Contents

Revision and copyright information
Table of contents
1. Introduction
2. Precautions
3. Initial inspection
4. QuickStart
5. Overview
6. Specifications
- 6.1 Temperature sensor
- 6.2 Relative humidity sensor
7. Installation
- 7.1 Wiring to data logger
- 7.2 Data logger programming
  - 7.2.1 VoltSE() instruction
  - 7.2.2 VoltDiff() instruction
- 7.3 Mounting
  - 7.3.1 Installation in a 41005-5 14plate shield
  - 7.3.2 Installation in a RAD14 14plate shield
  - 7.3.3 Mount the shield
8. Operation
- 8.1 Measurement
- 8.2 Long cable lengths
- 8.3 Absolute humidity
9. Troubleshooting and maintenance
- 9.1 Troubleshooting
- 9.2 Maintenance
  - 9.2.1 Cleaning
  - 9.2.2 Changing the probe filter
10. References
Appendix A. Importing Short Cut code into CRBasic Editor
Appendix B. RS485 output
- B.1 SDM-SIO1A or SDM-SIO4A serial I/O module interface option
- B.2 MD485 interface option
  - B.2.1 MD485 multidrop interface configuration
- B.3 Numeric display
Limited warranty
Assistance
Safety
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Campbell Scientific HMP155A Product Manual

Campbell Scientific HMP155A Sensor manual cover

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Campbell Scientific HMP155A Sensor Specification

The Campbell Scientific HMP155A Sensor is a high-precision instrument designed to measure relative humidity and air temperature in demanding environmental conditions. It utilizes a capacitive thin-film polymer sensor for humidity measurement, providing an accuracy of ±1% over a wide range, making it suitable for meteorological, hydrological, and environmental monitoring applications. For temperature measurement, the sensor employs a platinum resistance thermometer (PRT), ensuring a high level of accuracy with a range from -80°C to 60°C. The HMP155A is engineered to deliver reliable performance in harsh conditions, featuring a robust design with a stainless steel body and a sintered PTFE filter that protects the sensor element from dust and dirt.

This sensor includes a radiation shield to minimize the effects of solar radiation on temperature readings, enhancing its accuracy and reliability. It supports a variety of data communication options, including SDI-12 and RS-485, allowing for seamless integration with data loggers and other data acquisition systems. The sensor operates with minimal power consumption, making it ideal for remote applications where power supply may be limited. Its calibration is traceable to international standards, ensuring high-quality measurements that meet scientific and industrial requirements. The HMP155A's combination of precision, durability, and compatibility with standard data interfaces makes it a versatile choice for capturing critical environmental data in a wide range of operational scenarios.

Campbell Scientific HMP155A Sensor F.A.Q.

What is the recommended procedure for calibrating the Campbell Scientific HMP155A sensor?

The HMP155A sensor should be recalibrated annually. Calibration can be done using a two-point method with known humidity standards. Ensure the sensor is clean and dry before starting the calibration process. Refer to the user manual for detailed calibration steps.

How can I troubleshoot erratic humidity readings from the HMP155A sensor?

First, check the sensor's physical condition to ensure it is clean and free of obstructions. Verify the wiring connections are secure. If the issue persists, perform a factory reset and recalibrate the sensor. Consult the manual for specific error codes and troubleshooting guidance.

What maintenance procedures are recommended for the HMP155A sensor?

Regular maintenance includes cleaning the sensor with a soft brush or compressed air to remove dust and debris. Inspect the filter regularly and replace it if damaged. Also, check the cables and connectors for any signs of wear or corrosion.

How should the HMP155A sensor be installed for optimal performance?

Install the HMP155A sensor in a location with unobstructed air flow and away from any heat sources. Mount it vertically to allow for proper ventilation and accurate measurements. Ensure the sensor is shielded from direct sunlight and precipitation.

What are the common causes of sensor drift in the HMP155A, and how can it be minimized?

Sensor drift can be caused by contamination, aging of the sensor elements, or harsh environmental conditions. To minimize drift, regularly clean the sensor, protect it from extreme conditions, and perform periodic recalibration.

How can I verify the accuracy of the HMP155A sensor readings?

Compare the sensor readings with a calibrated reference sensor under controlled conditions. Ensure both sensors are exposed to the same environmental conditions for a fair comparison.

What should I do if the HMP155A sensor fails to communicate with the data logger?

Check the connection cables for any damage or loose connections. Ensure that the data logger is properly configured to recognize the sensor. If the problem persists, try resetting both the sensor and the data logger.

Can the HMP155A sensor be used in environments with high humidity levels?

Yes, the HMP155A is designed to operate in high humidity environments. However, ensure it is properly maintained and recalibrated regularly to maintain accuracy. Use a radiation shield to protect it from direct sunlight and precipitation.

What are the power requirements for operating the HMP155A sensor?

The HMP155A sensor requires a power supply of 7 to 28 VDC. Ensure the power supply is stable and within this range to avoid damaging the sensor.

How can I extend the lifespan of the HMP155A sensor?

To extend the lifespan, regularly clean and maintain the sensor, protect it from extreme environmental conditions, and perform routine calibrations. Store the sensor properly when not in use and ensure it is shielded from direct sunlight and precipitation during operation.