Thank you! Yes, I really like these probes, they make the measurements easy. However, I am a bit disturbed by the four individual BNC connectors. I will make a similar probing cable but with a single GX16-type connector. It looks more neat.
Nice project. I ordered the PCB on PCBWay even though all the active components are currently out of stock :) Would be nice if you published the combined schematics of the PCB (pdf file ok)
Hi and thanks for supporting me by buying my design from PCBWay. Please visit their webpage again for this project. I have uploaded the schematics in PDF format as well as I added an interactive BOM file. Please let me know if you found them.
very professional 🛠✅ this project keeps getting better ♻🏁 i have been using the esp32 with bluetooth and remoteXY with the android smart-phone 🤔 thanks a lot🤩
You can even use it as a microvolt meter. Just pay attention to the actual voltage levels that you are measuring because of the differential amplifier. Don't overload the input of the ADC.
Well, it is in the video clearly, and you can also read the datasheet of the parts. I mentioned everything in multiple places... The differential amplifier has a fixed 10x gain and the LTC2400 accepts maximum 1.12*Vref. Since the Vref is 4.096 V, then you can convert up to 4.58 V approximately. Keep it below 4.5 V to be safe. This is when you channel the voltage _directly_ to the input of the ADC. If the voltage that you want to measure goes through the diff. amp., then it is 10x less, so 450 mV.
At 2:24... I am not sure that you have your Kelvin clips wired correctly. You should have two current supply wires, two read wires and four earth grounds for the braided shields. I did not see the connection for the four wires' earth ground shields. Each cable should be as follows... One conducting wire with a braided wire earth ground shield over it. The shield is earth grounded at the case end and it is not attached to the Kelvin clip. Meaning, the shield is earth grounded, but isolated from the Kelvin clip. The shield shunts to earth ground any noise that is trying to enter the conductor wires. The shield's earth ground should be isolated from the circuit's ground. (Maintaining the earth ground's isolation takes extra attention, when using USB power.) As you are making very precise readings, noise isolation would be critical to making accurate readings. So, you need case shielding, as well. But, maybe you made the earth ground shield connection in the top of the case, where we could not see it? This is a great project and I do not mean to be negative. I am truly only trying to help. But, I am exhausted and I am afraid I sounded harsh. If so, I apologize.
Hi! It didn't sound harsh at all, and I am always happy to read constructive comments. There is no shielding earth or similar in any case. especially because I did not design the circuit to have it in such a way. The schematics are available, so you can see how the ground is connected. Also, just as a side note, Kelvin clip leads even for $4-500 are sold with only 4 terminals without any shielding or extra care for the earth or shielding.
@@CuriousScientist Thank you for your kind reply. "Kelvin clip leads even for $4-500 are sold with only 4 terminals without any shielding or extra care for the earth or shielding." That is because the clip, itself, is never grounded. The exterior braided shield is grounded at the device, but not the clip. This is because the shied is grounded to earth ground, not circuit ground. Therefore, the shield protects the inner wire from noise, but does not shunt that noise through the circuit ground. If it was tied to circuit ground in any way, the noise could get into the circuit. For each individual clip, you should have a supply wire, a read wire and two braided shield wires. Again, the braided wire is not terminated at the clip. However, because it covers the inner wire all the way up to the clip, it shunts any noise to earth ground. If your clips do not have a braided shield, then they were manufactured with the wrong type of wire. That would not be surprising, if they are an inexpensive import type. Because of the tiny measurements that you are making, you could greatly improve your accuracy by using the proper cable, case shielding and earth grounding, for both. HTH.
I forgot to say that you can easily add shielding to the inside of your nice case, by covering the inside with some type of metal tape. Just be sure to remember to make (solder) continuity between each and every piece of tape. And, to be careful to maintain the isolation between the earth and circuit ground. Cheers.
Thank you for the lengthy explanation! I am super happy that you took the time to explain this to me, or more precisely, to us, because the viewers will also learn from these. Thank you! Regarding the Kelvin clip leads, I specifically meant the wires, not the clips. However, I also saw cables that come with a 5th plug, exactly coming from the shielding. But yeah, even some expensive leads don't have that, but only the 2 current source and 2 sense connectors. Shielding the casing is a good idea, thank you! I actually have some adhesive aluminium tape at home, so I could line the inside of the enclosure with it. Then I could hook it to the earth.
@@CuriousScientist "However, I also saw cables that come with a 5th plug, exactly coming from the shielding." Yes, you clearly understand. Bravo. "But yeah, even some expensive leads don't have that, but only the 2 current source and 2 sense connectors." I had noticed that, as well, and found it curious, for their big price. If each of your cables has a shield that is terminated to the outside of the BNC, you could use a grounding grommet on each BNC connector inside the case and terminate them in to earth ground. Thank you for allowing me to participate and contribute. It feels good, when the world takes time to help each other. Kudos.
@@CuriousScientist I have watched both video's but you don't say anything about that display you have in the box? Is it just a purchased 2 volt display?, that's what I mean!
If I am not wrong, you can send them the components or have it partially assembled. I was really lucky with the components. For example, at that time when I bought the parts I bought some of the last few available LTC2400 ADCs from Mouser. It is not PCBWay, but it is rather the chip shortage why some parts are not available.
@@CuriousScientist not possible to send them the components since they are based in China from what I can see and I am in the UK. I will email them asking when they will have all the parts to pre assemble this fully. PS I am just a hobbyist so don't have heat gun reflow for smd component soldering hence why I wanted pcb way to do it.
Yes, they are China-based, but that should not be an issue. But of course if you have cost concerns, then it might be an issue with the shipping. Unfortunately, I don't have experience with sending parts to them. However, I used their assembly service once (I fully paid for it myself) and I was really satisfied. It went smoother and faster than I expected. By the way, I assembled several instances of this this circuit, and with a solid hand, a pointy soldering iron and some flux, it is perfectly possible to hand solder all the SMD components. Apply some flux on one solder tabs of the component, then melt a drop of solder on it. Then do the same on the opposite side (if it is a DIP-8 chip, do it on pin 1 and pin 5). Then, grab the component and hold it in place then remelt the drop of solders that you just applied on the tabs. Now you have the component fixed on the PCB at its corners. Apply some flux on the legs, touch a leg with the iron to preheat it and then touch the solder wire to the leg to solder it to the tab. It looks intimidating in the beginning, but actually the flux will help you a lot because it doesn't let the solder to go between two adjacent legs that easily, and it also helps you to reach better soldering quality.
