Having the sensor equipment is one thing, but what are best practices as they can be found on the Internet?
1. Temperature
Ambient temperature in a server room is typically the temperature that is being focused on. However one must realize that temperature in the room can be very different from the temperature in a server rack.
It is generally recommended that temperature inside a rack is not to exceed 23°C or 73° F.
Sensors are best located in the server racks rather than in the room as ambient temperature will rise at a slower pace compared to the temperature in the rack. As hot air climbs compared to cold air, it is recommended to put the sensor in the hotest spot of the rack.
Most people understand the need for having temperature sensors in a server room but the dangers of humidity are less known.
Low relative humidity (as of 35% rH) has the danger of causing electrostatic discharge (ESD). ESD is caused by static charges resulting from people movement, charges on furniture etc... These charges are mostly not noticeable but when discharged to or in proximity of IT equipment, they can cause severe damage to the equipment.
Another danger of low humidity is the break down of some plastics in your equipment resulting in premature aging of it.
To overcome the danger of low humidity, moisture is often added to temperature controlling systems to avoid too dry conditions in server rooms.
High humidity or rapid temperature drops result in condensation that can occur on any surface. Water can condensate on the inside of IT equipment and cause rust or dust & dirt being deposited. This pose a great risk to the components and as a result to the availability of the equipment.
Relative Humidity (rH) is server rooms should be around 50% with a +/- 10% margin.