EEVblog Electronics Community Forum

Products => Test Equipment => Topic started by: reyntjensm on October 04, 2020, 09:05:16 pm

Title: RTB2004: Can't zoom in on signal
Post by: reyntjensm on October 04, 2020, 09:05:16 pm
Hello everyone,

I have a strange problem with my Rohde&Schwarz oscilloscope. I'm trying to measure a 13,8V DC signal. As soon as i try to lower my volts/div the signal goes out of the screen and i can't change my offset. The offset is stuck at 1.2volt. I already tried different channels and different probe settings, still the same issue. I have no idea what i'm doing wrong? Does anyone have any explanation for this issue? Is it impossible to look at a 13,8 DC signal with a 10mV/div?
Thank you all!
Title: Re: RTB2004: Can't zoom in on signal
Post by: tautech on October 04, 2020, 09:09:00 pm
Nothing strange here, this is what AC input coupling is expressly for.......to remove the DC component of a signal.  ;)
Title: Re: RTB2004: Can't zoom in on signal
Post by: reyntjensm on October 04, 2020, 09:12:38 pm
Nothing strange here, this is what AC input coupling is expressly for.......to remove the DC component of a signal.  ;)

Seriously? I know AC coupling is there to remove the DC component. So it's impossible to look at a 13V DC signal with a low volts/div? How is the maximum calculated? Say for instance the 13VDC level has a signal on top of it, say a small block wave of around 20mV. It's impossible to see right?
Title: Re: RTB2004: Can't zoom in on signal
Post by: tautech on October 04, 2020, 09:27:15 pm
Nothing strange here, this is what AC input coupling is expressly for.......to remove the DC component of a signal.  ;)

Seriously? I know AC coupling is there to remove the DC component. So it's impossible to look at a 13V DC signal with a low volts/div? How is the maximum calculated? Say for instance the 13VDC level has a signal on top of it, say a small block wave of around 20mV. It's impossible to see right?
Max channel voltage offset will be specified in the datasheet and it commonly is different depending on the V/div range selected. RTFM.  ;)
Some scopes permit setting a fixed vertical position so to easily allow high magnification of a signal without it disappearing off the display, again RTFM.  ;)
Title: Re: RTB2004: Can't zoom in on signal
Post by: nctnico on October 04, 2020, 09:40:57 pm
Nothing strange here, this is what AC input coupling is expressly for.......to remove the DC component of a signal.  ;)

Seriously? I know AC coupling is there to remove the DC component. So it's impossible to look at a 13V DC signal with a low volts/div? How is the maximum calculated? Say for instance the 13VDC level has a signal on top of it, say a small block wave of around 20mV. It's impossible to see right?
Using AC mode is one way. Another option is to use zoom mode and keeping DC coupling. You'll get the best result by using the lowest V/div which allows to see the signal (with offset ofcourse). The limit will be the ADC resolution but with 10 bit you'll have an advantage. If the signal is not high frequency then turning on high-res is another step towards a clean signal but be aware that high-res mode also filters the signal.
Title: Re: RTB2004: Can't zoom in on signal
Post by: reyntjensm on October 04, 2020, 09:46:34 pm
Nothing strange here, this is what AC input coupling is expressly for.......to remove the DC component of a signal.  ;)

Seriously? I know AC coupling is there to remove the DC component. So it's impossible to look at a 13V DC signal with a low volts/div? How is the maximum calculated? Say for instance the 13VDC level has a signal on top of it, say a small block wave of around 20mV. It's impossible to see right?
Using AC mode is one way. Another option is to use zoom mode and keeping DC coupling. You'll get the best result by using the lowest V/div which allows to see the signal (with offset ofcourse). The limit will be the ADC resolution but with 10 bit you'll have an advantage. If the signal is not high frequency then turning on high-res is another step towards a clean signal but be aware that high-res mode also filters the signal.

