Femtoamp Measurement on your Desktop

[@kylencelia4328]

Wow!! You’ve done a great work! It’s worth a tangible beneficial result’s. You’re an amazing scientist and an inspiration to the younger scientist. God bless you and your knowledge.

[@joymiller162]

Your great work has resulted in tangible, beneficial results, keep it up. God bless you

[@instrumentfixer35yearsexp90]

Neat. Iwas a Field Service Engineer for 25 years, crosstrained into GC and Optics then after a time Chuck Burget seperated the company into Chromatography and Optics. I went with Optics.

[@AlexanderPerez-xg4vs]

Great work ...I am quite impressed . God bless you more. 🙏

[@richardcommins4926]

Thank you for the comment that I impressed you. Did you understand what I was talking about? Who is "user-lp6qb9cd1c"? Do I know this person? I do know a Helen! LOL

[@peggywilson-lb4gy]

Great work Richard .

[@HailieNichels]

Amazing Richards 💯

[@rachelbrown6118]

Great work 💪💪

[@marieagle5534]

Great work.

[@KylieScott-d4n]

Useful and helpful

[@MrNedelcuBogdan]

I want to buy one!!!

[@paultathagata]

Hi, we are currently trying out some low current measurements in our lab . We are characterising FETs and are interested in current measurements in the subthreshold region

[@wowepic2256]

Is there a schematic or more information available?

[@richardcommins4926]

Since I design it of course I have the schematic. But there is more to making this work than just a schematic. Even if I gave to the parts, you would not make it work. The PCB alone is very unusual so much so that the PCB manufacturer said they never saw anything like this before and asked be what is it used for. LOL Then there is the software to go with it. I spent years writing the software too. Then there is an extensive calibration procedure too using test equipment costing thousands of dollars. Why would you want the schematic anyway? What would you do with such an electrometer? What more information do you need and want. Maybe it is available from from without giving too much away. I had another electronic engineer at another company try to duplicate this design with all the parts and could not even get it to work without my direct help. He never did get even close. They he wanted to hire me as a consultant. I told him he couldn't afford me. LOL I do consulting work at $300 an hour now but to even understand what I tell you will require an engineering degree. The math alone will boggle your mind.

[@wowepic2256]

@@richardcommins4926 Hi, thank you for your reply. I am just interested in the theory of operation.

[@oliviarichard4988]

Wow

[@bradbury1542]

Is there USB isolation? Also, do you have plans to sell units? I would like to buy even if still at prototype stage.

[@rcommins2]

This electrometer is still in the development stage and I didn't include USB isolation yet. I added circuitry to minimize the noise from my desktop computer, but the noise from my laptop charging supply adds noise. My intent is to add transformer isolation in the future. I'm on my 8th prototype and I have only 2 of them. Building prototypes in small quantities is expensive, so I am trying to gage the market to see how many people are interested. What is your intended purpose for this electrometer and I will let you know if it will work for you. Remember that the connection to your source current can add lots of noise unless you use my ultra low noise cable that has BNC connectors. This design is a ground based design and is not meant to float at high voltage. The low noise cable is a custom design and I have limited stock. I will have to make a large investment in procuring the cable if I go into production. I will be making a new video that demonstrates how my electrometer can measure high meg-ohm resistors easily.

[@richardcommins4926]

Yes I have now added USB isolation from the computer. I did this by buying a "USB to USB Isolator" from Amazon.com for $40.00. When I initially installed the device my noise went up dramatically. I had to make circuit modifications to the electrometer to make it compatible with the USB isolator. Now my noise is back down to the shot noise limit at the measured current and calculated bandwidth. My electrometer no longer sees the noise from the power supply for my laptop like I described in the above comment or from my desktop computer.

[@kaybhee6]

keen... how much

[@richardcommins4926]

That depends on how many you want to buy from me! LOL Just one is a lot more expensive than say 100 of them. What are you going to do with one anyway? How familiar are you with measuring femtoamps?

[@kaybhee6]

@@richardcommins4926 sorry,,,was just curios,,peace

[@richardcommins4926]

@@kaybhee6 Why were you curious? Not too many people even know what a femtoamp is all about. I did give you a price in the video and said if was less than $100.

