Operator`s manual

SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-5
PARAM. DATA
NUMBER TYPE DESCRIPTION
01: 2 Repetitions
02: 2 Range code
03: 2 Input channel number for
first measurement
04: 2 Excitation channel
number
05: 4 Delay (0.01s)
06: 4 Excitation voltage
(millivolts)
07: 4 Input location number for
first measurement
08: FP Multiplier
09: FP Offset
Input locations altered: 1 per measurement
*** 9 FULL BRIDGE WITH EXCITATION ***
COMPENSATION
FUNCTION
This instruction is used to apply an excitation
voltage and make two differential voltage
measurements, then reverse the polarity of the
excitation and repeat the measurements. The
measurements are made on sequential
channels. The result is the voltage measured on
the second channel (V
2
) divided by the voltage
measured on the first (V
1
). If V
1
is measured on
the 5V range (code 5 or 15 in Parameter 2),
then the result is 1000 times V
2
/V
1
. A 1 before
the excitation channel number (1X) causes the
channel to be incremented with each repetition.
When used as a 6 wire full bridge (Figure 13.5-
1), the connections are made so that V
1
is the
measurement of the voltage drop across the full
bridge, and V
2
is the measurement of the bridge
output. Because the excitation voltage for a full
bridge measurement is usually in the 5V range,
the output is usually 1000 V
2
/V
1
or millivolts
output per volt excitation.
When used to measure a 4 wire half bridge, the
connections are made so that V
1
is the voltage
drop across the fixed resistor (R
f
), and V
2
is the
drop across the sensor (R
s
). As long as V
1
is
not measured on the 5V range, the result is
V
2
/V
1
which equals R
s
/R
f
.
PARAM. DATA
NUMBER TYPE DESCRIPTION
01: 2 Repetitions
02: 2 Range code for V1
03: 2 Range code for V2
04: 2 Input channel number for
first measurement
05: 2 Excitation channel
number
06: 4 Excitation voltage
(millivolts)
07: 4 Input location number for
first measurement
08: FP Multiplier
09: FP Offset
Input locations altered: 1 per measurement
*** 10 BATTERY VOLTAGE ***
FUNCTION
This instruction reads the battery voltage and
writes it to an input location. Battery voltage is
stored in volts.
PARAM. DATA
NUMBER TYPE DESCRIPTION
01: 4 Input location
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 15mV range and
then calculates the temperature in degrees C
with a polynomial. The maximum polynomial
error from -40
o
C to +55
o
C is given below:
Curve Fit Error --
Range (
o
C) Error (
o
C)
-40 to +55 +1.0
-35 to +48 +0.1
The fast integration time used in Instruction 11
does not provide rejection of 60 Hz noise. See
example 7.16 for a method of measuring the
107 thermistor where 60 Hz noise is a problem.