

[2N3055]

Those isolated scopes are very useful. For other purposes. Very nice machines.

If you need better detail, you have 12/14 Bit resolution.  That is 16x/64x more vertical pixels.  Which virtually enhances your vertical range that much times.

So on a 8bit scope on 1V/div and 12bit 12V/div and 14bit 64V/div you have same vertical resolution....  It is fascinating how much more detail you can get...

[nctnico]

SHS1000 isolated ch HH spec:

But it has 200x attenuation and only 1MHz bandwidth IIRC so not very useful. Better get a differential probe. MicSig has a very good differential probe for a reasonable price. And then there is always the Pintek DP-25.

[tautech]

SHS1000 isolated ch HH spec:

But it has 200x attenuation and only 1MHz bandwidth IIRC so not very useful.

<Sigh.>
You IIRC badly.

Standard supplied SHS1k probes are 250MHz, 10x and 1kV CATII rated. Pt# PB925. They are special high insulation probes and a little bulkier than std probes.
The SHS1k HH scopes are 60 or 100 MHz with 2Mpts memory.

The SHS800 series have models from 60 to 200 MHz and use std scope probes.

[nctnico]

SHS1000 isolated ch HH spec:

But it has 200x attenuation and only 1MHz bandwidth IIRC so not very useful.

<Sigh.>
You IIRC badly.

Standard supplied SHS1k probes are 250MHz, 10x and 1kV CATII rated. Pt# PB925. They are special high insulation probes and a little bulkier than std probes.
The SHS1k HH scopes are 60 or 100 MHz with 2Mpts memory.

The SHS800 series have models from 60 to 200 MHz and use std scope probes.

Since the topic moved to differential probes I was thinking about the isolation 'amplifier' box from Siglent and not a portable oscilloscope. My bad.

[tautech]

SHS1000 isolated ch HH spec:

But it has 200x attenuation and only 1MHz bandwidth IIRC so not very useful.

<Sigh.>
You IIRC badly.

Standard supplied SHS1k probes are 250MHz, 10x and 1kV CATII rated. Pt# PB925. They are special high insulation probes and a little bulkier than std probes.
The SHS1k HH scopes are 60 or 100 MHz with 2Mpts memory.

The SHS800 series have models from 60 to 200 MHz and use std scope probes.

Since the topic moved to differential probes I was thinking about the isolation 'amplifier' box from Siglent and not a portable oscilloscope. My bad.

Ah yes, the ISFE
https://www.siglentamerica.com/accessory/isolated-channel-optional-accessories%EF%BC%88isfe%EF%BC%89/

The Pintek DP-25 outperforms it.
ISFE's only benefits are physical size, direct coupling to DSO inputs and powered from USB.

[Wolfgang]

Hi,

IMHO your package should work if you dont mind the limited precision and frequency range (you have seen the datasheet) of your current probe.
Current probes tend to be *noisy*, too. This can be a real nuisance in the low current ranges.
It could make a lot of sense to measure smaller currents with a different probe.
 
Standard 1:10 voltage probes should work, too.

I would suggest that you make an extensive try before buy for your complete setup.

[Rohde_TestWalker]

Hey CraftyAndy,
There are a few other options to consider, like leasing or buying used. Is it for long-term use or a single project? Leasing is good for shorter term (and the leasing conpany take care of all the maintenance and calibration). If you opt for used equipment, you can get a good deal, but make sure you calibrate it before using.

There's a third option: wait for a major player to have special deals. I'll email you off-line about a special deal coming up from a "well known vendor of high-quality equipment." I can let the broader forum know about it when it goes more public. Standby for a direct email...

Good luck! And standby for that incoming email.
Rohde_TestWalker