Відео

Hi @jamessutherland1226, I just double checked mine and there was no connection between the output terminals and the chasis. There seems to be a relay between the green ground terminals and the chasis since they are not bonded together unless the channels are turned on. The negative terminals are kept separated from the ground terminals as well. How is it in your case, are the +Ve and grd shorted when the channels are on? That would not make any sense 🤔

You can toggle the main channels on and off using the on/off button but I bet you tried that already. Anyway, you should have seen some voltage on the 3rd channel, which is always on.

I assume that you also set at least a small current value.

Some devices are using SYST:PDOW but not sure if Siglent supports it. You may also have a command to emulate buttons and call the power switch with it.

I'm not sure how those over current/voltage protections are used. Are they used to constraint the PC control so that you do not exceed certain limits accidentially? S-LS-28 does not have remote connectivity or memory slots. On the other hand, you have separate knobs for the both channels and it supports series and parallel connections between the channels internally. Can you do that with S-LS-114? In principle, they seem very similar. 114 can be connected with a PC but 28 might be more convenient to operate manually.

Hi @realvmarks, the program writes its output to the standard output stream and you can pipe that to a file. The output consists of three whitespace separated values: time, value, unit. You can convert that to a CSV by simply replacing the delimiting whitespaces with commas. The following command saves your log into mylog.csv while showing them on the console: ./cli.sh pmd | stdbuf -o0 sed 's/\s/,/g' | tee mylog.csv The stdbuf command is used to flush lines immediatelly without buffering. Of course you can also change the formatting of the output from the code :)

Hi @SevenDeMagnus, I've always used non-rechargeable ones in my multimeters but have not been picky about their brand. I've used what's been on hand. I rarely use a backlight and thus the battery life has not been a real issue with the LCD meters. This PDM 300 C2 has a great bang for the buck as it costs only 15€ but I find most mid-priced auto-ranging multimeters good enough for well over 90% of the work. One model shines on one aspect whereas the other one has its own strengths. Uni-T UT211B is a good example of a niche product. It has a fairly clumsy user interface but it provides an mA range DC clamp meter, a nice NCV, and a small form factor that fits into your pocket. I really like that meter in those regards but I cannot recommend it for typical voltage or resistance measurements. Brymen BM869s does not cost nearly as much as some of the other high-end multimeters from Fluke, Keysight, or Gossen Metrawatt. Still, I am not sure if it fits into the range of affordable models with its ~220€ price tag. I am happy to use almost any decent multimeter - this is the one I love to use :) Best regards, Marko

It seems that the reader cannot detect the expected beginning (hexadecimal bytes DC + BA) of the message. Have you checked how the input looks in practice? Perhaps you can print bytes within the _synchronize() to see if they make any sense. Of course the protocol or some of the parameters of the serial output may have changed between the versions.

Here's the loop, which seeks for the beginning of the next message: github.com/AsserHic/alab/blob/33ada76e73ad12ec6816662cd87a4dd734b06658/src/pdm/pdm300c2.py#L119

@@asserslab A litle debugging on serial give something like this: b'`' b'\x06' b'\x00' b'\xfe' b'\x00' b'\x98' b'\x00' b'\xfe' b'\x00' b'\x00' b'\x00' b'\x00' b'\x00' b'\x1e' b'\x00' b'`'

I was testing how that looks to my C2 and the system was really unstable. I got all sort of errors and similar sequences of 00 bytes. It turned out that I was using pyserial 3.5b0. I updated that to 3.5 and now the connection works again. DC BA tokens are followed by 8 bytes for the data.

Those 4 subsequent 00 are actually quite normal if your value (say DC voltage) is 0 😀

That's a good question and I was wondering the same thing when I saw those new models in sale. I saw a tweet from Biglesp in Twitter suggesting that the serial output would be still there. I never bought a new one so I have not tested the protocol myself. Please let us know if you are planning to try it out!

@@asserslab Yes, I want to try. I will use a DB9 RS323 to USB, to connect multimeter to PC. I want to modify somehow your source code, to use it in Jupyter Lab with pandas and matplotlib, for two PDM300. All these will be use in didactic purpose.

@@catanaadrian5148 Sounds interesting! It's good to use an optocoupler unless the USB adapter includes them already. I am curious to hear how all that worked out 👍

@@asserslab Is it proper to use a 4N25 ?