The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset. What do you mean with the zoom mode?
Title: Re: RTB2004: Can't zoom in on signal
Post by: tautech on October 04, 2020, 10:05:56 pm
The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset.
Yes normally we might use 1x probes to look at low levels of ripple however if your R&S has sufficient input sensitivity 10x probes can be used which can often put you in another range of permissible channel offset.

Quote
What do you mean with the zoom mode?
Vertical zoom if this model provides for it.
Title: Re: RTB2004: Can't zoom in on signal
Post by: reyntjensm on October 04, 2020, 10:13:29 pm
The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset.
Yes normally we might use 1x probes to look at low levels of ripple however if your R&S has sufficient input sensitivity 10x probes can be used which can often put you in another range of permissible channel offset.

Quote
What do you mean with the zoom mode?
Vertical zoom if this model provides for it.

I don't think my model has any vertical zoom. i will check the manual  :-DD
If i use a 1: probe with a 13vdc signal i can't get below 200mV/div. So i was thinking to set the probe to 10:1 and keep the settings in the scope to 1:1. Is there another solution?
Title: Re: RTB2004: Can't zoom in on signal
Post by: tautech on October 04, 2020, 10:16:09 pm
The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset.
Yes normally we might use 1x probes to look at low levels of ripple however if your R&S has sufficient input sensitivity 10x probes can be used which can often put you in another range of permissible channel offset.

Quote
What do you mean with the zoom mode?
Vertical zoom if this model provides for it.

I don't think my model has any vertical zoom. i will check the manual  :-DD
If i use a 1: probe with a 13vdc signal i can't get below 200mV/div. So i was thinking to set the probe to 10:1 and keep the settings in the scope to 1:1. Is there another solution?
AC coupling.  ;)
Title: Re: RTB2004: Can't zoom in on signal
Post by: reyntjensm on October 04, 2020, 10:37:26 pm
The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset.
Yes normally we might use 1x probes to look at low levels of ripple however if your R&S has sufficient input sensitivity 10x probes can be used which can often put you in another range of permissible channel offset.

Quote
What do you mean with the zoom mode?
Vertical zoom if this model provides for it.

I don't think my model has any vertical zoom. i will check the manual  :-DD
If i use a 1: probe with a 13vdc signal i can't get below 200mV/div. So i was thinking to set the probe to 10:1 and keep the settings in the scope to 1:1. Is there another solution?
AC coupling.  ;)

Yep, looks like AC coupling is the way to go. stupid me.... i thought such a slow square wave signal wouldn't couple trough... :palm:
Title: Re: RTB2004: Can't zoom in on signal
Post by: nctnico on October 04, 2020, 10:41:16 pm
The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset.
Yes normally we might use 1x probes to look at low levels of ripple however if your R&S has sufficient input sensitivity 10x probes can be used which can often put you in another range of permissible channel offset.

Quote
What do you mean with the zoom mode?
Vertical zoom if this model provides for it.
I don't think my model has any vertical zoom. i will check the manual  :-DD
The RTM3004 has vertical zoom for sure. Just try to make the signal bigger in the zoom area. I can't imagine the RTB2004 doesn't have vertical zoom.
Title: Re: RTB2004: Can't zoom in on signal
Post by: reyntjensm on October 04, 2020, 10:49:10 pm
The manual says that with <200mV/DIV the max offset is 1.2V( i never had this situation before). So if i want to keep the DC coupling i guess i should have to tweak the probe settings to get the signal under the 1.2V, or at least the offset.
Yes normally we might use 1x probes to look at low levels of ripple however if your R&S has sufficient input sensitivity 10x probes can be used which can often put you in another range of permissible channel offset.

Quote
What do you mean with the zoom mode?
Vertical zoom if this model provides for it.
I don't think my model has any vertical zoom. i will check the manual  :-DD
The RTM3004 has vertical zoom for sure. Just try to make the signal bigger in the zoom area. I can't imagine the RTB2004 doesn't have vertical zoom.

It does!! i was looking over the button every time. I think i should better go to sleep instead of being stupid... Thank you for the support!