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1
here is my initial guess of the effects when the resistors will be removed (see previous sketch).

For normal use where the input voltage would be less than the forward bias voltage of the diodes (less than 0.7 Volts). There would be no harmful effects even if the diodes remain in place and the 2 resistors removed. Right?

But for surges or ESD events where the diodes conduct producing voltage potential of 8V (source is Ni-MH rechargeable batteries)-0.7 (diode) = 7.3 volts. The higher input surge voltage of say 50V  can charge the power source or rechargeable batteries. Can momentary charging by the surges/ESD cause the batteries to explode?

What ESD protection devices do  you know that don't use any resistor in series to the source? I have to avoid any resistors to eliminate any noises since I need ultra low noise sensor.
2
Metrology / Re: Null Detector based on Conrad Hoffman design check
« Last post by trobbins on Today at 06:47:56 am »
Thanks for the thread - it has inspired me to start preparing a null detector to drive the original galvanometer in a nice 1950's PYE wheatstone bridge I tweaked last year. 

I had been using the mV range on an Aneng AN8009 cheap DMM in lieu of the galvanometer for much better auto-ranging and discrimination, but I think a bit of interface circuitry based on an AZ opamp could well do a much better job, and could be easily powered by 5V from an external USB battery brick.  The application doesn't need accurate FS voltage ranging, and the load is likely a few tens of uA (although I haven't measured what the meter FS current actually is).  I'll try and keep the original initial/final keying of the galv, and retrofit the final key with a 'super final' press-button.
3
Test Equipment / Re: open source GPIB adapter
« Last post by dazz1 on Today at 06:46:22 am »
Hi
Well it looks like I will be making a break out board, but not like either of the linked designs.

I will make use of the connectors I have in the photo.
I got the Centronics gpib connectors from Aliexpress because they are dirt cheap.  I purchased the HP logic analyser compatible connector to see if it would fit.  It does, that gave me a solution looking for a problem.
I will design a board that will connect directly to an HP logic analyser, that I don't have, or my HP 54645D mixed signal scope that I do have.
The logic probes designated for the HP54xxx series scopes have the probes integrated with the flat cable.  They are rare an expensive. 
I purchased the cable  and probe set that plug together. Easier to find, cheaper and more versatile.

Along with the Centronics connectors, and HP compatible connector I will include pads for a separate header to make it easy to probe individual lines, if ever needed. Probably a feature I would never use but extra pads are a zero cost. 

I will be able to save a configuration in the scope, and just plug and play the break-out board.  The board will still be usable for someone without a logic analyser. 
4
Test Equipment / Re: Test Equipment Anonymous (TEA) group therapy thread
« Last post by K0ELB on Today at 06:39:28 am »
More pics with its cover on, sides and rear please.

I’ve uploaded the pics to Tekwiki, the first 8 are of mine:



https://w140.com/tekwiki/wiki/75A

5
That looks like a neat piece of software.

Tho if IVI VISA was used to communicate with the instruments it would open up the ability to talk to PSUs/Loads over other all the other protocols too (USB, LAN, GPIB, PXI, LAN to GPIB bridges etc..)
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Test Equipment / Re: Siglent SDS800X HD 12 bit DSO's
« Last post by Muttley Snickers on Today at 06:12:00 am »
Just a heads up for those in Australia interested in acquiring these new Siglent SDS800X HD Series Oscilloscopes.   :-DMM

Appvision have now listed them on their website with pricing and rumour has it they will arrive around the 1st of May, so another 4 weeks or so of reading about other peoples experiences with the new SDS800X HD series.   ::) 

https://appvision.com.au/index.php?id_category=167&controller=category&order=product.price.asc
7
How about the Twin-T oscillator?  It's suppose to be low distortion.
Simulation here.  Schematic below (12V single supply).
Recently, W2AEW #380 and IMSAI Guy #1807 both did videos on them.

EDIT: I've updated simulation and schematic to correct output part.
You'll need to update simulation speed to allow for the voltage after the output cap to settle about 0V after pot change.
8
Letw get this straight. You need to re patch after each update or you lose the options you added?
If so , them we should expect that the hack will be fixed at some point.
Finally I guess you can just return the scope to it's older self with the back and re hack it, keeping it in an older FW version.
Am I correct in my assumption?
9
Test Equipment / Re: SDS800X HD Bugs/Wanted Features
« Last post by eTobey on Today at 06:03:45 am »
Yes, I suggest everyone not to describe it casually as a bug. It can be said that "I have discovered a phenomenon. Is this reasonable?".

So far, if we merge bugs 5, 6, and 7, and merge bugs 2 and 3, bug 1 doesn't count, there are only four bugs, and there are no urgent bugs.

I can do my part here, but others have to do their part too IMHO.  :-+


I think you got bug no. 7 wrong (or i got your explaination of it wrong) so i try again. Others are welcome to try it out for themselfes or point me to a solution/cause:
When moving the cursors on a frame from the history, it changes to the next history frames simultaneously, when the cursor menu is open.
When it is closed, then only the curser will move, as is expected. But when i push the knob, then the curser menu opens (which is rather inconvenient, as the picture will jump when rearanging the UI) and the problem is there again.

You write about closing the history list to "solve" this issue, but i cant find a way to do this. But giving the user the burden of many button presses to solve an issue is not the way to go anyway.


It may be arguable for bug no. 1 not beeing a bug, but it will be at the very least very missleading to be able to set up a "save type" for the button in the "save button" menu, but at the same time, beeing able to change this very setting from a different menu! Just give this button its own private setting that will not be changed, when saving something else using the "save menu".
10
Hi bostonman,

The lab power supplys that I knew do have galvanical isolated outputs. this makes it possible to connect them in any order, you want.

eg: bipolar supply needed:
output 1 negative connected to output 2 positive and acts as GND / common
Output 1 positive connection acts as positive rail
Output 2 negative connection acts as negative rail

If you need an additional rail eg. use as input signal for your circuit, you could use a 3rd output (or another power supply) and connect negative output to common if positive signal is needed or connect positive output to common if a negative signal is needed.

Some power supplies do have a button, where you could turn on / off all rails at the same time, very practical.

Guido
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