Siglent LPA10 Active Probe Adapter

[Martin72]

Hi,
Now that I finally have a siglent scope with active probe interface(SDS3000X HD), I am interested in the adapter for active probes from lecroy, the LPA10:

https://www.meilhaus.de/siglent-lpa10.htm?b2b=0

Almost 300€.....Puhhh....
Nevertheless, the prospect of being able to use Lecroy probes/current clamps with it is very tempting.
But....
If you look at the data sheet, only 4 types are listed as compatible - that is very meager.
Compatibility stands and falls with the implementation in the software - hardware is simply...
Symmetrical supply plus data bus, done.
Question to the group, is that really so few supported probes?
Question to the absolute Siglent experts:
Are further updates regarding list of supported probes in the pipeline?
Only 4 models are definitely too few for the price.

Another link (datasheet included):

https://www.siglent.eu/product/10676408/siglent-lpa10-active-probe-adapter

[tautech]

I suspect the listed probes supported is outta date just as the list of DSO's it can be used with. 
As you can see only later scope FW versions support these so it's anyone's guess if the SDS3000X HD you have supports these either.....yet.

Best you nag EU HQ for some answers however China HQ is on May holidays until next week so it might take a few days to get the latest info.

But at least LPA10 is a good bit cheaper than TPA10 that supports Tek active probes.

[Martin72]

Hi Rob,
I think I´ll ask Siglent EU HQ for loaning me one.
Because all known dealers do not have it in stock and only order it when needed, which makes sense.
If I really get an adapter, I will take our lecroy current clamps and test it with them and report back here.

[alm]

I would indeed verify compatibility rather than assume. For the TPA10 TekProbe adapter Siglent seems to have messed up the offset feature to the point where it's only usable with a few Tektronix probes that have their own offset control, and partly usable (no control over the vertical position) with Tektronix probes that ignore the offset signal. I have not seen an update that this was fixed.

Lecroy's probe interface is purely digital except for the scaling resistor in passive probes, as far as I understand. But there are a number of features, like controlling nulling, offset and attenuation from the scope, that came later in the life of their probe interface. Earlier probes like AP033 would have buttons on the probe / compensation box, which have been mostly moved to being controlled from the scope in later probes. So I'll be curious of the Siglent adapter supports those features. It might be that such functionality only works for supported probes since I believe Lecroy generally releases software updates to support newer probes.

The other thing is that DC current probes may draw a fair amount of current, since the way they work by sending a reverse current (multiplied by the transformer ratio) through the Hall effect sensor to null the magnetic field. Tektronix had problems with this on some of their scopes. I wonder if that's a reason for the short compatibility list. A test would be to connect a current probe measuring its max DC or LF current, and then see if this introduces ripple on the power rail that affects other probes powered by other channels (of course this also depends on their NMRR).

[tautech]

I would indeed verify compatibility rather than assume. For the TPA10 TekProbe adapter Siglent seems to have messed up the offset feature to the point where it's only usable with a few Tektronix probes that have their own offset control, and partly usable (no control over the vertical position) with Tektronix probes that ignore the offset signal. I have not seen an update that this was fixed.

To quote an edit to the last post:

EDIT for those who are late to the party: The TPA10 was confirmed defective. The voltage rails (+-15V, +-5V) are fine, but the offset on Pin 5 is stuck at Vmax = +-2.5V depending on the position of the offset knob).

[alm]

EDIT for those who are late to the party: The TPA10 was confirmed defective. The voltage rails (+-15V, +-5V) are fine, but the offset on Pin 5 is stuck at Vmax = +-2.5V depending on the position of the offset knob).

But the "non-defective" replacement barely worked any better because the offset range was well below spec (+/- 200 mV instead of +/- 1 V) and the polarity was inverted. Also, I doubt this fixed vertical position control for probes that do not use the analog offset voltage or have their own offset control like the Tek P6243. Do you have reports of either issue being fixed? The end result of that thread appeared to be to ditch the Siglent adapter and buy a Tek power supply instead which would fix all issues.

[Martin72]

I think I´ll ask Siglent EU HQ for loaning me one.

The support is just great, I will get an LPA10 next week.

[Martin72]

Tadaa...

A cute little thing, but solidly made and quite heavy.
Next week I can borrow current clamps from work.
We have a few Lecroys, but basically only 2 different models - but that would be enough for me to test.
I'm curious to see if they will be recognized...
With the release of the new SCP5000 series from siglent, it could be that this adapter will no longer be manufactured.
I think that would be unclever, I would rather make sure that the scopes support as many samples as possible.
Because the current clamps are/were very expensive and this is often a reason to stay with the brand if a new scope is to be purchased.
But first try it out next week.
The adapter on the SDS3000X HD definitely fits and is really precise.

[Martin72]

Hi,

The first attempt....And already a failure.
I took an AP011 current clamp home and connected it.....Nothing.
Tomorrow I will take a current clamp with me, which is also available from Siglent.
If this is also not recognized, the adapter is worthless for me.
Or the scope is so new that little or no data from Lecroy probes is stored...
So tomorrow is the next attempt.

[Martin72]

Well...
Even a new current clamp, the CP500 from Lecroy, is not recognized.
I have tested an old and a new current clamp with negative results, so it can be assumed that no current clamps are recognized at all.
I took a closer look at the adapter itself, as I suspected it is a completely mechanical solution (pin3 and pin6 swapped, which is correct), so that can't be the problem, it's just what was stored in the Scope software.
Obviously no current clamps...
Will this be changed? I have my doubts.
Well, now we know exactly and so the effort was worth it.
I am glad that Siglent gave me the chance to try it out first instead of buying it.
I will still report to Siglent, if anything comes up I will post it in the thread.

Martin

[KungFuJosh]

Hopefully they add that support with a firmware update.

[alm]

Thanks for testing this!

I have tested an old and a new current clamp with negative results, so it can be assumed that no current clamps are recognized at all.

The datasheet shows one current probe (CP030), so I'd hope that probe would at least work with some of their scopes?

I took a closer look at the adapter itself, as I suspected it is a completely mechanical solution (pin3 and pin6 swapped, which is correct), so that can't be the problem, it's just what was stored in the Scope software.
Obviously no current clamps...
Will this be changed? I have my doubts.
Well, now we know exactly and so the effort was worth it.
I am glad that Siglent gave me the chance to try it out first instead of buying it.
I will still report to Siglent, if anything comes up I will post it in the thread.

Is there any way to override / ignore this dialog? On older Lecroy scopes, my experience has been that newer probes are not supported, but will still mostly work (except not being able to control any of the functions like zeroing from the scope). The scopes will allow you to adjust the units (V or A) and attenuation setting for the channel. The bus is just power + I2C, basically. For the older probes, as long as they get power, they should work. Newer ones might be stuck on a single attenuation / offset setting if the scope doesn't know how to adjust this. Maybe it would help if you could isolate the I2C pins? Lecroy actually sold a power supply for some of their probes that I'm sure doesn't do any I2C communication. It's not rated for current probes. My guess is that it's because it can't supply the relatively high current such probes demand.