doggy

Thanks. Okay. I've ditched the BNC module and using 1+ and 1- directly and it all works fine, thank you. No problem with signal levels for my application, 'though one would have to be careful with higher voltages where the BNC module and probes would give divide by 10. Regards, David

I am already using the BNC module with the scope inputs in differential mode- i.e. maths channel = C1-C2. I need to trigger from the differential signal. I understand you saying you cannot trigger from the Maths channel. Triggering off a single input is no good because it can/will then trigger off Common Mode noise. I do not understand what you say here. Can I somehow set a trigger= C1-C2? This is SO SIMPLE on an analogue scope- even my old NEC 100MHz one from about 30+ years ago. Is there some way to trigger off Channel1 rising simultaneous with Channel2 falling (or the inverse)? I suspect that would achieve what I want.

I can't show you a screenshot because I cannot trigger it! It is a RS485 signal so balanced differential. There is a common mode 2.5VDC on each of the A & B lines. It is ASCII data at 115200baud and just a short burst of about 48 characters but only once every 5seconds. Peak to peal voltage is +-2.5Volts I can see and trigger it on an analogue scope but it is non storage so not possible to see well (which is why I want to use the Discovery 3) I cannot see any way to trigger but triggering via the maths channel (Ch1 minus ch2) would be easy (if it existed) and how I triggered my analogue scope, just set in differential mode. I had a look at the logic analyser and it does not seem to handle a differential signal.

This seems a simple question but I cannot figure it out. AD3 with Waveforms. I have a differential signal with a fair bit of common mode noise. The signal of interest is only every 5secs and lasts about 50msecs. I am using C1 and C2 with a simple Maths channel to display it. Triggering off C1 or C2 does not work because of the noise. I cannot see how to trigger off the Maths channel, which is what I really want to do. I'me sure there must be a simple way and I'd appreciate if someone more experienced could please point me in the right direction. Thanks, David Sydney, Australia

Thanks very much. All working okay as you described and I am pleased to know the electrical limits. I'm FFTing the subtracted channels and that is also working very nicely. Thanks again...

Hello, I have just received my AD3. Very nice! I also have on order the BNC module. I want to do scope measurements using the Scope on a 24V 5kW inverter, specifically the full bridge low voltage output. I am running from a lab power supply so I can ensure the bridge output is +-24V. Here are my questions: 1. I do not (yet) know if there are any spikes, although I cannot see anything on my 100MHz analogue scope. How resilient is the front end differential amp if there is a spike which exceeds 25V? I will be very close to the +-25V with my 24V system. 2. I would prefer to use BNC probes, particularly with 10:1. However I note that the two channels will not be differential. Can I use both channel 1 and channel 2 and display the sum of both channels and force one of them to be negative? I can easily do this simple thing on my analogue scope to produce a single channel differential input. I assume this is possible on the AD3 as it is a very simple and common requirement and I'm just not yet knowledgeable enough on the AD3 to see how to do it. I suspect that I can add a Maths channel and define it to be C1 minus C2? Advice appreciated....