Contents

Revision and Copyright Information
Warranty and Assistance
Table of Contents
Model HMP45C Temperature and Relative Humidity Probe
- 1. General Description
- 2. Specifications
  - 2.1 Temperature Sensor
  - 2.2 Relative Humidity Sensor
- 3. Installation
  - 3.1 Siting
  - 3.2 Assembly and Mounting
- 4. Wiring
- 5. Example Programs
- 6. Long Lead Lengths
- 7. Absolute Humidity
- 8. Sensor Maintenance
- 9. Troubleshooting
- 10. References
Appendix A. Wiring for Older HMP45C Probes
Campbell Scientific Contact Information

Campbell Scientific HMP45C Instruction Manual

Campbell Scientific HMP45C Sensor manual cover

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Campbell Scientific HMP45C Sensor Specification

The Campbell Scientific HMP45C Sensor is a precision instrument designed for measuring temperature and relative humidity in various environmental conditions. It employs a capacitive thin-film polymer sensor for humidity and a platinum resistance thermometer for temperature, ensuring accurate and reliable measurements. The sensor is suitable for a wide range of applications, including meteorological, hydrological, and environmental monitoring.

The HMP45C provides a temperature measurement range from -40 to +60 degrees Celsius, with an accuracy of ±0.2 degrees Celsius at 20 degrees. For relative humidity, the sensor measures from 0 to 100% with an accuracy of ±2% RH over 0 to 90% RH and ±3% RH over 90 to 100% RH. Its design allows for long-term stability and minimal maintenance, featuring a protective sintered PTFE filter to shield the sensing elements from dust and contaminants.

This sensor operates with a 7 to 28 VDC power supply, drawing minimal current, which makes it ideal for remote or solar-powered applications. It is compatible with Campbell Scientific dataloggers, allowing for seamless integration into existing data acquisition systems. The HMP45C communicates via an analog output, providing a straightforward connection to dataloggers or other measurement devices.

Housed in a robust, weather-resistant enclosure, the HMP45C is designed to withstand harsh environmental conditions, ensuring durability and longevity in field deployments. With its high accuracy, reliability, and ease of integration, the Campbell Scientific HMP45C Sensor is a trusted choice for professionals requiring precise environmental data.

Campbell Scientific HMP45C Sensor F.A.Q.

How do I properly install the Campbell Scientific HMP45C sensor?

To install the HMP45C sensor, mount it in a location that represents the area of interest, ensuring it is shielded from direct sunlight and precipitation. Use the proper radiation shield and ensure the sensor is mounted vertically for accurate measurements.

What is the recommended method for calibrating the HMP45C sensor?

Calibration can be performed using a two-point process with reference to known humidity standards. It's advised to perform this calibration annually or as indicated by your data's performance requirements.

How can I troubleshoot inaccurate readings from the HMP45C sensor?

Check for any physical obstructions or contamination on the sensor, verify cable connections, and ensure the sensor is properly calibrated. Also, inspect the power supply and data acquisition system for malfunction.

What maintenance is required to ensure optimal performance of the HMP45C sensor?

Regularly inspect the sensor for dirt and moisture, clean with a soft cloth and mild detergent if necessary, and check the wiring connections. Calibration should be checked annually.

Can the HMP45C sensor be used in extreme weather conditions?

Yes, the HMP45C is designed to operate in a wide range of environmental conditions. However, ensure it is adequately shielded and the operating temperature and humidity ranges specified by Campbell Scientific are not exceeded.

What is the correct way to clean the HMP45C sensor?

To clean the sensor, gently wipe it with a soft cloth dampened with a mild detergent solution. Avoid using solvents or abrasive materials that could damage the sensor elements.

How do I verify the data accuracy from the HMP45C sensor?

Compare the sensor's data with a reliable reference measurement or standard. Regular calibration checks and data validation against known environmental conditions can help verify accuracy.

What should I do if the HMP45C sensor is not communicating with the data logger?

Check the cable connections between the sensor and the data logger for any signs of damage or disconnection. Ensure the data logger's configuration matches the sensor's specifications and the power supply to the sensor is adequate.

How often should the HMP45C sensor be recalibrated?

It is recommended to recalibrate the HMP45C sensor at least once a year or more frequently if used in environments with extreme conditions or if data accuracy is critical.

What are the typical signs that the HMP45C sensor needs maintenance?

Signs include erratic data readings, physical damage to the sensor or cable, significant discrepancies compared to reference data, and visible dirt or moisture accumulation on the sensor.