Greisinger gmh 3350 thermo hygrometer and flow rate meter greisinger gmh 3350 the greisinger gmh 3350 is a thermo hygrometer and flow rate meter and is suitable for the rapid measurement of humidity and temperature making it ideal for applications in buildings factories and warehouse environmentswhats in the boxgreisinger gmh 3350battery 9v blockuser manual greisinger gmh 3350 thermo hygrometer amp flow rate meter