Campbell HMP155A User manual

Revision: 10/2021
Copyright © 1990 – 2021
Campbell Scientific, Inc.

Table of contents
1. Introduction 1
2. Precautions 1
3. Initial inspection 1
4. QuickStart 2
5. Overview 4
6. Specifications 5
6.1 Temperature sensor 7
6.2 Relative humidity sensor 8
7. Installation 8
7.1 Wiring to data logger 8
7.2 Data logger programming 10
7.2.1 VoltSE() instruction 10
7.2.2 VoltDiff() instruction 11
7.3 Mounting 11
7.3.1 Installation in a 41005-5 14-plate shield 13
7.3.2 Installation in a RAD14 14-plate shield 14
7.3.3 Mount the shield 14
8. Operation 15
8.1 Measurement 15
8.2 Long cable lengths 15
8.3 Absolute humidity 16
9. Troubleshooting and maintenance 17
9.1 Troubleshooting 17
9.2 Maintenance 17
9.2.1 Cleaning 18
9.2.2 Changing the probe filter 18
Table of Contents - i

10. References 19
Appendix A. Importing Short Cut code into CRBasic Editor 21
Appendix B. RS-485 output 22
B.1 SDM-SIO1A or SDM-SIO4A serial I/O module interface option 22
B.2 MD485 interface option 23
B.2.1 MD485 multidrop interface configuration 27
B.3 Numeric display 29
Table of Contents - ii

1. Introduction
The HMP155A probe monitors relative humidity (RH) for the range of 0 to 100% RH and
temperature for the range of –80 to 60°C. It provides reliable measurements for a wide range of
applications as part of a weather station system or as a single instrument. All Campbell Scientific
data loggers are compatible.
NOTE:
This manual provides information only for CRBasic data loggers. For retired Edlog data logger
support, see an older manual at www.campbellsci.com/old-manuals .
2. Precautions
lREAD AND UNDERSTAND the Safety section at the back of this manual.
lCare should be taken when opening the shipping package to not damage or cut the cable
jacket. If damage to the cable is suspected, contact Campbell Scientific.
lAlthough the HMP155A is rugged, it should be handled as a precision scientific instrument.
lDo not touch the sensor element.
lSantoprene® rubber, which composes the black outer jacket of the cable, will support
combustion in air. It is used because of its resistance to temperature extremes, moisture,
and UV degradation. It is rated as slow burning when tested according to U.L. 94 H.B. and
passes FMVSS302. However, local fire codes may preclude its use inside buildings.
3. Initial inspection
lUpon receipt of the HMP155A, inspect the packaging and contents for damage. File
damage claims with the shipping company.
lThe model number and cable length are printed on a label at the connection end of the
cable. Check this information against the shipping documents to ensure the expected
product and cable length were received.
HMP155A Temperature and Relative Humidity Probe 1

4. QuickStart
A video that describes data logger programming using Short Cut is available at:
www.campbellsci.com/videos/cr1000x-data logger-getting-started-program-part-3 .Short
Cut is an easy way to program your data logger to measure the sensor and assign data logger
wiring terminals. Short Cut is available as a download on www.campbellsci.com . It is included
in installations of LoggerNet,RTDAQ, and PC400.
The following procedure also shows using Short Cut to program the HMP155A.
1. Open Short Cut and click Create New Program.
2. Double-click the data logger model.
3. In the Available Sensors and Devices box, type HMP155A or locate the sensor in the
Sensors >Meteorological >Relative Humidity & Temperature >HMP155 Temperature and
Relative Humidity Sensor folder. Double-click either HMP155 (constant power) or HMP155
(panel switched power); the panel switched power option uses less current but requires a
scan rate that is greater than 5 seconds. Data defaults to degree Celsius. This can be
changed by clicking the Deg C box and selecting Deg F, for degrees Fahrenheit, or Kfor
Kelvin.
HMP155A Temperature and Relative Humidity Probe 2

