Solution
Some of the most notable advantages that the NI 9237 has over the NI 9219 are:
| | NI 9237 | NI 9219 |
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| Sampling Voltage | 50 kS/s | 100 S/s/ch |
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| Excitation Voltage | Programmable up to 10V | Fixed 2.0 or 2.7 (dependant on Bridge Type and Load Resistance) |
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| Remote Sensing* | Inputs available for remote sensing, high impedance input lines that do not allow current flow and therefore do not exhibit a voltage drop due to lead resistance. | Not Available |
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| Nominal Voltage Range | Half-Bridge: +/- 25 mV / V
Full-Bridge: +/- 62.5 mV / V | Half-Bridge: +/- 500 mV / V
Full-Bridge: +/- 7.8 mV / V |
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| Quarter-Bridge Termination | Includes resistors for half-bridge termination.
Includes additional accessories for quarter-bridge termination; the NI 9944 and NI 9945 threaded terminal blocks (120 or 350Ohm) | Includes resistors for half-bridge termination.
NI 9219 has no such accessory and therefore cannot complete the Wheatstone Bridge. For quarter-bridge measurements, the NI 9219 relies on 2-wire measurements. For the same reason, it is not as accurate and does not support 3-wire quarter-bridge measurements. |
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*If your sensor is far from the data acquisition module, your measurement may reflect an error due to the resistance of the leads. The NI 9219 does not have remote sense inputs, so you may experience an additional error on the NI 9219.
In summary, the NI 9219 Universal Module is excellent if aiming to perform basic stress measurements that do not require a high sample rate, and if the sensor does not include Sense + and Sense- outputs for connection to remote sense lines. The NI 9219 offers application flexibility and the possibility of future reuse given its ability to support other types of analog input. If there is a need for a higher sample rate, the sensor being used includes Sense+ and Sense- outputs or are interested in quarter-bridge stress measurements, then the NI 9237 is the recommended one.