NI-9237 Specifications

NI-9237 Specifications

These specifications apply to the NI-9237.

Revision History

Version Date changed Description
378964B-01 February 2025 Updated accuracy table.
378964A-01 March 2023 Initial release.

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Definitions

Warranted specifications describe the performance of a model under stated operating conditions and are covered by the model warranty.

Characteristics describe values that are relevant to the use of the model under stated operating conditions but are not covered by the model warranty.

  • Typical specifications describe the performance met by a majority of models.
  • Nominal specifications describe an attribute that is based on design, conformance testing, or supplemental testing.

Specifications are Typical unless otherwise noted.

Conditions

Specifications are valid for the range -40 °C to 70 °C unless otherwise noted.

Connector Types

The NI-9237 has more than one connector type: NI-9237 with RJ-50 and NI-9237 with DSUB. Unless the connector type is specified, NI-9237 refers to both connector types.

NI-9237 Pinout

The NI-9237 provides connections for four half or full bridges, and an external excitation voltage source.

NI-9237 with RJ-50 Pinout



Caution Do not use RJ-45 cables with the NI-9237 with RJ-50. RJ-45 cables damage the RJ-50 connector, permanently disabling the shunt calibration, regardless of which connector you use.
Table 1. NI-9237 with RJ-50 Signal Descriptions
Signal Name Description
AI+ Positive analog input signal connection
AI- Negative analog input signal connection
RS+ Positive remote sensing connection
RS- Negative remote sensing connection
EX+ Positive sensor excitation connection
EX- Negative sensor excitation connection
T+ TEDS data connection
T- TEDS return connection
SC Shunt calibration connection

NI-9237 with DSUB Pinout



Table 2. NI-9237 with DSUB Signal Descriptions
Signal Name Description
AI+ Positive analog input signal connection
AI- Negative analog input signal connection
RS+ Positive remote sensing connection
RS- Negative remote sensing connection
EX+ Positive sensor excitation connection
EX- Negative sensor excitation connection
T+ TEDS data connection
T- TEDS return connection
SC Shunt calibration connection

