Measuring nanoamps and below like a Ninja

[bsw_m]

the ATTO Amp resolution of the meter.

Resolution != sensitivity. 

I'm measure leakage current for PTFE and saphire insulators in BNC triax connectors with test voltage 15V.
Leakage current for PTFE insulator is about 10E-18A...25E-18A(noisy reading). And 16E-18A for saphire insulator. But PTFE is worst for noise and settling time.
And I think that no problem to measure insulator leakage of engine spark plug.

[MiDi]

Why would one want to get exact numbers for leakage resistance of spark plugs?
If it cannot be measured with electrometer, it simply is high enough 
More relevant for spark plugs is if the spark ignites where it is supposed to be and nowhere else...

[guenthert]

     That and further the 'leakage' of a bad spark plug will be break-down, not ohm'sche resistance.  So if the plug looks ok at 100V the electrometers can drive, it isn't necessarily at 10...100kV operational voltage.

[HighVoltage]

Well, I must clarify that of course measuring a used spark plug for insulation resistance does not make any sense at all.
At least not for the purpose to find out if the spark plug is good or bad.

The only reason why I tested some new spark plugs was for pure science to find a high enough resistance to see where the limit of the instrument was.

[Vtile]

Why? Because one can (to try at least ). ...and pure technological interest what (not pure) CARBON deposition on high insulator surface will do etc...

Ps. I do not have electrometer nor picoammeter. Just household analog multimeter (which just happens to be one of the most sensitive chopper-Fet multimeter models ever build). Made in Poland 1980.

Pps. One could assume that surface that is as black as seen on picture would be something like 1Gohm at max... NOT.

[HighVoltage]

Vtile:
Best to open a new thread for testing insulation properties of spark plugs.
This discussion does not really fit in this metrology section.

[Vtile]

Testing insulation of spark plugs/gaps via resistance makes absolutely no sense and is just a waste of time. It should be done like a dielectric strength test (IEC 60243) with a high voltage source (meaning a source of at least 10kV) until discharge occurs

Most of the things in life do not make any sense, metrology included tbh. I was not interested at all of how the townsend avalance forms on sparkplug, or how the dielectric strength of the material might statistically behave.

Vtile:
Best to open a new thread for testing insulation properties of spark plugs.
This discussion does not really fit in this metrology section.

I might (but do not know where as of there is no "measurement and technologies" section other than metrology), but there were reason I did use this particular thread to begin with Measuring nanoamps and below like a Ninja is not the most scientific subject window if I'm not terribly mistaken.

Besides the outcome is the same "spark plugs/gaps via resistance makes absolutely no sense", we definitely would need a "measurement and technologies" section where people could actually discuss measurements without loosing scientific credibility.

[Vtile]

I did create a sparkplug interest group as this seems to generate so much discussion.
https://www.eevblog.com/forum/repair/sparkplug-resistance-and-dielectric-and-surface-avalances/

[Alex Nikitin]

I think it is better to continue in this thread, to keep all this information in one place. Recently I've saved from the bin a small number of proper electrometer grade reed relays, custom made by Crydom/synergy3 probably  about 9-10 years ago. I've measured (using the Keithley 617) the leakage across the open contact at 100V for this relay and for the Meder HI05-1A66 already mentioned in this thread. Results are below, 5 min at 0V, then 5min at +100V and  5min at 0V. The electrostatic screen on the Crydom relay was grounded, on the Meder I've grounded the coil at one end. As clear from the graphs the Crydom has about 20 times less leakage than the Meder and also almost no visible dielectric absorbtion. I have also tested both relays switching 100mV through 10G resistor = 10pA current and both relays performed well.

Cheers

Alex

P.S. The room temperature was ~26C, RH ~ 55%

[1audio]

To add a small datapoint to this thread I just noticed that my HP 4329A High Resistance Meter has a current range that goes down to 50 pA (with significant limitations).It uses a parametric amplifier for the low current measurements. https://www.keysight.com/us/en/product/4329A/hr-meter.html

[HighVoltage]

@Alex Nikitin
Thanks for the nice graphs and pictures.
May I ask, what is your method of getting the data from the 617 to such graphs?

[Alex Nikitin]

Oh, normally I would just use GPIB directly from the 617, however right now the GPIB interface on my 617 doesn't work  , so I use one of my two Keithley 2015, connected to the 2V analogue output on the 617, and read over GPIB, the data is then imported into Excel.

Cheers

Alex

[guenthert]

Oh, normally I would just use GPIB directly from the 617, however right now the GPIB interface on my 617 doesn't work  , so I use one of my two Keithley 2015, connected to the 2V analogue output on the 617, and read over GPIB, the data is then imported into Excel.

Cheers

Alex

     When I got my 617, the GPIB connector was bust.  On my 181 (same vintage) however both output drivers needed to be replaced (and fortunately nothing else).

[bsw_m]

@Alex Nikitin, your post piqued my interest in measuring custom relays produced by MNIPI, which were used in their electrometers.
I checked how the relay commutes the current 1pA.
Leakage of an open contact at a test voltage of 100V(But here it is more likely injection through the capacitance of the contacts, and not leakage. Since in fact, structurally leakage in this relay is impossible. The absence of leakage was checked using a V7-45 electrometer, the sensitivity of which is not enough to measure any leakage at a voltage of 100V ).
The measurements were made with a V7-49 electrometer.
Charts were built according to data from V7-49
The resistance of the closed contacts of these relays is 50mOhm
Everything else is presented in the graphs.

