Campbell Scientific HMP45C User Manual
Model HMP45C Temperature
and Relative Humidity Probe
Revision: 3/09
Copyright © 1990-2009
Campbell Scientific, Inc.
Warranty and Assistance
The MODEL HMP45C TEMPERATURE AND RELATIVE HUMIDITY
PROBE is warranted by CAMPBELL SCIENTIFIC, INC. to be free from
defects in materials and workmanship under normal use and service for twelve
(12) months from date of shipment unless specified otherwise. Batteries have
no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this
warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC,
INC.'s option) defective products. The customer shall assume all costs of
removing, reinstalling, and shipping defective products to CAMPBELL
SCIENTIFIC, INC. CAMPBELL SCIENTIFIC, INC. will return such
products by surface carrier prepaid. This warranty shall not apply to any
CAMPBELL SCIENTIFIC, INC. products which have been subjected to
modification, misuse, neglect, accidents of nature, or shipping damage. This
warranty is in lieu of all other warranties, expressed or implied, including
warranties of merchantability or fitness for a particular purpose. CAMPBELL
SCIENTIFIC, INC. is not liable for special, indirect, incidental, or
consequential damages.
Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone (435) 753-2342. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784
CAMPBELL SCIENTIFIC, INC. does not accept collect calls.
HMP45C Table of Contents
PDF viewers note: These page numbers refer to the printed version of this document. Use
the Adobe Acrobat® bookmarks tab for links to specific sections.
1. General Description.....................................................1
2. Specifications ..............................................................2
2.1 Temperature Sensor..................................................................................2
2.2 Relative Humidity Sensor .........................................................................2
3. Installation....................................................................3
3.1 Siting.........................................................................................................3
3.2 Assembly and Mounting...........................................................................3
4. Wiring............................................................................5
5. Example Programs......................................................6
6. Long Lead Lengths......................................................9
7. Absolute Humidity.....................................................12
8. Sensor Maintenance..................................................15
9. Troubleshooting ........................................................16
10. References ...............................................................16
Appendix
A. Wiring for Older HMP45C Probes..........................A-1
Figures
3-1. HMP45C and 41003-5 Radiation Shield on a Tripod Mast....................4
3-2. HMP45C and 41003-5 Radiation Shield on a CM200 Series Crossarm.4
A-1. HMP45C Probe to Datalogger Connections...................................... A-1
i
HMP45C Table of Contents
Tables
1-1. Recommended Lead Lengths ................................................................. 1
4-1. Connections for Single-Ended Measurements........................................ 5
4-2. Connections for Differential Measurements........................................... 6
4-3. Power Connections using SW12V Peripherals....................................... 6
5-1. Calibration for Temperature................................................................... 7
5-2. Calibration for Relative Humidity.......................................................... 7
5-3. Wiring for Single-ended Measurement Examples.................................. 7
6-1. Wiring for Differential Measurement Examples.................................. 10
7-1. Wiring for Vapor Pressure Examples................................................... 13
8-1. Chemical Tolerances of HMP45C ........................................................ 16
A-1. Connections for Single-Ended Measurements for Old Wiring
Configuration...................................................................................... A-1
A-2. Connections for Differential Measurements for Old Wiring
Configurations ....................................................................................A-2
ii
Model HMP45C Temperature and Relative Humidity Probe
1. General Description
NOTE
The HMP45C Temperature and Relative Humidity probe contains a Platinum
Resistance Temperature detector (PRT) and a Vaisala HUMICAP
capacitive relative humidity sensor.
The -L option on the model HMP45C Temperature and Relative Humidity
probe (HMP45C-L) indicates that the cable length is user specified. This
manual refers to the sensor as the HMP45C.
The HMP45C can be powered continuously or the power may be switched to
conserve battery life. The HMP45C consumes less than 4 milliamperes current
at 12 volts. Approximately 0.15 seconds is required for the sensor to warm up
after power is switched on. At measurement rates slower than once per
second, the overall power consumption (datalogger and sensors) may be
reduced by switching power to the HMP45C. Most current Campbell
Scientific dataloggers have a built-in switched 12 volts that can be used to
control power.
The CR9000, CR510, CR500, CR7, CR10 and 21X dataloggers do not have a
built-in switched 12 volts. Users with these dataloggers can power the sensor
continuously or purchase the model SW12V to switch power.