Input Characteristics

Number of channels 4 analog input channels
Table 3. Bridge Completion
Half and Full Internal
Quarter External
ADC resolution 24 bits
Type of ADC Delta-Sigma (with analog prefiltering)
Sampling mode Simultaneous
TEDS support IEEE 1451.4 TEDS Class II (Interface)
Note The NI-9237 also has TEDS circuitry. Refer to IEEE 1451.4 TEDS Sensor Templates Overview for more information.
Table 4. Internal Master Timebase (ƒM)
Frequency 12.8 MHz
Accuracy ±100 ppm maximum
Table 5. Data rate range (ƒs) using internal master timebase
Minimum 1.613 kS/s
Maximum 50 kS/s
Table 6. Data rate range (ƒs) using external master timebase
Minimum 391 S/s
Maximum 51.36 kS/s
Data rates (ƒs) (ƒM ÷ 256) ÷ n, where n = 1, 2, …, 31
Typical input range ±25 mV/V
Scaling coefficient 2.9802 nV/V per LSB
Overvoltage protection between any two pins ±30 V
Table 7. Accuracy
Measurement Conditions[1]1 Before offset null or shunt calibration. Within 1 Year of Calibration Within 10 Years of Calibration
Percent of Reading (Gain Error[2]2 Applies at a data rate of 50 kS/s. Lower data rates can have up to 0.20% of reading additional gain error. ) Percent of Range[3]3 Range equals 25 mV/V. (Offset Error) Percent of Reading (Gain Error[4]4 Applies at a data rate of 50 kS/s. Lower data rates can have up to 0.20% of reading additional gain error. ) Percent of Range[5]5 Range equals 25 mV/V. (Offset Error)
Calibrated Typical (25 °C, ±5 °C) 0.05% 0.05% 0.10% 0.07%
Maximum (-40° C to 70 °C) 0.20% 0.25% 0.30% 0.28%
Uncalibrated[6]6 Uncalibrated accuracy refers to the accuracy achieved when acquiring data in raw or unscaled modes and in which calibration constants that are stored in the module are not applied to the data. Typical (25 °C, ±5 °C) 0.20% 0.10% 0.28% 0.19%
Maximum (-40 °C to 70 °C) 0.55% 0.35% 0.59% 0.37%
Note NI recommends a calibration interval of 1 year and only provides calibration services referencing the 1-year specification limits. If you choose to calibrate less often, the 10-year column provides predicted performance over this extended interval. Choose an appropriate interval based on your application requirements. Longer calibration intervals are more likely to result in As-Found calibration failures when the device is sent back for calibration and compared against the 1-year specification limits.
Gain drift 10 ppm/°C maximum
Table 8. Offset Drift
2.5 V excitation 0.6 µV/V per °C
3.3 V excitation 0.5 µV/V per °C
5 V excitation 0.3 µV/V per °C
10 V excitation 0.2 µV/V per °C
Table 9. Half-Bridge Completion
Tolerance ±1,200 µV/V maximum
Drift 1.5 µV/V per °C
Table 10. Channel-to-Channel Matching (Calibrated)
Input Signal Frequency (ƒin) Gain Phase
Typical Maximum Maximum
0 to 1 kHz 0.15% 0.3% 0.125°/kHz · ƒin
1 to 20 kHz 0.4% 1.1%
Table 11. Phase Nonlinearity
ƒin = 0 to 1 kHz <0.001°
ƒin = 0 to 20 kHz ±0.1°
Input delay (40 + 5/512)/ƒs + 4.5 µs
Table 12. Passband
Frequency 0.45 · ƒs
Flatness 0.1 dB maximum
Table 13. Stopband
Frequency 0.55 · ƒs
Rejection 100 dB
Alias-free bandwidth 0.45 · ƒs
Oversample rate 64 · ƒs
Table 14. Rejection at oversample rate
ƒs = 10 kS/s 60 dB @ 640 kHz
ƒs = 50 kS/s 90 dB @ 3.2 MHz
Note Rejection by analog prefilter of signal frequencies at oversample rate.
Common-mode voltage, all signals to earth ground ±60 VDC
Common-mode voltage range, with respect to EX- ±1 V from the midpoint of the excitation voltage
Table 15. Common-Mode Rejection Ratio (CMRR)
Relative to earth ground[7]7 Measured with a balanced cable on the NI-9237 with RJ-50 and with no cable on the NI-9237 with DSUB. Shielded cables that are not twisted-pair may be significantly unbalanced, which can impact CMRR performance. To improve the balance of shielded cables, NI recommends twisting together the AI+/AI– pair, the RS+/RS– pair, and the EX+/EX– pair. (ƒin = 0 to 60 Hz) 140 dB
Relative to EX– (ƒin = 0 to 1 kHz) 85 dB
SFDR (1 kHz, –60 dBFS) 115 dB
Table 16. Total Harmonic Distortion (THD)
1 kHz, –20 dBFS –95 dB
8 kHz, –20 dBFS –95 dB
Table 17. Input Noise
Excitation Voltage Density, (nV/Vrms per √1 Hz ) Total, ƒin = 0 to 1 kHz (nV/Vrms) (signal sampled at 50 kHz) Total, ƒin = 0 to 25 kHz (µV/Vrms)
Full Bridge Full Bridge Full Bridge Half Bridge
2.5 V 8 250 1.3 1.6
3.3 V 6 190 1.0 1.2
5 V 4 130 0.6 0.8
10 V 2 65 0.3 0.5
Excitation noise 100 µVrms
Table 18. Crosstalk (Not Including Cable Effects)
ƒin = 1 kHz -110 dB
ƒin = 10 kHz -100 dB
Table 19. Excitation
Internal voltage 2.5 V, 3.3 V, 5.0 V, 10.0 V
Internal power 150 mW maximum
External voltage 2 V to 10 V
Table 20. Shunt Calibration
Resistance 100 kΩ
Resistor accuracy 25 °C ±110 Ω
– 40 °C to 70 °C ±200 Ω
Table 21. MTBF
NI-9237 with RJ-50 603,359 hours at 25 °C; Bellcore Issue 2, Method 1, Case 3, Limited Part Stress Method
NI-9237 with DSUB 704,148 hours at 25 °C; Bellcore Issue 2, Method 1, Case 3, Limited Part Stress Method

Power Requirements

Power consumption from chassis

Active mode

740 mW maximum

Sleep mode

25 µW maximum

Thermal dissipation (at 70 °C)

Active mode

740 mW maximum

Sleep mode

25 µW maximum

Physical Characteristics

Dimensions

Visit ni.com/dimensions and search by module number.

