Recent Posts

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Projects, Designs, and Technical Stuff / Reactive Source Resonant Transformer

« Last post by Thor on Today at 02:02:10 pm »

This aims to make a resonant transformers output dominate in the parasitic Xc and the XL component of the output coils while reducing its ability to pass current in the R component of said coils.

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Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by xvr on Today at 02:00:29 pm »

> One option is that: do not care.

Than use square waves. They can be considered as sinus with a lot of distortion.

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Test Equipment / Re: Cheap oscilloscope for checking mains power quality? Also logging equipment.

« Last post by Kean on Today at 01:51:54 pm »

I don't think an oscilloscope is the best solution based on your usage.  You want a power quality analyser with data logging.  Something that can also safely be left alone.

Maybe one of these.  https://powertronics.com/collections/single-phase-power-line-monitors

See these other related discussions
https://www.eevblog.com/forum/testgear/power-line-quality-monitor-that-does-not-cost-/
https://www.eevblog.com/forum/testgear/looking-for-a-cheap-but-good-single-phase-120v-power-line-glitch-logger/

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Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by xvr on Today at 01:51:44 pm »

In LTSpice schematic you again connect all 4 pins of MOSFET to different nets. I guess that one of them directly shot some MOSFET terminal to ground. There should not be.

As for 20V - power for your amplifier should be connected to terminal that in your schematic labeled 'After relay. 24V (ar)'. I don't know what relay was connected ant where, but definitely here should be connected just plain +20V. No any +24V from any relay should be used in final schematic.

In LTSpace change voltage of V1 to +20V and remove V3

> because this floating voltage is confusing. i am used to this of voltage where each node has exact voltage with respect to some reference.

Yes, but for flying voltage will be another reference - not common ground, as for all others.
If you want to see voltage on MOSFET gate set a probe to V(Gate)-V(Souce)

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Beginners / Re: LM324 Power Supply with variable voltage and current

« Last post by xavier60 on Today at 01:49:38 pm »

Do you mean that I need a separate winding on the transformer or another small transformer for the DVM and tap changer ?

Yes.

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Test Equipment / Re: Fun With Low Leakage/Bias Current: Femtompere, Electrometer, Keithley 617

« Last post by BD1QMP on Today at 01:47:57 pm »

After put back the original BNC connector, I recorded the offset. Is it normal or not?  thanks

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Beginners / Re: LM324 Power Supply with variable voltage and current

« Last post by mike_mike on Today at 01:47:07 pm »

Do you mean that I need a separate winding on the transformer or another small transformer for the DVM and tap changer ?

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Test Equipment / Re: Siglent SSA 3021X... Ooops

« Last post by Joel_l on Today at 01:45:43 pm »

I put things back together enough to turn it on. what I found this morning was slight different that what I found ( thought I found ) last night.

Frequency is OK. I checked several points  and all were good ( Agilent E4432B )

Amplitude seems OK, worst I saw was .6 dBm low. TG trace was not horrible but I don't know what it looked like before. ( pic attached )

Input impedance is still off, the only way I have to gauge this is using one of my transmitters and TX'ing into the SA. Before the over power, I was getting a near perfect SWR, now I get high SWR on all 3 TXs I tried.

When I measure the switches, U1 is different than the others.

I went back and rechecked all the diodes in the path at each stage, all were OK.

I will replace U1 ( maybe all just cause )

Thanks

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Test Equipment / Re: Hacking the Rigol MSO5000 series oscilloscopes

« Last post by BTO on Today at 01:45:35 pm »

I've updated the other post and there is a DETAILED PDF there............ GO FOR IT !!!
i still haven't made the video but the pdf should take care of everyone i think

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Beginners / Re: LiPo battery charging problem

« Last post by Gyro on Today at 01:45:34 pm »

No. In fact you should use the manufacturer's utility of some other s/w to terminate the charge at around 80%. Your battery will last far longer then.