Recent Posts

1

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by MK14 on Today at 01:29:26 pm »

I am still NOT convinced.  I don't think an LED and a resistor are the same.

Apart from anything else, an LED is normally used as a light source or indicator.  Functions which a normal, non-overloaded resistor can't do.  At least in the visible spectrum.

2

General Technical Chat / Re: Big Brother air monitoring.

« Last post by tom66 on Today at 01:28:41 pm »

The first area to affect you financially via this style of exploit is insurance.

Some insurance companies already charge a hefty extra premium for smokers, that includes the health insurance plan I get through work. (They apparently offer a program to quit smoking included in the extra premium, don't know the details as I have never smoked.) I think it's a good idea, the nonsmokers shouldn't have to pay for the costs of smoking. How it is determined is by self reporting, with threat of legal action or having claims be denied being the deterrent to lying about it.

I guess they'd look closely at someone with lung cancer or throat cancer and if the doctor reported a likely cause of smoking they'd not pay out.

An interesting counter-example is pension annuities which pay out more for people who smoke (because you're likely to die sooner.)  How can they prove you smoke?  Is once a month enough to meet the standard of being "a smoker"?  If it meant an extra £500 a month (which it did in one example I chose) then, heck, it almost seems worth it, provided you can keep it to once a month!!

3

Beginners / Re: Switching a 3KW (240V) immersion heater: Solid state or mechanical relays?

« Last post by IanB on Today at 01:28:39 pm »

ones who provide the necessary SDOC

Curious why the SDOC is required? Is this an Australian thing?

4

Beginners / Re: display current on scope

« Last post by jpanhalt on Today at 01:27:55 pm »

Here's what I made.  The clamp is a hobby clamp that was called a Hayes clamp (2005).  I used it to qualitatively see what saturation looked like and waveforms. It presumably could be calibrated, but for accuracy a linear Hall or resistor is probably a better method.

5

Test Equipment / Re: Looking for a replacement general purpose oscilloscope for home use

« Last post by Kosmic on Today at 01:26:34 pm »

So there I am, waiting for my illusive event and the scope's temperature/time/whatever has changed and it wants to autocal but is stuck waiting for the trigger, just like I am.   Then it happens, the elusive trigger that both the autocal and me have been waiting on.  The scope starts the autocal.  A second event happens immediately and it is still running the autocal. 

Did you try disabling from the service menu ? I was reading the service manual for the WaveRunner 6k series and they have a chapter about autocal. I have no idea if those settings are permanent though.

6

Test Equipment / Re: Siglent SDS800X HD 12 bit DSO's

« Last post by tv84 on Today at 01:26:25 pm »

English is actually very bad language for engineering. As someone that was exposed to both English and, to some extent, German technical literature, German language is much easier to be precise.

My friend, we're in total disagreement in that one. IMHO english is a perfect language for engineering. The use you make of it is the cause of the misunderstandings. BTW, I wouldn't call the "feature" thing an engineering term.

And I'm one of those that can easily distinguish "ser" from "estar".

7

Test Equipment / Firmware update for Gratten ADS1102CAL+ oscilloscope

« Last post by Sergo on Today at 01:18:38 pm »

Hi all   
Help please I wanted to update my device.
I've been looking for firmware for Gratten ADS1102CAL+ for a few days now.
I wrote to the manufacturer and suppliers of different countries, they do not answer me.
 I tried to upload the results from other oscilloscopes, but the problem is that my oscilloscope does not open the flash drive, but just gives an error if it does not find the right one.
The chip is installed Cyclone® IV EP4CE10 FPGA.
Photo attached:

8

General Technical Chat / Re: Big Brother air monitoring.

« Last post by NiHaoMike on Today at 01:09:06 pm »

The first area to affect you financially via this style of exploit is insurance.

Some insurance companies already charge a hefty extra premium for smokers, that includes the health insurance plan I get through work. (They apparently offer a program to quit smoking included in the extra premium, don't know the details as I have never smoked.) I think it's a good idea, the nonsmokers shouldn't have to pay for the costs of smoking. How it is determined is by self reporting, with threat of legal action or having claims be denied being the deterrent to lying about it.

9

Beginners / Re: buying a oscilloscoop

« Last post by tggzzz on Today at 01:06:23 pm »

Indeed this is good advice. One suggestion that I can give regarding the choice of oscilloscope that mitigates this issue is a fully portable unit, which is isolated from anything else. I have one of these newer portable oscilloscopes from Zoyi/Zotek (ZT-702S) that allows troubleshooting several minor issues common in computers such as power supply ripple, RTC clocks, activivity on data or control lines, monitor reset lines, etc. Naturally, you might find yourself wanting for a better unit later in time, but these units are a great starter.

Before all the traditional scope-floating hell breaks loose, it should be mentioned that while these portable (aka floating) scopes are good for preventing the damage of the scope and DUT (as long as all ground leads are connected to the same potential), they do not inherently make measurements safer for the user. That part should be understood, and it was a good advice to accumulate some experience and knowledge before proceeding to probing higher voltage circuits.

Actually they might make it marginally safer. Avoids deafening/blinding/lung damage/heart attack when something blows up and/or catches fire
Apart from those minor considerations, you are right: an isolated scope woudn't make it safer.

HV differential probe are, for some use-cases, the appropriate choice of probe.

The OP might like to consider that they will probably end up spending money on a scope plus X, and hence to leave budget available for X. (X=probes. PSU, signal generator, meter, protocol analyser etc)

10

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by Sredni on Today at 01:06:13 pm »

non linear system has linear approximation around a small operating point....

STOP THE PRESSES!

... oh wait, that's the underlying principle of how spice AC analysis works.

Small signal analysis has nothing to do with what we are discussing here.
The resistance I talk about is the static resistance, not the dynamic or incremental resistance of small signal analysis.

Try again.

That was your long winded and dithering proof:

So, we are now seeing the diode as a voltage dependent resistor. Let's see... what is the resistance 400mV? Let's zoom in:

[MASSIVE IMAGE]

I'd say it's about 23.2 kohm.
Let's see what is the resistance at, I don't know, 660 mV (about 5mA of diode current). We can compute it by hand of course, but on the graph we see it is 132 ohm.

[MASSIVE IMAGE]

Now, let's see if we can make something with these values...
[snipping conversational fluff]
Ok, exact same results, if we neglect a bit of rounding error in reading and setting the values.
Now, take your black boxes out of the fridge. Put the diodes D1 and D2, and the resistors R1 and R2 inside a black box each. Shuffle them around. And tell me: without looking inside the black boxes and without resorting to second order effects (like temperature dependence, or changing the other circuital parameters to change the operating points) can you tell me which are the diodes and which are the resistors, by simply measuring voltages, currents and powers?

So to try and claim you're not relying on the well known small signal AC parameters is plainly incorrect.

If you dont like relying on small signal characteristics, perhaps "try again" with your explanation/justification.

Again, small signal analysis has nothing to do with anything I have written in that post.
Nothing.
I zoomed in on the V-R characteristic to find an accurate value of the static resistance. Not the dynamic, or incremental, or small signal resistance.
Then I used the static resistance at a chosen voltage or current to choose the limiting resistor that would have set the chosen operating point.
Then I showed that using a resistor with the correct static resistance value would give the same variables in the circuit..
If you want to waste a bit of time you can create in LTspice a voltage controlled resistor that has the same R=R(V) dependence of a 1N4148. You will then see that it will behave (secondary effects apart) as a diode, confirming that it's the variable resistance. that gives a diode its behavior.

Go ahead and try.