Need assistance with building a LabVIEW setup for Pressure/Temperature/RPM/Voltage/Amperage

Question

I'm working on assembling a LabVIEW setup that has the ability to measure Pressure, Temperature, RPM, Voltage and Amperage. I believe I have identified the correct modules but am looking for another opinion before giving anyone a lot of money.

Requirements:

• Temperature: Able to measure 7 channels of temperatures ranging from ambient to 300 degrees F.
• RPM: Able to measure shaft RPM up to 3600.
• Voltage: Able to measure up to 500 Volts, 3 phase AC.
• Amperage: Able to measure up to 400 Amps, 3 phase AC.
• Pressure: Able to measure 2 channels of various ranges of PSI
  (specific transducers to be identified at a later date).

The Gear:

• Chassis: cDAQ-9174 with the PS-14.
• Temperature: T type thermocouples and NI-9212.
• RPM: Monarch Instrument Remote Optical Laser Sensor and NI-9421. Laser uses 24 volts but returns 19 volts when target is present and 0 volts when the target is not present.
• Voltage*: ATO three phase AC voltage sensor ATO-VOS-3AC500 outputting 0-5 volts and either NI-9224 or NI-9252.
• Amperage*: 3, Fluke i400 units returning 1mV per Amp and either NI-9224 or NI-9252.
• Pressure: 2, 4-20mA 2 or 3 wire pressure transducers to be identified at a later date, and either NI-9203 or NI-9253.

*Voltage and amperage will be measured on the same unit

Questions:

• RPM: Will the NI-9421 record a pulse of 19 volts?
• Voltage and Amperage: What is difference between the NI-9224 and the NI-9252, which one would work best for my application?
• Pressure: What is the difference between the NI-9203 and the NI-9253 other than input resolution and which one would work best for my application? Resolution is not a priority.
• Overall: Anything stand out as a red flag?

I have not tried any of this equipment out myself.

Thanks in advance for your expertise and patience.

Answer 1

First things first, I would encourage you to strike up a conversation with whichever NI distributor is local to you. Checking specifications and compatibility between sensors, modules, chassis, etc. is very much in their wheelhouse, and typically falls in the pre-sales phase of discussion so you shouldn't need to spend money to get their expertise.

(Also, if you're new to LabVIEW and NI: I very much recommend checking out the NI forums in addition to Stack Exchange. Both are generally pretty helpful communities!)

One thing I'm not seeing in the requirements you listed that would be very helpful are timing requirements/sample rates. What frequency do you need to sample each of these inputs, and for how long? How much jitter and skew between samples is acceptable? Building a table of signal characteristics including: original project specification, specification in units of the measurement device, minimum sample rate, analog/digital, and which module the channel is on will make configuring a chassis to meet your needs a lot easier.

For a cDAQ system the sample rates you measure at, and how many different ones you can run at one time, is determined by the chassis rather than the module. (PCI/PXI data acquisition cards have the timing engine on the card.) For the cDAQ-9174 you can run multiple tasks per chassis but only one task per module. You may need to group your inputs onto modules that run at similar rates to fit into the available tasks. I put a link to NI's documentation of the cDAQ timing engine at the bottom.

Now to try to summarize the questions:

• Homer512 is correct about voltage, 11V is the ON threshold. However, the NI-9421 can only count pulses up to 10kHZ into the counter. How many pulses are generated per rotation? Napkin math says one pulse per rotation at 3600RPM means you're capturing a 216kHz pulse stream at minimum. (This is why timing is everything. You also probably don't want to transfer every single pulse to calculate the RPM constantly, more likely you need the counter to sum up the pulses as fast as they happen, and at a slower rate you check to see how many counts went by since your last check-in.)
• Homer512 is correct again, NI 9252 has additional hardware filtering before the ADCs. This would be for frequency filters on the input source, not usually something you would use if you're just reading a 5V signal from a sensor.
• NI 9203 uses a SAR ADC (200kS/s), NI 9253 uses a Delta-Sigma (50kS/s/ch). Long story short: NI 9253 is more accurate but slower. I'd need more information to make a best for application judgement, specifically numerical requirements on resolution and timing.
• Red flags: kinda captured it in the other points, but the project requirements have some gaps. I've had " is not a priority" and requirements in a unit other than the measurement device (RPM vs. pulses/s or Hz) bite me enough times that I highly recommend having it written down even if it's blatantly obvious.

Links may move in the future, and the titles are weird, but here are a few relevant NI docs:

• "Number of Concurrent Tasks on a CompactDAQ Chassis Gen II" https://www.ni.com/en-us/support/documentation/supplemental/18/number-of-concurrent-tasks-on-a-compactdaq-chassis-gen-ii.html
• "cDAQ Module Support for Accessing On-board Counters" https://www.ni.com/en-us/support/documentation/supplemental/18/cdaq-module-support-for-accessing-on-board-counters.html