Humidity & Dew Point Sensor KPH300

The KPH300 measures relative humidity, temperature and dew point in one compact industrial sensor and delivers the selected value on a standard 4–20 mA loop. It is built for condition monitoring: dew point is the fourth signal alongside vibration, motion and temperature, and it detects condensation risk before visible moisture appears.

Three climate values on one 4–20 mA loop

The measurement is selected in the M12 connector: connected as standard, the KPH300 transmits relative humidity; supply voltage on pin 2 switches the signal to temperature, and on pin 3 to dew point. The selection can be driven from a PLC output or a simple relay circuit and changed while the sensor runs, so one installed sensor covers all three measurements.

Dew point is the condensation threshold

Dew point is the temperature at which air becomes saturated and water starts to condense. Comparing the measured dew point with the temperature of nearby surfaces gives a direct margin to condensation — the figure climate control acts on in electrical cabinets and enclosures. The KPH300 measures dew point across a −20 to +80 °C range, alongside 0–100 % RH and −40 to +80 °C temperature.

The fourth signal in condition monitoring

Four signals cover most condition monitoring applications: vibration is the earliest warning on rotating machinery, motion carries the story where structures and vessels move, temperature watches bearings and whole engine rooms — and dew point guards cabinets, AHUs and nacelles against condensation. The KPH300 delivers that fourth signal, working alongside the vibration sensor KPV200, the motion sensor KPM100 and the TempMux-8 multipoint sensor in the condition monitoring program.

Built for harsh electrical environments

EMC emission and immunity follow the industrial EN 61000-6-4 and EN 61000-6-2 standards, and the sensor is rated for 5 g random vibration (EN 60068-2-34) and 30 g shock (EN 60068-2-27). The housing measures 40 × 72 × 25 mm, mounts with two M5 screws, connects through an A-coded M12 connector and works from −40 to +80 °C, indoors and outdoors.

Condensation control where electronics live

Typical installations follow the moisture risk: electrical cabinets and enclosures where PLCs, relays and drives need protection from condensation, air-handling units and technical rooms, wind turbine nacelles, substations, and compartment climate on defence platforms. For duct-mounted relative humidity in HVAC systems, the KPH101 is the companion sensor among KP’s humidity sensors — the KPH300 is the one that adds temperature and dew point.

Simple to install, simple to integrate

The KPH300 runs from 13.5–30 VDC and is compensated for a 20–28 VDC supply with a 50 Ω burden resistor; the user guide gives the burden formula for other supplies and recommends the dew point output for those setups, including a worked function for calculating relative humidity from dew point and ambient temperature. Mounted on a good thermal conductor with the M12 connector facing down, the sensor settles to ambient temperature and measures correctly.