Weight

NI-9237 with RJ-50

152 g (5.4 oz)

NI-9237 with DSUB

149 g (5.25 oz)

Safety Voltages

Connect only voltages that are within the following limits.

Between any two pins

±30 V maximum

Isolation, channel-to-channel

None

Isolation, channel-to-earth ground
Up to 3,000 m

Continuous

60 VDC, Measurement Category I

Withstand

1,000 Vrms, verified by a 5 s dielectric withstand test

Up to 5,000 m

Continuous

60 VDC, Measurement Category I

Withstand

860 Vrms, verified by a 5 s dielectric withstand test

Measurement Category I

Warning Do not connect the product to signals or use for measurements within Measurement Categories II, III, or IV, or for measurements on MAINs circuits or on circuits derived from Overvoltage Category II, III, or IV which may have transient overvoltages above what the product can withstand. The product must not be connected to circuits that have a maximum voltage above the continuous working voltage, relative to earth or to other channels, or this could damage and defeat the insulation. The product can only withstand transients up to the transient overvoltage rating without breakdown or damage to the insulation. An analysis of the working voltages, loop impedances, temporary overvoltages, and transient overvoltages in the system must be conducted prior to making measurements.
Mise en garde Ne pas connecter le produit à des signaux dans les catégories de mesure II, III ou IV et ne pas l'utiliser pour des mesures dans ces catégories, ou des mesures sur secteur ou sur des circuits dérivés de surtensions de catégorie II, III ou IV pouvant présenter des surtensions transitoires supérieures à ce que le produit peut supporter. Le produit ne doit pas être raccordé à des circuits ayant une tension maximale supérieure à la tension de fonctionnement continu, par rapport à la terre ou à d'autres voies, sous peine d'endommager et de compromettre l'isolation. Le produit peut tomber en panne et son isolation risque d'être endommagée si les tensions transitoires dépassent la surtension transitoire nominale. Une analyse des tensions de fonctionnement, des impédances de boucle, des surtensions temporaires et des surtensions transitoires dans le système doit être effectuée avant de procéder à des mesures.

Measurement Category I is for measurements performed on circuits not directly connected to the electrical distribution system referred to as MAINS voltage. MAINS is a hazardous live electrical supply system that powers equipment. This category is for measurements of voltages from specially protected secondary circuits. Such voltage measurements include signal levels, special equipment, limited-energy parts of equipment, circuits powered by regulated low-voltage sources, and electronics.

Note Measurement Categories CAT I and CAT O are equivalent. These test and measurement circuits are for other circuits not intended for direct connection to the MAINS building installations of Measurement Categories CAT II, CAT III, or CAT IV.

Environmental Characteristics

Temperature

Operating

-40 °C to 70 °C

Storage

-40 °C to 85 °C

Humidity

Operating

10% RH to 90% RH, noncondensing

Storage

5% RH to 95% RH, noncondensing

Ingress protection

IP40

Pollution Degree

2

Maximum altitude

5,000 m

Shock and Vibration
Operating vibration

Random

5 g RMS, 10 Hz to 500 Hz

Sinusoidal

5 g, 10 Hz to 500 Hz

Operating shock

30 g, 11 ms half sine; 50 g, 3 ms half sine; 18 shocks at 6 orientations

To meet these shock and vibration specifications, you must panel mount the system.

Calibration

You can obtain the calibration certificate and information about calibration services for the NI-9237 at ni.com/calibration.
Recommended calibration interval 1 year

1 Before offset null or shunt calibration.

2 Applies at a data rate of 50 kS/s. Lower data rates can have up to 0.20% of reading additional gain error.

3 Range equals 25 mV/V.

4 Applies at a data rate of 50 kS/s. Lower data rates can have up to 0.20% of reading additional gain error.

5 Range equals 25 mV/V.

6 Uncalibrated accuracy refers to the accuracy achieved when acquiring data in raw or unscaled modes and in which calibration constants that are stored in the module are not applied to the data.

7 Measured with a balanced cable on the NI-9237 with RJ-50 and with no cable on the NI-9237 with DSUB. Shielded cables that are not twisted-pair may be significantly unbalanced, which can impact CMRR performance. To improve the balance of shielded cables, NI recommends twisting together the AI+/AI– pair, the RS+/RS– pair, and the EX+/EX– pair.