you are brought a request by someone they have a widget for measuring something but depending on wavelength, movement, pressure etc but the constraint is that the out put from this device is measured anything from a maximum of 200x10-15 down to 30X10-18 amps. how in gods name would you bring that up to a 1mA needed out from your Amp. The guys down where I once worked have that problem to deal with by a photodiode array that they just got in. I would not know where to begin my job would start after the amp interpreting and classifying the output signal. at the electronics game I am a rank amateur at best. not even close to my ballpark.

 

I can't find it right now, but National Semi had an application note on measuring femtoamp and pico amps.

 

[ΠΑΡΑΣΚΕΥΗ="robp1956, δημοσίευση: 2037869, μέλος: 1091514"]
Σας ζητάει κάποιος ότι έχουν ένα widget για τη μέτρηση κάποιου πράγματος, αλλά ανάλογα με το μήκος κύματος, την κίνηση, την πίεση κ.λπ., αλλά ο περιορισμός είναι ότι η έξοδος από αυτήν τη συσκευή μετριέται από ένα μέγιστο 200x10-15 έως 30X10-18 αμπέρ. Πώς, για όνομα του Θεού, θα το ανέβαζες αυτό στο 1mA που χρειάζεται από τον ενισχυτή σου; Τα παιδιά εκεί που δούλευα κάποτε έχουν αυτό το πρόβλημα να αντιμετωπίσουν με μια συστοιχία φωτοδιόδων που μόλις έβαλαν. Δεν θα ήξερα από πού να ξεκινήσω, η δουλειά μου θα ξεκινούσε αφού ο ενισχυτής ερμηνεύσει και ταξινομήσει το σήμα εξόδου. Στο παιχνίδι ηλεκτρονικών είμαι στην καλύτερη περίπτωση ερασιτέχνης. Ούτε καν κοντά στο δικό μου επίπεδο.
[/ΠΑΡΑΘΕΤΩ]
Τhe issue is how you differentiate it from thermal noise?

 

[FRIDAY="robp1956, post: 2037869, member: 1091514"]
Someone asks you that they have a widget for measuring something, but depending on wavelength, motion, pressure, etc., but the limitation is that the output from this device measures from a maximum of 200x10-15 to 30X10-18 amps. How in the world would you get that up to the 1mA your amplifier needs? The guys where I worked once had this problem with a photodiode array they just put in. I wouldn't know where to start, my job would start after the amplifier interprets and sorts the output signal. In the electronics game I'm an amateur at best. Not even close to my level.
[/QUOTE]

 

I can't find it right now, but National Semi had an application note on measuring femtoamp and pico amps.

There is test equipment that can see the signal from it and read current information from it also but to build an amplifier for it that's a different thing even if the amp was directly attached to the detector and they are. Still so much to think about at that level I would think that the parasitic stuff on the board would also be there to bite you in the ass. maybe just one little amp that could would help. if you had enough resolution at the 10-15 scale you could catch the 10-18 signals to.

 

A lot depends on details not given. In particular, how much control they have over how the array is driven and interfaced to. Also, what kind of noise has to be contended with and what the characteristics of the signal are that is being sought. We designed some chips that counted single photon events over periods of many minutes. One technique that is often used is correlated double sampling, which removes (greatly mitigates) many forms of noise. Another technique, which may or may not be feasible in that situation, is to use a lock-in amplifier. We did a chip that stared into a laser and looked for modulations on the order of 10e-8 by putting a lock-in amplifier in every pixel.

 

A lot depends on details not given. In particular, how much control they have over how the array is driven and interfaced to. Also, what kind of noise has to be contended with and what the characteristics of the signal are that is being sought. We designed some chips that counted single photon events over periods of many minutes. One technique that is often used is correlated double sampling, which removes (greatly mitigates) many forms of noise. Another technique, which may or may not be feasible in that situation, is to use a lock-in amplifier. We did a chip that stared into a laser and looked for modulations on the order of 10e-8 by putting a lock-in amplifier in every pixel.

Well typically these sensors are in a tank filled with liquid kept at an exact temperature and very very dark as close to 0 light leakage as they can. that is what they are looking for single flashes of light that randomly come through and interact with something in the liquid medium. so that kind of control. from the amp end here is the connector plug in there and that is a direct connection to the device. After the amp the output is sent by fiber optics lines to the computer. It's sort of amazing that at 1X10-18 amps you are talking just a few electrons/sec in the wire. Also whet you are talking about is something they used on the machines they built to catch a gravitational wave passing through. moves 2 beams sent about 4 miles bounces back to a target and with a gravitational wave the lasers would move out of alignment one way and then the other something on the order of a width about as wide as a hydrogen nucleus.

