Thanks to lukier for kick in the butt, I got around to run some python snakes to measure (or should I better say, estimate?) linearity errors of the above mentioned Hulk calibrator.
So here are some pretty charts, impressed even me... Can't be that good.
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
Method is rather simple, python application programs DC voltage of the Hulk output from -10.9 to +10.9, with range locked to 11V. Steps in programming are 0.1V, for good resolution. Calibrator ran internal zero before test.
As detector we use ADC with best linearity possible : 3458A. Actually two of them, connected to Hulk output, using Belden cable and bare copper spade lugs.
![](https://xdevs.com/doc/Fluke/5720A/cal/test_hulk_3458ab_10v_noac.png)
Then collected data points are calculated for deviation from best-fit polynom, and error calculated in ppms from 10VDC scale. Numpy code to do that:
p = np.polyfit(real,ideal,1) # Fit polynom to data
pv = np.polyval(p,real) # Calculate deviation from polynom
diff = ideal-pv # Determine delta
diff_ppm = (diff/10)*1000000.0 # Calculate scale in ppms
Some comments for less verse readers:
* Thin blue line is meter 3458A (GPIB 3)
* Thin pink line is second meter 3458B (GPIB 2)
* Thick brown line is INL data of 3458B minus INL data of 3458A. This essentially to remove INL of the calibrator source itself, to get difference between two 3458As.
* Orangle line is bonus, Fluke 8508A versus Hulk calibrator. Settings RESL8, FAST_OFF, equivalent to about NPLC1040.
![Blah :blah:](https://www.eevblog.com/forum/Smileys/default/blah.gif)
Differential INL between 3458A is quite cool +0.09 to -0.06 ppm peak to peak. Matching the 0.1 ppm specification of the 3458A well, for what it's worth.
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)
Then I turned off aircon in calroom, and let ambient temperature to climb +29C. Idea is that it may help INL data, by removing drafts and temperature variations?
![](https://xdevs.com/doc/Fluke/5720A/cal/test_hulk_3458ab_2002_10v_noac_1.png)
This test still running (Beware, full sweep takes multiple hours, so not 100% correct way, as best INL specified only for minutes/tens minutes periods, not hours), that's why data not finished.
* Thin blue line is meter 3458A (GPIB 3)
* Thin pink line is second meter 3458B (GPIB 2)
* Thick brown line is INL data of 3458B minus INL data of 3458A. This essentially to remove INL of the calibrator source itself, to get difference between two 3458As.
* Orangle line is bonus, Fluke 8508A versus Hulk calibrator. Settings
RESL7 this time, FAST_OFF, equivalent to about
NPLC104.
![Blah :blah:](https://www.eevblog.com/forum/Smileys/default/blah.gif)
* This graph also have Keithley 2002 meter added for giggles. NPLC50, DFILT OFF.
* Bold magenta and violet lines are difference of K2002 from either of 3458s.
As sanity check, I got remote access to <90day calibrated Fluke 5730 in far far away galaxy. So I ran very same code on 5730A and 3458A (another one, not mine) so we can glance over the data from this setup as well.
10V , NPLC50. Same configuration of the calibrator as my 5720A Hulk.
![](https://xdevs.com/doc/Fluke/5730A/test_5730_3458_10v_nplc50_1.png)
1V range, NPLC 100. Rangelock at 2.2V range.. Otherwise same configuration.
![](https://xdevs.com/doc/Fluke/5730A/test_5730_3458_1v_nplc100_1.png)
Comments?
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)