Campbell HMP60 User manual

Revision: 10/2021
Copyright © 1995 – 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 5
6.2 Relative humidity sensor 5
7. Installation 6
7.1 Wiring to data logger 6
7.2 Data logger programming 7
7.2.1 VoltSE() instruction 7
7.3 Mounting 8
7.3.1 Installation in a 41303-5A or 41303-5B 6-plate shield 9
7.3.2 Installation in a RAD06 6-plate shield or RAD10 10-plate shield 10
7.3.3 Mount the shield 10
8. Operation 11
8.1 Measurement 11
8.2 Long cable lengths 11
8.3 Absolute humidity 12
9. Troubleshooting and maintenance 13
9.1 Troubleshooting 13
9.2 Maintenance 13
9.2.1 Procedure for removing RH chip 14
10. Attributions and References 15
Appendix A. Importing Short Cut code into CRBasic Editor 16
Appendix B. Example programs 17
Table of contents - i

1. Introduction
The HMP60 probe measures temperature for the range of –40 to 60°C, and relative humidity for
the range of 0 to 100% RH. It is suitable for long-term, unattended monitoring, and is compatible
with all Campbell Scientific data loggers.
For Edlog data logger support, check the availability of 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 HMP60 is rugged, it should be handled as a precision scientific instrument.
lDo not touch the sensor element.
lRemove the yellow cap prior to installation.
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 HMP60, 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.
HMP60 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.
Use the following procedure to get started.
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 HMP60 or locate the sensor in the Sensors >
Meteorological >Relative Humidity & Temperature >HMP50/HMP60 Temperature &
Relativite Humidity folder. Double-click HMP50/HMP60 Temperature & Relative Humidity
Sensor. 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.
HMP60 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.
HMP60 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 HMP60 Temperature and Relative Humidity probe contains a Platinum Resistance
Temperature detector (PRT) and a Vaisala INTERCAP® capacitive relative humidity sensor. It is
suitable for long-term, unattended monitoring. The humidity chip is field-replaceable,
eliminating recalibration downtime.
Features:
lField-replaceable humidity chip eliminates recalibration down time
lCompatible with the following data loggers: CR6, CR1000X, CR800 series, CR350 series,
CR300 series, CR3000, CR1000
HMP60 Temperature and Relative Humidity Probe 4

6. Specifications
Operating temperature: –40 to 60 °C
Probe length: 7.1 cm (2.8 in)
Probe body diameter: 1.2 cm (0.47 in)
Filter: 0.2 μm Teflon membrane
Filter diameter: 1.2 cm (0.47 in)
Housing
Body material: AISI 316 stainless steel
Filter cap material: Chrome-coated ABS plastic
Classification: IP65
Power consumption: 1 mA typical; 5 mA maximum
Supply voltage: 5 to 28 VDC
Settling time after power is
switched on: 1 s
Output signal range: 0 to 1 VDC
6.1 Temperature sensor
Sensor: 1000 Ω PRT, DIN 43760B
Temperature
measurement range: –40 to 60 °C
Temperature accuracy: ±0.6 °C (–40 to 60 °C)
6.2 Relative humidity sensor
Sensor: INTERCAP®
Relative humidity
measurement range: 0 to 100% non-condensing
HMP60 Temperature and Relative Humidity Probe 5

Typical accuracy
from 0 to 40 °C: ±3% RH over 0 to 90%
±5% RH over 90 to 100%
Typical Accuracy
from –40 to 0 °C
and 40 to 60 °C: ±5% RH over 0 to 90%
±7% RH over 90 to 100%
7. Installation
If you are programming your data logger with Short Cut, skip Wiring to data logger (p. 6) and
Data logger programming (p. 7). Short Cut does this work for you. See QuickStart (p. 2) for a
Short Cut tutorial.
7.1 Wiring to data logger
CAUTION:
Always connect the blue wire to the data logger first, followed by the black, white, and clear
wires. Connect the brown (power) wire last.
Table 7-1: Wire color, function, and data logger connection
Wire color Wire function Data logger connection terminal
Black Temperature signal Uconfigured for single-ended analog input1,
SE (single-ended, analog-voltage input)
White Relative humidity signal Uconfigured for single-ended analog input,
SE
Blue Power ground and
signal reference G
Brown Power 12V or SW12
Clear EMF Shield ⏚(analog ground)
1Uterminals are automatically configured by the measurement instruction.
HMP60 Temperature and Relative Humidity Probe 6