[bsw_m]

Measured the input bias current of the op-amp ADA4530-1
And the input bias current of the NT002 - an old electrometric assembly of transistors designed and manufactured by MNIPI. This assembly of transistors was introduced in the early 80s.
ADA4530-1 was used as buffer (measured Ib+ current) and was powered from ± 6V
NT002 was used in a similar connection as it is used in electrometers developed by MNIPI. Any input bias current compensation not used.
T ambient during measurement: 22℃ 

Blue line - is ADA4530-1
Please excuse me for the x-axis in samples. To translate into seconds, divide by 10 (10 samples is equal to one second)

[bsw_m]

NT002 teardown and DIE photo: https://www.eevblog.com/forum/projects/transistors-die-pictures/msg3713347/#msg3713347

[Echo88]

While trying to find some N- or P-Channel Enhancement MOSFETs with the following specs Udsmax >=20V, RDSon <=20R and Ids-leakage (with gate-source shorted) <=1pA at Uds=10V i tested a few already and just wanted to list them here with measured leakage values.
I didnt find any similar examples for mosfet leakage (Art of Electronics X-Chapters has a JFET/Bipolar leakage chart on page 102 though), so those may be of interest to people who want to know which round about real values can be expected compared to the very conservative/automatic test equipment limited values in the mosfet-datasheets. 
Leakage measurements were generally done with Uds = 10V, as thats the maximum voltage in the circuit that the mosfets would be used at in my circuit.
Sometimes i tested also at lower voltages to see how the leakage behaves.
Maybe you guys also have mosfet-measurements, especially of those with <=1pA?

IRLR2908: N-Channel 80V 30A 28mR D-Pak
0.5V: 10.7pA
1V: 28.9pA
2V: 71.8V
10V: 69pA

SUD50P10: P-Channel -100V -35A 0.04R TO252
-10V: -196pA

SI4410DY: N-Channel 30V 8A 14mR SO8
1V: 395pA

SI4467DY:  P-Channel -12V -12A 11mR SO8
-10V: -1040pA

SI9407: P-Channel -60V -3.5A 0.15R SO8
-10V: -244pA

SI2327DY: P-Channel -200V -0.5A 2.4R SOT23
-10V: -68.6pA

SI2337DS: P-Channel -80V -2.2A 0.2R SOT23
-10V: -31.6pA

2N7002L: N-Channel 60V 115mA 7.5R SOT23
5V: 14.65pA
10V: 16pA

2N7002L: second specimen:
10V: 22.1pA

2N7002L: third specimen:
10V: 22.8pA

NTS4409: N-Channel with Gate-ESD-protection 25V 0.75A 250mR SC70
1V: 2.9pA
10V: 3.2pA

PMV130ENEA: N-Channel with Gate-ESD-protection 40V 2.1A 120mR SOT23
10V: 40.6pA

BSS131: N-Channel 240V 0.1A 14R SOT23
10V: 0.6pA
20V: 0.73pA

All measurements done with my trusty K617. 

[bsw_m]

PVT412PbF mosfet solid state relay:
Leakage:
at 20V: 6.5pA
at 300V: 107pA
EMF at 10mA led current: 0.6uV

Measurement done by my V7-49 electrometer and V2-38 nanovoltmeter.

[bsw_m]

Tests for AGN210S4H relay.
Leakage current after 20min with 50V test voltage is 1E-16A
1pA current commutation very good, but with spikes from charge injection.
Charge injection is big, about 12pC.

[Echo88]

@bsw_m:
My tests on mosfet solid state relays indicated that a lower LED drive current reduces the mosfet output EMF.
When the led current is just above the threshold to switch on the mosfet output it should produce the lowest EMF.
In my case the measured EMF was <100nV afair at about 1 or 2mA LED drive current.

I also measured the PVT412 a while ago and came to nearly the same leakage value at 20V for three tested samples: 5pA 
Heres the thread with my leakage results https://www.eevblog.com/forum/metrology/measurements-of-leakage-current-and-offset-voltage-on-some-optofets-and-relays/

[David Hess]

My tests on mosfet solid state relays indicated that a lower LED drive current reduces the mosfet output EMF.
When the led current is just above the threshold to switch on the mosfet output it should produce the lowest EMF.
In my case the measured EMF was <100nV afair at about 1 or 2mA LED drive current.

Is that a thermocouple effect from self heating of the optocoupler by the LED?

[bsw_m]

Is that a thermocouple effect from self heating of the optocoupler by the LED?

I think, yes.

[Echo88]

Yeah, i think its coming from the heat, leading to a thermal offset.
Datasheets like the PVA3054-DS also refer to it as "thermal offset voltage" http://www.irf.com/product-info/datasheets/data/pva30.pdf

[David Hess]

That would explain why I have seen old precision designs using optocouplers with the emitter separated from the detector by a light pipe, although this is also done to reduce coupling capacitance.

[Kleinstein]

For photo-mos couplers the separation can also be at the detector side. There are 2 seprate parts: some photovoltaic opto-coupler to produce a voltage and than back to back MOSFETs that are controlled from that voltage.  The PV coupler and the MOSFETs can also be a bit apprat. It still is a copromise with size and leakage.