Overload protection on 526?

Topics related to the Dataman 520 Series
Basil
Posts: 7
Joined: 03 Dec 2011 19:18

Overload protection on 526?

Postby Basil » 03 Dec 2011 19:31

Am I really the first user to post here? ;)
I am using, carefully and with trpidation, my 526 for automotive diagnostics. All my colleagues tell me to get a picoscope automotive USB scope that has internal fusing and overload protection, plus inputs that will view 100 volts with no attenuation. I like my 526, and have had it from new, so for that reason, plus to confound them, I persevere. I have two questions though. If I was careless with it and it saw a few hundred flyback volts from injectors, or I had grounding issues, what's the worst that could happen? Could it be rendered scrap, would it be only factory return repairable (where is the factory, do you make these in the UK), or could I take the lid off and do "something" myself?

Is there any external protection I could easily add?

The Picoscope automotive scopes, and their dedicated automotive software, allows for timebases of up to 1000 sec / division, allowing over 2.5 hours of slow updating monitoring. I bought your 520 RM roll mode licence the other month, but have had little time to play with it, does this allow me to do something similar?


Finally, do you do any USB signal generators? If so, do any have separate power supplies than from the USB port, to up their voltage at load outputs?

Thank you.

Dataman (Neil Parker)
Posts: 810
Joined: 10 Nov 2011 09:51

Re: Overload protection on 526?

Postby Dataman (Neil Parker) » 07 Dec 2011 15:06

Hello Basil,

The Dataman-M526 has a guaranteed maximum input voltage of +-200V (twice as much as the Pico). We carried out some internal tests in our lab by connecting 400V to the input whilst set to maximum sensitivity! and everything was O.K. (however we do not recommend using it under these conditions!). If the measuring probe set to 1:10 is used the guaranteed maximum input voltage is +-600V. Many of our customers uses the M520 family of oscilloscopes for automotive measurements and we have not received reports of any problems.

So I would not worry, it is absolutely safe to use the Dataman-M526 scope for these type of measurements. However for safer and clearer measurements we do not recommend that you connect directly to the chassis of the vehicle in order to the ground the computer (only by the ground pole of the measuring probe).

The Roll Mode software for this scope allows the collection and display of data and to save this data to the computer's HDD in real time (it is very useful for oxygen sensor (lambda sensor) measurements). The length of recorded data is limited only by free HDD space. To give you an example, a 1 hour long recording with a sampling rate of 1000 samples/second takes about 7.5 MBytes of disc space.

We can offer the USB Arbitrary Waveform Generator (Dataman-M531) with the possibility to output a waveform with 50 Vpp (no load) and an output impedance of 600 Ohm. To use this feature it would be necessary to use the external power supply (it is part of the package anyway) as the power from the USB bus alone is not sufficient for this level of output.

In case of any other questions please do not hesitate to ask.

Regards,
Neil Parker
Dataman Programmers

Basil
Posts: 7
Joined: 03 Dec 2011 19:18

Re: Overload protection on 526?

Postby Basil » 11 Dec 2011 10:15

Neil, thank you very much for taking the time to make such a detailed response, much appreciated, I feel a lot happier now! Just one more question though, if I may? When oscilloscope makers take of deep memory, and 56k or in the case of the Pico scopes, 32m, just what form does this acquisition memory take? I am curious, with memory for, say, my PC being cheap, (or at least before the floods upset things), why are makers seemingly so stingy? Or is it a "different sort" of faster memory? Is it really that relevant to the sort of tasks I may be performing?

Again thanks for the reply, I wonder if some of this m********n that seems to have appeared on the forum in the form of Spam, might speed *ME* up a bit.... ;)

Dataman (Neil Parker)
Posts: 810
Joined: 10 Nov 2011 09:51

Re: Overload protection on 526?

Postby Dataman (Neil Parker) » 22 Dec 2011 08:54

Hello Basil,

The memory inside the oscilloscope acts as the fast buffer for the acquired data. The question is why is it necessary to put data into an internal buffer and then transfer it to the computer. The answer is, because the internal buffer ensures the integrity of the acquired data. There are several reasons why:

- the connection to the computer is not synchronous with data acquisition (it does not allow the transfer of data to the computer at any time with the full transfer speed)
- because from time to time the operating system of the computer needs the attention of the processor and does not allow communication with the peripherals (oscilloscope hardware) during this time.
- because the computer's memory uses dynamic technology and needs a periodic refresh. During this refresh it cannot transfer data and would interrupt the data acquisition.

The capacity of the oscilloscope's on board memory influences the length of the waveform which is acquired with a high sampling rate. The long memory allows us to acquire a relatively long sequence of data with full acquisition speed. It can be interesting when finding bugs in serial communication channels or when performing some special measurements. In 99% of measurements the long on board memory is not necessary and using it only slows down the waveform refresh rate.

I hope that I have answered your question.

Regards
Neil Parker
Dataman Programmers

Basil
Posts: 7
Joined: 03 Dec 2011 19:18

Re: Overload protection on 526?

Postby Basil » 22 Dec 2011 10:18

You have answered it perfectly Neil, I understand now, once again thank you for such a detailed reply. May I wish you and your colleagues a very happy Christmas and a healthy and prosperous New Year? All the very best.


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