This product is no longer available.
CWS900 900 MHz Configurable Wireless Sensor Interface
Services Available
Repair No
Calibration No
Free Support Yes


The CWS900 allows a sensor with a special connector to be used in a wireless sensor network; the special connector is available as an option for a large variety of sensors. (See the Compatibility information on the web page.)

The CWS900 contains an internal 900 MHz spread-spectrum radio that transmits data to the CWB100 Wireless Base Station or to another wireless sensor. The frequency of the CWS900's internal radio is commonly used in the US and Canada.

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Benefits and Features

  • Allows a wide variety of sensors to be used in a wireless network
  • Internal frequency-hopping, spread-spectrum radio provides longer range and less interference
  • Battery powered
  • A reliable, low-maintenance, low-power method for making measurements in applications where cabled sensors are impractical or otherwise undesirable
  • Transmissions can be routed through up to three other wireless sensors

This product will be discontinued as of 10 April 2017. Please review the CWS-Series and CWB-Series Discontinuation Notice for further details. 


Detailed Description

The CWS900 has a sealed connector for attaching one rain gage, wind sensor, temperature/RH probe, or another low power sensor. It measures analog voltages, low level AC, pulse counts, and can supply an excitation voltage for powering some sensors or making bridge measurements. The type of measurement that the sensor performs is configured using Wireless Sensor Planner, Network Planner, or DevConfig software. The CWS900 interfaces with the PC for configuration via the A205 CWS Sensor to PC Interface.

The CWS900 can route its transmissions through up to three other wireless sensors. A data logger is connected to the CWB100 base station for processing and storing the CWS900's data.

The CWS900 is battery powered using either alkaline batteries or a rechargeable battery and a solar cell.

Why Wireless?

There are situations when it is desirable to make measurements in locations where the use of cabled sensors is problematic. Protecting cables by running them through conduit or burying them in trenches is time consuming, labor intensive, and sometimes not possible. Local fire codes may preclude the use of certain types of sensor cabling inside of buildings. In some applications measurements need to be made at distances where long cables decrease the quality of the measurement or are too expensive. There are also times when it is important to increase the number of measurements being made but the data logger does not have enough available channels left for attaching additional sensor cables.

Note: The internal radio is not designed to move a lot of data quickly. It takes 15 to 30 seconds per hop when moving data from a sensor, through a sensor used as a repeater, and ending up at the base radio. Going through three repeaters could take a data packet anywhere from 45 to 90 seconds to get to the base radio.


Weather Resistance IP67 rating for sensor and battery pack (Battery pack must be properly installed. Each sensor is leak tested.)
Operating Temperature Range -25° to +50°C
Operating Relative Humidity Range 0 to 100%
Power Source 2 AA batteries with a battery life of 1 year assuming sensor samples taken every 10 minutes. (Optional solar charging available.)
Average Current Drain 300 μA (with 15-minute polling and depending on attached sensor)
Analog Channels
  • SE1, SE2, SE3 (single-ended)
  • DF (differential)
Analog Input Range -1 to +2.5 Vdc
Resolution 0.3 μV
Excitation Voltage 2.5 V, 3.3 V, 5.0 V (20 mA maximum)
Excitation Voltage Accuracy ±2% (-35° to +70°C)
Low-Level AC Input 20 mV minimum (10 kHz maximum frequency)
Temperature Accuracy ±0.2ºC
Analog Measurement Accuracy
  • ±(0.02% of reading + 2 µV) (0° to 50°C)
  • ±(0.05% of reading + 2 µV) (-35° to +70°C)
Bridge Measurement Accuracy (+2.5 V excitation only)
  • ±(0.03% of reading + 3 µV) (0° to 50°C)
  • ±(0.07% of reading + 3 µV) (-35° to +70°C) Not including sensor and measurement noise, and external bridge resistor errors.
Dimensions 15 x 6 x 4.5 cm (5.9 x 2.4 x 1.77 in.)
Weight 184 g (6.5 oz)

Switch Closure

Maximum Count Rate 100 Hz
Minimum Open Time 5 ms
Minimum Closed Time 5 ms
Maximum Bounce Time 4 ms
Maximum Number of Counts Records 1,000,000 counts before it rolls over.

