TECHNICAL
3
DATA
H
UMIDITY
M
EASUREMENT USING
HM1500
Typical HM 1500 relative Humidity measurement
100
80
Relative Humidity (% RH)
70
60
50
40
30
% RH = 0.0391 Vout -42.5
from 10 to 95 % RH
20
with Vout in mV and RH in %
10
0
1000
1500
2000
2500
3000
3500
4000
Output Voltage (mV)
Internal block diagram of HM1500
Reference Oscillator
L.P. Filter
Sensor Oscillator
Gain
Vout --
>
Suggested applications for HM1500
Steps of 1% RH are
achievable by using
8-bit A/D.
If more resolution is
required a 10 -bit A/D
needs to be used and a
third display will be
added, giving steps of
0.2% RH
Read AINO
VCC5
VCC5
U1
3
4
16
15
RTCC
MCLR
OSC1
OSC2/CLK
RA/AIN0
RA/AIN1
RA/AIN2
RA/AIN3
RBO
RB1
RB2
RB3
RB4
RB5
RB6
RB7
17
18
1
2
C2
X1
PIC16CXXX
With A/D
6
7
8
9
10
11
12
1317
HM150X
C1
VCC5
1
3
Calculate RH%
using equation
or
using alook up table
VI
7805
GND
VO
VCCIN
Convert RH% to
BCD code
Send data to display
2
HPC009 Rev. H October 2001
HUMIREL [ Humirel ]
