Getting unusual data point from sensor

Hello~

I am getting sensor data through analog input of my Meag2560.

The problem is below

Time: 1400452 455.70 303.80
Time: 1401956 455.70 289.10
Time: 1403459 475.30 294.00
Time: 1404963 455.70 289.10
Time: 1406467 49.00 225.40
Time: 1407971 455.70 294.00
Time: 1409474 445.90 294.00
Time: 1410978 475.30 294.00
Time: 1412482 455.70 289.10
Time: 1413986 88.20 142.10
Time: 1415489 455.70 294.00
Time: 1416993 450.80 294.00
Time: 1418497 475.30 294.00
Time: 1420001 460.60 289.10
Time: 1421504 107.80 166.60
Time: 1423008 455.70 298.90
Time: 1424512 455.70 289.10
Time: 1426016 470.40 294.00
Time: 1427519 450.80 289.10
Time: 1429023 19.60 739.90
Time: 1430526 455.70 294.00
Time: 1432031 450.80 294.00
Time: 1433534 465.50 289.10
Time: 1435038 455.70 294.00
Time: 1436541 460.60 294.00
Time: 1438046 455.70 298.90
Time: 1439549 450.80 289.10
Time: 1441053 465.50 294.00
Time: 1442556 450.80 294.00
Time: 1444061 151.90 460.60
Time: 1445564 455.70 294.00
Time: 1447068 450.80 289.10
Time: 1448571 470.40 298.90
Time: 1450076 455.70 294.00
Time: 1451579 377.30 294.00
Time: 1453083 450.80 294.00
Time: 1454586 460.60 294.00
Time: 1456091 465.50 294.00

as you guys see, the value is almost stable around 460 but at some point it drops 48, 88, 19, 151, etc..

Do you know what is happening here?

This is CO sensor data and I do not think the sensor output changes like that...

Is it the problem of Arduino? or my readout circuit?

Does anybody have experience of this weird point when you use analog input?

In the real world, sensors sometimes give false readings.

You have to program your application to handle those false readings properly, and ignoring them is one valid possibility. However, to do so you have to decide when a reading is “false” and that is not always easy.

I suspect that you're loosing significant bits during calculations. Add 512 to the inconsistent values, and they fit into the sequence. I'd suggest that you check (or post) the calculations and related variable declarations.