Teardown : ESI DB52 resistance decade check

[TiN]

RAWR, precision-nuts.



Since I got 60% (3 from 5) of my 2001 meters repaired and ready for calibration, its time to get some resistance box. And as I already have some foils in main values, addition of more fine decade resistor was wanted.

I had no intention to spend big money, it is also my first ever decade box, so end up winning this ESI 5-decade resistor for a 95$ excluding shipping. Seller state it was good and calibrated January 2013.







It is dirty and little rusty outside, but that is fine if the thing performs well.

Don't turn it on, take it apaaart







That is well and robust construction, but switches are not as fancy as in higher grade decades, which I saw on web review before.

There are no trimpots or jumpers elsewhere, how does such resistance decades are usually calibrated?

[TiN]

Performance and verification

I had two meters to check this DB52 :

Agilent 34970A with 34901A mux card, in 4W ohms mode, 200NPLC (Calibrated in 2013)
Keithley 2001 , 4W ohms with offset compensation, 10NPLC (Calibrated February 2014).

Not to jam thread with gazillion of photos, here are thumbnails.



First connect meter 4W to ESI decade. Set all decades to zero.
Null meter using offset(relative) function. This will be our zero reference.

Adjust decades, measure resistance.







I am impressed as for it's money. Definately a keeper unit.

Will use this box for KX project circuits tests, such as ADC, DACs and current sources.

[TiN]

Measured accuracy for all decades (by 34970A)

--	1E1	1E2	1E3	1E4	1E5
00	0.00007 Ohm	0.00007 Ohm	0.00038 Ohm	0.02559 Ohm	1.93515 Ohm
01	10.00067 Ohm	99.99229 Ohm	999.93156 Ohm	9999.91797 Ohm	100001.12500 Ohm
02	19.99982 Ohm	200.00353 Ohm	1999.89009 Ohm	19999.94097 Ohm	200016.91667 Ohm
03	29.99740 Ohm	300.00983 Ohm	2999.82813 Ohm	30000.11719 Ohm	300011.90625 Ohm
04	40.00387 Ohm	400.01471 Ohm	3999.79818 Ohm	40000.22656 Ohm	400014.12500 Ohm
05	49.99859 Ohm	500.02953 Ohm	4999.77409 Ohm	50000.20313 Ohm	500017.66667 Ohm
06	59.99515 Ohm	600.03055 Ohm	5999.70898 Ohm	59999.72396 Ohm	600026.75000 Ohm
07	69.99643 Ohm	700.03494 Ohm	6999.64355 Ohm	70000.16667 Ohm	700028.00000 Ohm
08	79.99512 Ohm	800.04053 Ohm	7999.60482 Ohm	80000.16667 Ohm	800028.50000 Ohm
09	89.99380 Ohm	900.04500 Ohm	8999.57552 Ohm	90000.13542 Ohm	900032.16667 Ohm
10	99.99229 Ohm	999.93156 Ohm	9999.91797 Ohm	100001.12500 Ohm	1000029.60000 Ohm

--	1E1	1E2	1E3	1E4	1E5
00	Invalid data	Invalid data	Invalid data	Invalid data	Invalid data
01	67.043 ppm	-77.133 ppm	-68.420 ppm	-8.203 ppm	11.250 ppm
02	-8.965 ppm	17.624 ppm	-54.932 ppm	-2.930 ppm	84.609 ppm
03	-86.594 ppm	32.756 ppm	-57.292 ppm	3.906 ppm	39.688 ppm
04	96.703 ppm	36.774 ppm	-50.476 ppm	5.664 ppm	35.313 ppm
05	-28.305 ppm	59.082 ppm	-45.215 ppm	4.063 ppm	35.313 ppm
06	-80.808 ppm	50.964 ppm	-48.503 ppm	-4.622 ppm	44.583 ppm
07	-51.008 ppm	49.874 ppm	-50.921 ppm	2.344 ppm	40.000 ppm
08	-61.035 ppm	50.659 ppm	-49.377 ppm	2.051 ppm	35.625 ppm
09	-68.834 ppm	49.981 ppm	-47.201 ppm	1.476 ppm	35.764 ppm
10	-77.133 ppm	-68.420 ppm	-8.203 ppm	11.250 ppm	29.625 ppm

Attached dirty spaghetti code to calculate ppm table from raw data samples.

[Vgkid]

Nice score, I picked up a DB62 last year for 80tot, and a DB655 for 30tot(still need to put it back together).
I noticed my DB62 is pretty stable, my favorite test is to set all dials to '2', and my 3456 reads '222,225' though sometimes it reads 222,222

[TiN]

Added decade tolerance data in third post, based on 34970A measurements.

Don't shoot for code.