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?
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?
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:
Can you see my obvious flaw in this wiring?
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?
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
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.