What is the difference between mh-z19b and mh-z19c?

1. MH-Z19C has one window to receive CO2 gas, while MH-Z19B has two windows.
2. Sampling period for MH-Z19C is 1 second, while MH-Z19B is 5 seconds.
3. Power supply for MH-Z19C is (5+/-0.1)V, while MH-Z19B is 4.5~5.5V.
4. MH-Z19C has analog output, while MH-Z19B does not have。
5. Preheat time for MH-Z19C is 2.5mins, while for MH-Z19B is 1 min.
6. MH-Z19C default auto-calibration cycle is 1 day, but you can choose 7-day cycle if necessary. While MH-Z19B is 1 day.
Genernally, MH-Z19C has better consistency and performance than MH-Z19B, and can directly replace MH-Z19B. They share same size and price.