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 .
Страница 1: ...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 ...
Страница 2: ...eu 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 ...
Страница 3: ...ion of the bridge resistors and the polynomial error In a worst case all errors add to an accuracy of 0 4 C over the range of 24 C to 48 C and 0 9 C over the range of 38 to 53 C The major error component is the interchangeability specification of the thermistor tabulated in Table 1 For the range of 0 to 50 C the interchangeability error is predominantly offset and can be determined with a single p...
Страница 4: ...the HMP35C to be mounted at a 2 meter height on a CM6 CM10 tripod Use a lead length of 9 feet for the UT10 tower or a UT30 tower respectively NOTE The black outer jacket of the cable is Santoprene rubber This 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...
Страница 5: ...ive Humidity Green Single Ended Input Single Ended Input Single Ended Input Temperature Signal Reference White AG Temperature Excitation Black Excitation Channel Excitation Channel Excitation Channel Power Control Yellow Control Port Control Port Control Port Power Red 12 V 12 V 12 V RH Signal Power Control Reference Purple AG Shield Clear G Orange Temperature Signal Green Relative Humidity Signal...
Страница 6: ... information for temperature and relative humidity CAUTION Do no turn the HMP35C on before measuring the thermistor Doing so will induce a transient signal spike on the thermistor leads that will result in an erroneous temperature measurement Always measure the HMP35C temperature first TABLE 4 Calibration for Temperature Units Multiplier degrees mV 1 Offset degrees Celsius 1 0 Fahrenheit 1 8 32 TA...
Страница 7: ... are required the measurement settling time for the temperature measurement must be increased For HMP35Cs with lead lengths greater than 300 feet use the DC Half Bridge instruction Instruction 4 with a 20 millisecond delay to measure the thermistor Example 2 Long lead lengths cause errors in the measured relative humidity The approximate error in relative humidity is 0 6 RH per 100 feet of cable l...
Страница 8: ...the temperature in degrees Celsius 02 Polynomial P55 1 1 Reps 2 1 X Loc T_C 3 1 F X Loc T_C 4 53 46 C0 5 90 807 C1 6 83 257 C2 7 52 283 C3 8 16 723 C4 9 2 211 C5 Apply the temperature multiplier 03 Z X F P37 1 1 X Loc T_C 2 1 F See Table 4 for alternate multipliers 3 1 Z Loc T_C Apply the temperature offset 04 Z X F P34 1 1 X Loc T_C 2 0 F See Table 4 for alternate offsets 3 1 Z Loc T_C Turn the H...
Страница 9: ...HMP35C with Campbell Scientific s dataloggers The relative humidity signal reference and the power reference black are the same lead in the HMP35C When the measuring relative humidity both the signal and power references are connected to ground at the datalogger The signal power reference lead serves as the return path for 12 V There will be a voltage drop along this lead because the wire itself h...
Страница 10: ...1 Reps 2 22 7 5 mV 60 Hz Rejection 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 2000 mV Excitation CR500 CR23X 2000 mV 21X CR7 4000 mV 6 1 Loc T_C 7 800 Mult 8 0 Offset Compute the temperature in degrees Celsius 02 Polynomial P55 1 1 Reps 2 1 X Loc T_C 3 1 F X Loc T_C 4 53 46 C0 5 90 807 C1 6 83 257 C2 7 52 ...
Страница 11: ...t a given air temperature The relationship between dew point 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 that a cha...
Страница 12: ...lack wire EX 1 4 1 Loc T_C 5 1 Mult See Table 4 for alternate multipliers 6 0 Offset See Table 4 for alternate offsets Turn the HMP35C on 02 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 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 s...
Страница 13: ...g a fifth order polynomial equation correlating Vs Vx with temperature The polynomial coefficients are given in Table 10 The polynomial input is Vs Vx 800 Resistance and datalogger output at several temperatures are shown in Table 11 FIGURE 5 Thermistor Probe Schematic TABLE 10 Polynomial Coefficients Coefficient Value C0 53 4601 C1 90 807 C2 83 257 C3 52 283 C4 16 723 C5 2 211 10 MAINTENANCE The ...
Страница 14: ...0 187803 12 07 14 00 169924 14 06 16 00 153923 16 05 18 00 139588 18 02 20 00 126729 19 99 22 00 115179 21 97 24 00 104796 23 95 26 00 95449 25 94 28 00 87026 27 93 30 00 79428 29 95 32 00 72567 31 97 34 00 66365 33 99 36 00 60752 36 02 38 00 55668 38 05 40 00 51058 40 07 42 00 46873 42 07 44 00 43071 44 05 46 00 39613 46 00 48 00 36465 47 91 50 00 33598 49 77 52 00 30983 51 59 54 00 28595 53 35 5...
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