[@kaybhee6]

@@richardcommins4926 thanks good to know,, trying to do basic materials sci type experiments

[@kaybhee6]

@@richardcommins4926 really wierd cannot find your youtube,,, pls give link

[@scottgulas]

Did you ever decide to sell these? I'd be interesting in trying one out in my lab.

[@richardcommins4926]

+Scott Gulas Unfortunately, I'm waiting for a greater interest to develop and a better economy. I don't want to invest 10's of thousands of dollars to just sell a few. I would be interested to demonstrate my electrometer in your lab. Where is your lab? What is your application that needs an electrometer? What will you use as a current source and how do you plan to connect to it? You can email me at: [e-mail] to discuss this further.

[@richardcommins4926]

+Scott Gulas Are you Scott Gulas the Validation Manager at Texas Instruments in Sahuarita, Arizona?

[@scottgulas]

I got the pleasure of spending some time with Richard looking at (and actually measuring) his electrometer solution. Lots of clever techniques and a lot of great lab war stories from a rich career in the field of chromatography. The accuracy of his solution is superb (tested with a calibrated Keithley 263 SMU) with reasonable settling times. A lot of great work has gone into making his square root electrometer solution as good as it is. A very nice guy to boot!

[@ronniepirtlejr2606]

I am a beginner Electronics guy, I don't even have a oscilloscope yet. I feel like it's holding me back on furthering my learning. But I got to say this looks like a beautiful thing you have worked hard at! Could you recommend a halfway decent beginners oscilloscope to me?

[@richardcommins4926]

It will all depend on what you want to do with it and how much you want to spend. As a beginner, doing beginner electronics, any oscilloscope will do. You can get many of them on Ebay for very little money like $100. As your needs increase with time, then speed and features makes the cost of the oscilloscope go up. I would get a old working (guaranteed) Tektronix scope on Ebay. I would stay away from the digital scopes for now. They all have their problems and are expensive. I would look for something like a Tektronix 100MHz scope on Ebay.

[@ronniepirtlejr2606]

@@richardcommins4926 okay thank you! That makes a lot of sense the way you word it " as your needs increase, upgrade!' I just placed a bid on one that fits your description. :-)

[@ronniepirtlejr2606]

@@richardcommins4926 I want to thank you for your recommendation! I got a good deal on a tektronix 2247A for $150.00 from a Electronics recycle place. They gave me a guarantee that it works! After looking at other prices on eBay for the same thing, I feel like I got a pretty good deal? ( I don't think they realize what they had) thanks again for your recommendation! :-)

[@richardcommins4926]

I am glad you got a good deal. I hope you get many years of use from that scope. Now you can spend the next 20 years learning how to fully use it and find all of its limitations. Read all of its manuals, both user and service manuals, check the calibration of the instrument and don't forget the manual for the 100 MHz probes that you will be using. If you bought a 1x/10x probe, learn the difference for the two settings. They need response calibration too on each input you use them on.

[@ronniepirtlejr2606]

@@richardcommins4926 okay thank you, sounds good! Yes I had purchased 2 1X-10X 100 MHz probes. I will read the manuals about them also, To my understanding the 10 times is a 10 mega Ohm resistor built in so, we can measure the high voltage safely. I'm sure there's more to it than that. I will read up on termination. I'm looking forward to the learning experience , calibration and everything that's involved !Thank you for everything!

[@CafeBikeGirl]

interesting...

[@MrNedelcuBogdan]

Until now, you didn't disclosed any information about how can a device like this can be built. We can only see the ADC you've used. Nor do you sell units. At least you could teach us how to build the low cost, ultra-low noise cables, and what connectors to use. Thank you!

[@richardcommins4926]

You know the ADC that I used? How did you figure that out? Even if you know the ADC part number, that would not tell you how I can put an ADC running at 10 MHz and 3 switching power supplies running at 100 MHz next to my electrometer on the board and still get the 1 uv low noise on the 24 bit ADC and the shot noise limited electrometer performance. You mean that I don't sell units YET! LOL Maybe you don't understand what you are looking at here. One of the commenters here just wanted a demonstration of my electrometer. He flew out from Arizona with a calibrated Keithley 263 current source to see if my electrometer really did as I claim. He was at my home for 3 - 8 hour days to learn some of my secrets of this design. I also told him that I don't work for nothing and charged him $200/hour just to talk to me. I did not tell him all the secrets of my design either and he did sign a non-disclosure agreement too. He was amazed at what he saw. Yes, you can go buy a 3 foot Keithley low noise cable for around $1,000 and they won't tell you either how they made it. My cable goes for around $1.00 a foot with two $3.00 connectors on it. My costs would be around $10 for the cable. With a break through like this you just want me to tell you the secrets of how to make the cable? LOL I will tell you to go get the "Low Level Measurements Handbook - 7th Edition" and read it cover to cover and if you understand it all, you will have some of the secrets you will need to get someone to build that cable for you to your specifications. They of course will have a minimum run of between 5,000 to 10,000 feet to make your low noise cable. You don't think that the cable came from Digikey or Newark do you? It is a custom cable design made especially to my design requirements. www.tek.com/document/handbook/low-level-measurements-handbook

