Measure Humidity

How to measure relative air humidity with dry and wet bulb temperatures

The air humidity can easy be estimated by measuring

dry bulb temperature
wet bulb temperature

humidity measurement dry wet bulbe temperature

Dry bulb temperature - T_db - can be measured with a simple thermometer as shown above.

Wet bulb temperature - T_wb - can be measured with a standard thermometer with some wet clothing, cotton or similar, around the bulb. Note that an continuously air flow is import to evaporate water from the wet clothing and achieve the correct wet bulb temperature.

Air movement can be achieved by moving the thermometer as done with a sling thermometer or similar.

Relative humidity can be estimated from the tables below or alternatively from psyhrometric diagrams.

Temperature in Fahrenheit

Relative Humidity - RH (%)
Difference Between Dry Bulb and Wet Bulb Temperatures T_db- T_wb(^oF)	Dry Bulb Temperature - T_db (^oF)
	60	64	68	72	76	80	84	88
1	94	95	95	95	96	96	96	96
2	90	90	90	91	91	92	92	92
3	84	85	85	86	87	88	88	89
4	78	80	81	82	83	84	84	85
5	73	75	76	78	79	80	80	81
6	68	70	72	73	75	76	77	78
7	63	66	67	69	71	72	73	74
8	58	61	63	65	67	68	70	71
9	54	57	59	61	63	65	66	68
10	49	52	55	57	59	61	63	64

dry and wet bulb temperature - relative moisture diagram degrees fahrenheit

Temperature in Celsius

Relative Humidity - RH (%)
Difference Between Dry Bulb and Wet Bulb Temperatures T_db- T_wb(^oC)	Dry Bulb Temperature - T_db (^oC)
	15	18	20	22	25	27	30	33
1	90	91	91	92	92	92	93	93
2	80	82	83	84	85	85	86	87
3	71	73	75	76	77	78	79	80
4	62	65	67	68	70	71	73	74
5	53	57	59	61	64	65	67	69
6	44	49	52	54	57	59	61	63
7	36	42	45	47	51	53	55	58
8	28	34	38	41	45	47	50	53
9	21	27	31	34	39	41	45	48
10	13	20	25	28	33	36	40	43

dry and wet bulb temperature - relative moisture diagram degrees celsius

How to measure relative air humidity with dry and wet bulb temperatures

Temperature in Fahrenheit

Temperature in Celsius

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