New low-cost ($170) 100MHz Differential scope probe from Micsig

[17_29bis]

IMHO a high voltage 1:100 probe is more suitable for this kind of measurement since one side of the inverter output and CFL is likely tied to ground anyway.

That's true, although I don't have schematics for this particular inverter but I think one side of each CCFL is connected to the ground. And speaking about  high voltage 1:100 passive probes. Yes, fancy ones from Tektronix will have low capacitance (4pF for 300$ USD / 2.5pF for 470$USD / 1.8pF for 840$ USD),  cheap ones (20$-50$) will have capacitance is double digits. Knowing that this is why I bought DP10013 with its 1pF for 180$  in the first place. But anyway thanks for the input.

Consider that low value caps can be made by twisting wires together. If the inverter is that sensitive and running close to it's trip point....... well you get the picture. 

Somehow I thought that parallel wires have the biggest capacitance. Anyway, thanks for the hint, will try to untwist the wires and see what happens.

[Mechatrommer]

I own a DP10013 and wonder how the following can be explained.

The probe input resistance/capacitance is 10M / 1pF (in diff mode),  I am checking the voltage on the CCFL  connected to the 21" monitor power supply AIP-0121 (it powers  4 CCFL).

I know that this particular size of CCFL  runs at 700V(normal mode) - 1400V (start) Volts and draws about 4-8 mA (the frequency is about 62kHz). It is easy to calculate the equivalent resistance of the  CCFL which is about 150K -200K.

What am I missing here?

The total load of the probe and wires is likely several pf which at 700V and 62kHz can easely draw a mA extra.

the probe is a single wire. its not like coax which has surrounded gnd wires which contribute to high capacitance. i suspect the probed voltage exceed the diff probe common mode. it also can be due to high transient that capacitors paralleled across 5MOhm divider got into short circuit creating low impedance path. but i could be wrong.

IMHO a high voltage 1:100 probe is more suitable for this kind of measurement since one side of the inverter output and CFL is likely tied to ground anyway.

i dont find it relevant or rational. one should be fine with 1:50 (or 1:10 etc) probe as long as its working in its commong mode range.

[Dwaine]

I have one coming.  Has anyone confirmed if there really is different firmwares.

[PedroDaGr8]

Just purchased one for $113.60 (EBay has a 20% off coupon code, that the sellers haven't adjusted to yet!). Looking forward to using it on a few projects!

[Mr. Scram]

No, attenuation is too high for low voltage signals.
For low voltage audio frequency range stuff, you can build your own differential to single-ended converter with one or more op-amps (google instrumentation amplifier). With careful tweaking of resistors, you can get the common mode rejection to be very good.

What would be considered low voltage signals in this context?

[nctnico]

No, attenuation is too high for low voltage signals.
For low voltage audio frequency range stuff, you can build your own differential to single-ended converter with one or more op-amps (google instrumentation amplifier). With careful tweaking of resistors, you can get the common mode rejection to be very good.

What would be considered low voltage signals in this context?

Less than +/-10V. I've built such a differential amplifier myself using a differential amplifier from Analog devices. It is powered by +/-15V which gives a permitted input range and output swing about +/-12V.

[tautech]

No, attenuation is too high for low voltage signals.
For low voltage audio frequency range stuff, you can build your own differential to single-ended converter with one or more op-amps (google instrumentation amplifier). With careful tweaking of resistors, you can get the common mode rejection to be very good.

What would be considered low voltage signals in this context?

It depends a little on the input sensitivity of your scope.

A 1000:1 HV passive probe I got recently can easily resolve the scope 3V compensation signal and allow probe compensation adjustments, no problem.

[David Hess]

What would be considered low voltage signals in this context?

Low voltage differential amplifiers have no input attenuation.  For the best ones, this limits their input common mode and differential input range to about +/-10 volts although conceivably a good design could extend that a few times at the expense of bandwidth.

[stenbror]

I just bought two MicSig 100Mhz Differential probes from Banggood for under 300 dollars. (NOK 2620) including delivering in about 17days from China straight to my mailbox in Norway without any import fees. Yes......

[tsman]

Micsig have added a new model. DP20003 which is 100MHz still but 200x + 2000x instead of 50x + 500x.

[edit]Corrected mistake. 150 -> 50 and 1500 -> 500[/edit]

[CustomEngineerer]

The DP10013 (assuming this is the one you are referring to at least) is 50x/500x, not 150x/1500x.

[tsman]

The DP10013 (assuming this is the one you are referring to at least) is 50x/500x, not 150x/1500x.

Oops. Yes. Not sure where that extra 1 sneaked in from.

[slloyd]

i have two of these probes.  on x50 scale and both on the probe compensation terminals of RTM3004 350MHz scope.  it shows an offset between the two measurements.  to calibrate the probe, i have to open the case and adjust the multiturn pot?