[@MrNedelcuBogdan]

​@@richardcommins4926 First of all, don't get my comment wrong. I want to thank you for showing that it is possible to build such a exceptional device with low budget. Also, tank you for the recommended book. The ADC that I think you've used, is seen in the right lower corner of your pc software. If i would have the possibility to sign the confidentiality agreement with you, so you can teach me, even if I will need to guarantee with my life that I don't disclose anything, I will not hesitate! Unfortunately, that is not possible. I respect your work! My email is nbogdan.contact at gmail.com.

[@richardcommins4926]

Yes, you are correct (you have a good eye) that the ADC that I used is a older model Analog Devices AD7712. I would love to find a cheaper 24 bit ADC that works as well. There are many tricks to get the performance out of that device or any device that delivers 1uv of noise peak to peak and a full scale range of +10V using all the different supplies that it uses that is generated from the noisy USB +5V from the computer. If the supply power up sequence is not controlled, the part will latch up and burn. The ADC is just for the demo board that I designed. Any 5 1/2 digital meter like the HP34401 will do the same job of digitizing the analog output of the electrometer. Some of the magic used in the design is in the software too that I wrote in Visual Basic 6. Even if I gave you the schematic and the parts list, if you put it together, it probably still would not work for you. There are many secrets that I have discovered like the PCB design, the low noise cable and the cleaning procedure. Remember this runs from the USB port of the computer and the grounds loops need to be controlled also. Thank you for being gracious and respecting my work. If you email me at [e-mail] we can talk more.

[@williamcase426]

I WANT TO COUNT ELECTRONS

[@richardcommins4926]

Well this is not the way to do it. I can measure around one fA (femtoamps) which is around 6,000 electrons per second. You will need another way to count electrons.

[@williamcase426]

@@richardcommins4926 ok

[@musicasminhavida]

Hi... I would like to know more about your solution, can you give your e-mail?

[@richardcommins4926]

+Fernando Henrique Cardoso What would you like to know about my solution? Would you post your email here? If you do, I will email you and answer your questions if I can.

[@musicasminhavida]

@@richardcommins4926 my e-mail is: [e-mail]

[@ghlscitel6714]

Thank you for your reply in the social networks. My contact email is [e-mail]. I use this in publicly visible platforms. Your description is more than fascinating. I have some experience with charge sensitive amplifiers for radiation detectors, but neither in terms of sensitivity nor dynamic range they come close to what you describe. Well, there is a difference beteween measuring charge and current. For a new project I am investigating different solutions to measure currents coming from solid state crystals excited by photons with energies around 5 to 10 electronvolts. The planned detection limit at the lower end is around 25 femtoampere photocurrent at a signal to noise ratio of 1:1 - hopefully lower. Present amplifier attempts however show a limit at 100 femtoampere and the dynamic range is around 10^4, which is at leas t2 orders of magnitude too low. I received AD's ADA4530-1 Amplifier ICs the day before yesterday and will experiment with them in the next time to learn what I can achive with them. However, the next two weeks I will be out of lab and return by end of august. Let us discuss then how to proceed. A short message from you in advance would be great.

[@AlexeyKozel-x5k]

Hello! I'm have test 2 samples of ADA4530-1. This is very good OPAMP. Real parasitic input current is only 3.8E-17A for one sample and 5.2E-17A for another (tested in temp range 23-45 Celsius). Also this current can be canceled. Noise floor in classic transimpedance amplifier with 1T Rf resistor is about 2E-16A p-p. Temperature stability of this OPAMP is very good. This OPAMP good for build electrometer AFE, that can real measure 1E-15A current, and also lower (1E-16A), but with filtering.