Channel Overange problem

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paullap
OneWave
OneWave
Posts: 13
Joined: Sat Oct 27, 2018 2:07 pm

Channel Overange problem

Post by paullap »

Hi I am new to this forum, I have just started to use my pico scope i got a month age and all I can manage to get is a channel overange warning, what am I doing wrong.

Paul

Technician
TwoWaves
TwoWaves
Posts: 706
Joined: Thu Apr 24, 2014 8:32 pm

Re: Channel Overange problem

Post by Technician »

The channel 'Over Range' is advising you that either you have not installed the attenuator to the BNC connector of the channel you are using, or the voltage scale being used is incorrect (Too small) for the size of the voltage being measured.

Have a read of these and become familiar with the basics;

https://www.picoauto.com/library/training :)

paullap
OneWave
OneWave
Posts: 13
Joined: Sat Oct 27, 2018 2:07 pm

Re: Channel Overange problem

Post by paullap »

Hi, I am scoping a o2 sensor signal wire on a citroen c2 1.4 petrol. if i select a 10/1 attenuater and a auto voltage range and I still keep getting channel overange warning popping up. an o2 sensor is only low voltage so I am confused.


Regards


Paul

Technician
TwoWaves
TwoWaves
Posts: 706
Joined: Thu Apr 24, 2014 8:32 pm

Re: Channel Overange problem

Post by Technician »

Paul,

Have a read of this post;

Reference Steve Smith_id=72231 refers to over range problems, or do a search for it in the search bar if this fails

speck
TwoWaves
TwoWaves
Posts: 63
Joined: Sun Mar 25, 2012 5:20 am

Re: Channel Overange problem

Post by speck »

Hi
how about putting up a psdata file.

Technician
TwoWaves
TwoWaves
Posts: 706
Joined: Thu Apr 24, 2014 8:32 pm

Re: Channel Overange problem

Post by Technician »

I think he has tried previously but the file size appears to prevent the upload for some reason!

ben.martins
Pico Staff Member
Pico Staff Member
Posts: 539
Joined: Tue May 16, 2017 1:02 pm

Re: Channel Overange problem

Post by ben.martins »

Hi Paul,

Thank you for your post and thanks also to Technician and Speck for offering a helping hand.

Paul, are you still having concerns with an over voltage warning? If so we need to establish the scope model you are using and how you are making the connection to the O2 sensor. From here we can move forward and try to understand what is going on.

For a start though, do you get the warning when carrying out a simple measurement such as across the battery?

As Technician has already pointed you towards the training section of the website you may have already seen this https://www.picoauto.com/library/training/filtering. In this page we talk a lot about O2 sensors and how particularly noisy they are. You will notice the large 'spikes' that occur which can cause an over voltage warning and as we tend to look at a small window with O2 sensors, normally between 0V and 1V, these spikes can exceed 1V. If the range you have selected is +-1V then this could be the reason for the over voltage warning.

When measuring sensor signals (such as lambda) with the new PicoScope 4425 or PicoScope 4225 the option to connect our test lead ground cable to the lambda sensor ground wire is available, and often helps to reduce noise on our signal. Here we have a differential measurement utilising the lambda sensor ground, which is partially shielded from such EMI (via the PCM) so producing a cleaner signal. This method is often overlooked by some users with the newer scopes as we are used to reference everything to battery or chassis ground. For most signals this is more than ok but for some, such as lambda, there can be real benefit and less filtering required when reviewing data post capture. Please note though that there is a max of 30V only when using this method so some sensors, such as inductive crank sensors, can exceed this voltage so please be mindful of the what is you are trying to measure.

I hope this helps and please feel free to get in touch if you need further assistance.

Kind regards

Ben

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