Recent Posts

1

Test Equipment / Re: SDS800X HD Wanted Features

« Last post by Martin72 on Today at 06:31:28 pm »

Speaking of cursors...
I don't really like it when the screen is plastered with data, so I find the MAUI from lecroy a more discreet solution:

The decoder functions are also "more", including search functions and what you want to show/hide.
The following pictures are an example of how it could work, I can hardly imagine that something similar could be realized with the 800X HD, then rather with the larger models(On the other hand, I would of course be very pleasantly surprised if it did).
You should keep that in mind anyway, just because a lot of feature requests have been included here doesn't mean that all of them will (or can) be implemented.
And certainly not in a short space of time.

2

Test Equipment / Re: DER-EE DE-5000 ESR zero measurement problem.

« Last post by sonpul on Today at 06:30:23 pm »

You can view ESR in RS mode.

3

Test Equipment / Re: SDS800X HD Wanted Features

« Last post by eTobey on Today at 06:27:10 pm »

Suggestion:
Some more details in the manual. Just 3 sentences is not enough to explain a trigger ( this may also apply to other topics in the manual).
Especially i dont really see what the difference of the qualified trigger is to the delay trigger.

What set conditions?

"The settings of source A is similar..." in which way? Where is the difference?

I dont know how i could combine a level and an edge to source A. 

4

Test Equipment / Re: DER-EE DE-5000 ESR zero measurement problem.

« Last post by TA3UIS on Today at 06:25:53 pm »

Your meter works fine. All meters have limitations, and right now you're learning the limits of this one.

The purpose of adding a known resistance in series is so that you can subtract the difference to find your ESR. So you need to also measure your resistor(s) separately to know that value. If you add a 1ohm resistor in series with the cap, and you get 1.1ohm reading, your ESR is 0.1ohm.

As far as I understand, the purpose here is to bypass the limitations of the device, right?
Some kind of hack by connecting a 1ohm series resistor.

5

News/Suggestions/Help / Re: Search is useless

« Last post by Andy Watson on Today at 06:21:47 pm »

Useless - isn't it!

put "site:https://www.eevblog.com/forum/ SDS800 or whatever" into your favourite web search engine.

6

Beginners / Re: Amplifier type

« Last post by Zero999 on Today at 06:20:52 pm »

The circuit won't work, at least not properly.

If it works in simulation, then it's because the op-amp power supply isn't being modelled correctly.

If it appears to work in real life, then the op-amp must be going into phase inversion or something weird.

7

Beginners / Re: Signal generator question

« Last post by CamJam on Today at 06:19:42 pm »

Hi RoGeorge,

I am using a E275-10 LED from InternationalLight (it was some of the more powerful surface mount UV LEDs I could find at the time). Just need one LED for my enclosure/project.

The datasheet only mentions that the LED should be operated at -30 to 60°C. Tested one out today (powered the LED with DC power supply 6.5 V, current limited it to 180 mA) with a MOSFET transistor driver (IRL2703PbF model, applied 2.5 V at the gate).

It worked (i.e., the LED was emitting UV), but got bloody hot (leftover flux on pads of LED smoked).

I attached the datasheet (had to scan it as what is provided on the website is not the same).

Thanks for your insight!

Cam

8

General Technical Chat / Re: Model Trains

« Last post by joeqsmith on Today at 06:19:31 pm »

Pull testing the Lionel 1666 after service.  The value in these trains is a reminder of a different time in my life.   When I handle these old relics, I wonder about the kids that came before me who had their fun with them. 

9

Projects, Designs, and Technical Stuff / Re: Identify an old (mid-1970s) 10-bit ADC

« Last post by coromonadalix on Today at 06:18:40 pm »

i got it   almost   loll

https://www.analog.com/media/en/technical-documentation/obsolete-data-sheets/249731ADC1130.pdf

10

Beginners / Re: hFE of a NPN transistor

« Last post by mariush on Today at 06:16:13 pm »

i want to use the transistor to turn an LED on and off, the transistor will be connected to a 9v 200mah battery and i think that LED can have maximum input of 5v and 25ma.

atteched you can find the a screenshot of the datasheet of the LED, i have a green one.

A green led will have a forward voltage of around 2.2v to 2.4v , it would be silly to power it with a 9v battery because majority of the battery power would be wasted as heat in the resistor that limits the current.

You limit the current going through the led using formula derived from Ohm's law :  Input voltage - (number of leds in series x forward voltage of led) = Current x Resistance

Your input voltage will be 9v , minus around 0.2-0.4v in the transistor, between collector and emitter.

If you want to limit the current to 20mA (0.02A) and you use 2.2v for the forward voltage of the led, then your formula becomes  9v - 0.4v  - 1 led x 2.2v = 0.02A x R   so  R = 6.4/0.02 = 320 ohm ... I'd probably use 330 ohm and get a bit less than 20mA through the led.

The problem is you're gonna waste a lot of energy in the resistor :  Power = Current²xR = 0.02 x 0.02 x 320 = 0.128 watts .... while your led will consume 2.2v x 0.02A = 0.044 watts


Change your battery to 2 AA rechargeable batteries (2.4v) or 2 alkaline batteries (3v) and not only you'll have more energy, you'll also waste less in the resistor.

With rechargeable batteries  you'd have  R = (2.4v - 2.2v ) / 0.02A = 10  ... so a 10 ohm resistor would be perfect, and the power wasted in resistor would be 0.004 watts


You want to use the transistor as an on/off switch, you won't use it to limit the current.  So even with a hFe of 25 you'd get the transistor going with as little as 1mA on the base.

Assuming same batteries are used to turn transistor on or off

Input voltage - ~0.6v drop on the base = Current x Resistance ... for 1mA you'd have  R = (2.4v - 0.6v) / 0.001A = 1800 ohm ... so even with a 1kOhm, you'd get more than 1mA on the base.