7.2 Data logger programming
Short Cut is the best source for up-to-date programming code for Campbell Scientific data
loggers. If your data acquisition requirements are simple, you can probably create and maintain a
data logger program exclusively with Short Cut. If your data acquisition needs are more complex,
the files that Short Cut creates are a great source for programming code to start a new program
or add to an existing custom program.
NOTE:
Short Cut cannot edit programs after they are imported and edited in CRBasic Editor.
AShort Cut tutorial is available in QuickStart (p. 2). If you wish to import Short Cut code into
CRBasic Editor to create or add to a customized program, follow the procedure in Importing
Short Cut code into CRBasic Editor (p. 16). Programming basics for CRBasic data loggers are
provided in the following sections. Complete program examples for select data loggers can be
found in Example programs (p. 17).
Measure the HMP60 with either the VoltSE() or VoltDiff() measurement instruction as
described in the following sections.
For a discussion on errors caused by long cable lengths, see Long cable lengths (p. 11).
7.2.1 VoltSE() instruction
When cable lengths are shorter than 6.1 meters or when power is switched, use the VoltSE()
measurement instruction to measure the temperature and relative humidity. The HMP60 output
scale is 0 to 1000 millivolts for the temperature range of –40 to 60°C and for the relative humidity
range of 0 to 100%.
VoltSE(Dest, Reps, Range, SEChan, MeasOff, SettlingTime, Integ/FNotch, Mult, Offset)
Variations:
lTemperature reported as °C – set Mult to 0.1 and Offset to –40
lTemperature reported as °F – set Mult to .18 and Offset to –40
lHumidity reported as a percent – set Mult to 0.1 and Offset to 0
lHumidity reported as a fraction – set Mult to 0.001 and Offset to 0
HMP60 Temperature and Relative Humidity Probe 7

NOTE:
When the probe is connected to a CS110 Electric Field Meter, the probe is measured by the
CS110 internal CR1000 data logger module using VoltSE() instructions. Relative humidity
and temperature signals are measured on single-ended terminals 1 and 2, respectively.
250µs integration should be used in the VoltSE() instructions.
7.3 Mounting
Sensors should be located over an open level area at least 9m (EPA) in diameter. The surface
should be covered by short grass or the natural earth surface where grass does not grow.
Sensors should be located at a distance of at least four times the height of any nearby
obstruction, and at least 30m (EPA) from large, paved areas. Sensors should be protected from
thermal radiation, and adequately ventilated.
Standard measurement heights:
1.5 m (AASC)
1.25 to 2.0 m (WMO)
2.0 m (EPA)
See Attributions and References (p. 15) for a list of references that discuss temperature and
relative humidity sensors.
When used in the field, the HMP60 must be housed inside a solar radiation shield. Typically, the
41303-5A or RAD06 6-plate solar radiation shield is used. The HMP60 is held within the 41303-5A
by a mounting clamp (FIGURE 7-2 (p. 9)).
This probe may also be housed in a 41003-5 or RAD10 10-plate shield. Additional hardware must
be used with the 41003-5. No additional hardware is required with the RAD10. A 10-plate shield
adapter allows the HMP60 to be mounted in the lower part of the 41003-5 shield.
The white color of these shields reflects solar radiation, and the louvered construction allows air
to pass freely through, thereby keeping the probe at or near ambient temperature. The RAD06
and RAD10 use a double-louvered design that offers improved sensor protection from insect
intrusion and driving rain and snow. In addition, the RAD06 and RAD10 shields have lower self-
heating in bright sunlight combined with higher temperatures (>24°C (75°F)) and low wind
speeds (<2m/s (4.5mph)), giving a better measurement.
Each of these solar radiation shields attaches to a crossarm, mast, or user-supplied pipe with a 2.5
to 5.3cm (1.0 to 2.1in) outer diameter.
HMP60 Temperature and Relative Humidity Probe 8

Tools required:
l1/2 inch open-end wrench
lsmall screwdriver provided with data logger
lUV-resistant cable ties
lsmall pair of diagonal-cutting pliers
lAdjustable wrench with a minimum 1-7/8 inch jaw size
FIGURE 7-1. HMP60 as shipped
7.3.1 Installation in a 41303-5A or 41303-5B 6-plate shield
1. Pull off the yellow shipping cap (see FIGURE 7-1 (p. 9)).
2. With a small Phillips screwdriver, loosen the plastic split collar at the base of the shield
(reversing the removable portion if necessary) and gently insert the probe.
3. Tighten the screws on the collar until it firmly grips the probe body (see FIGURE 7-2 (p. 9)).
FIGURE 7-2. HMP60 and 41303-5A Radiation Shield
HMP60 Temperature and Relative Humidity Probe 9

