EEVblog HVP70 Differential Probe

[JonM]

Has anyone found any nicer probes for the thing?

I really don't like the ones that come with them. They are really hard to open up sometimes if you are in a tight space or funny angle.

probemaster.com has many choices for probe connections. For AC mains, I have a couple of banana to "big metal blade" that came with a Triplett wire tracer. I will probably keep them with my HVP-70 since I don't use the wire tracer very often.

[Dubbie]

My favourite bench meter probes are probemaster so I did check out their site. They didn’t seem to have anything suitable.

[JonM]

My favourite bench meter probes are probemaster so I did check out their site. They didn’t seem to have anything suitable.

Upon further study it appears that I have only one Probemaster probe that fits the HVP-70 leads, and it it insulation piercing which may not be appropriate for HV work.

Because the HVP-70 leads do not have retractable sheaths (maybe a requirement of 1000V Cat III ?) only select probe adapter will work. In the photo, from the top:

 - "Big blade" mains probe from Triplett wire tracer
 - Big alligator clip marked 1000V Cat III, possibly from Fluke Scopemeter kit
 - The original HVP-70 probe, for reference
 - Minigrabber, probably from Franky: http://stores.ebay.com/99centhobbies
 - Probemaster 9174 Piercing Probe, marked 1000V Cat III

Looks like I may need a few more probes for the HVP-70.

[NiHaoMike]

I decided to finally do a teardown on mine and the build quality, while definitely not the worst I have seen, was nowhere as good as I was expecting. Three bodge wires that aren't even tacked down, a lot of other bodges, and poor soldering quality in general. There's also a trace routed under one of the switches such that tiny movements from use can cause it to short. The worst part is that I cannot touch it up (except the switch - very carefully bend the metal to give more clearance) because doing so will almost certainly affect the calibration.

Another odd part is that the chips were painted over in different colors. If it was to slow down reverse engineering, it was certainly ineffective since it only took a few minutes with a pocket knife to scrape it off and identify the important parts.

It looks like it uses basically two very well matched X100 attenuators with an impedance high enough to be considered isolated when used with mains voltage. It then goes to an AD8129, with a gain of 10, for the X10 mode and an AD8130, with unity gain, for the X100 mode. One switch selects which is used and a THS3061 drives the coax output. On the PSU side, there's a flyback converter with a very unusual transformer being driven by an unidentified chip with the markings 487D S18B. A common 393 drives the power LED.

[bicycleguy]

NiHaoMike,

Wow, as you noted that looks surprisingly crapy.  I opened mine to see if the same but chickened out at the metal cans.  I really like the unit and didn't want to risk messing it up.

Up to that point it looked good although the tamper stickers were easily defeated, however, the solder joints I could see between the cans looked as dirty and cold soldered as your's.  I have gotten a little cocky about safety since I started using this but seeing your pictures will hopefully make me sober up.

[Hydron]

Thanks for the pictures, I was interested in how this probe was constructed. The use of the AD8130/29 is unsurprising, they fit the bill well for a diff-probe (I have played around myself using them in exactly the same way).

The J1 and J2 "bodge" wires are actually probably designed to be there (in order to make it possible to construct with a 2 layer PCB), rather than being hacked in afterwards. They are only being used to switch between the 2 input chips (go to the shutdown pins), so could definitely be tacked down without any change to calibration. I can't tell what the third wire does from your photo - is there any chance of getting a clearer, high-resolution picture of the top of the PCB?

[Zbig]

Kinda ironic, considering Dave's eagerness to point out any PCB's (or product's overall) quality issues or general nastiness on every occasion, in no uncertain terms. I definitely won't rush to drop my $350 (current Amazon list price) on one anytime soon, unless I need one badly. Well, that's the lack of competition at works, I guess...

[bitseeker]

Well, I guess Dave needs to take a look at the recent batch of them and open one up. If their QC has dropped, I'm sure he'll say something about it.

I haven't torn mine down, but now I'm getting curious.

[TheSteve]

Hmmm, did Dave ever do a teardown on camera? It does look from the picture to be rather "how ya doing".

[bitseeker]

I don't recall, exactly. Might have been an actual Sapphire he took apart before?

Sent Dave a quick message to check out Mike's post. The forum is too big to keep track of everything.

[The Soulman]

Construction quality and overall design of the Dave probe seems very similar to the lecroy (sapphire) from video 932. 

[EEVblog]

I don't recall, exactly. Might have been an actual Sapphire he took apart before?

Sapphire make all the probes, including this one, Lecroy, Keysight and many others, they all re-badge Sapphire.

[NiHaoMike]

Is anything being done to address the problem so that newer units will be built with better quality?

