Testo 0560 4251 425 anemometer testo 0560 4251 p this thermal anemometer from testo enables you to make quick spot measurements in ventilation ducts by recording the flow speed calculating the volumetric flow and also measuring the temperature with a measurement range of 0 to 20m s the anemometer is particularly well suited to low air flow velocity this instrument features a telescopic flow probe that can be extended up to 820mm and has a probe head diameter of 7 5mm p p as well as f