Author Topic: New low-cost ($170) 100MHz Differential scope probe from Micsig  (Read 40624 times)

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Offline alm

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #50 on: July 14, 2017, 09:40:35 am »
If you zoom in onto the AliExpress picture, you can see the silkscreen stating 'Output <= 3 V into 1 MOhm'. So the impedance mismatch would be no worse than with a 50 Ohm output. The only issue that could arise is with extending the cable, but first, you should probably not do that anyway, and secondly I doubt the small impedance mismatch would be that noticeable at only 100 MHz with an unterminated line.

It is an odd choice. I did not even know that you could get 75 Ohm insulated BNC connectors. Maybe they used a video buffer designed for driving 75 Ohm loads?
« Last Edit: July 14, 2017, 09:42:40 am by alm »
 

Offline nidlaX

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #51 on: July 14, 2017, 11:33:26 am »
Is there any CAT rating on this differential probe? Without it I wouldn't want to use it on anything mains powered.
I'll get back to you on this, but it is CAT rated according to their R&D. I've asked them to update their catalogue and manuals with this info.
 

Offline nctnico

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #52 on: July 15, 2017, 05:26:12 am »
not enough grey matter. that thing need mains supply or power bank around in order to work. i wish someone has enough wisdom of using 2 rechargable li-on stacked inside (preferably 18650 size hence easily replacable) 7.2V with charging circuitry (from 5V USB) that doesnt block operation during charging (ie charging while probing)...
No, they got it right! You power it from the scope's USB port and MicSig's tablets already have a battery inside. So why use an extra battery inside the differential probe?
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline exe

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #53 on: July 15, 2017, 06:25:48 pm »
No, they got it right! You power it from the scope's USB port and MicSig's tablets already have a battery inside. So why use an extra battery inside the differential probe?

To use it with other scopes? :)
 

Offline nctnico

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #54 on: July 15, 2017, 07:11:23 pm »
No, they got it right! You power it from the scope's USB port and MicSig's tablets already have a battery inside. So why use an extra battery inside the differential probe?
To use it with other scopes? :)
Those have USB ports too so no problem.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Jeroen13

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #55 on: July 18, 2017, 04:22:12 pm »
Comparison between Micsig DP10013, Tektronix THDP0100, TekTronix TIVM05 on a Tektronix 5 series MSO58



High-side gate-emitter (IGBT) with 400V switchnode:




400V switch node:




Overall I think it is a very good probe especially for that price. The measurement leads are a bit long which probably causes some extra ringing.
« Last Edit: July 18, 2017, 04:41:22 pm by Jeroen13 »
 

Online BravoV

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #56 on: July 18, 2017, 04:32:14 pm »
Jeroen13, thank you for the comparison !  :-+

Online EEVblog

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #57 on: July 18, 2017, 05:03:37 pm »
Is there any CAT rating on this differential probe? Without it I wouldn't want to use it on anything mains powered.

FYI my HVP70 probe is fully independently tested and CAT III rated.
I also have the full test report for it with test photos and setup etc, some of which I think I showed in the CE mark video.
 
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Online BravoV

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #58 on: July 18, 2017, 05:24:07 pm »
Is there any tear down photos of it's internal yet ? ... wishful thinking ...  :P

Online wraper

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Re: New low-cost ($170) 100MHz Differential scope probe... actually $160
« Reply #59 on: July 18, 2017, 06:02:55 pm »
Actually it's $160, not $170 if you click to claim $10 off coupon
Quote
Spend US $120.00 to get US $10.00 off.
(includes shipping costs)
Expires 2017/07/25
 

Offline Hydron

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Re: New low-cost ($170) 100MHz Differential scope probe... actually $160
« Reply #60 on: July 18, 2017, 06:15:12 pm »
Actually it's $160, not $170 if you click to claim $10 off coupon
Quote
Spend US $120.00 to get US $10.00 off.
(includes shipping costs)
Expires 2017/07/25
...or just over $100 each (plus 22% tax, ouch) if you order 2 for 185 EUR like I just did

If a teardown hasn't already gone up by the time I receive mine then I'll have a look inside and post some pics. Jeroen13 - thanks for the measurements, they gave me enough confidence to buy a couple.
 

Online Electro Detective

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #61 on: July 18, 2017, 07:00:32 pm »
I prefer to wait for Christmas and get the EEV probe for a tad more than the generic Pintek and know what I'm getting   :-+

otherwise I'll stick to proven old school techniques in the meantime    >:D


Unless the teardown of this cheapie isn't too shabby for 50 hz prod work    ;D
« Last Edit: July 18, 2017, 07:24:42 pm by Electro Detective »
 

Offline JPortici

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #62 on: July 18, 2017, 07:05:04 pm »
Comparison between Micsig DP10013, Tektronix THDP0100, TekTronix TIVM05 on a Tektronix 5 series MSO58

[porn]

Overall I think it is a very good probe especially for that price. The measurement leads are a bit long which probably causes some extra ringing.

thanks for the photos. very jealous of the test setup :D
 

Offline jacklee

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #63 on: July 18, 2017, 09:49:04 pm »
 :)  ;)

To be or not to be, who care this question?
 
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Offline Hydron

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #64 on: July 18, 2017, 10:11:22 pm »
From the pics it looks like the front end is handled by one of these:
http://www.analog.com/media/en/technical-documentation/data-sheets/ADA4817-1_4817-2.pdf

Won't be able to confirm until better pics come along or mine arrives though.
 

Offline H.O

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #65 on: July 18, 2017, 11:56:00 pm »
The USB jack on the side is labeled power output but do they feed both power and data thru to that jack so that you can plug your thumb drive into it when the scopes USB jack is occupied by the probes "power cable"?
 

