Strain- and Bridge-Based Measurements
Specifications
>>
For complete specifications, see the
NI USB-9237 User Guide and
Excitation Voltages
Although the sensor industry does not recognize a single standard
excitation voltage level, excitation voltage levels of between 2.5 and
10 V are common. You can program the USB-9237 to supply 2.5, 3.3,
5, or 10 V of excitation voltage, and the module can provide up to
150 mW of excitation power. Unless you supply external excitation
voltage, National Instruments recommends that you set the excitation
voltage to a value that keeps the total power below 150 mW. The
USB-9237 automatically reduces internal excitation voltages as needed
to stay below 150 mW.
The power consumed by a single bridge is
Specifications
manual at
ni.com/manuals.
Input Characteristics
Internal
External
24 bits
Delta-sigma
(with analog prefiltering)
Sampling mode............................... Simultaneous
Data rates (ƒ
s
) ................................. (50 kS/s)/n, n= 1, 1, …31
Master timebase (internal)
Frequency........................................ 12.8 MHz
Accuracy ......................................... ±100 ppm max
Nominal full-scale range ................ ±25 mV/V
Scaling coefficient .............................. 2.9802 nV/V per LSB
Overvoltage protection
between any two terminals ........... ±30 V
Accuracy
Error
1
Percent of Reading
Percent of Range
2
Calibrated max (-40 to 70 °C)
0.20%
0.25%
Calibrated typ (25 °C, ±5 °C)
0.05%
0.05%
Uncalibrated max (-40 to 70 °C)
0.60%
0.35%
Uncalibrated typ (25 °C, ±5 °C)
0.20%
0.1%
1
Excluding offset null or shunt calibration.
2
Range equals 25 mV/V.
Number of channels............................
Bridge completion
Full and half ....................................
Quarter............................................
ADC resolution................................
Type of ADC ....................................
4
V
ex
---------
-
R
2
where
R
is the total resistance of the bridge.
For a full bridge,
R
is equal to the resistance of each element. For a
half or quarter bridge,
R
is equal to two times the resistance of each
element.
With the 150 mW limit, you can power full and half bridges as
follows:
• Four 350
Ω
half bridges at 5.0 V
• Four 350
Ω
full bridges at 3.3 V
• Four 120
Ω
half bridges at 2.5 V
If you need an excitation voltage greater than 150 mW, use the
four-position external excitation voltage connector to connect an
external excitation source to the USB-9237.
Gain drift .............................................
Offset drift
2.5 V excitation...............................
3.3 V excitation...............................
5 V excitation..................................
10 V excitation................................
10 ppm/°C max
0.6
μV/V
per °C
0.5
μV/V
per °C
0.3
μV/V
per °C
0.2
μV/V
per °C
Channel Signal Names
RJ50 (10p10c) Modular Plug and RJ50 RJ45 Signal
Receptacle Pin Numbers
Pin Pin Name
1
2
3
4
5
6
7
8
9
10
1
Signal Description
Shunt calibration
Positive input signal
Negative input signal
Positive remote sense signal
Negative remote sense signal
Positive excitation signal
1
Negative excitation signal
1
TEDS DATA
TEDS Return
1
Shunt calibration
Safety
Safety Voltages
Connect only voltages that are within these limits.
Between any two terminals ............... ±30 V max
Isolation
Channel-to-channel............................. No isolation between channels
Channel-to-earth ground
Continuous...................................... 60 VDC, Measurement Category I
Withstand ....................................... 1,000 V
rms
, verified by a 5 s
dielectric withstand test
–
1
2
3
4
5
6
7
8
–
SC
AI+
AI-
RS+
RS-
EX+
EX-
T+
T-
SC
These signals are shared by all four RJ50 connectors on the USB-9237.
BUY ONLINE
at
ni.com
or
CALL 800 813 3693 (U.S.)
2
NI [ NATIONAL INSTRUMENTS CORPORATION ]