Internal 25 mW FHSS Radio

Frequency 902 to 918 MHz
Where Used US and Canada
FHSS Channel 50
Transmitter Power Output 25 mW (+14 dBm)
Receiver Sensitivity -110 dBm (0.1% frame error rate)
Standby Typical Current Drain 3 μA
Receive Typical Current Drain 18 mA (full run)
Transmit Typical Current Drain 45 mA
Average Operating Current 15 μA (with 1-second access time)
Quality of Service Management RSSI
Additional Features GFSK modulation, data interleaving, forward error correction, data scrambling, RSSI reporting


Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.

Data Loggers

Product Compatible Note
CR1000 (retired)
CR200X (retired)
CR206X (retired)
CR211X (retired)
CR216X (retired)
CR295X (retired)
CR9000X (retired)


Product Compatible Note
03002-L With -CWS option
034B-L With -CWS option
05103-45-L (retired) With -CWS option
05103-L With -CWS option
05106-L (retired) With -CWS option
05305-L With -CWS option
109 With -CWS option
109SS-L With -CWS option
110PV-L With -CWS option
CMP11-L With -CWS option
CMP6-L With -CWS option
CS215-L (retired)
CS300-L (retired) With -CWS option
CS511-L With -CWS option
CSAT3 (retired)
HC2S3-L (retired) With -CWS option
HMP60-L With -CWS option
LI190SB-L (retired) With -CWS option
LI200S-L (retired) With -CWS option
LI200X-L (retired)
OBS-3+ (retired)
OBS300 (retired)
OBS500 (retired)
TB4-L With -CWS option
TB4MM-L With -CWS option
TE525-L With -CWS option
TE525MM-L With -CWS option
TE525WS-L With -CWS option
WINDSONIC-L (retired)

Additional Compatibility Information

Data Logger Considerations

Compatible Data Logger Operating Systems
  • CR800-Series: CR800.Std.21 and higher
  • CR1000: CR1000.Std.21 and higher
  • CR3000: CR3000.Std.21 and higher
  • CR6: Version 4.0 and higher


One sensor can be connected to the CWS900. Sensors with the -CWS option will include a connector that mates with the CWS900. Alternatively, a sensor can connect with the CWS900 via the A150 Desiccant Case.

A150 Desiccated Case

The A150 Desiccated Case has a -CWS cable termination option. It allows our CS451 and CS456 pressure transducers or other sensors that have a vented cable to be connected to the CWS900. Sensors that measure analog voltages, frequency, and pulse can also use the A150 to connect with the CWS900.


CWS900 Firmware v.5 (448 KB) 03-30-2016

Latest firmware for the CWS900.  

View Update History

Wireless Sensor Planner v.1.7 (30.5 MB) 08-08-2013

The Wireless Sensor Planner is a tool for use with Campbell Scientific wireless sensors.  It assists in designing and configuring wireless sensor networks.

Frequently Asked Questions

Number of FAQs related to CWS900: 6

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  1. An A205 is required to write the radio address of the wireless base station to the wireless sensor firmware so that the sensor will respond to polling from the base station. This is done using the Device Configuration Utility software. The A205 is also useful for connecting a computer directly to the CWS655, CWS220, or CWS900 for diagnosis, changing the base station radio address, uploading new firmware, and verifying sensor functionality. It is only necessary to purchase one A205—unless multiple users with multiple computers need to perform these tasks.

  2. Because the devices and the radios use the same frequency bands, there will be interference. Factors affecting the amount of interference include the distances between the communications radio and the CWS radios, and the distances between the CWS base and the sensors. Also, the amount of interference is affected by whether the communications radio is set up as a master.

  3. To incorporate a sensor that is compatible with wireless sensor interfaces into a wireless network, a CWS900-series wireless sensor interface is needed, as well as an A205 CWS-to-PC interface to configure it. 

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