I've been using ready made isolation circuits with an input buffering. Not sure how much current you can draw from the pin so I rather kept that low.

It really depends on what kind of graphs you need. Matplotlib is a good general purpose library and it is very popular. I also like the descriptive way used in ggplot2. That library is available for Python as Plotnine package.

Hi @Pieter Vermeer, Those were Brymen BL21S2-T4SC silicone test leads that were shipped with the BM869s multimeter. In addition, I used few pairs of unlabelled banana wires and some accessory hooks for the probes.

Hi! As a matter of fact, I am using this Raspberry PI as my desktop computer most of the time. I've connected oscilloscope via a USB port but you may use an ethernet option as well. All you need to change is the address configuration. I've used these Python codes in various Linux laptops already. Changes are that some small adjustments are needed if you use a different operating system. Still, the oscilloscope will be used the same way. You can just put your PC in place of the Raspberry PI and you are good to go 🙂 One thing that I noticed with my signal generator was that I was not able to upload new waveforms via USB but the exactly same code works fine via ethernet. Not sure if that's a bug in Sigrok drivers or in the firmware. I wonder if someone else have tried that?

@@asserslab Thank you so much🙂🙂

The fact that this auto-ranging multimeter costs 15€ and it's of reasonable build quality does not leave much competition on its price range. It is definitely worth every penny. A rubber case would be a nice addition to the meter but again, it is hard to fit for that price. The serial output has been left active (at least in the first versions of the multimeter), which makes this device hackable for hobby electricians. I've made another video on this topic ua-cam.com/video/2YlhSKf9n0c/v-deo.html and used my device for some data logging tasks. I can imagine people doing pretty crazy stuff by embedding this device into their projects especially if they replace the manual dial with some relays 😉

@@asserslab I have one. For the price, it's a bargain.

@djsbriscoe: Thank you for your word of warning! I wonder what has been the motivation for the link you mentioned. Is it possible that you've obtained a second hand item and it was originally used somewhere where the link was used to ensure that the device was not turned off by accidentally pressing the button? I double checked my MII 2000 transformer and I got no current flow between the primary and the secondary circuits when the device was turned on. The case grounding was working perfectly fine too. Still, I have not measured the actual dielectric strength of the coil insulation.

You have a resolution of four digits but that is three digits after the decimal point for the current i.e. 1mA. The dial modes are: A, dA, cA, and mA.

@@asserslab even better! I've been looking to buy a lab psu for a while now and thanks to your video found this: eleshop.eu/korad-kd3305d-5195.html That almost beats the cheapest options on aliexpress (for 2 channels) so I'm pretty thrilled. BTW, they do sell the programmable unit but haven't found a reason to spend the extra 30€ or so for it... Am I missing something?

I prefer the front panel layout of the manual model (KD3305D) but the computer interface would be handy. You can do fairly advanced automation and tests if you build some feedback loops from your device under the test to the computer. The computer may use these data to adjust the PSU.

Thanks! I also lost one VGA display at a thunderstorm and then upgraded to a SVGA, which led to that funny situation where the video card had more RAM than the motherboard itself.

The 7 segment display works well although you may get some reflections from the cover. Having the device below the level of my eyes I have never noticed them in practise. To my mind, this power supply is a nice general purpose device and good value for money. It has worked well for analog circuits and I often need more than 3A per channel, which is not a problem for the device. The rotary encoders with adjustable resolution are really nice. You can adjust the voltage and current just like water from the tap :) What I've been missing the most is a computer interface for a remote control. In the absence of that, I find myself modulating the supply output with my function generator quite often. A less powerful, single channel, programmable precision supply with a four-wire configuration would make perfect companion for this device.

@@asserslab Thank you very much for your answer very grateful ok

Yeah, it has been of exceptional value for money and I've used it quite frequently for some data logging tasks since I connected it with the computer.

@@asserslab Indeed! One hint that helps with data logging is rather burried in the manual: holding the red button, while turning the multimeter on will disable auto-power-off, so you can, given it's connected to a bench power supply, keep it running forever.

@@asserslab May I ask, how are you datalogging the readings to a file? What information is logged?

