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first time scope user, probablyasking the earth

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first time scope user, probablyasking the earth

Postby Y I man » Tue Dec 08, 2015 8:36 pm

Hi all, have just purchased my first scope it's a 2205a model, though I have never used one before. I get the impression that it's going to be of limited use as it's intended for automotive use, but you've got to start somewhere with something and in and in fairness I was never going to be allowed the cost of a dedicated model in a dedicated price range. Was a bit surprised the 2205 didn't cause more trouble. So can anyone please help with just how limited i am with the jobs it is capable of?
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Re: first time scope user, probablyasking the earth

Postby AndrewA » Thu Dec 10, 2015 10:49 am

Hello,
Any of the 2200 series scopes are fine for basic automotive fault finding.
Here is list of limitations and things to watch out for when using them;

• If using two channels I would avoid connecting both grounds on each channel, to avoid accidental damaging the scope inputs. (Simply remove the earth clip from the second probe) This would happen if one of the grounds is connected to a different point in the circuit.
This especially important as the current 4425/4225 automotive scopes have floating inputs with upto 30 volts these are for non-chassis gnd measurements.

• It may be good idea use scope probes on x10 setting, when measuring switching devices - solenoids/relays etc because of the large voltage spikes present. (you may wish to tape/glue the x10 switch on probe to avoid accidental being changed)
I would avoid connecting the anything directly to the BNC input without the probe, for this reason. (Also using the probes on the x10 setting gives you the full bandwidth of the probe.)
This will avoid any change of damaging the scope inputs, as they will only see 1/10 of the measured voltage (2200 series - do have overvoltage protection of ±100 V (DC + AC peak) )

• If you are looking a relay switching with scope set to +-100v input range (using the probe on x10) and zoom in to say 0- 12volt area you notice the resolution will be lower than a automotive scope which is 12 bits (4096 levels) verse 8-bit (256 levels)
If you need more resolution in the 0-12v area of the waveform, you could set the voltage range down to +-20v range on this channel, this will clip the any voltage spikes in the waveform, and scope report a out of range condition, but will not damage the scope.

• The main different between this and automotive scope or any of the Test and measurement scope is the limited buffer memory for capturing long traces.
Even thought serial protocols like CAN are supported with 2200 series, you would be able to capture trace long enough to do any decoding on.
The 2200 series buffer memory range from only 8kS to 48k Samples.
The best you can do if need a large capture for these scopes is get them to operate in streaming mode;
Set the time base to 100ms/div or greater, and the number of requested samples to 10M.
Note the 2204A and 2205A have a max. streaming sample rate of 1us/1MHz and the
2206A , 2207A and 2208A have a max. streaming sample rate of 104ns/9.6MHz
You can view the actual sample interval and samples captured by opening the view properties panel. ('view' menu - view properties)

• As this a test and measurement scope you won't be able use automotive version of picoscope, the main disadvantage is not being able to access the waveform library. Also the automotive menu is missing contains example setups for various sensors and tests. You can also install the picscope automotive version and you use it demo if you wish.
The example test waveforms and connection information can be found on the http://www.picoauto.com website.
Regards Andrew
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Re: first time scope user, probablyasking the earth

Postby Y I man » Thu Dec 10, 2015 7:09 pm

That is brilliant mate, thanks very much for your help. It is greatly appreciated! Real shame I hadn't took more notice of the old man as a child, after leaving the R.E.M.E. as an avionics tech he had a T.V. repair shop. Remember fiddling with his scope and the wavey line, who'd have thought it!
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