The HMP155A, manufactured by Vaisala, monitors relative humidity (RH) for the range of 0 to 100% RH and temperature for the range of -80° to +60°C. It can provide reliable measurements for a wide range of applications, as part of a weather station system or as a single instrument. All Campbell Scientific dataloggers are compatible.Read More
This product is supplied with a standard length of cable (typically 3 m) - other lengths may be available to order.
The HMP155A uses a HUMICAP180R capacitive thin film polymer sensor to measure RH, and a PRT to measure temperature.A warmed probe option ensures accurate measurements and better long-term stability in high-condensing environments, where required.
To reduce the current drain, power can be supplied to the HMP155A only during measurement when the sensor is connected to the datalogger’s switched 12 V terminal. Dataloggers 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.
|Electromagnetic Compatibility||Complies with EMC standard EN61326-1 Electromagnetic|
|Filter Description||Sintered PTFE|
|Housing Body Material||PC|
|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.)|
|Sensing Element||HUMICAP 180R|
|Measurement Range||0 to 100% RH (non-condensing)|
|Factory Calibration Uncertainty||
|Sensing Element||PT 100 RTD 1/3 class B IEC 751|
|Measurement Range||-80° to +60°C|
|Accuracy (RS-485)||±(0.176 - 0.0028 x temperature) °C (-80° to +20°C)|
|±(0.07 + 0.0025 x temperature) °C (+20° to +60°C)|
|Entire Temperature Range||Refer to graph in probe manual.|
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
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.
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.
Number of FAQs related to HMP155A-L: 7
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The maximum cable length is 304 m (1000 ft).
No. The HMP155A-L requires the 41005-5 14-Plate Solar Radiation Shield.
Not every sensor has different cable termination options. The options available for a particular sensor can be checked by looking in two places in the Ordering information area of the sensor product page:
If a sensor is offered in an –ET, –ETM, –LC, –LQ, or –QD version, that option’s availability is reflected in the sensor model number. For example, the 034B is offered as the 034B-ET, 034B-ETM, 034B-LC, 034B-LQ, and 034B-QD.
All of the other cable termination options, if available, are listed on the Ordering information area of the sensor product page under “Cable Termination Options.” For example, the 034B-L Wind Set is offered with the –CWS, –PT, and –PW options, as shown in the Ordering information area of the 034B-L product page.
Note: As newer products are added to our inventory, typically, we will list multiple cable termination options under a single sensor model rather than creating multiple model numbers. For example, the HC2S3-L has a –C cable termination option for connecting it to a CS110 instead of offering an HC2S3-LC model.
Most Campbell Scientific sensors are available as an –L, which indicates a user-specified cable length. If a sensor is listed as an –LX model (where “X” is some other character), that sensor’s cable has a user-specified length, but it terminates with a specific connector for a unique system:
If a sensor does not have an –L or other –LX designation after the main model number, the sensor has a set cable length. The cable length is listed at the end of the Description field in the product’s Ordering information. For example, the 034B-ET model has a description of “Met One Wind Set for ET Station, 67 inch Cable.” Products with a set cable length terminate, as a default, with pigtails.
If a cable terminates with a special connector for a unique system, the end of the model number designates which system. For example, the 034B-ET model designates the sensor as a 034B for an ET107 system.
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:
Many Campbell Scientific sensors are available with different cable termination options. These options include the following:
Note: The availability of cable termination options varies by sensor. For example, sensors may have none, two, or several options to choose from. If a desired option is not listed for a specific sensor, contact Campbell Scientific for assistance.
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).