What is stability of this standard if you reach 14A ? It can be quite interesting measurement.
What is stability of this standard if you reach 14A ? It can be quite interesting measurement.That might be a challenge, how do I get a stable 14A and how to measure it?
It seems I have to look in to the metrology way of measuring high DC currents exactly with high precision.
Not easy and probably be very expensive.
This thread triggered a memory of an old L&N low resistance box I keep stashed on the lower shelf of a scope cart. It needs a good cleaning, but I brushed off the dust. It doesn't seem to have a model number, but it's 300 ohms max in 0.001 ohm increments. I can't believe the cal sticker is original, as I doubt they made that style in '92.
I can't believe the cal sticker is original, as I doubt they made that style in '92.
Ok, here is the last set of measurements at 7A.
At least this SMU has reached its limit
Also interesting, the fan stays at full power for a long time, after the current has been reduced from 7A to 100 mA and the instrument is very loud.
This cable I assembled seems to work very well for this test.
The L&N box has two metal plates that I thought were owner tags, but looking closer I think they're the L&N tags. The top one is two lines, "L.T." followed by "4171". Below that is a similar tag "Sp. Inst."
Reading up on it, Leeds & Northrup did built a Thomas 4210 with one Ohm and they built it to 1 ppm specification.
I bought one of these 4210 a few weeks ago but it has not arrived.
An interesting aside, the resistor is quite old (chrome body) and when I first tried to have it certified, they rejected it as defective- too far out. Then we realized it was built before the ohm was adjusted (can't remember the year, '60s?) and it was actually almost dead on what it should have be.
If you like low ohms, I have one of these in my office. It is about 4 nano-ohms. It is a challenge to measure.
If you like low ohms, I have one of these in my office. It is about 4 nano-ohms. It is a challenge to measure.
I would love to try
If you like low ohms, I have one of these in my office. It is about 4 nano-ohms. It is a challenge to measure.
I would love to try
Where are you located? What instruments do you have that will force 1A DC? Do you have a nanovoltmeter?
As far as equipment, I have 2 Datron 4808s available, 2 Fluke 5520As, currently 1 Fluke 5700, as far as meters go, Keithley 181 or perhaps one of our 2002's or Agilent 3458As. I also have a Fluke 752A Reference divider and Fluke 845AB Null detector if I want to get stupid with it
As far as equipment, I have 2 Datron 4808s available, 2 Fluke 5520As, currently 1 Fluke 5700, as far as meters go, Keithley 181 or perhaps one of our 2002's or Agilent 3458As. I also have a Fluke 752A Reference divider and Fluke 845AB Null detector if I want to get stupid with it
4nR * 1A = 4nV
Only the Keithley 2002 in your list is capable to resolve 1nV. Isn't it?