Campbell HMP35C Instruction Manual
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Campbell HMP35C Instruction Manual

Temperature and relative humidity probe
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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 .

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Summary of Contents for Campbell HMP35C

  • Page 1 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 ,...
  • Page 2 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.
  • Page 3 The bridge resistors The -L option on the model HMP35C are 0.1% tolerance with a 10 ppm temperature Temperature and Relative Humidity probe coefficient. Polynomial errors are tabulated in (HMP35C-L) indicates that the cable length is Table 2 and plotted in Figure 1.

  • Page 4: Installation

    H.B. and will pass FMVSS302. Local fire codes may preclude its use inside buildings. A lead length of 6 feet allows 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.
  • Page 5 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 Power Control...

  • Page 6: Example Programs

    The number of HMP35C probes that can be Always measure the HMP35C temperature excited by one excitation channel is physically first.

  • Page 7: Long Lead Lengths

    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) Ex Channel Delay W/Ex (units = 0.01 sec) 3: 15 Delay After Ex (units = 0.01 sec) mV Excitation ;Measure the HMP35C relative humidity.
  • Page 8 HMP35C TEMPERATURE AND RH PROBE Example 2. Sample CR10(X) Program measuring HMP35C Temperature using DC Half Bridge with Delay ;Measure the HMP35C thermistor. Excite-Delay (SE) (P4) Reps 7.5 mV Slow Range ;CR500 (7.5 mV); CR23X (10 mV); 21X, CR7 (15 mV) SE Channel ;Orange wire (SE 3), White wire (AG)

  • Page 9: Electrically Noisy Environments

    Understanding the following details are not 4 mA when it is powered. The wire used in the required for the general operation of the HMP35C (P/N 9721) has a resistance of 13.9 HMP35C with Campbell Scientific’s Ω/1000 feet. Using Ohm’s law, the voltage drop dataloggers.
  • Page 10 12 V RH Signal, Power, & Control Reference Purple Shield Clear Example 3. CR10(X) Program that Measures the HMP35C in an Electrically Noisy Environment ;Measure the HMP35C thermistor. AC Half Bridge (P5) Reps 7.5 mV 60 Hz Rejection Range ;CR500 (7.5 mV); CR23X (10 mV) ;21X, CR7 (15 mV)

  • Page 11: Absolute Humidity

    It follows then from Eq. (2) that a 8. ABSOLUTE HUMIDITY change in air temperature will change the The HMP35C measures the relative humidity. relative humidity, without causing a change in Relative humidity is defined by the equation absolute humidity.
  • Page 12 HMP35C TEMPERATURE AND RH PROBE TABLE 9. Wiring for Example 4 Description Color CR10(X) Temperature Orange SE 3 (2H) Relative Humidity Green SE 4 (2L) Temperature Signal Reference White Temperature Excitation Black Power Control Yellow Power 12 V RH Signal, Power, & Control Reference...

  • Page 13: Instruction 11 Details

    9. INSTRUCTION 11 DETAILS Coefficient Value -53.4601 Understanding the details in this section are not 90.807 necessary for using the HMP35C Probe with -83.257 Campbell Scientific's dataloggers. 52.283 Instruction 11 outputs a precise 2 VAC -16.723 excitation (4 V with the 21X) and measures the 2.211...
  • Page 14 HMP35C TEMPERATURE AND RH PROBE TABLE 11. Temperature, Resistance, and 11. REFERENCES Datalogger Output Goff, J. A. and S. Gratch, 1946: Low-pressure Temperature Resistance Output properties of water from -160° to 212°F, (°C) (Ω) (°C) Trans. Amer. Soc. Heat. Vent. Eng. , 51, -40.00...
  • Page 15 This is a blank page.
  • Page 16 Campbell Scientific Companies Campbell Scientific, Inc. (CSI) 815 West 1800 North Logan, Utah 84321 UNITED STATES www.campbellsci.com info@campbellsci.com Campbell Scientific Africa Pty. Ltd. (CSAf) PO Box 2450 Somerset West 7129 SOUTH AFRICA www.csafrica.co.za sales@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA)

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