Offline alm

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #66 on: July 19, 2017, 12:14:49 am »
What surprises me is that they went through the trouble of using an insulated BNC connector, presumably because the Micsig scopes can be operated without a ground connection, and so the shell is not guaranteed to be at a safe potential. But then use USB connectors that most likely have their shell connected to the BNC shell. They could have used a deep barrel connection, like on some Fluke/Agilent differential probes, if they were worried about safety.

Does the manual say anything about requiring a grounded scope?
 

Offline MasterTech

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #67 on: July 19, 2017, 03:46:36 am »
Just ordered a couple.
I'm actually thinking of 'upgrading' one of them to x50, x1000... lets see how I'll do that. :P
 

Offline nctnico

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #68 on: July 19, 2017, 03:51:25 am »
@Jacklee: do you have a picture of the solder side of the board? I'm wondering whether the USB interface is fully routed so you can plug a USB stick into the probe.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Hydron

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #69 on: July 19, 2017, 05:03:51 am »
Just ordered a couple.
I'm actually thinking of 'upgrading' one of them to x50, x1000... lets see how I'll do that. :P
From looking at the PCB picture there are a few things which might make changing the gain of these difficult:
- The input divider is only 5x SMD resistors/capacitors. This will be difficult to run at higher voltages than 1.3kV (look at voltage ratings of SMD resistors - even special HV ones do not have high voltage ratings)
- The gain change appears to be done after the input stage. If the input of the ADA4817 is at the limit of it's common mode input rating at 1300Vin then the input divider ratio would have to be changed, rather than just the gain resistors for the range you want to modify.
- Other than the trimcaps/pot on the the input (for CMRR) all other trimming (for offset etc) seems to be done digitally, probably during production. If this varies with different ranges then it could be tricky to get right if you change the gain of one range.

That said, hopefully it doesn't end up too hard to mod these - personally I'd be interested in changing at least one to 20/500X for (hopefully giving lower noise on small signals)

I'm a bit confused myself as to how the gain switching is being done - there appear to be 2 different sets of series resistors between the input and output amplifier stages (switched via the relay) but this would be a nightmare to match for correct CMRR, so I'm not sure how it's being managed or if I'm completely wrong in my analysis. Has anyone got any ideas? I second the request for solder-side.
 
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Online tautech

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #70 on: July 19, 2017, 05:48:05 am »
Request:
Please identify U7.
Avid Rabid Hobbyist
 

Offline nctnico

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #71 on: July 19, 2017, 05:49:20 am »
Request:
Please identify U7.
Looks like an isolated DC-DC converter.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Floyo

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #72 on: July 19, 2017, 05:50:41 am »
For the price/introduction deal they seem pretty good. I like the USB power option, the supplies are just so ubiquitous, there are probably at least five sockets around the bench at any time. I have the Pintek DP25 with its center negative 9V barrel jack, and that is slightly less than ideal for a few reasons.

It looks to me like they used an isolated DC-DC brick for powering the probe, there seems to be a lack of traces between both sides of U7,
possibly indicating isolation. But then the data traces of the "host" USB-A port seem to sneak off to R99/R100 right close to the "secondary" circuitry, so that contradicts the isolated theory.
 

Online tautech

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #73 on: July 19, 2017, 05:57:02 am »
Request:
Please identify U7.
Looks like an isolated DC-DC converter.
Yes of course.

Its specs will be interesting.  :popcorn:
Avid Rabid Hobbyist
 

Offline MasterTech

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Re: New low-cost ($170) 100MHz Differential scope probe from Micsig
« Reply #74 on: July 19, 2017, 06:08:22 am »
Just ordered a couple.
I'm actually thinking of 'upgrading' one of them to x50, x1000... lets see how I'll do that. :P
From looking at the PCB picture there are a few things which might make changing the gain of these difficult:
- The input divider is only 5x SMD resistors/capacitors. This will be difficult to run at higher voltages than 1.3kV (look at voltage ratings of SMD resistors - even special HV ones do not have high voltage ratings)
- The gain change appears to be done after the input stage. If the input of the ADA4817 is at the limit of it's common mode input rating at 1300Vin then the input divider ratio would have to be changed, rather than just the gain resistors for the range you want to modify.
- Other than the trimcaps/pot on the the input (for CMRR) all other trimming (for offset etc) seems to be done digitally, probably during production. If this varies with different ranges then it could be tricky to get right if you change the gain of one range.

That said, hopefully it doesn't end up too hard to mod these - personally I'd be interested in changing at least one to 20/500X for (hopefully giving lower noise on small signals)

I'm a bit confused myself as to how the gain switching is being done - there appear to be 2 different sets of series resistors between the input and output amplifier stages (switched via the relay) but this would be a nightmare to match for correct CMRR, so I'm not sure how it's being managed or if I'm completely wrong in my analysis. Has anyone got any ideas? I second the request for solder-side.

The input resistors shouldn't be a problem, both the voltage rating and power have to be considered. There are hv smd resistors, easy to buy 3kv ones at 2512 size, 1kV @1210 . At 2500V input however 5 1Meg resistors in series will dissipate 250mW each and those in the picture don't seem big enough. The input compensating ceramic caps would need to be upped in voltage rating too

The gain setting is another story of course that will have to be studied. I hope that it is not fixed before the diff amplifier as you mentioned, that would be weird.

The frequency compensation that goes along these dividers will get affected too and a before/after comparison in a network analyzer will come in handy.

This is something Ill look into as I'm very interested in having the input limit raised to about 2500V
« Last Edit: July 19, 2017, 06:39:59 am by MasterTech »
 


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