Electron Plus SPA100 Source Picoammeter / High Resistance Meter - Page 1
Forum section: electronics / general

author: MegaVolt
author_rank: Frequent Contributor
timestamp: November 26, 2021, 01:39:28 pm
content: Does anyone know what's inside it? Any pictures?https://electron.plus/product/spa100-source-picoammeterhttps://www.ebay.com/itm/124791936727

author: HighVoltage
author_rank: Super Contributor
timestamp: November 26, 2021, 02:14:19 pm
content: "<2fA resolution (200pA range)"That is a bold claim especially on normal BNC cables.Someone probably needs to buy one and perform a tear down.

author: Kosmic
author_rank: Super Contributor
timestamp: November 26, 2021, 06:57:44 pm
content: Just contact the owner of Electron Plus. He is a member of the forum. Username is fcbhttps://www.eevblog.com/forum/profile/?u=25995

author: fcb
author_rank: Super Contributor
timestamp: November 26, 2021, 08:48:21 pm
content: Fairly 'standard' transimpedance amplifier design with careful layout that's gone through a couple of iterations, lots of slots in PCB's etc..The front-end and the bias generator are isolated with a transformer and opto-couplers.We are updating our website at the moment (as well as manuals/datasheets/etc...) , so the picture is a little out-of-date, most of our products now have a label on-top and all have stainless steel front & rear panels. Here's a picture courtesy of our US distributor, Saelig.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: November 30, 2021, 01:21:27 pm
content: Quote from: fcb on November 26, 2021, 08:48:21 pmPerhaps you can answer some questions?1. BNC instead of triax? Why did you decide not to use them?2. What was the noise level on the lower range?3. Any pictures inside?

author: fcb
author_rank: Super Contributor
timestamp: November 30, 2021, 02:54:35 pm
content: Quote from: MegaVolt on November 30, 2021, 01:21:27 pmBNC's tend to be used on picoammeters (i.e. Keithley 6485), generally there is no requirement for a guard system - the inner and outer parts of the BNC are typically at the same potential; it can be thought of as essentially zero ohms.Also cost is a major consideration - BNC's are low-cost and fairly readily available - triax connectors are very expensive (40-100x more), more difficult to obtain, etc.. Two triax connectors would equal the retail price of the SPA100. I bought some recently for my Keithley 237 SMU, eye-wateringly expensive and that was without the cable.Noise. On the lower range will depend on sample rate (2/10Hz) a little and sample (rolling) averaging (1x to 64x) - however it tends to be dwarfed by aliased mains hum pick-up. We have another SPA100 batch finishing production this week, so will post a few screen captures of the o/c noise if you'd like.Sorry no pix inside.

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 30, 2021, 06:51:34 pm
content: Quote from: MegaVolt on November 30, 2021, 01:21:27 pmThere is no need to use a triax connector for a transimpedance amplifier. The reason is simple, the potential difference between the ground and the input terminals is practically zero (to be precise equal to the amplifier offset). And this offset doesn't generate tangible leakage current.But warning in noise that can be generated by not a very high quality insulator.

author: fcb
author_rank: Super Contributor
timestamp: November 30, 2021, 07:34:38 pm
content: Quote from: bsw_m on November 30, 2021, 06:51:34 pmWe haven't noticed any noise we can trace back to insulator materials. The insulated 50R BNC's are made from white polypropylene (so without black/carbon fillers).On the lowest current range you can create a small transient shift in the reading by changing the bias generator output from say -40V to +40V, but then waving your hand 3 feet away does the same when the nothing is plugged in.

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 30, 2021, 08:33:34 pm
content: Quote from: fcb on November 30, 2021, 07:34:38 pmThis is the simplest way to test whether the electrometer input is still alive.The dielectric noise will be lower than the noise of your amplifier. Therefore, it is not noticeable.P.S.Unfortunately, I am not able to test this amplifier.Its parameters and design look very balanced.But I don't believe in 1E-15A noise free, only if with a very "evil" filter, with a long settling time.I think you used a 10GΩ feedback resistor for the low range?

author: fcb
author_rank: Super Contributor
timestamp: November 30, 2021, 09:10:53 pm
content: Quote from: bsw_m on November 30, 2021, 08:33:34 pmI don't quite understand the context of the last few lines of your post.1G/PGA/ADC if that helps

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 30, 2021, 10:13:12 pm
content: Thanks.My interest in the resistance of the Rf is only in the context of a rough estimate of the possible noise floor of the amplifier.

