Model HMP45C Temperature and Relative Humidity Probe Revision: 3/09 C o p y r i g h t © 1 9 9 0 - 2 0 0 9 C a m p b e l l S c i e n t i f i c , I n c .
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.
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.......................................
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.
Model HMP45C Temperature and Relative Humidity Probe 1. General Description The HMP45C Temperature and Relative Humidity probe contains a Platinum Resistance Temperature detector (PRT) and a Vaisala HUMICAP® 180 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.
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.
Model HMP45C Temperature and Relative Humidity Probe 3. Installation 3.1 Siting 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.
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 FIGURE 3-2.
Model HMP45C Temperature and Relative Humidity Probe 4. Wiring Connections to Campbell Scientific dataloggers are given in Tables 4-1 through 4-3. The probe can be measured by two single-ended or differential analog input channels. CAUTION When measuring the HMP45C with single-ended measurements, the purple or white and black leads must both be connected to AG on the CR10(X) and on the CR1000, CR5000, and CR500/CR510 or to CR23X.
Model HMP45C Temperature and Relative Humidity Probe TABLE 4-2.
Model HMP45C Temperature and Relative Humidity Probe The temperature and relative humidity signals from the HMP45C can be measured using a single-ended analog measurement or a differential analog measurement. Use a single-ended analog measurement when the HMP45C signal lead length is less than 6.1 m (20 ft.) or if the probe will be turned on and off under datalogger control between measurements. For lead lengths greater than 6.1 m (20 ft.
Model HMP45C Temperature and Relative Humidity Probe CR1000 Program using Single-Ended Measurement Instructions Using SW12V on Datalogger 'CR1000 program to measure HMP45C with single-ended measurements Public AirTC Public RH DataTable(Temp_RH,True,-1) DataInterval(0,60,Min,0) Average(1,AirTC,IEEE4,0) Sample(1,RH,IEEE4) EndTable BeginProg Scan(1,Sec,1,0) 'HMP45C Temperature & Relative Humidity Sensor measurements AirTC and RH: SW12 (1 ) Delay(0,150,mSec) VoltSE(AirTC,1,mV2500,2,0,0,_60Hz,0.1,-40.
Model HMP45C Temperature and Relative Humidity Probe ;Measure the HMP45C temperature. ; 03: Volt (SE) (P1) 1: 1 Reps 2: 5 2500 mV Slow Range 3: 4: 5: 6: 3 1 .1 -40 SE Channel Loc [ T_C Mult Offset ] ;See Table 5-1 for alternative multipliers ;See Table 5-1 for alternative offsets ;Measure the HMP45C relative humidity. ; 04: Volt (SE) (P1) 1: 1 Reps 2: 5 2500 mV Slow Range 3: 4: 5: 6: 4 2 .
Model HMP45C Temperature and Relative Humidity Probe Ω/1000 feet, or 13.9 Ω/1000 feet. Using Ohm’s law, the voltage drop (Vd), along the signal reference/power ground, is given by Eq. (1). Vd = I ∗R = 4 mA ∗ 13.9 Ω 1000 ft (1) = 55.6 mV 1000 ft This voltage drop will raise the apparent temperature and relative humidity because the difference between the signal and signal reference lead, at the datalogger, has increased by Vd. The approximate error in temperature and relative humidity is 0.56°C and 0.
Model HMP45C Temperature and Relative Humidity Probe BeginProg Scan(1,Sec,1,0) 'HMP45C Temperature & Relative Humidity Sensor measurements AirTC and RH: SW12 (1 ) Delay(0,150,mSec) VoltDiff (AirTC,1,mV2500,2,True,0,_60Hz,0.1,-40) VoltDiff (RH,1,mV2500,1,True,0,_60Hz,0.1,0) SW12 (0) If RH>100 And RH<108 Then RH=100 CallTable(Temp_RH) NextScan EndProg CR10(X) Program using Differential Measurement Instructions Using SW12V on Datalogger ;Turn the HMP45C on.
Model HMP45C Temperature and Relative Humidity Probe ;Measure the HMP45C relative humidity. ; 04: Volt (Diff) (P2) 1: 1 Reps 2: 5 2500 mV Slow Range 3: 4: 5: 6: 1 2 .1 0 DIFF Channel Loc [ RH_pct ] Mult Offset ;Turn the HMP45C off.
Model HMP45C Temperature and Relative Humidity Probe 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 on-line by the datalogger as shown in the following examples. TABLE 7-1.
Model HMP45C Temperature and Relative Humidity Probe SatVP(e_Sat, AirTC) 'Compute Vapor Pressure, RH must be a fraction e_kPa = e_Sat * RH_Frac CallTable(Temp_RH) NextScan EndProg CR10(X) Program that Computes Vapor Pressure and Saturation Vapor Pressure ;Turn the HMP45C on.
Model HMP45C Temperature and Relative Humidity Probe ;Turn the HMP45C off. ; 05: Do (P86) 1: 51 Set Port 1 Low ;Compute the saturation vapor pressure. ;The temperature must be in degrees Celsius. ; 06: Saturation Vapor Pressure (P56) 1: 1 Temperature Loc [ T_C 2: 3 Loc [ e_sat ] ;Jumper wire from SW12V control to C1 ;Orange wire (C1) if older wiring ;Green wire (C1) if using SW12V device ;For CR23X or CR5000 use 59 for SW12V internal ;control port ] ;Compute the vapor pressure.
Model HMP45C Temperature and Relative Humidity Probe TABLE 8-1. Chemical Tolerances of HMP45C Chemical Concentration (PPM) Organic solvents 1000 to 10,000 Aggressive chemicals (e.g. SO2, H2SO4, H2S, HCl, Cl2, etc.) 1 to 10 Weak Acids 100 to 1000 Bases 10,000 to 100,000 Recalibrate the HMP45C annually. Obtain an RMA number before returning the HMP45C to Campbell Scientific for recalibration. 9. Troubleshooting Symptom: -9999, NAN, -40 deg C, or 0 % relative humidity 1.
Appendix A. Wiring for Older HMP45C Probes Color Description Yellow Temperature Signal Blue Relative Humidity Signal Purple Signal Reference Orange Power Control Red Power Black Power Ground Shield Shield FIGURE A-1. HMP45C Probe to Datalogger Connections TABLE A-1.
Appendix A. Wiring for Older HMP45C Probes TABLE A-2.
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