INSTRUCTION MANUAL Model HMP35C Temperature and Relative Humidity Probe Revision: 1/99 C o p y r i g h t ( c ) 1 9 9 0 - 1 9 9 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 HMP35C 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.
MODEL HMP35C TEMPERATURE AND RELATIVE HUMIDITY PROBE 1. GENERAL DESCRIPTION The HMP35C Temperature and Relative Humidity probe contains a thermistor for measuring temperature and a Vaisala capacitive polymer H chip for measuring relative humidity. The -L option on the model HMP35C Temperature and Relative Humidity probe (HMP35C-L) indicates that the cable length is user specified. This manual refers to the sensor as the HMP35C. -38° to 53°C.
HMP35C TEMPERATURE AND RH PROBE FIGURE 1. Error Produced by Polynomial Fit to Published Values 3. INSTALLATION The HMP35C must be housed inside a radiation shield when used in the field. The 41002 Radiation Shield (Figure 2) mounts to a CM6/CM10 tripod or UT10 tower. The UT018 mounting arm and UT12VA Radiation Shield mount to a UT30 tower (Figure 3). A lead length of 6 feet allows the HMP35C to be mounted at a 2 meter height on a CM6/CM10 tripod.
HMP35C TEMPERATURE AND RH PROBE FIGURE 3. HMP35C with UT018 Mounting Bracket and Crossarm and UT12VA Radiation Shield Mounted on a UT30 Tower Orange Temperature Signal Green Relative Humidity Signal White Temperature Signal Reference Black Temperature Excitation Yellow Red Purple Clear Power Control Power RH Signal, Power, & Control Reference Shield FIGURE 4. HMP35C Probe to Datalogger Connections TABLE 3.
HMP35C TEMPERATURE AND RH PROBE 4. WIRING Connections to Campbell Scientific dataloggers are given in Table 3. The probe is measured by two single-ended input channels, one for temperature and one for relative humidity. A single excitation channel is used for the temperature measurement. measurement (Instruction 1). Tables 4 and 5 provide calibration information for temperature and relative humidity. CAUTION: Do no turn the HMP35C on before measuring the thermistor.
HMP35C TEMPERATURE AND RH PROBE ;Pause 150 milliseconds, before making the measurement, so the ;probe can stabilize on the true relative humidity. ; 03: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0 Delay W/Ex (units = 0.01 sec) 3: 15 Delay After Ex (units = 0.01 sec) 4: 0 mV Excitation ;Measure the HMP35C relative humidity.
HMP35C TEMPERATURE AND RH PROBE Example 2. Sample CR10(X) Program measuring HMP35C Temperature using DC Half Bridge with Delay ;Measure the HMP35C thermistor. ; 01: Excite-Delay (SE) (P4) 1: 1 Reps 2: 2 7.5 mV Slow Range ;CR500 (7.5 mV); CR23X (10 mV); 21X, CR7 (15 mV) 3: 3 SE Channel ;Orange wire (SE 3), White wire (AG) 4: 1 Excite all reps w/Ex 1 ;Black wire (EX 1) 5: 2 Delay (units 0.01 sec) ;CR500, CR23X (2000 mV); 21X, CR7 (4000 mV) 6: 2000 mV Excitation 7: 1 Loc [ T_C ] ;CR500, CR23X (0.
HMP35C TEMPERATURE AND RH PROBE ;Measure the HMP35C relative humidity. ; 07: Volt (SE) (P1) 1: 1 Reps 2: 5 2500 mV Slow Range ;CR500 (2500 mV); CR23X (1000 mV); 21X, CR7 (5000 mV) 3: 4 SE Channel ;Green wire (SE 4), Purple wire (AG) 4: 2 Loc [ RH_pct ] ;See Table 5 for alternate multipliers 5: 0.1 Mult 6: 0 Offset ;Turn the HMP35C off. ; 08: Do (P86) 1: 51 Set Port 1 Low ;Yellow wire (C1) 6.
HMP35C TEMPERATURE AND RH PROBE TABLE 8. Wiring for Example 3 Description Temperature Relative Humidity Temperature Signal Reference Temperature Excitation Power Control Power RH Signal, Power, & Control Reference Shield Color Orange Green White Black Yellow Red Purple Clear CR10(X) SE 3 (2H) SE 4 (2L) AG E1 C1 12 V AG G Example 3. CR10(X) Program that Measures the HMP35C in an Electrically Noisy Environment ;Measure the HMP35C thermistor. ; 01: AC Half Bridge (P5) 1: 1 Reps 2: 22 7.
HMP35C TEMPERATURE AND RH PROBE ;Turn the HMP35C on. ; 05: Do (P86) 1: 41 Set Port 1 High ;Yellow wire (C1) ;Pause 150 milliseconds, before making the measurement, so the ;probe can stabilize on the true relative humidity. ; 06: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0 Delay W/Ex (units = 0.01 sec) 3: 15 Delay After Ex (units = 0.01 sec) 4: 0 mV Excitation ;Measure the HMP35C relative humidity.
HMP35C TEMPERATURE AND RH PROBE TABLE 9. Wiring for Example 4 Description Temperature Relative Humidity Temperature Signal Reference Temperature Excitation Power Control Power RH Signal, Power, & Control Reference Shield Color Orange Green White Black Yellow Red Purple Clear CR10(X) SE 3 (2H) SE 4 (2L) AG E1 C1 12 V AG G Example 4. Sample CR10(X) Program that Computes Vapor Pressure and Saturation Vapor Pressure ;Measure the HMP35C temperature.
HMP35C TEMPERATURE AND RH PROBE ;Compute the saturation vapor pressure in kPa. The temperature must be in degrees Celsius. ; 06: Saturation Vapor Pressure (P56) 1: 1 Temperature Loc [ T_C ] 2: 3 Loc [ e_sat ] ;Compute the vapor pressure in kPa. Relative humidity must be a fraction. ; 07: Z=X*Y (P36) 1: 3 X Loc [ e_sat ] 2: 2 Y Loc [ RH_frac ] 3: 4 Z Loc [ e_kPa ] 9.
HMP35C TEMPERATURE AND RH PROBE TABLE 11. Temperature, Resistance, and Datalogger Output Temperature (°C) -40.00 -38.00 -36.00 -34.00 -32.00 -30.00 -28.00 -26.00 -24.00 -22.00 -20.00 -18.00 -16.00 -14.00 -12.00 -10.00 -8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 58.00 60.
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