7.3.2 Installation in a RAD06 6-plate shield or RAD10
10-plate shield
1. Pull off the yellow shipping cap (see FIGURE 7-1 (p. 9)).
2. Loosen the nut on the entry gland at the bottom of the shield.
3. Insert the sensor up into the gland as far as it will go (see FIGURE 7-4 (p. 11)).
4. Using an adjustable wrench, tighten down the nut on the gland until the sensor is held
firmly in place. Do not overtighten.
7.3.3 Mount the shield
1. Attach the radiation shield to the tripod mast, crossarm, or tower leg using the supplied
U-bolt. See FIGURE 7-3 (p. 10) and FIGURE 7-4 (p. 11) for examples of shield mounting.
2. Route the cable to the data logger, and secure the cable to the mounting structure using
cable ties.
CAUTION:
Failure to secure the cable can lead to breakage of the wires due to fatigue caused by
blowing back and forth in the wind.
FIGURE 7-3. HMP60 and 41303-5A Radiation Shield
on a tripod mast (left) and on a CM202 Crossarm (right)
HMP60 Temperature and Relative Humidity Probe 10

FIGURE 7-4. HMP60 and RAD06 Radiation Shield on a tripod mast
8. Operation
8.1 Measurement
The HMP60 Temperature and Relative Humidity Probe uses a Platinum Resistance Temperature
detector (PRT) and a Vaisala INTERCAP® capacitive relative humidity sensor.
8.2 Long cable lengths
Long cable lengths cause errors in the measured temperature and relative humidity. The
approximate error in temperature and relative humidity is 0.52°C and 0.52% per 100 feet of cable
length, respectively.
When long cable lengths are required and the above errors in temperature and relative humidity
are unacceptable, use the EE181 or HMP155A temperature and relative humidity probe instead.
Understanding the following details are not required for the general operation of the HMP60
with Campbell Scientific data loggers. The signal reference and the power ground (black) are the
same wire in the HMP60. When the HMP60 temperature and relative humidity are measured,
both the signal reference and power ground are connected to ground at the data logger. The
signal reference/power ground wire serves as the return path for 12V. There will be a voltage
drop along this wire because the wire has resistance. The HMP60 draws approximately 2mA
(worst case) when it is powered. The wire used in the HMP60 has resistance of 26.2Ω/1000 feet.
HMP60 Temperature and Relative Humidity Probe 11

Using Ohm’s law, the voltage drop (Vd), along the signal reference/power ground wire, is given
by Eq. 1 (p. 12).
Eq. 1
This voltage drop will raise the apparent temperature and relative humidity because the
difference between the signal and signal reference at the data logger has increased by Vd.
8.3 Absolute humidity
The HMP60 measures relative humidity. Relative humidity is defined by the following equation:
Eq. 2
where RH is the relative humidity, e is the vapor pressure in kPa, and esis the saturation vapor
pressure in kPa. The vapor pressure, e, is an absolute measure of the amount of water vapor in
the air and is related to the dewpoint temperature. The saturation vapor pressure is the
maximum amount of water vapor that air can hold at a given air temperature. The relationship
between dewpoint and vapor pressure, and air temperature and saturation vapor pressure are
given by Goff and Gratch (1946), Lowe (1977), and Weiss (1977).
When the air temperature increases, so does the saturation vapor pressure. Conversely, a
decrease in air temperature causes a corresponding decrease in saturation vapor pressure. It
follows then from Eq. 2 (p. 12) that a change in air temperature will change the relative humidity,
without causing a change absolute humidity.
For example, for an air temperature of 20°C and a vapor pressure of 1.17kPa, the saturation
vapor pressure is 2.34kPa and the relative humidity is 50%. If the air temperature is increased by
5°C and no moisture is added or removed from the air, the saturation vapor pressure increases
to 3.17kPa and the relative humidity decreases to 36.9%. After the increase in air temperature,
the air can hold more water vapor. However, the actual amount of water vapor in the air has not
changed. Thus, the amount of water vapor in the air, relative to saturation, has decreased.
Because of the inverse relationship between relative humidity and air temperature, finding the
mean relative humidity is meaningless. A more useful quantity is the mean vapor pressure. The
mean vapor pressure can be computed online by the data logger. CRBasic data loggers use the
VaporPressure() instruction to calculate vapor pressure from temperature and relative
humidity measurements (see CRBasic Example 2 (p. 18)).
HMP60 Temperature and Relative Humidity Probe 12

