Recent Posts

1

Microcontrollers / Re: rp2040 MCU pll derived clocks jitter?

« Last post by iMo on Today at 09:26:03 pm »

Yep, that has been mentioned in the other thread (DYI Multislope ADC) as well, where the Pico is used as the inguard MCU. The jitter has been identified as a potential source of errors (talking 6+ digits), therefore my interest on getting some numbers on the jitter provided somebody has measured that already..

2

Test Equipment / Re: Are 'premium' scope brands still justified?

« Last post by Martin72 on Today at 09:25:22 pm »

Evaluating an 800X HD series at first might be an option indeed

I've had the SDS800X HD here for just over a month now, as a "stopgap" until the SDS3034X HD finally arrives....
This is by far the "best" oscilloscope you can get for around €500.
There is nothing comparable on the market and not so long ago I would have said that's it, that's all you need as a hobbyist.
But I know/had the 2000Xplus and most recently the 2000X HD, so I'm a bit biased.
However, it is ideal for testing whether you might like Siglent's "philosophy" in general.

3

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

« Last post by ebastler on Today at 09:22:18 pm »

]Either you are missing the point or you just want to be contrary.  Not sure which.

The point is, if the OS is getting it's clock from the scope reference, then 150ppm is way out of spec.

Personally I'm not too concerned about what time is displayed as I do sync via NTP and give or take a few seconds is no problem for file timestamps.

Plus what Rob just said for affected use cases..

Sorry , I did not mean to sound contrarian. Had missed reply #1226, and I see that this would indeed be a use case which benefits from stable long-term timekeeping. But it also seem like a niche case. Normally I would expect long-term operation to occur in an automated setup, where there is a network connection and the possibility to re-sync the time.

I don't think you should make conclusions about the scope's reference clock accuracy based on its long-term time-keeping. The time may be affected by factors like missed low-priority interrupts, or may be derived from another source entirely. Others have measured external 10 MHz reference clocks using the scope's counter, which seems like a much more direct and reliable method, and have found in-spec accuracy.
 

4

Projects, Designs, and Technical Stuff / Re: I think I need a little help. AC IN switch circuit.

« Last post by Zero999 on Today at 09:21:39 pm »

I used a transformer, bridge rectifier and filter capacitor, to power the relay, rather than a switched mode power supply. I don't remember whether I used the usual back-EMF diode, or switched the AC and allowed the bridge rectifier to act as the freewheeling diode.

I thought about that too. I've seen a ton of those from back in the day working on TV's and Hi-Fi stereos. They are seemed to have little "standby" transformers. I honestly don't know which is better nowadays.

A mains transformer has a higher standby power consumption, but is fairly noise-free.

A modern switched mode power supply has a much lower standby power consumption, but is more noisy.

The device I built simply turned on a compressor, when a pressure calibrator demanded it, via a dry contact. This was to save power, noise and ware on the compressor running continuously. Standby power consumption wasn't an issue, since it isn't left running all the time. The whole thing fitted into a small 150mmx75mm*50mm diecast aluminium enclosure, with a UK 13A socket on the side and a cable to a 37-D connector to the pressure calibrator.

5

Projects, Designs, and Technical Stuff / Re: Studio Grade Headphones on the cheap - A DIY 3D Printable Project.

« Last post by colorado1876 on Today at 09:17:05 pm »

Excellent thread!  You inspired me to try a DIY headphone project.

There are many headphone amplifiers with the TPA6120A2 chip. However, I am confused. Some with identical PCB layouts are listed as VAC while others are VDC.  For example, the listing for this one (https://www.aliexpress.com/i/2251832821951317.html?gatewayAdapt=4itemAdapt) is VDC (12 & 24 VDC), but the board clearly states VAC. It seems identical to the one in your photo. As you mention you are using USB for power, I assume that the amplifier has VDC input. Can you clarify?  I am looking for one of these amplifier variants for portable use with battery power.

6

Test Equipment / Re: SDS800X HD Bugs/Wanted Features

« Last post by eTobey on Today at 09:13:38 pm »

If you enable Show statistics, it shows it is not counting.  If you enable [Stop on fail] it will not exit Mask mode but only stop testing.

It shows counting, but what if an event takes a dozend of seconds to appear? Than you wait that long?
Efficient would be you just beeing able to tell with a quick glimpse, if it is activated.

7

Manufacturing & Assembly / Re: Green shmutz on trimpot screwheads

« Last post by coppercone2 on Today at 09:13:21 pm »

does it smear? they must be lubricated with a damping compound of some sort to allow for smooth adjustment, possibly with a electrical grease in the wiper area and then a purely mechanical damping grease in the shaft area. they have alot of grades of the stuff. orange green and red are common colors of this grease used for ID purposes

8

Other Equipment & Products / Re: What's the highest magnification you use on a microscope and why?

« Last post by joeqsmith on Today at 09:13:03 pm »

About 2.5x to 50x depending what I am working on.  There have been times I would have liked to go up higher but not 700x.   

9

Other Equipment & Products / Re: What's the highest magnification you use on a microscope and why?

« Last post by magic on Today at 09:11:23 pm »

Is it a purely optical microscope (you look into a tube with glass in it) or some digital gadget with a screen or USB/HDMI output?

The latter may boast crazy magnification numbers which are not necessarily comparable with traditional magnification specs of optical microscopes. OTOH a conventional microscope with 700x mag is too much for wirebonding, let alone soldering And you likely won't find a stereoscopic microscope with such magnification, and working distance will be essentially zero.

BTW, the magnification of optical microscopes (and magnifying glasses) is defined as approximately how larger the object appears to be compared to viewing it with naked eye from 25cm distance.

10

Manufacturing & Assembly / Green shmutz on trimpot screwheads

« Last post by aeccles on Today at 09:11:15 pm »

My company has recently received PCBAs from our CM that have some sort of green discoloration on the trimpot screwheads.
I do not think that this is oxidation, it seems sort of like glyptol or something. I know that this isn't a lot to go on but I would appreciate hearing from anyone who has seen something like this.
These are brand-name trimpots and a very reputable CM. Obviously we'll be contacting the CM and, if necessary, the trimpot manufacturer.
Thanks!