[LaurentR]

I managed to get my hands on a few differential probes to compare noise levels for low-voltage use.
Compared:
* Pintek DP-25 25MHz X20/X50/X200. ~$300
* EEVBlog HVP70 70MHz X10/X100. $350 on Amazon US. This is a Sapphire design (not on their web site) and is now also available as the Cal Test CT4192 ($795) and Testec TT-SI 9071
* CT3688 200MHz X10 (really X5). $989 on Amazon US, but seen as low as $568. This is a Sapphire design (SI-200) and it is available under some other names like Testec TT-SI 200. Seems similar to the Keysight N2792A ($1917)

Note: The CT3688 is quoted as X10, but it's X10 "into 50 Ohms", so it's really a X5 probe for comparison.

Advertised noise levels are:
* DP-25: 1mv RMS = 20mV RMS input equivalent at X20.
* EEVBlog: 1.5mV RMS = 15mV RMS input equivalent at X10.
* CT3688: 0.3mV RMS = 3mV RMS input equivalent at X10 (really X5)

Below is a screenshot of the three probes with a shorted input. Std Dev at the bottom of the screen.

Comments:
* All probes are within spec with a bit of margin.
* The EEVBlog probe has a somewhat but not dramatically better noise level than the Pintek. It has more intrinsic output noise, but wins because of the 10X divider. However, the Pintek has proportionally more peak noise (p2p approx values for the 3 probes: 24mV, 110mV, 205mV).
* The CT3688 really has a much lower noise level than the others. It is the only probe I have seen that has a noise level substantially lower than 1mV output.

[bitseeker]

Interesting. Thanks for the comparisons. I also like having the X10 on the HVP70.

[s_lannan]

Hi There,
Went to buy one earlier today, noticed they were 'out of stock'
Does anyone have a rough ETA on when they'll return?

Thanks.

[Hydron]

* The CT3688 really has a much lower noise level than the others. It is the only probe I have seen that has a noise level substantially lower than 1mV output.

It may be a bit late (didn't see the post at the time), but would you happen to have a pic of the insides of the CT3688? Am interested in what they are doing to get the low noise level compared to the others. From the datasheet it looks to be lower input impedance than the others (which maybe do a 100:1 divider first then multiply by 10x for the 10:1 range - would explain extra noise), but it'd be nice to know what they're actually doing.

[bitseeker]

Went to buy one earlier today, noticed they were 'out of stock'
Does anyone have a rough ETA on when they'll return?

Dave discounted them not too long ago to clear out his inventory. So, it doesn't sound like they're coming back. However, I haven't heard definitively one way or the other.

[Octane]

Any update on those probes? Dave?

[Mechatrommer]

...One switch selects which is used and a THS3061 drives the coax output....

i just noticed this 2 years old post.. THS3061 is not designed for repetetive high slewrate more than 900V/us.. it will burn. so for ±700V input, it has to output ±14V swing to the 50 ohm termination to produce ±7V on the dso. if anyone can design a 1400V that contains about 30MHz harmonics, THS3061 will burn, for normal 240Vac system, limit your BW to 40MHz, this opamp is in my ban list. i guess why we dont see this thing burnt is because users mostly from 110Vac countries (can safely go to max 70MHz spec limit) or nobody built 1400V 30MHz circuit with it, so i guess for normal usage of target customers, its ok. better replacement is something like THS3091 imho, fwiw..

[EEVblog]

Went to buy one earlier today, noticed they were 'out of stock'
Does anyone have a rough ETA on when they'll return?

Dave discounted them not too long ago to clear out his inventory. So, it doesn't sound like they're coming back. However, I haven't heard definitively one way or the other.

Sapphire have apparently just found a buyer, so they have been saved from going under. But not sure about production of this probe, I think I can make another buy order though.
But I'm also currently investigating getting another probe customised to match the HVP70 specs.

[bdamson]

Hello, I'm an avid EEVblog watcher for few years now and this is my first forum post. I'm new to electronics and just purchased my first oscilloscope. +1 on interest in another Dave branded differential probe! 

[NiHaoMike]

i just noticed this 2 years old post.. THS3061 is not designed for repetetive high slewrate more than 900V/us.. it will burn. so for ±700V input, it has to output ±14V swing to the 50 ohm termination to produce ±7V on the dso. if anyone can design a 1400V that contains about 30MHz harmonics, THS3061 will burn, for normal 240Vac system, limit your BW to 40MHz, this opamp is in my ban list. i guess why we dont see this thing burnt is because users mostly from 110Vac countries (can safely go to max 70MHz spec limit) or nobody built 1400V 30MHz circuit with it, so i guess for normal usage of target customers, its ok. better replacement is something like THS3091 imho, fwiw..

It's designed to output to a 1M load, so the coax itself is the only significant load it sees.

[Tarloth]

THANKS DAVE! I'm really interested in a new differential probe!

[EEVblog]

FYI, I have more stock coming mid August.
No word on the other design yet.