Higher-end sensor where higher accuracy is required
Overview
The HMP155A provides reliable relative humidity (RH) and temperature measurements for a wide range of applications. It uses a HUMICAP®180R capacitive thin film polymer sensor to measure RH over the 0 to 100% RH range. A PRT measures temperature over the -80° to +60°C range. This rugged, accurate temperature/RH probe is manufactured by Vaisala.
Read MoreBenefits and Features
- Well-suited for long-term, unattended applications
- Accurate and rugged
- Mounts to a mast, crossarm, or user-supplied pole
- Compatible with most Campbell Scientific data loggers
Images
Detailed Description
To reduce the current drain, power can be supplied to the HMP155A only during measurement when the sensor is connected to the data logger’s switched 12 V terminal. Data loggers that do not have a switched 12 V terminal, such as the CR510 or CR7, can use the SW12V switched 12 V device to switch power to the sensor only during measurement.
Compatibility
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) | ||
| CR1000X (retired) | ||
| CR300 (retired) | ||
| CR3000 (retired) | ||
| CR310 | ||
| CR350 | ||
| CR6 | ||
| CR800 (retired) | ||
| CR850 (retired) |
Additional Compatibility Information
Sensor Mounts
When exposed to sunlight, the HMP155A must be housed in a 41005-5 or RAD14 14-plate naturally aspirated radiation shield. The 41005-5 and RAD14 attach to a crossarm, mast, or user-supplied pipe with a 2.5 to 5.3 cm (1.0 to 2.1 in.) outer diameter. The RAD14 uses a double-louvered design that offers improved sensor protection from driving rain, snow, and insect intrusion, It also has lower self-heating in bright sunlight combined with higher temperatures (> 24°C [~75°F])
and low wind speeds (< 2 m s-1 [~4.5 mph]), giving a better measurement.
Specifications
| Electromagnetic Compatibility | Complies with EMC standard EN61326-1 Electromagnetic |
| Filter Description | Sintered PTFE |
| Housing Body Material | PC |
| Housing Classification | IP66 |
| Voltage Output | 0 to 1 Vdc |
| Average Current Consumption | ≤ 3 mA (analog output mode) |
| Operating Voltage | 7 to 28 Vdc |
| Settling Time | 2 s (at power up) |
| Field-Replaceable Chip or Recalibrate | Recalibrate |
| Tip Diameter | 1.2 cm (0.5 in.) |
| Length | 27.9 cm (11 in.) |
| Head Height | 4 cm (1.6 in.) |
| Body Height | 2.4 cm (0.9 in.) |
| Body Width | 2.0 cm (0.8 in.) |
Relative Humidity |
|
| Sensing Element | HUMICAP 180R |
| Measurement Range | 0 to 100% RH (non-condensing) |
| Response Time |
|
| Factory Calibration Uncertainty |
|
| Accuracy |
|
Air Temperature |
|
| Sensing Element | PT 100 RTD 1/3 class B IEC 751 |
| Measurement Range | -80° to +60°C |
| Accuracy |
|
| Entire Temperature Range | Refer to graph in probe manual. |
Documents
Technical Papers
Downloads
HMP155A Example Programs (4 KB) 10-15-2021
Description: Example CR1000X programs that measure either the analog voltage or RS-485 output of the HMP155A. The analog voltage programs use either the VoltSE or VoltDiff instruction and switch power to the sensor only during measurements. One program also calculates the mean vapor pressure. The RS-485 program measures the RS-485 output with an SDM-SIO1A/SIO4A. Although these programs are written for the CR1000X, programs for other dataloggers will be similar.
Frequently Asked Questions
Number of FAQs related to HMP155A-L: 3
Expand AllCollapse All
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No. The HMP155A-L requires the 41005-5 14-Plate Solar Radiation Shield.
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Note the difference between calibration and a field check. Calibration cannot be done in the field, as it requires an experienced technician and specialized equipment.
Field checks of measurements can be done to determine if the data make sense with the real-world conditions. Follow these steps to field check a sensor:
- Find a second sensor of the same type as the installed sensor whose data is in question. The second sensor will be used as a benchmark sensor and should be known to be accurate or recently calibrated.
- At the site, take readings using both sensors under the same conditions. The best practice is to measure both sensors side-by-side at the same time. Note that the sensors will never have the exact same measurement.
- Depending on the sensor model, if the difference in the readings of the installed and benchmark sensors is greater than the sum of the accuracies for both sensors, either return the installed sensor to Campbell Scientific for calibration or replace the appropriate chip.
- The 107, 108, 109, 110PV-L, and BlackGlobe-L temperature sensors can be calibrated.
- The HC2S3-L and HMP155A-L temperature and relative humidity sensors can be calibrated.
- The CS215-L has a replaceable chip for temperature and relative humidity. For more information, refer to the “Maintenance and Calibration” section of the CS215 instruction manual.
- The HMP60-L has a replaceable chip for relative humidity only. For more information, refer to the “Maintenance” section of the HMP60 instruction manual.
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Single-ended channels are typically used when it is desirable to use fewer channels and the cable length is shorter—less than 6.1 m (20 ft). Differential channels are preferable when the cable needs to be longer than 6.1 m (20 ft).
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