Humidity measuring device

A humidity measuring device configured to measure humidity of a gas, the humidity measuring device comprising:

• a measurement unit including a temperature sensing element configured to measure temperature, and a humidity sensing element configured to measure humidity;
• a casing including an accommodating section in which the measurement unit is accommodated;
• a display unit including a display device, and which is fixed to the casing;
• and
• a coupling tube connected in the middle between tube portions through which the gas flows and configured to enable the gas to flow between one of the tube portions and another of the tube portions, wherein
• the coupling tube is provided outside the casing and includes an orifice,
• a filter is mounted in the coupling tube, and
• the casing includes a first tube connecting the accommodating section with the coupling tube at one side of the orifice in the gas flow direction, and a second tube connecting the accommodating section with the coupling tube at the other side of the orifice in the gas flow direction, to enable the gas to flow between the coupling tube and the accommodating section due to a gas pressure drop at the orifice.