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 01, 2021, 12:34:21 pm
content: Quote from: fcb on November 30, 2021, 07:34:38 pmMeasuring current generation after physical impact (connection) and noise. Pay attention to how long it takes to settle (More that 2 hours). Also You can view noise of this triax connector.Case and inner ring(guard ring) are connected to ground, central pin connected to electrometer input. Direct connection without using a cable. The input connector of the electrometer served as a measuring chamber.In addition to the graph, I also attach the raw data in the archive.

author: fcb
author_rank: Super Contributor
timestamp: December 01, 2021, 01:03:46 pm
content: Interesting. What picoammeter/electrometer are you using, and what did the test setup look like?Your data is approx -0.28fA to -0.04fA (40aA!) - what makes you think this is purely noise from the triax insulator and not from elsewhere?

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 01, 2021, 01:26:59 pm
content: Quote from: fcb on December 01, 2021, 01:03:46 pmFor this measurement I'm use my V7-45 electrometer. Self noise of this electrometer in attach.Also measurement setup looks like at the photo in the attachment.In these photos, I not connect the ground. As I quickly reassemble it to show how it looked.Quote from: fcb on December 01, 2021, 01:03:46 pmI think the above description and the attached graphs and photographs describe why I am confident that I have measured the noise and parasitic current of a standard triaxial connector with PTFE insulator.

author: fcb
author_rank: Super Contributor
timestamp: December 01, 2021, 01:42:42 pm
content: Great. Looks like a beast of instrument. I'm assuming these are only available used in FSR countries?I'm assuming the V7-45 is a two box unit. Any pix of the insides??

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 01, 2021, 01:47:26 pm
content: Also, if we refer to the table of the maximum permissible errors for performance verification procedure. We can see the checked point 20aA with a maximum permissible error of 39.4% or ±8aA. (screen in attach).Quote from: fcb on December 01, 2021, 01:42:42 pmYou right!Some pics and video You can see in this topic:https://www.eevblog.com/forum/metrology/v7-45-electrometer-made-in-belarus-(welcome-in-attoamps-world)/And if You have interest, little info about ultra low current and ultra high resistance standard, that able calibrate this electrometer:https://www.eevblog.com/forum/metrology/nk4-1-low-current-and-high-resistance-calibrator-(made-in-belarus)/

author: fcb
author_rank: Super Contributor
timestamp: December 01, 2021, 01:52:09 pm
content: bvi = does this connect to the head?kop = control/computer?vb1chod analog vb1y = analog output?

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 01, 2021, 01:55:37 pm
content: Quote from: fcb on December 01, 2021, 01:52:09 pmthis connector for connect external measurement block (yes, head)Quote from: fcb on December 01, 2021, 01:52:09 pm- this is GPIB IEEE488.1Quote from: fcb on December 01, 2021, 01:52:09 pmYes.

author: fcb
author_rank: Super Contributor
timestamp: December 01, 2021, 02:07:12 pm
content: Love those vintage eastern block instruments. Performance looks amazing - did they build an updated unit or did it fissile (pun intended) with the end of the cold war?So do you have different heads for current and voltage?Interesting lunch-time reading:https://ampnuts-com.translate.goog/v7-45/?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=nui

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 01, 2021, 02:21:06 pm
content: Quote from: fcb on December 01, 2021, 02:07:12 pmThe updated device was called B7-57 / 2, produced after the collapse of the USSR. Its production was piece and the device was unobtanium.I'm restore one. Found it in a very poor condition and unfortunately not complete. Some photos "as received" in attach.Quote from: fcb on December 01, 2021, 02:07:12 pmNo, one head can measure currents, voltages and charges.

author: snik
author_rank: Contributor
timestamp: December 07, 2021, 02:55:10 pm
content: Quote from: MegaVolt on November 26, 2021, 01:39:28 pmHere some pictures :Didn't use or test it until now.

author: fcb
author_rank: Super Contributor
timestamp: December 07, 2021, 03:51:02 pm
content: The 'dust' at the corners of the PCB is from opening the enclosure and is a mixture of the blacking of the taptite screws and the aluminium extrusion - it isn't there when assembled.Worth tapping the empty-box on a desk before reassembling, and brushing the dust off the PCB.