HM1008-2 strange effect

[DonRon]

Hi guys and girls,

got my brandnew Hameg HM1008-2 a few days ago. Made some first test and I am really happy with the decision to buy it.
But I observed some strange effect and I am not sure wether this is okay or there is some defect.

If sensitivity is very high (1, 2 5 and 10 mV/div) I can see some signals while knocking gently onto the chassis. With 1 and 2 mV/div those signals appear also while I rub the chassis gently. Channel 2 shows more Aplitude then Channel 1. With Input grounded the base line is stable.
Is that due to static electricity or due to "microphonic" sensitivity of the input stage (I can remember that Dave shows us the vibration sensitivity of the probes). Attached you will find a screen shot (probes were not attached).
Maybe someone with a Hameg 1008-2 can make a test or knows this effect. (Also sent an E-Mail to Hameg today). Really would appreciate your info.

EDIT:
Connected a signal generator via coaxial-cable and 50 ohms with the scope - even with very low signal amplitude the described effect cannot be seen any longer ... maybe a little bit with 1 mV/Div.
So only with probe disconnected or probe connected but probe not coneccted to any signal.
 

Thanks and cheers from Germany

Ronald

[DonRon]

Hello to all,

so I wanna keep you informed.

Got an answer from Hameg:
That behaviour is really a microphonic effect and so everything is okay.
If one observe the effect with a signal fed to gthe inputs, than there is a problem with the relais in the input stage.

So - everything is okay with my scope ... uff :-)

BTW:
Hameg answered after one day and send me a really informative and friendly mail ... so a big thumbs up for their support.

Cheers,

Ronald

[Axel1973]

thanks for the feedback!

what email/telephone did you used to contact Hameg's tech support?

Im curious since i am also a brand new HAMEG MSO owner myself.

best wishes
Axel

[DonRon]

Hi Axel,

wrote an e-mail to service@hameg.com and got an answer from Michael Leichum. Had an additional question and he answered immediatly. Very friendly and really fast.
(They offered me to check the scope. I am not far away from Mainhausen, so maybe I can bring them the scope myself. But first I will play with it to learn better how to use it).

As I wrote, I have the Combiscope HM1008-2. Which scope do you have ... can you observe the same effect?

Made several tests with low amplitude signals (Upp= 2 - 50 mV) with different frequencies. Everything works fine on both channels (really same amplitude on both channels - same frequency result .... ). So with correct signal input you can't see the effect or only a little bit with highest sensitivity?

Do you have trouble with ur instrument ... are u satisfied??
Would be nice to share some infos

Regards

Ronald

[Axel1973]

thanks for the info.

i bought me a HMO2024 lately. of course its WAY OVERKILL for what i use it. but hey. once in a lifetime... u know.
till now im pretty satisfied with it. but im ALL NEW to DSO/MSOs. I once learned 20yrs ago on analog scopes.

the signals shown when moving the scope around i dont think i had yet.
BUT i dont know exactly what setup you used to reproduce your signal or if your probes are shorted out or what the thing is.

What i detected yet on my bench is that im living in a PRETTY NOISY environment. If i go down on mV Ranges with open probes or (even worse) when used with BNC to banana adapter i catch PLENTY OF LOW FREQ + HIGH FREQ noises.

I figured that my CFT Lamp at the Desk fires a lot of LF/RF. Also a close PowerLine Adapter no more than 2m in distance injects A LOT of heavy RF noise around 30Mhz.

So it seems the inputs are pretty HIGH impedance and will catch up lots of crap when not properly connected to a circuit and when used without well shielded probes.

Daves experiment with the shorted probes "slammed" to the table i did test. However it did not perform as well. So either i didnt slammed my expensive probes hard enough to my desk or they are less sensitive to mechanical shock than his probes.

If you can re-describe your setup more precisely, what probes, how connected, shorted or not ect ect i would do the test too on my setup and can report.

BTW: as far as i see your scope on the HAMEG website it looks more like a regular "old school" scope housing. my HMO is "tiny" compared to an ol'time Scope. Just about 10cm deep/depth. And even less wide than a regular 1990s Scope. So i guess there is also some major differences in the scope design which "could" make yours more sensible to shocks or vibrations than my HMO. but as i said, willing to re-test when you can explain me the exact setup.

best wishes
Axel