WSN 3226 Wiring for 4-20mA Vibration Sensor

[Dickroach]

Trying unsuccessfully to get a 4-20mA accelerometer (12-30 VDC) working properly using NI WSN 3226; I am successful if I use an external power supply, but unsuccessful when 3226 (only) supplies power to sensor.  Anyone know the proper wiring connections for this application or where I'm going wrong?

[SoarOnSon]

What accelerometer are you using? Can you post a diagram of how the accelerometer is wired when the WSN-3226 is the only power source for the device?

Check out the specifications section of the document below for more information on the WSN-3226.

USER GUIDE AND SPECIFICATIONS - NI WSN-3226

Josh

Applications Engineer

National Instruments

[Dickroach]

Thanks for your help Josh - much appreciated!

Wiring for the 4-20 vibration sensor to the NI3226:  black wire (neg) from the sensor is wired into slot #1 (AI0) on 3226; resistor (have tried various values) jumped between slot #1 and #2 (COM0); white wire (pos) from sensor to slot #12 (Sen Pwr).

Sensor is from IMI/PCB - 640B02 – found here:

https://www.imi-sensors.com/4_20_mA_Transmitters/Products.aspx?m=640B02

Can you see my obvious flaw in this wiring?

Thanks again

[SoarOnSon]

It looks like your wiring is correct. However, I noticed in the data sheet under Note in the Operation and Wiring section that the resistor value must be less than (V_supply - 12) x 50. Since you are currently supplying 12 V to the sensor, this would mean your sensor requires more than 12 V to operate correctly. Is your external power supply providing a voltage greater than 12 V?

Josh

Applications Engineering

National Instruments

[Dickroach]

Thanks Josh; I think you're on the right track.  I've never attempted to use these type of sensors, let alone make them work with a wireless network, so pardon my ignorance.  Apparently with battery power only, the supply voltage is about 12.3 v, so we're now getting somewhat valid data with a 15 ohm resistor.  From my understanding of 4-20mA devices we will obtain more accurate vibration readings if we can use higher supply voltage (meaning we will likely use the external 24v PS), higher resistor values - opening up our window of voltage range.  Am I thinking correctly?  Thanks again

[SoarOnSon]

I think using the external 24 V power supply would be the best option since that would allow for some minor voltage fluctuations without a loss in sensor power. I'm not familiar with the sensor you are working with, but I think the sensor is only activated when excitation voltage is great enough to power the device, but that shouldn't affect accuracy.

Josh

Applications Engineer

National Instruments