Heated Humidity Sensor for Radiosondes and Weather Balloons HMC03M is optimized for short response time even at very low temperature (T) in the upper atmosphere. It combines on a silicon substrate a capacitive relative humidity (RH) sensor and a heating resistor (heater). The heater is dedicated for fast recovery of the humidity sensor after condensation or icing. The construction with the heater positioned all around the RH sensor grants uniform temperature throughout the HMC03M structure, which leads to outstanding measuring performance in high-end weather observation. Features Very short RH response time at low T Fast recovery after condensation or icing due to sensor heating High sensitivity Technical Data Humidity sensor Nominal capacitance C0 (at 30 °C / 86 °F) 120 ± 40 pF Sensitivity (for C0 = 120 pF, in average) 0.41 pF / % RH1) Working range Humidity 0...100 % RH Temperature -80...60 °C (-112...140 °F) Linearity error (0...98 % RH) < ± 2 % RH Hysteresis 1.9 ± 0.25 % RH Response time RH t63 Temperature dependence2) Loss tangent Supply voltage DC voltage Operating frequency Heater (Molybdenum) Nominal resistance R0 Temperature coefficient Self heating coefficient (SHC), typical (at 980 hPa) 5 m/s 1 m/s 0.1 m/s Max. power 1) More details see „Characteristics 2) Basic formula. Details for t < -20 °C on request v1.3 / Modification rights reserved

Humidity sensor Alternatively, a polynomial approximation of the characteristic can be used for high accuracy requirements: Alternative formula according IEC60751: For shortest response time, in case of mounting onto a printed circuit board (PCB), HMC03M shall be positioned over an opening to allow enough air circulation around the sensor. For best accuracy it is important to avoid moisture accumulation such as at the edge of the PCB by selecting appropriate board material or gold-plating the edge of the opening. HMC03M is an SMD (surface mounted device) sensor, appropriate for automatic assembling...