NI 9219 Calibration Procedure
18
ni.com
7.
Reconnect the DMM as shown in Figure 10. To minimize mismatch between the NI 9219 and the
DMM, connect the
HI
and
senseHI
leads of the DMM as close as possible to the same point where
the LO lead from the NI 9219 connects to the resistor and the
LO
and the
senseLO
leads of the
DMM directly to the spring-terminal connector of the NI 9219.
Figure 10.
3-Wire RTD Accuracy Verification Connections to the NI 9219
8.
Configure the DMM for a 4-wire resistance measurement in the 100
range or the smallest range
available.
9.
Enable Auto Zero on the DMM.
10. Acquire a resistance reading with the DMM. Record this measurement as
BottomHalfDMM
.
11. Disconnect the DMM from the resistor and the NI 9219.
12. Calculate the DMM measurement of the 3-wire system from the following equation.
13. Clear the task.
14. Create an AI RTD channel on the NI 9219. Configure the channel according to Table 18.
15. Acquire 20 unscaled I32 3-wire readings with the NI 9219. Record the average of the readings as
data
unscaled
.
Table 18.
NI 9219 Configuration for 3-Wire RTD Accuracy Verification
Measurement
Type
Min
(°C)
Max
(°C)
Excitation
Source
Excitation
Value
Resistance
Config
r0
*
ADC
Timing
Mode
Sample
Timing
Type
3-Wire RTD
Pt1000
0
800
Internal
0.0005
3-Wire
1000
High
Resolution
On
Demand
3-Wire RTD
Pt100
100
*
RTD nominal resistance at 0 °C.
R
TestPoint
Ω
HI
LO
DMM
Ω
SENSE
HI
LO
NI 9219
EX+ (3)
LO (6)
EX– (5)
Ch
x
ref
TopHalfDMM
2
BottomHalfDMM
–
=