LT-2M LEAF TEMPERATURE SENSOR

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The LT-2M sensor is designed for monitoring absolute
temperature of leaves. The sensor has a semiconductor bead thermistor equipped with a special clamp for attaching it directly to the leaf under study.

There are two basic requirements when conducting measurements of a leaf temperature:
Minimal effect on the leaf temperature;
Maximal thermal contact between leaf and sensor.

The LT-2 sensors design generally meets both requirements. A miniature bead thermistor has extremely fine glassy cover. It is also spring-loaded that provides firm but gentle contact to the leaf surface. The thermal conductance of thermistor body is small but not negligible. Because of this conductivity, the difference between leaf and air temperatures may cause a systematic deviation, which has been estimated as 10% of the leaf-air temperature difference. Usually, the leaf-air temperature difference does not exceed 5 C and, therefore, the appropriate maximal deviation may be estimated as 0.5 C respectively. If the leaf-air temperature difference is known, the correction can be applied to the result of measurement. Absolute measurements of leaf temperature can be fruitfully used for investigating temperature gradients in plants (Fig 1) and for testing technological regimes (Fig 2).


Fig 1. An example of diurnal monitoring of air (red), soil (black), leaf (green) and flower bud (blue) temperatures in greenhouse roses. Being the same during nighttime, the temperatures dispersed after sunrise. Midday values: Air temperature - 27.5 C; Leaf temperature - 24.5 C; Flower bud temperature - 31 C; Soil temperature 20 C.
Fig 2. The test of three alternative regimes of cooling overhead sprinkling of greenhouse tomatoes: 15 s, 45 s and 30 s. Each test continued until the leaf-air temperature difference returned to its initial value. Apparently, the 45-sec sprinkling produced the best cooling effect, which continued about 25 minutes.
 

 


LT-2M unit includes two leaf temperature sensors and two-channel dc powered signal
conditioner with optional power adapter for unipolar power supply.
 

 

SPECIFICATIONS:
Measurement Range: 5-50 C typical
Instrumental accuracy: 0.2 C
Stability: 0.5 C over 1 year period
Leaf-Air Temperature Difference Effect: less than
+10%(Tl-Ta), where Tl-leaf temperature, Ta - air temperature
Overall dimensions: 35 x 15 x 15 mm3
Output: 0-2 V or 4-20 mA (optional)
Supply Voltage: +15 Vdc 10%
Optional power adapter operates on 10 to 30 Vdc