The UltraFast Thermometer UFT

The precise and fast measurement of cloud temperature is a challenge. Most fast-response thermometers are based on fine-wire sensors and impacting cloud droplets can destroy the wire or bias the signal due to evaporative cooling. To overcome this problem the so-called UltraFast Thermometer (UFT) was developed at the University of Warsaw, Poland. The basic principle is a shielding rod in front of the sensing wire. Due to their inertia cloud droplets impact on the rod or the droplet trajectory is around the sensing wire, therefore, no droplets impact on the wire itself. The sensing element consists of a platinum-coated tungsten wire with 2.5 micron in diameter. This thin wire allows sampling frequencies of up to 10 kHz. Figure 1 shows a special type of UFT developed in cooperation between University of Warsaw and IfT. This device consists of two identical sensors. The device can rotate around the vertical axis (5) and is kept in the mean flow with a small vane (4). This ensures that the shielding rod (2) is always placed in front of the sensing wire (1). Droplets impacting on the rod are sucked away through small inlets in the back of the rod with help of a venturi nozzle (3).

Last Modifications: 2006-05-18