4. Click the Wiring tab to see how the sensor is to be wired to the data logger. Click OK after
wiring the sensor.
5. Repeat steps three and four for other sensors.
6. In Output Setup, type the scan rate, meaningful table names, and Data Output Storage
Interval.
NOTE:
The HMP155A has a five second settling time after power up; therefore the scan rate
must be greater than five seconds when using the panel switched power option.
HMP155A Temperature and Relative Humidity Probe 3

7. Select the measurement and its associated output option.
8. Click Finish and save the program. Send the program to the data logger if the data logger
is connected to the computer.
9. If the sensor is connected to the data logger, check the output of the sensor in the data
display in LoggerNet,RTDAQ, or PC400 to make sure it is making reasonable
measurements.
5. Overview
The HMP155A Temperature and Relative Humidity probe contains a platinum resistance
temperature detector (PRT) and a Vaisala HUMICAP®180 capacitive relative humidity sensor.
The HMP155A outputs a 0 to 1VDC signal for temperature and relative humidity that can be
measured by all models of Campbell Scientific data loggers with model HMP155ACBL1 cable. The
HMP155A also has RS-485 outputs for temperature and relative humidity that can be directly
interfaced to the CR6 and CR1000X data logger using the HMP155ACBL2 cable. The RS-485
output can also be used with our CR800, CR850, CR3000, and CR1000 data loggers, but they
require both the HMP155ACBL2 cable and the SDM-SIO1A or SDM-SIO4A Serial I/O Module
(RS-485 output (p. 22)). The RS-485 output has a higher current drain than that listed in the
specifications.
The HMP155A can be powered continuously, or the power may be switched to conserve battery
life. The HMP155A consumes less than 3 milliamps current at 12VDC. Approximately 2 seconds is
required for the sensor to warm up after power is switched on. At measurement rates slower than
once per 5 seconds, the overall power consumption (data logger and sensors) may be reduced
HMP155A Temperature and Relative Humidity Probe 4

by switching power to the HMP155A. Current Campbell Scientific data loggers have a built-in
switched 12VDC that can be used to control power.
NOTE:
HMP155A sensors purchased directly from Vaisala with serial numbers < E4430001 require
approximately 5 seconds warm up time.
Features:
lWell-suited for long-term, unattended applications
lAccurate and rugged
lCompatible with the following data loggers: CR6, CR1000X, CR800-series, CR300-series,
CR3000, CR1000
6. Specifications
Dimensions in mm [inches]
FIGURE 6-1. Probe dimensions
HMP155A Temperature and Relative Humidity Probe 5

8-Pin Connector
FIGURE 6-2. Wiring of HMP155A 8-pin connector
*HMP155ACBL1 Cable provided by Campbell Scientific
1 = VOUT1 (yellow, temp)
2 = no connection
3 = AGND (white)
4 = VOUT2 (blue, RH)
5 = no connection
6 = no connection
7 = VCC (red)
8 = GND (black)
– = SHIELD (clear)
*Note: HMP155ACBL2 for RS-485 is described in
RS-485 output (p. 22).
Operating temperature range for
humidity measurement: –80 to 60 °C (–112 to 140 °F)
Storage temperature range: –80° to 60 °C (–112 to 140 °F)
Electromagnetic compatibility: Complies with EMC standard EN61326-1, Electrical
equipment for measurement control and laboratory use
- EMC requirements for use in industrial locations
Filter: Sintered PTFE
Housing material: PC
Housing classification: IP66
HMP155A Temperature and Relative Humidity Probe 6

Weight: 86 g (3 oz)
Voltage outputs: 0 to 1 VDC
Average current consumption: <3 mA (analog output mode)
Operating voltage: 7 to 28 VDC
Settling time at power-up: 2 s
6.1 Temperature sensor
Measurement range: –80 to 60 °C (–112 to 140 °F)
Accuracy with voltage output
at –80 to 20 °C: ±(0.226 – 0.0028 x temperature) °C
at 20 to 60 °C: ±(0.055 + 0.0057 x temperature) °C
See the following graph:
Temperature sensor: Pt 100 RTD 1/3 Class B IEC 751
Response time (63 %) for additional
temperature probe in 3m/s air flow: 63% <20 s
90% <35 s
HMP155A Temperature and Relative Humidity Probe 7