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NI 9219 Calibration Procedure
2.
Acquire an
Ω
ref
measurement.
a.
Create an AI voltage channel in the 1 V range on the NI 9219.
b.
Commit the task to place the NI 9219 in voltage mode. This prevents the module from
interfering with the resistance measurements of the DMM.
c.
Configure the DMM for a 4-wire resistance measurement in the appropriate range
according to the appropriate test point from Table 22.
d.
Enable Auto Zero on the DMM.
e.
Acquire a resistance reading with the DMM. Record this measurement as
Ω
ref
.
f.
Clear the task.
3.
Disconnect the DMM from the resistor to ensure that the terminals on the DMM do not
interfere with the resistor while the NI 9219 makes measurements.
4.
Acquire and average samples.
a.
Create an AI RTD task on the NI 9219 according to Table 20.
b.
Configure the AI RTD task timing according to Table 15.
c.
Start the task.
d.
Acquire 20 unscaled I32 4-wire readings with the NI 9219.
e.
Record the average of the readings as data
unscaled
.
f.
Clear the task.
5.
Scale the data by using the formula below to change the unscaled data into
Ω
.
where
range
max
is the maximum value for the selected range in Table 22.
Table 20.
NI 9219 Configuration for 4-Wire RTD Accuracy Verification
Measurement
Type
Min (°C)
Max
(°C)
Excitation
Source
Excitation
Value
Resistance
Config
r0
*
4-Wire RTD
Pt1000
0
800
Internal
0.0005
4-Wire
1000
4-Wire RTD
Pt100
100
*
RTD nominal resistance at 0 °C.
Table 21.
NI 9219 Timing Configuration
ADC Timing Mode
Sample Timing Type
High Resolution
On Demand
Ω
channel
data
unscaled
2
24
-------------------------------
range
max
×
=