Contents

Revision and Copyright Information
Warranty and Assistance
Model HMP35C Temperature and Relative Humidity Probe
- 1. General Description
- 2. Specifications
  - 2.1 Temperature Sensor
  - 2.1.1 Temperature Sensor Accuracy
  - 2.2 Relative Humidity Sensor
- 3. Installation
- 4. Wiring
- 5. Example Programs
- 6. Long Lead Lengths
  - 6.1 Temperature
  - 6.2 Relative Humidity
- 7. Electrically Noisy Environments
- 8. Absolute Humidity
- 9. Instruction 11 Details
- 10. Maintenance
- 11. References
Campbell Scientific Contact Information

Campbell Scientific HMP35C Instruction Manual

Campbell Scientific HMP35C Sensor manual cover

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Campbell Scientific HMP35C Sensor Specification

The Campbell Scientific HMP35C Sensor is a precision instrument designed for the accurate measurement of temperature and relative humidity in environmental monitoring applications. This sensor integrates a capacitive polymer chip for humidity measurements and a Platinum Resistance Thermometer (PRT) for temperature measurements, ensuring high accuracy and reliability. The temperature measurement range spans from -40 to +60 degrees Celsius, with an accuracy of ±0.4 degrees Celsius over this range. For relative humidity, the sensor offers a range from 0 to 100%, with an accuracy of ±2% from 0 to 90% and ±3% from 90 to 100%. The sensor is equipped with a multi-stage filter that protects the sensing elements from dust and dirt, enhancing longevity and accuracy. It requires an excitation voltage of 7 to 18 VDC and provides a linear voltage output, making it compatible with a variety of data loggers and data acquisition systems. The sensor is housed in a durable, weather-resistant casing that allows it to function effectively in harsh environmental conditions. Its design includes a radiation shield that minimizes errors due to solar radiation, thus ensuring more accurate readings. The HMP35C is known for its long-term stability and minimal maintenance requirements, making it ideal for meteorological, agricultural, and hydrological applications. Its robust performance in diverse conditions makes it a reliable choice for researchers and professionals in need of precise environmental data.

Campbell Scientific HMP35C Sensor F.A.Q.

How do I connect the HMP35C sensor to a datalogger?

To connect the HMP35C sensor to a datalogger, use the appropriate cable to connect the sensor's output wires to the datalogger's input channels. Refer to the sensor and datalogger manuals for the correct wiring configuration.

What is the recommended calibration frequency for the HMP35C sensor?

Campbell Scientific recommends calibrating the HMP35C sensor at least once a year to ensure accurate measurements. Calibration frequency may vary depending on environmental conditions and usage.

How can I troubleshoot inaccurate readings from the HMP35C sensor?

First, check the wiring and connections for any damage or loose connections. Ensure the sensor is properly calibrated. If issues persist, consult the troubleshooting section of the user manual or contact technical support.

What maintenance procedures are necessary for the HMP35C sensor?

Regular maintenance includes cleaning the sensor housing and checking the cable for wear and tear. Periodically verify the sensor's calibration and inspect for any physical damage.

Can the HMP35C sensor be used in extreme weather conditions?

The HMP35C sensor is designed to operate in a wide range of environmental conditions. However, it is important to consult the sensor's specifications for temperature and humidity limits to ensure it is suitable for your specific application.

What output signal does the HMP35C sensor provide?

The HMP35C sensor typically provides an analog output signal that can be read by compatible dataloggers and monitoring equipment. Specific signal types and ranges are detailed in the sensor's technical documentation.

How do I verify the accuracy of the HMP35C sensor readings?

To verify accuracy, compare the sensor's readings with a calibrated reference instrument. Conduct tests in controlled conditions to ensure reliable comparison.

What precautions should be taken during the installation of the HMP35C sensor?

Ensure that the sensor is mounted securely and away from any potential sources of interference. Follow the installation guidelines in the manual to prevent damage and ensure accurate measurements.

Is it possible to repair a damaged HMP35C sensor in the field?

While some minor repairs can be performed in the field, it is generally recommended to send the sensor to an authorized service center for repairs to ensure proper functionality and accuracy.

What are the common causes of sensor drift in the HMP35C?

Common causes of sensor drift include environmental factors such as dust, pollutants, and temperature fluctuations. Regular calibration and maintenance can help minimize drift.