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SECTION
9.
INPUT/OUTPUT INSTRUCTIONS
PARAM.
DATA
NUMBER
TYPE
DESCRIPTION
Repetitions
Input
channel number of
first measurement
Excitation channel
number
Input location for first
measurement
Multiplier
Offset
Input locations
altered:
1
for each thermistor
channel
*** 12
207
RELATIVE HUMIDITY
PROBE
***
FUNCTION
This instruction applies
a
3 VAC excitation
across Campbell Scientific's Model 207
Temperature
and RH Probe, makes
a
fast
single-ended measurement across
a
series
resistor on
the 150mV range, calculates the
result with
a
fifth order polynomial, and performs
the required temperature compensation before
outputting
the result in %
RH.
When measuring several probes,
allthe
RH
elements should
be
connected sequentially.
The temperature values used to correct
the
RH
measurements should also be stored
sequentially
to make use
of
the REP feature
in
Instruction
11.
NOTE:
The temperature
value used
in
compensating
the
RH
value
(Parameter
5) must be obtained (see
Instruction
1
1)
prior
to executing
Instruction
12.
The RH results are placed sequentially into the
input locations beginning with the
first
RH
value.
In
the
207 probe, the
RH
and temperature
elements use
a
common
excitation
line.
NEVER
EXCITE
THE2O7 PROBE WITH
DC
EXCITATION (this includes
ohm meters) as the
RH
chip will be damaged.
The maximum error from the polynomial used
for
calculating RH
is
given
here:
Range (%RH)
10
- 100
15-94
Error (%RH)
PARAM.
DATA
NUMBER
TYPE
DESCRIPTION
Repetitions
First
channelfor
RH
measurement
Excitation channel
number
Input location for first
compensating
temperature
measurement
Input location for
first
RH
measurement
Multiplier
Offset
Input locations
altered:
1
for
each
RH
measurement
***
13
THERMOCOUPLE TEMPERATURE.
SINGLE-ENDED
FUNCTION
This instruction uses the selected
calibration to calculate the thermocouple output
voltage at
the reference temperature, then
it
makes
a SINGLE-ENDED VOLTAGE
MEASUREMENT (Section 13.2) on the
thermocouple and adds
the measured voltage
to the
calculated reference voltage, then
converts the voltage to temperature in
oC.
Select the smallest
voltage range that will
accommodate the
temperatures
bein g
measured (Table 9-4).
PARAM.
DATA
NUMBER
TYPE
DESCRIPTION
Repetitions
Range code
First TC channel
Thermocouple type code
Reference
temperature
location
Destination input location
Multiplier
Offset
Input locations
altered:
1
for each
thermocouple channel
t4
t1
01:
02:
03:
05:
06:
2
2
2
4
FP
FP
2
2
2
4
01:
o2:
03:
o4:
05:
06:
07;
FP
FP
2
2
2
2
4
4
FP
FP
01:
02:
03:
Q4:
05:
06:
07:
08:
9-6
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