HTF3000LF - Temperature and Relative Humidity Module
HTF3000LF HPC077 Rev J www.meas-spec.com October 2012
4/7
• Temperature influence on HTF3000LF humidity measurement
Calibration data are traceable to NIST standards through CETIAT laboratory.
For demanding application, temperature coefficient could be compensated over operating temperature range
using following formula:
RH
corr
= RH + 0.08 * ( T – 25 )
Fout
Corr
= Fout – 0.88 * ( T – 25 )
T in °C, RH in %, Fout in Hz
TEMPERATURE SENSOR
• Typical temperature output
Depending on the needed temperature measurement range and associated accuracy, we suggest two methods
to access to the NTC resistance values.
)
11
(
N
TT
NT
eRR
−
∗=
β
R
T
NTC resistance in Ω at temperature T in K
R
N
NTC resistance in Ω at rated temperature T in K
T, T
N
Temperature in K
β Beta value, material specific constant of NTC
e Base of natural logarithm (e=2.71828)
The exponential relation only roughly describes the actual characteristic of an NTC thermistor can, however,
as the material parameter β in reality also depend on temperature. So this approach is suitable for describing a
restricted range around the rated temperature or resistance with sufficient accuracy.
For practical applications, a more precise description of the real R/T curve may be required. Either more
complicated approaches (e.g. the Steinhart-Hart equation) are used or the resistance/temperature relation as
given in tabulation form. The below table has been experimentally determined with utmost accuracy for
temperature increments of 1 degree.
Actual values may also be influenced by inherent self-heating properties of NTCs. Please refer to MEAS-France
Application Note HPC106-0 “Low power NTC measurement”.
