The compatibility issue of NI-9234 with the IEPE sensor

[Chali]

I am currently preparing to use the NI-9054 and NI-9234 to collect data from the IEPE sensor. The specification sheet of NI-9234 states: 1.If you are using an IEPE sensor, use the following equation to make sure your configuration meets the IEPE compliance voltage range. (Vcommon-mode + Vbias ± Vfull-scale) must be within the range of 0 to 19. I am currently planning to use the wilcoxon786-500. Its Vbias is 12V and Vfull-scale is 5V, which clearly meets the requirements. However, the specification sheet of the 786-500 states (Acceleration range, VDC > 22V 10g peak) Here, it is required that VDC should be greater than 22V. Does this conflict with the compliance voltage of 19V? Moreover, when I was choosing other sensors, its Vbias ± Vfull-scale was within 19V, but it required a working voltage of 20-30V. I'm not sure if this sensor is also applicable. How to select the sensor that is compatible with NI-9234? What criteria should be used? Can anyone explain the principle behind this? Thank you all!

[santo_13]

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@Chali wrote:
I am currently preparing to use the NI-9054 and NI-9234 to collect data from the IEPE sensor. The specification sheet of NI-9234 states: 1.If you are using an IEPE sensor, use the following equation to make sure your configuration meets the IEPE compliance voltage range. (Vcommon-mode + Vbias ± Vfull-scale) must be within the range of 0 to 19. I am currently planning to use the wilcoxon786-500. Its Vbias is 12V and Vfull-scale is 5V, which clearly meets the requirements. However, the specification sheet of the 786-500 states (Acceleration range, VDC > 22V 10g peak) Here, it is required that VDC should be greater than 22V. Does this conflict with the compliance voltage of 19V? Moreover, when I was choosing other sensors, its Vbias ± Vfull-scale was within 19V, but it required a working voltage of 20-30V. I'm not sure if this sensor is also applicable. How to select the sensor that is compatible with NI-9234? What criteria should be used? Can anyone explain the principle behind this? Thank you all!

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What is the maximum acceleration you plan to measure and is that signal within the IEPE drive signal range?

[Chali]

Hi The measurement range of the sensor is 10g, and the range I need is around 5g. It falls within this range. I'm just wondering how the NI-9234 and the IEPE type sensor work together. Also, what is the actual excitation voltage that the NI-9234 can reach? Is it the compatible voltage of 19V as stated in the specification of 9234? Or is it some other value? Because there are other sensors whose operating voltage is above 20V. I don't know if these sensors can be compatible with 9324.

[santo_13]

Since the compliance voltage is 19V, when sensor tries to generate more than 19V, the IEPE circuit cannot maintain constant current.

If your sensor operating voltage is more than 19V, you need a different card instead of 9234 or use an external IEPE signal conditioner.

I believe you already read this Excitation and Compliance Voltage for IEPE Sensors in NI Cards - NI

[Chali]

OK. Here's the situation. I used another sensor, whose specification states that the operating voltage is 20-30V, but its Vbias + Vfull-scale = 17V. When I used the NI-9234 to collect data from it, the data appeared and seemed normal. So I'm confused. When choosing a sensor, 1. Do I need to check if the operating voltage is less than the compatible voltage of 19V? 2. Or do I only need to ensure that Vcommon-mode + Vbias + Vfull-scale is within 0 to 19V, without caring about the size of the operating voltage? 3. Also, if Vcommon-mode + Vbias + Vfull-scale is within 0 to 19V, but I only use a part of the sensor's range, and the total voltage does not exceed 19V, can it still be used normally in this case?

[santo_13]

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@Chali wrote:
OK. Here's the situation. I used another sensor, whose specification states that the operating voltage is 20-30V, but its Vbias + Vfull-scale = 17V. When I used the NI-9234 to collect data from it, the data appeared and seemed normal. So I'm confused. When choosing a sensor, 1. Do I need to check if the operating voltage is less than the compatible voltage of 19V? 2. Or do I only need to ensure that Vcommon-mode + Vbias + Vfull-scale is within 0 to 19V, without caring about the size of the operating voltage? 3. Also, if Vcommon-mode + Vbias + Vfull-scale is within 0 to 19V, but I only use a part of the sensor's range, and the total voltage does not exceed 19V, can it still be used normally in this case?

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As long as your sensor value range results in Vcommon-mode + Vbias + Vfull-scale is within 0 to 19V, you're good. 

Please share datasheet of the other sensor that had 20-30V operating range to verify if that is a minimum.

[Chali]

Hello
MegaSig is a sensor that I have tried out. My Vbias + Vfull-scale is less than 19v, but the operating voltage is written as 20-30v. However, when I tried to measure the acceleration with a smaller amplitude, it seemed fine.
There is another HBK sensor. I saw that its Vbias + Vfull-scale is greater than 19V. Is this HBK sensor unusable? It can still be used, but Vcommon-mode + Vbias + Vmeasure cannot be greater than 19V.

[Chali]

Hello. I wonder if you have time to check my reply. If you do, could you please take a look at the sensor specification sheet I uploaded? It would be great if you could reply. Thank you very much!

[santo_13]

I would interpret the range as the required voltage range for full range operation and you may be still fine to operate both sensors as long as the sensor signal is within 19V