9. Troubleshooting and
maintenance
NOTE:
All factory repairs and recalibrations require a returned materials authorization (RMA) and
completion of the “Declaration of Hazardous Material and Decontamination” form. Refer to
the Assistance page at the end of this manual for more information.
9.1 Troubleshooting
Symptom: Relative Humidity is reported as –9999, NAN, or 0%
1. Check that the sensor is wired to the correct analog input terminals as specified by the
measurement instructions.
2. Verify the range code for the single-ended measurement instruction is correct for the data
logger type.
Symptom: Incorrect temperature or relative humidity
1. Verify the multiplier and offset parameters are correct for the desired units (VoltSE()
instruction (p. 7)).
9.2 Maintenance
Check the radiation shield monthly to make sure it is free from dust and debris. To clean the
shield, first remove the sensor. Dismount the shield. Brush all loose dirt off. If more effort is
needed, use warm, soapy water and a soft cloth or brush to thoroughly clean the shield. Allow
the shield to dry before remounting.
The white screen at the tip of the HMP60 should also be checked for contaminants.
When installed in close proximity to the ocean or other bodies of salt water (e.g., Great Salt Lake),
a coating of salt (mostly NaCl) may build up on the radiation shield, sensor, filter and even the
chip. NaCl has an affinity for water. The humidity over a saturated NaCl solution is 75%. A buildup
of salt on the filter or chip will delay or destroy the response to atmospheric humidity.
HMP60 Temperature and Relative Humidity Probe 13

The filter can be rinsed gently in distilled water. If necessary, the chip can be removed and rinsed
as well (see FIGURE 9-1 (p. 14) and Procedure for removing RH chip (p. 14)). Do not scratch the
silver chip while cleaning. It might be necessary to repeat rinsing.
FIGURE 9-1. Exploded view of HMP60 (as shipped)
The offset and gain on the HMP60 electronics cannot be adjusted as part of a recalibration.
Generally, the RH chip should be replaced every two years. To determine if the chip needs to be
replaced, compare the RH reading with a reference, and replace the RH chip when the relative
humidity measurement is out of tolerance.
9.2.1 Procedure for removing RH chip
1. Unscrew the protective cap.
2. Hold the plastic sides of the RH chip and unplug it.
CAUTION:
To prevent scratching, avoid touching the silver RH chip, and handle the RH chip with
care.
3. Rinse the RH chip or dispose of the old RH chip.
4. Hold the sides of the rinsed or new chip and plug it in.
5. Screw on the protective cap.
HMP60 Temperature and Relative Humidity Probe 14

10. Attributions and References
Santoprene®is a registered trademark of Exxon Mobile Corporation.
AASC, 1985: The State Climatologist (1985) Publication of the American Association of State
Climatologists: Heights and Exposure Standards for Sensors on Automated Weather Stations,
v. 9, No. 4 October, 1985. (www.stateclimate.org/publications/state-climatologist/NOAA-
NCY-SCBOOKS-SC77097/00000029.pdf)
EPA, 2008: Quality Assurance Handbook for Air Pollution Measurement Systems, Vol. IV,
Meteorological Measurements, Ver. 2.0, EPA-454/B-08-002 (revised 2008). Office of Air
Quality Planning and Standards, Research Triangle Park, NC 27711.
Goff, J. A. and S. Gratch, 1946: Low-pressure properties of water from -160° to 212°F, Trans. Amer.
Soc. Heat. Vent. Eng.,51, 125-164.
Lowe, P. R., 1977: An approximating polynomial for the computation of saturation vapor pressure,
J. Appl. Meteor.,16, 100-103.
Meyer, S. J. and K. G. Hubbard, 1992: Nonfederal Automated Weather Stations and Networks in
the United States and Canada: A Preliminary Survey, Bulletin Am. Meteor. Soc.,73, No. 4,
449-457.
Weiss, A., 1977: Algorithms for the calculation of moist air properties on a hand calculator, Amer.
Soc. Ag. Eng.,20, 1133-1136.
WMO, 2008. Guide to Meteorological Instruments and Methods of Observation. World
Meteorological Organization No. 8, 7th edition, Geneva, Switzerland.
HMP60 Temperature and Relative Humidity Probe 15