[Hydron]

A DC offset can be nulled by shorting the inputs together and then holding both range buttons down until it starts clicking and flashing the lights.

I would be very interested to see inside the 200x/2000x version if anyone gets one (unfortunately it's annoying to get inside, have to carefully peel up the front sticker, though it's possible to do it without damage).

Edit: I'd also be interested in the frequency response of the new version - it seems to have even longer leads, and the old one already has issues where they can ring (due to L and C of the fairly long leads) within the claimed 100MHz bandwidth.

[tsman]

I'd also be interested in the frequency response of the new version - it seems to have even longer leads, and the old one already has issues where they can ring (due to L and C of the fairly long leads) within the claimed 100MHz bandwidth.

Same length leads. The DP20003 photo is just bigger. The specifications say ~60cm for both of them.

[lordvader88]

So what's the pro's/con's of these for someone that could afford these but not +400 ? I have a hard time saving money without spending it

People have had them for a while, what are they like ?

[Mr. Scram]

Micsig have added a new model. DP20003 which is 100MHz still but 200x + 2000x instead of 50x + 500x.

[edit]Corrected mistake. 150 -> 50 and 1500 -> 500[/edit]

That's quite nice, though the spelling errors on the official page don't instill much confidence.

[nctnico]

Micsig have added a new model. DP20003 which is 100MHz still but 200x + 2000x instead of 50x + 500x.

[edit]Corrected mistake. 150 -> 50 and 1500 -> 500[/edit]

That's quite nice, though the spelling errors on the official page don't instill much confidence.

Learn Chinese then 

[Mr. Scram]

Learn Chinese then 

I'd never comment on an individual making an effort, but this is a proper business.

[nctnico]

Learn Chinese then 

I'd never comment on an individual making an effort, but this is a proper business.

Still in many countries it is extremely hard to find someone who knows how to speak/write decent English. It is not a given everybody on earth can understand English.

[Mr. Scram]

Still in many countries it is extremely hard to find someone who knows how to speak/write decent English. It is not a given everybody on earth can understand English.

I don't think a competent Chinese to English translator would be hard to find for pretty much anyone with internet access. This is a legitimate business, not a Tindie shop.

[nctnico]

Still in many countries it is extremely hard to find someone who knows how to speak/write decent English. It is not a given everybody on earth can understand English.

I don't think a competent Chinese to English translator would be hard to find for pretty much anyone with internet access. This is a legitimate business, not a Tindie shop.

But as a customer who can't understand English: how do you know the translator is any good? After all In the land of the blind, the one-eyed man is king and given the amount of Chinglish we are subjected to the Chinese translators aren't afraid to oversell themselves. All in all it is foolish to dismiss a company because their foreign language website has some spelling / grammer errors.

[GreyWoolfe]

Still in many countries it is extremely hard to find someone who knows how to speak/write decent English.

Unfortunately, it is just as hard here in the US.

[Mr. Scram]

But as a customer who can't understand English: how do you know the translator is any good? After all In the land of the blind, the one-eyed man is king and given the amount of Chinglish we are subjected to the Chinese translators aren't afraid to oversell themselves. All in all it is foolish to dismiss a company because their foreign language website has some spelling / grammer errors.

You know a translation is good if you've hired a proper translator. There are various translators who specialise in the Anglo-Chinese market that can provide a decent a high quality translation for a modest fee. It can hardly be the first text that Micsig requires to be translated, so I'd expect them to have some experience with translators at this point. Even if just for foreign official documents.

I guess that you don't get it if you don't get it. I'm not nearly dismissing a company because of spelling errors. It does however reflect badly on the quality of the product and how one does business. In this case it's even a safety critical product. Some people might be tempted to wonder where else they cut corners. If you spend tens of thousands of dollars on the development and certification of a product and go through some effort to set up a decent website it's painful to drop the ball with the finish line in sight. That also applies to the Chinglish in device menus, by the way. Paying next to nothing for a proper translation is how a company can separate itself from all the hopefuls that occupy the lower tiers of the market. You can bet the Keysights and Flukes get their texts translated by very capable translators.

If you don't get it you don't get it, but a little goes a long way. That's all.

[Hydron]

...so I finally got around to cutting off ~20cm of lead length on one my DP10013 probes. I haven't done any proper measurements of the new frequency response after the mod, but it sure did make an improvement regarding ringing!
The attached pic shows 3 different probes measuring the same signal, yellow is a (decent) 300MHz 100:1 passive probe, green is the modified DP10013, and orange is the un-modified DP10013. Ignoring the skew between the signals, the modded Micsig is much closer to the passive reference probe (which here I am regarding as being a lot more likely to represent the true signal).
Time permitting I'll try and check out the frequency response of the modded vs original probe, but given what I've seen so far I suspect I'll be doing the same change to the other one of the pair I bought.

Note: both diff probes had their leads twisted together. Results would be different if not doing this - unfortunately it makes a fairly big change in their response.