EEVblog Electronics Community Forum

Products => Test Equipment => Topic started by: dstahlke on June 15, 2018, 01:51:37 pm

Title: TTi MX180TP switching noise
Post by: dstahlke on June 15, 2018, 01:51:37 pm
Has anybody noticed any switching noise on the MX180TP?  A review of the MX100TP https://www.eevblog.com/forum/testgear/tti-mx100tp-triple-power-supply-teardown-and-review/ (https://www.eevblog.com/forum/testgear/tti-mx100tp-triple-power-supply-teardown-and-review/) showed very little noise.  But the attached picture is what I get from my 100x differential amplifier when it's just near the power supply, not plugged into it.  This noise (inductively picked up?) was high enough to swamp anything actually coming out of the supply terminals.

An interesting spec not in the datasheet: the capacitance to ground is 1.49uF, compared to 70nF for my BK 9129B.
Title: Re: TTi MX180TP switching noise
Post by: maginnovision on June 16, 2018, 01:40:46 am
What do you get from the terminals with a load? It should be fairly low. I think these are primarily a switcher but feed a linear on the output to cut noise.
Title: Re: TTi MX180TP switching noise
Post by: dstahlke on June 17, 2018, 10:09:00 am
With a load, without a load, or with the differential probe terminals shorted to each other and not even connected to the supply, the result looks the same.  I think this is EM radiation from the supply rather than noise on the terminals.  In fact this radiated noise is so large I can't even begin to measure what's actually on the terminals.  If the probe terminals are connected to ground the result is even worse.  In that case there is an additional sinusoidal component at the same frequency, 100kHz.  This is with a custom built probe based on the AD8421.
Title: Re: TTi MX180TP switching noise
Post by: maginnovision on June 18, 2018, 01:53:49 am
Well you could always contact TTi. With custom probes I'm not even going to try and guess. When I sampled a 100mx I did not see that issue.