Prior to April 2004, the HMP45C included a power switching
circuit in the cable. The in-cable switching circuit was
discontinued because in most cases it is no longer necessary and
it made the cable difficult to route through the entry port on
environmental enclosures.
®
180
Lead length for the HMP45C is specified when the sensor is ordered. Table
1-1 gives the recommended lead lengths.
TABLE 1-1. Recommended Lead Lengths
2 m Height Atop a tripod or tower via a 2 ft crossarm such as the CM202
Mast/Leg CM202 CM6 CM10 CM110 CM115 CM120 UT10 UT20 UT30
9' 11' 11' 14' 14' 19' 24' 14' 24' 37'
Note: Add two feet to the cable length if you are mounting the enclosure on the leg base of a light-weight tripod.
The HMP45C ships with:
(1) Adjustment Screwdriver from mfg
(1) Calibration Sheet
(1) Resource CD
1
Model HMP45C Temperature and Relative Humidity Probe
2. Specifications
Operating Temperature: -40°C to +60°C
Storage Temperature: -40°C to +80°C
Probe Length: 25.4 cm (10 in.)
Probe Body Diameter: 2.5 cm (1 in.)
Filter: 0.2 μm Teflon membrane
Filter Diameter: 1.9 cm (0.75 in.)
Power Consumption: <4 mA @ 12 V
Supply Voltage: 7 to 35 VDC
Settling Time: 0.15 seconds
2.1 Temperature Sensor
Sensor: 1000 Ω PRT, IEC 751 1/3 Class B
Temperature Measurement Range: -40°C to +60°C
Temperature Output Signal range: 0.008 to 1.0 V
Temperature Accuracy:
0.4
0.2
o
0.0
-0.2
Error( C)
-0.4
-40 -20
0 20 40 60
Temperature ( C)
o
2.2 Relative Humidity Sensor
Sensor: HUMICAP® 180
Relative Humidity Measurement Range: 0 to 100% non-condensing
RH Output Signal Range: 0.008 to 1 VDC
Accuracy at 20°C
±2% RH (0 to 90% Relative Humidity)
±3% RH (90 to 100% Relative Humidity)
Temperature Dependence of Relative Humidity Measurement: ±0.05% RH/°C
Typical Long Term Stability: Better than 1% RH per year
Response Time (at 20°C, 90% response): 15 seconds with membrane filter
NOTE
The black outer jacket of the cable is Santoprene
compound was chosen for its resistance to temperature extremes,
moisture, and UV degradation. However, this jacket will
support combustion in air. It is rated as slow burning when
tested according to U.L. 94 H.B. and will pass FMVSS302.
Local fire codes may preclude its use inside buildings.
®
rubber. This
2
3. Installation
3.1 Siting
Model HMP45C Temperature and Relative Humidity Probe
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 where grass does
not grow, the natural earth surface. 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 +/- 1.0 m (AASC)
1.25 – 2.0 m (WMO)
2.0 m (EPA)
2.0 m and 10.0 m temperature difference (EPA)
See Section 10 for a list of references that discuss temperature and relative
humidity sensors.
3.2 Assembly and Mounting
Tools Required:
• 1/2” open end wrench
• small screw driver provided with datalogger
• UV resistant cable ties
• small pair of diagonal-cutting pliers
The HMP45C must be housed inside a radiation shield when used in the field.
The 41003-5 Radiation shield has a U-bolt for attaching the shield to tripod
mast / tower leg (Figure 3-1), or CM200 series crossarm (Figure 3-2). The
radiation shield ships with the U-bolt configured for attaching the shield to a
vertical pipe. Move the U-bolt to the other set of holes to attach the shield it to
a crossarm.
Loosen the split-nut on the bottom plate of the 41003-5. Remove the yellow
protective cap on the HMP45C, and insert the sensor into the shield. Tighten
the split-nut to secure the sensor in the shield. Route the sen s or cable to the
instrument enclosure. Secure the cable to the tripod/tower using cable ties.
The HMP45C must be housed inside a radiation shield when used in the field.
The 41003-5 Radiation Shield (Figure 3-1 and 3-2) mounts to a tripod mast,
tower leg, or CM200 series crossarm.
3
Model HMP45C Temperature and Relative Humidity Probe
41003-5
Split Nut
U-bolt
FIGURE 3-1. HMP45C and 41003-5 Radiation Shield on a Tripod Mast
CM200 Series Crossarm
4
FIGURE 3-2. HMP45C and 41003-5 Radiation Shield
on a CM200 Series Crossarm
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