Product · Humidity Sensors
Humidity Sensor for Refrigerated Containers
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Application
The humidity sensor for refrigerated containers measures relative humidity in the cargo space and delivers the reading over Modbus RTU on RS485, for reefer units in cold chain transport.
Capacitive Sensirion element behind a PTFE membrane
A capacitive Sensirion SHT30 element sits behind a 1 µm hydrophobic and oleophobic PTFE membrane and goes on reading in the condensing air of a loaded reefer. Response time is under 8 seconds and the element is instant on.
Accuracy, drift and the SHT31 option
The standard SHT30 element is factory calibrated to ±3 %RH across 10–90 %RH at 0–60 °C. An SHT31 version is available where a tighter figure is required: ±2 %RH across the full 0–100 %RH. Long-term drift is under 1.5 %RH per year in both cases, and neither needs recalibration.
One measurement, or three
The same housing carries a CO2 sensor for refrigerated containers or an O2 sensor for refrigerated containers for controlled atmosphere (CA) units, and the Hybrid Sensor for refrigerated containers carries all three at once.
Properties
| Measurement | Relative humidity, 0–100 %RH (condensing); 16-bit resolution |
|---|---|
| Measuring principle | Capacitive Sensirion SHT30 element with PTFE filter; SHT31 available as an option |
| Accuracy | SHT30: ±3 %RH at 10–90 %RH, 0–60 °C. SHT31 option: ±2 %RH at 0–100 %RH, 0–60 °C. Factory calibrated |
| Long-term drift | < ±1.5 %RH per year; no recalibration required |
| Response time | τ63% < 8 s; instant on |
| Operating conditions | −20 to +80 °C, resistant to condensing environments. Storage −40 to +80 °C |
| Communication | 2-wire RS485, Modbus RTU; 9600, 19200 or 115000 bit/s, software selectable |
| Supply | 12 VDC (8–15 V), protected against overvoltage and reverse polarity; peak < 60 mA, average < 10 mA |
| Electrical connection | Integrated Deutsch DT04 receptacle (DT06 plug); RS485 circuit protected to 60 V, no damage from miswiring |
| Housing and mounting | 52.5 × 52.5 × 36.5 mm; two Ø6 mm holes, 54 mm centre to centre, for rivet or screw |
| Protection | IP67; measuring cuvette behind a 1 µm hydrophobic and oleophobic PTFE membrane |
| Environmental testing | Salt spray ASTM B117, 168 hours, no visible corrosion; vibration IEC 60068-2-64; shock IEC 60068-2-27 |
| EMC | EN 61000-6-3 (emission); EN 61000-6-2 (immunity) |
| Also available as | A CO2 sensor and an O2 sensor for refrigerated containers, and the Hybrid Sensor — same housing, same connector, same Modbus interface |