Appendix A. Importing Short
Cut code into CRBasic Editor
Short Cut creates a .DEF file that contains wiring information and a program file that can be
imported into the CRBasic Editor. By default, these files reside in the C:\campbellsci\SCWin folder.
Import Short Cut program file and wiring information into CRBasic Editor:
1. Create the Short Cut program. After saving the Short Cut program, click the Advanced tab
then the CRBasic Editor button. A program file with a generic name will open in CRBasic.
Provide a meaningful name and save the CRBasic program. This program can now be
edited for additional refinement.
NOTE:
Once the file is edited with CRBasic Editor,Short Cut can no longer be used to edit the
program it created.
2. To add the Short Cut wiring information into the new CRBasic program, open the .DEF file
located in the C:\campbellsci\SCWin folder, and copy the wiring information, which is at
the beginning of the .DEF file.
3. Go into the CRBasic program and paste the wiring information into it.
4. In the CRBasic program, highlight the wiring information, right-click, and select Comment
Block. This adds an apostrophe (') to the beginning of each of the highlighted lines, which
instructs the data logger compiler to ignore those lines when compiling. The Comment
Block feature is demonstrated at about 5:10 in the CRBasic | Features video .
HMP60 Temperature and Relative Humidity Probe 16

Appendix B. Example programs
The following CR1000X program uses the switched 12 V terminal to switch power on only during
measurement, reducing power consumption. Other data loggers are programmed similarly.
CRBasic Example 1: Temperature and RH program
'Program measures the HMP60 probe once every 5 seconds and stores the average
'temperature and a sample of the relative humidity every 60 minutes.
'Wiring Diagram
'==============
'HMP60
'Wire
'ColorFunctionTerminal
'----------------------
'BlackTemperature signalSE1
'WhiteRelative Humidity signalSE2
'BrownPowerSW12_1
'BlueSignal & Power ReferenceG
'ClearShieldGround Symbol
Public AirTC
Public RH
DataTable(Temp_RH,True,-1)
DataInterval(0,60,Min,0)
Average(1,AirTC,FP2,False)
Sample(1,RH,FP2)
EndTable
BeginProg
Scan(5,Sec,1,0)
SW12 (SW12_1,1 ) 'Turn on switched 12V
Delay(0,3,Sec) '3-second delay
'HMP50/HMP60 Temperature & Relative Humidity Sensor measurements AirTC and RH
VoltSe(AirTC,1,mV1000,1,0,0,60,0.1,-40)
VoltSe(RH,1,mV1000,2,0,0,60,0.1,0)
If RH>100 AND RH<108 Then RH=100
SW12 (SW12_1,0)
CallTable(Temp_RH)
NextScan
EndProg
HMP60 Temperature and Relative Humidity Probe 17

The VaporPressure() instruction has the following syntax:
VaporPressure(Dest,Temp,RH)
Where:
Dest is the variable in which the results of the instruction will be stored.
Temp is the program variable that contains the value for the temperature sensor. The
temperature measurement must be in degrees Celsius.
RH is the program variable that contains the value for the relative humidity sensor. The relative
humidity measurement must be in percent of RH.
CRBasic Example 2: Vapor pressure program
'Wiring Diagram
'==============
'HMP60
'Wire
'ColorFunctionTerminal
'----------------------
'BlackTemperature signalSE1
'WhiteRelative Humidity signalSE2
'BrownPower12V
'BlueSignal & Power ReferenceG
'ClearShieldGround Symbol
Public AirTC
Public RH
Public VP
DataTable(Temp_RH,True,-1)
DataInterval(0,60,Min,0)
Average(1,AirTC,FP2,0)
Sample(1,RH,FP2)
Average(1,VP, FP2,0)
EndTable
BeginProg
Scan(5,Sec,1,0)
'HMP60 Temperature & Relative Humidity Sensor measurements AirTC and RH:
VoltSe(AirTC,1,mV1000,1,0,0,60,0.1,-40.0)
VoltSe(RH,1,mV1000,2,0,0,60,0.1,0)
If (RH>100) AND (RH<108) Then RH=100
VaporPressure(VP,AirTC,RH)
CallTable(Temp_RH)
NextScan
EndProg
HMP60 Temperature and Relative Humidity Probe 18