 

Like a neutrino detector?

 

Like a neutrino detector?

Much like that yes but a different energy level than a Neutrino. but the principal is the same.

 

Well typically these sensors are in a tank filled with liquid kept at an exact temperature and very very dark as close to 0 light leakage as they can. that is what they are looking for single flashes of light that randomly come through and interact with something in the liquid medium. so that kind of control. from the amp end here is the connector plug in there and that is a direct connection to the device. After the amp the output is sent by fiber optics lines to the computer. It's sort of amazing that at 1X10-18 amps you are talking just a few electrons/sec in the wire. Also whet you are talking about is something they used on the machines they built to catch a gravitational wave passing through. moves 2 beams sent about 4 miles bounces back to a target and with a gravitational wave the lasers would move out of alignment one way and then the other something on the order of a width about as wide as a hydrogen nucleus.

We designed the readout IC for a Japanese neutrino detection system (it wasn't Super-Kamiokande, because our chip was designed several years later) that sounds similar to what you are doing. It sounds like you are not really trying to measure a small current as much as trying to detect the pulses that result from a photon hit. Those are quite different challenges, with difference solution options.

 

We designed the readout IC for a Japanese neutrino detection system (it wasn't Super-Kamiokande, because our chip was designed several years later) that sounds similar to what you are doing. It sounds like you are not really trying to measure a small current as much as trying to detect the pulses that result from a photon hit. Those are quite different challenges, with difference solution options.

Not me when I worked there I was A simple dumb physicist it's the smart guys in the engineering dept that get that task. I'm only an armature at the electronics stuff and that might be selling me up. but I just thought even from a physics point of viw to think about a solution to that problem. the Neutrino detectors are usually working with signal strength a bit larger that these. on the order of picoamps I thought. This one from what I have read about it is in the order of 10-15 amps at best and down to the 30 x 10-18 amps 5 or 6 electrons worth.

 

We designed the readout IC for a Japanese neutrino detection system (it wasn't Super-Kamiokande, because our chip was designed several years later) that sounds similar to what you are doing. It sounds like you are not really trying to measure a small current as much as trying to detect the pulses that result from a photon hit. Those are quite different challenges, with difference solution options.

Yes that is what your doing on my end of things but that pulse of light comes through the detector and out to the amp as a pulse of current.

 

Yes that is what your doing on my end of things but that pulse of light comes through the detector and out to the amp as a pulse of current.

But because it's a pulse, it can be integrated on a capacitor and turned into a voltage signal that is much easier to detect. The key parameter isn't what the current level is, it's how many electron-hole pairs are generated in the device and the efficiency with which they can be collected. That depends on a number of factors and those factors can lead to some detection schemes working better than others.

 

Not me when I worked there I was A simple dumb physicist it's the smart guys in the engineering dept that get that task.

We had a preliminary meeting with a customer in which they described what they were doing in order to take proteins from a jellyfish and modify them such that they would give of photons if they encountered specific virus cells. After they described what they were doing, I asked, "You mean you can really do that shit?" To which they said, "Yes, this is all pretty mundane stuff in our world." We then described how we planned to go about detecting and counting the individual photons that would be expected to hit the detectors and, after we finished, one of their guys goes, "You mean you can really do that shit?" To which we responded that this was very routine stuff in our world. What struck me from that meeting, in ways that had never hit home before, is the degree to which people with expertise in different areas can have an idea, the core of which is relatively simple for them, but that as soon as they consider what else has to be done to make it a reality, they conclude that there are insurmountable hurdles. Sometimes, why they see as insurmountable are really bread-and-butter tasks for people with a different expertise. Just imagine what bringing the right people together to discuss ideas and cross-pollinate could produce! This is the goal of lots of efforts, from Ted Talks to a variety of speculative research initiatives by government, educational, and corporate organizations. A lot of cool tech has come out of that, though the most common outcome is a dead end with some papers published, some of which contain nuggets that end up being useful at some point down the road. The problem, of course, is that it is very hit and miss -- you have to have the right people discussing the right problem at the right level.

 

We have used Cremat CSP (Charge Sensitive Preamplifier).

https://www.cremat.com/why-use-csps/