Figure 1. Duct Installation Overview 1 Make sure there is a minimum clearance of 5 m (16.5 ft) between the probe body and any possible humidifier. Avoid installing in a location where condensation can fall on the sensor inside the duct. 2 When installing the transmitter, drill a second hole approximately 30 cm (12 in) from the installation hole, towards the direction of the air flow, and plug it with a removable seal. This second hole is intended for later use in reference measurement with another device when calibrating or adjusting the transmitter. 3 Check that the duct diameter is suitable for the probe body (see Transmitter Dimensions). Ideally, the sensor (probe head) should be installed in the middle of the duct. 4 Maximum air flow speed: 50 m/s (with sintered filter). 5 Avoid installing the transmitter in dead legs. Supersaturation can occur in areas where there is no air flow. 6 Do not install the probe in a downward angle. Condensation can travel to the sensor along the probe body if the probe points down. 7 Install the probe in a 90° angle so that the sensor is placed as close to the middle of the duct as possible.