I've improved the code a bit since the video but it still follows the same principles. The output consists of tab-delimited triplets having a timestamp, measured value and a unit. Each triplet is printed on a separated line but lines are produced only when the value changes. This means that the interval between the timestamps varies. I'm using the same base units for all ranges so that you do not need conversions such as mA to A. The exact unit depends on the mode of the multimeter but the program supports them all. Measurements are written to the standard output stream so that you can pipe them pretty much anywhere. You can show them on the terminal, save them to files or pass them to some subsequent processes for visualisation, summation, etc.

Blown to the air 💨 Yeah, the linear power supplies are not famous for their efficiency, which is typically around that 60%. I have not measured the maximum input current in practice and the 550W is based on the data-sheet. It has not been emphasised but the power rating refers to the total consumption of the device. Thanks for pointing out this important thing 👍🏾

No power supply is 100% efficient, even regular ATX power supplies are 85-95% efficient. There are losses in the bridge rectifiers converting AC from transformer to DC (for example for a single 30v 5A you'll have around 1.5x5A = 7.5w of losses) and you have losses in the pass transistors that regulate the output (the rectified AC voltage will be around 35-40v , the pass transistor outputs 30v and the difference of 10v x 5A = 50w gets dissipated as heat) and you also have losses in the transformer itself ... so 60-70% is an OK efficiency for such linear power supply

@@mariushmedias Yes, in fact, that's what I meant, 550W is the absorbed power not the supplied one.

And I did also use some rubber cement/glue to stop the heatsinks for the voltage regs from hanging freely in the air. I glued them down to the board as leaving them like that worries me that in the long run that the legs might break or get bad solder joints in the future.

Yeah, that's a good advice! I may do the same thing. Thanks!

Nope, EEPROM has calibration & memory data only. Unfortunately, NuMega MCU firmware is locked for reading (for now, at least - see EEVBLOG forum for any progress).

Thank you Rohith! I am glad that you asked. It seems that I forgot to explain that on the video. The Python code was running on the Raspberry PI and the instruments were connected to it. I clarified this now on the description but the command line usage is probably better illustrated by the next video (ua-cam.com/video/2gegKQt6nNo/v-deo.html) where we use the same Python script for some X-Y rendering. Best regards, Asser

@@asserslab But i couldn't see the implementation of Raspberry pi in the code. Like how is it controlling the function generator? We could directly use the python script to control the Func Gen without Microcontroller and to use the multiple devices we can use GPIB interface also.

Vielen dank! :)

Hi @Schwalbe262, That would be an interesting exercise 😊 I have not seen any tear down pictures of the clamp multimeter but it seems that there is also a pen multimeter with the same model name (PMZ 2 A1). The PCB of the pen multimeter has RX & TX pads, which is promising and I bet those both devices have a lot in common. The latest version (A2) of the pen multimeter seems to have some small structural changes and it is slightly lighter than A1. I noticed no visible changes on the clamp meter. Input ranges of the new version start from zero, which means that at least the firmware has changed. I would not expect major changes on the serial protocol though. Let’s see if I’ll tap into these multimeters so that I could test them. I’m also curious on this topic if you or the others are already working on them.

@@asserslab I'm just considering getting one. Do you have one, where you could check, if it outputs anything on the serial port? If so, I'd buy one for a pretty elevated price, since they sold out here.

@@benedikts-workshop I wonder how many people have modified their Parkside meters and would there be enough users for a Sigrok driver? I was considering that option with PDM 300 already. I have not seen those clamp meters here in Finland but happy to try if I'll find one.

@@asserslab I’ve just purchased the clamp meter for more than double the price. Let’s hope, that it will not disappoint :-) I’ll keep you updated. Concerning the PDM300 C2, it’s one of my more popular projects and I keep getting multiple clones a week on GitHub. It might be worth writing a driver for.

benedikts-workshop/ParksideView

Hi Benedikt! To be honest, I found your repository last week and attached a connector for the ground and TX pins over the weekend. Thank you very much for the decoding of the serial protocol! So far, I've only tried it with an oscilloscope. I planned to read the serial output with a Raspberry Pi GPIO but I do not have a suitable optocoupler yet. I've used Sigrok and PyVisa for my other instruments and I could perhaps follow your great example and write a Python driver for the multimeter.