Campbell Scientific CR7 Measurement and Control System User Manual
Page 95
SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-5
PAR.
DATA
NO.
TYPE
DESCRIPTION
01:
2
Repetitions (47 max)
02:
2
Excitation range code (Table
9-1)
03:
2
Bridge range code for (Table
9-1)
04:
2
Analog card number for first
measurement
05:
2
Differential channel number
for first measurement
06:
2
Excitation card for first
measurement
07:
2
Excitation channel number
for first measurement
08:
2
Number of measurements
per excitation channel
09:
4
Excitation voltage (millivolts)
10:
4
Input location number for first
measurement
11:
FP
Multiplier
12:
FP
Offset
Input locations altered: 1 per repetition
*** 10 BATTERY VOLTAGE ***
FUNCTION
This instruction reads the battery voltage from
the currently active I/O module and writes it to
an input location. The units for battery voltage
are volts.
PAR.
DATA
NO.
TYPE
DESCRIPTION
01:
4
Input location number
Input locations altered: 1
*** 11 107 THERMISTOR PROBE ***
FUNCTION
This instruction applies a 4 VAC excitation
voltage to Campbell Scientific's Model 107
Thermistor Probe, makes a fast, single ended
voltage measurement on the 15 mV range
across a resistor in series with the thermistor
and calculates the temperature in oC with a
polynomial. The maximum polynomial error
from -40 oC to +55 oC is given below:
Curve Fit Error --
Range (oC)
Error (oC)
-40 to +55
±1.0
-35 to +48
±0.1
This instruction uses a single excitation channel
since several hundred probes can be driven by
a single excitation output. For this reason,
Instruction 11 does not require a
"measurement/excitation" parameter.
A multiplier of 1 and an offset of 0 yields
temperature in degrees C.
PAR.
DATA
NO.
TYPE
DESCRIPTION
01:
2
Repetitions
02:
2
Analog card number for first
measurement
03:
2
Single-ended channel
number for first
measurement
04:
2
Excitation card number for
first measurement
05:
2
Excitation channel number
for first measurement
06:
4
Input location of first
measurement
07:
FP
Multiplier
08:
FP
Offset
Input locations altered: 1 per repetition
*** 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 150 mV range, linearizes the
result with a 5th order polynomial and performs
the required temperature compensation before
outputting the result in % RH.
When measuring several probes, all the RH
elements should be connected sequentially.
Any temperature elements used for
compensating the respective RH value should
also be sequentially connected to make use of
the REP feature in Instruction 11.