Test and Measurement Forum

Input protection.

Post any questions you may have about our current range of oscilloscopes

Input protection.

Postby GregerG » Sun Jul 10, 2011 2:46 pm

I kind of busted the A-channel input on my picoscope 3205,
my inductive pickup (for ignition testing) was picking up a bit too much. :)

I don't have schematics for the unit unfortunately, but perhaps someone here know some common fault of an overload?
http://rfelektronik.se/temp/div/Dsc_1006.jpg

Would it be the reed relays? Or the SST5912 gain block, or could it be the HA4600CBZ buffer?
Or the A/D's? But it looks like the other circuits would take the biggest hit...

Cheers!
//Greg.
GregerG
Newbie
 
Posts: 0
Joined: Sun Nov 21, 2010 1:45 am

Re: Input protection.

Postby Hitesh » Tue Jul 12, 2011 9:16 am

Hi Greg,

The best thing would be to send an e-mail to our support address (via this link http://www.picotech.com/support.html#pre) with details of the unit model and serial number and your address and contact details. We can then issue a returns number before you send it in.

Trying to undertake a self-fix might prove difficult as some parts may be difficult to obtain and could potentially cause further damage to the Unit.

Best wishes,
Hitesh

Technical Specialist
Pico Technology
Hitesh
Site Admin
Site Admin
 
Posts: 2063
Joined: Tue May 31, 2011 3:43 pm
Location: St. Neots, Cambridgeshire

Re: Input protection.

Postby GregerG » Wed Jul 13, 2011 8:56 pm

Well, the unit is fairly old by now, I don't think it'd be worth the cost...
I'm an electronics engineer so there should be no problem repairing it myself,
however since I don't have the schematics it could take some time to find the fault - which is why I asked here :)
GregerG
Newbie
 
Posts: 0
Joined: Sun Nov 21, 2010 1:45 am

Re: Input protection.

Postby GregerG » Thu Jul 14, 2011 8:01 am

Also the unit is a bit off, with inputs shorted it should read 0v but it isn't...
In Picoscope <6 there was a checkbox to null the offset, but not in Picoscope 6.
I have two picoscopes and they are both a bit offset so I guess it's a fairly common problem,
and Picotech doesn't seem to want to implement an offset null button for some reason even though I pointed this out long time ago... (should be a fairly easy fix since it was there in earlier versions).

So I defenitely won't be buying a new picoscope until they fix a way to null the offset.
(I know you can semi-fix-it with math but then the scales are wrong).
GregerG
Newbie
 
Posts: 0
Joined: Sun Nov 21, 2010 1:45 am

Re: Input protection.

Postby GregerG » Fri Jul 15, 2011 7:38 pm

I ordered a few CALOGIC SST5912 circuits (the first buffer amplifier).
They are hard to find so if anyone else need these - let me know... $3/piece.
I shouldn't be the only one with a busted frontend? :) After all picoscopes only allow 20V input...
GregerG
Newbie
 
Posts: 0
Joined: Sun Nov 21, 2010 1:45 am

Re: Input protection.

Postby alan » Mon Jul 18, 2011 7:21 am

Hi Greg,

Just to add a few comments to the above. I am suprised that a channel was damaged by an inductive pickup for a couple of reasons. The first is that our inductive pickups attenuate by 10,000:1 so its unlikely that any output exceeded the 100V overload protection. Even if there was a direct hit with secondary ignition from a damaged HT lead, the earth clip protects for this.

Anyway you obviously have a damaged channel somehow so we need to work out the best way of solving this. If you want to have a go at fixing it yourself then obviously this is your choice, but we can not recommend it. After fixing the unit should really be retested / recalibrated on one of our test jigs.

If you want us to have a look at the unit, we can issue a returns number and all you are risking is the cost of getting the unit to us (we pay the return). Even if the unit is out of warranty we often make no charge if the fix is a simple one. If there is going to be a cost we contact you first and you have the choice of saying no and asking for the unit back.

Regards
Alan

PS As for offset null, you can do this with maths without making the scales wrong but I accept your point about a PicoScope 5 type null function. This will be implemented within in the next couple of software releases.
alan
Site Admin
Site Admin
 
Posts: 171
Joined: Thu May 25, 2006 8:02 am


Return to USB PC Oscilloscopes

Who is online

Users browsing this forum: No registered users and 0 guests