User manual

CS215 Temperature and Relative
Humidity Probe
The CS215 Temperature and Relative Humidity probe is designed as a reasonably priced
probe for general meteorological and other datalogging applications. It utilises the SDI-12
communications protocol to communicate with any SDI-12 recorder simplifying installation
and programming.
1. Introduction
The CS215 probe utilises a novel single chip element that incorporates both a
temperature and RH sensor. Each element is individually calibrated with the
calibration corrections stored on the chip. The element is easily changed in the
field. Replacement of the element effectively fully recalibrates the probe both for
temperature and humidity thus minimising downtime and calibration costs.
Low power electronics within the CS215 controls the measurement made by the
sensor element, applies temperature and linearization corrections to the readings
and presents the data via an SDI-12 compatible interface to a datalogger.
The probe is fitted with a custom-made, yet low-cost sintered plastic filter to
minimise the effects of dust and dirt on the sensor. The filter is lightweight and
hydrophobic thereby minimising the effect of the time response of the sensor.
The probe housing is designed to withstand permanent exposure to all weathers
and to fit into a range of radiation shields including lower cost compact shields
2. Specifications
Sensing Element: Sensirion SHT75
Temperature Measurement:
Operating Range:
-40°C to +70°C
Accuracy:
±0.3°C at 25°C, ±0.4°C over +5°C to +40°C, ±0.9°C
over -40°C to +70°C
Response Time With
Filter:
120 s (63% response time in air moving at 1 m/s)
Default units: Degrees celsius
Relative Humidity:
Operating Range:
0 to 100% RH (-20 to +60°C; see Appendix A)
Accuracy (at 25°C): ±2% over 10-90% , ±4% over 0–100%
Short Term Hysteresis: <1% RH
Temperature
Dependence:
Compensated to better than ±2% over -20 to 60°C
Typical Long-Term
Stability:
Better than ±1.0% per year
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