Humidity System

Modified Meteolabor TP3-ST dewpoint and Viasala HMP45C relative humidity sensors form the core of a dedicated humidity sensing system.

The humidity system sensors are enclosed within the main MET system enclosure and aspirated via a small pump and flow controller. The sensors are temperature stabilised to prevent condensation and to reduce the number of variables affecting performance, and are maintained at a slight positive pressure to prevent entrainment of local air.

The principle sensors employed are:

Meteolabor TP3-ST chilled mirror dewpoint hygrometer

Viasala HMP45C relative humidity sensor

Pressure in each sensor housing is measured to allow us to calculate the mixing ratio; Druck RPT410F pressure sensors are used for this.

A Licor 7500 open path gas analyser, and a Picarro G2301m CRDS analyser also provide humidity measurements, but are described seperately.

Basic Specifications:

For more detail information please refer to the instrument manuals and datasheets.

Meteolabor TP3-ST

(content coming soon)

HMP45C

Operating temperature: -40C to +60C

Storage temperature:  -40C to +80C

Supply Volatge:  7 to 35 VDC

Power consumption: <4mA @ 12 VDC

Humidity Accuracy @ 20C: +/- 2% RH (0-90%RH); +/-3% RH (90-100% RH)

Temp. Dependence of RH Measurement: +/-0.05%RH/degree C

Response time at 20C, 90% response: 15s with filter

Long term stability: <1%RH per year