ST-21M Soil Temperature sensor

Overview

The ST-21M sensor measures absolute temperature of the soil once it is buried in. The sensor's body has low thermal conductivity that provides accurate measurements in shallow substrate like a Rockwool slab, for instance.

The probe is connected by a standard 1-meter cable to the waterproof box with the signal conditioner inside.

The output cable length should be specified in the order if required.

Every sensor is tuned and calibrated within the measurement range. The tolerance range is ±0.08 ℃ only.

Specifications

Measurement range	0 to 50 ℃
Output
ST-21M	0 to 2 VDC
ST-21Mi	4 to 20 mA
Supply voltage	10 to 30 VDC
Power
ST-21M	1.5 W max
ST-21Mi	2 W max
Instrumental accuracy	< 0.15 ℃
Probe dimensions, mm	90 L × 6 ∅
Probe weight	1.6 g
Signal conditioner Protection index	IP 64
Standard calibration	T(℃)=ƒ(V, Volt)
Best fit:	T= 1.8649V³ − 4.5048V² + 26.542V − 0.0099
Approximation error	< ±0.06 ℃
Linear fit:	T= 24.477V − 0.1352
Approximation error	< ±1 ℃
Tolerance range	±0.08 ℃
Cable length between probe and signal conditioner	1 m