Vacuum gauges will tell you the pressure of your vacuum system. Any single vacuum gauge will not cover the entire range of pressure, so we use multiple vacuum gauge types on any given vacuum system, to cover the whole range.
Some require an external controller to operate the gauge. Others have a display built in.
controller:
Note: Images are links to product pages/manuals
types
Pirani gauge
pressure range: atmosphere (700 torr) to ~1e-3 torr
cold cathode gauge (CCG)
pressure range: ~1e-3 - 1e-11 (minimum pressure depends on model, some don't go below 1e-8 torr)
Hot cathode gauge
Brands:
MKS
Note: the Instruech 501 CCG has a Viton (a type of rubber) seal
Other?
Gauge resources:
MKS vacuum gauges product selection guide