Duct probe with a clean 4-20 mA loop
The Schneider SH3XD22 is a duct-mount temperature and humidity probe in the SH3 series, carrying a 2-wire 4...20 mA analogue output that drops straight onto a standard controller input card or a loop-powered indicator without a separate supply pair. It measures temperature, relative humidity and derived dew point on the same channel, so a single duct insertion covers the three variables an AHU or clean-room panel typically logs.
82 mm probe, 101 mm body — what fits the duct
With an 82 mm probe diameter and 43 mm installation depth, the SH3XD22 seats into a standard duct tap without protruding into the airflow far enough to disturb the reading — the 182 mm overall height and 101 mm body width clear most terminal-box lids once the probe is committed. Internal mounting and IP65 around the housing keep the electronics side of the partition clean while the sensing tip reads the airstream; the gasket at the duct face is the wet-side barrier, so torque it down on a flat gland surface to keep the IP65 rating honest.
0-40 °C, 0-100 %RH — coverage that matches HVAC duty
The 0...40 °C temperature range and 0...100 % humidity span line up with conditioned-air and process-room envelopes rather than outdoor or freezer duty — this is an indoor-air probe, not a chiller or rooftop sensor. A 4...20 mA loop on two wires lets the cable run share conduit with other low-voltage instrumentation, and scaling both ranges into the same 4-20 mA channel means the downstream PLC or BMS card reads either variable from one analogue input.