6 full bridge with single differential measurement, 7 three wire half bridge, 8 differential voltage with excitation and delay – Campbell Scientific CR10X Measurement and Control System User Manual
Page 137
SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-5
*** 6 FULL BRIDGE WITH SINGLE ***
DIFFERENTIAL MEASUREMENT
FUNCTION
This Instruction is used to apply an excitation
voltage to a full bridge and make a differential
voltage measurement of the bridge output. The
measurement is made with the polarity of the
excitation voltage both positive and negative
(Figure 13.5-1). The result is 1000 times the
ratio of the measurement to the excitation
voltage. A 1 before the excitation channel
number (1X) causes the channel to be
incremented with each repetition.
PARAM.
DATA
NUMBER
TYPE
DESCRIPTION
01:
2
Repetitions
02:
2
Range code (Table 9-1)
03:
2
Differential channel
number for first
measurement
04:
2
Excitation channel
number
05:
4
Excitation voltage
(millivolts)
06:
4
Input location number
for first measurement
07:
FP
Multiplier
08:
FP
Offset
Input locations altered: 1 per repetition
*** 7 THREE WIRE HALF BRIDGE ***
FUNCTION
This Instruction is used to determine the ratio of
the sensor resistance to a known resistance
using a second voltage sensing wire from the
sensor to compensate for lead wire resistance.
The measurement sequence is to apply an
excitation voltage, make two voltage
measurements on two adjacent single-ended
channels, the first on the reference resistor and
the second on the voltage sensing wire from the
sensor (Figure 13.5-1), then reverse the
excitation voltage and repeat the measurements.
The two measurements are used to calculate the
resulting value, which is the ratio of the voltage
across the sensor to the voltage across the
reference resistor. A 1 before the excitation
channel number (1X) causes the channel to be
incremented with each repetition.
PARAM.
DATA
NUMBER
TYPE
DESCRIPTION
01:
2
Repetitions
02:
2
Range code for both
measurements (Table
9-1)
03:
2
Single-ended channel
number for first
measurement
04:
2
Excitation channel
05:
4
Excitation voltage
(millivolts)
06:
4
Input location number
for first measurement
07:
FP
Multiplier
08:
FP
Offset
Input locations altered: 1 per repetition
*** 8 DIFFERENTIAL VOLTAGE WITH ***
EXCITATION AND DELAY
FUNCTION
This measurement consists of applying a single
excitation voltage, delaying a specified time,
and making a differential voltage measurement.
The result stored is the voltage measured.
"Delay" (Parameter 5) refers to increasing the
signal settling time by increasing the time
between the start of excitation and the start of
signal integration (Section 13.2). If a delay of 0
is specified, the inputs for the differential
measurement are not switched for a second
integration as is normally the case. With the 0
delay, Instruction 8 does not have as good
resolution or common mode rejection as other
differential measurements. It does provide a
very rapid means of making bridge
measurements. This instruction does not
reverse excitation. A 1 before the excitation
channel number (1X) causes the channel to be
incremented with each repetition.
The 50 and 60 Hz rejection ranges (Section
13.1) do not have enough time between
integrations to allow a delay.
PARAM.
DATA
NUMBER
TYPE
DESCRIPTION
01:
2
Repetitions
02:
2
Range code (Table 9-1)
03:
2
Differential channel
number for first
measurement
04:
2
Excitation channel number