I use the ADS1120 to realize measures between ±20mA.
The equipment has 8 cells with one ADS per cell. This cells are isolated between itself.
In many of this cells the funcionality is Ok, the componente work well.
But in the last production i see 6 componentes that have a compression mistake in negative measures, only, and near FS.
One of the test is a curve for test the lineality of input. I put in the inputs, values between -20 and 20mA with 1mA of step.
The table of results is:
Input | CH1 | Dif-esl | CH2 | Dif-esl |
0 | 0 | -1 | ||
1 | -818 | 818 | -818 | 817 |
2 | -1637 | 819 | -1636 | 818 |
3 | -2456 | 819 | -2454 | 818 |
4 | -3274 | 818 | -3273 | 819 |
5 | -4093 | 819 | -4090 | 817 |
6 | -4911 | 818 | -4908 | 818 |
7 | -5730 | 819 | -5727 | 819 |
8 | -6549 | 819 | -6545 | 818 |
9 | -7368 | 819 | -7363 | 818 |
10 | -8185 | 817 | -8182 | 819 |
11 | -9004 | 819 | -8999 | 817 |
12 | -9823 | 819 | -9817 | 818 |
13 | -10641 | 818 | -10636 | 819 |
14 | -11460 | 819 | -11454 | 818 |
15 | -12587 | 1127 | -12577 | 1123 |
16 | -13434 | 847 | -13427 | 850 |
17 | -14205 | 771 | -14200 | 773 |
18 | -14998 | 793 | -14992 | 792 |
19 | -15747 | 749 | -15739 | 747 |
20 | 0 | -15747 | 0 | -15739 |
0 | 0 | -1 | ||
1 | 819 | 819 | 819 | 820 |
2 | 1637 | 818 | 1637 | 818 |
3 | 2457 | 820 | 2455 | 818 |
4 | 3275 | 818 | 3274 | 819 |
5 | 4093 | 818 | 4091 | 817 |
6 | 4911 | 818 | 4910 | 819 |
7 | 5730 | 819 | 5727 | 817 |
8 | 6548 | 818 | 6545 | 818 |
9 | 7367 | 819 | 7363 | 818 |
10 | 8185 | 818 | 8181 | 818 |
11 | 9004 | 819 | 8999 | 818 |
12 | 9823 | 819 | 9818 | 819 |
13 | 10641 | 818 | 10636 | 818 |
14 | 11459 | 818 | 11453 | 817 |
15 | 12279 | 820 | 12272 | 819 |
16 | 13097 | 818 | 13090 | 818 |
17 | 13915 | 818 | 13908 | 818 |
18 | 14733 | 818 | 14726 | 818 |
19 | 15553 | 820 | 15544 | 818 |
20 | 16371 | 818 | 16363 |
819 |
Dif-Esl this tbale is de differencie between one step and the next step.
If the lineality is ok, all steps would be identical and the part positive and negative would be like each other.
This measure is of one of this cells, in the other cells the measure is ok, and the side positive and negative are identical.
My question is about if this problem has seen any time? Or if this is a problem with these ADC's.
The circuit of cell, if you want, i can send you.