Hi, we are using a NI 9219 module for current measurements. We have 2 position sensors and 2 flow meters connected to one module. We have 3 systems containing 3 modules. Normally everything works fine, but after a restart of a system there is a chance you get the maximum reading of an input (25 mA). After some resistance measurement's on the input I discovered that the module switches off his current measurement (shunt) resistor. Ofter some while the resistor is back online again, but we are certain that the sensor aren't giving this value so I started to dig in the module. Thanks to NI support we established the following: The system resets, and the shunt resistor is disconnected the sensors are increasing their outputs in attempt to deliver the correct current The module comes back online, configures and puts the shunt resistor back in place The sensor decreases its output, but sometimes (because the problem doesn't occur at all restarts) this happens not fast enough. This is on both the position sensor and the flow sensor. The protection circuit (which is the one described in the paragraph about excitation protection) switches off the shunt resistor, because it detects to high power The sensor increases again its output because it sees a high resistance So to avoid this from happening, or to get everything going again the sensors should be disable giving the protection circuit the chance to recover and put the 30 ohm resistor back in place again. For us this means that we need to design this in the control system since all three locations are very remote. With other modules (like the NI 9203) the resistor is never switched off. So with other applications we didn't take a reset circuit in account. So we ever implemented it this way, but should it normally be this way? So if you reset (software reset or hard reset) your system is it common to switch off your sensors, then reboot your system and after reboot enable your sensors again? I know this isn't really a problem question, but I'm curious if it is just us who missed something. Best regards,

Multifunction DAQ

NI 9219 reads maximum in current mode

Hi,

we are using a NI 9219 module for current measurements. We have 2 position sensors and 2 flow meters connected to one module. We have 3 systems containing 3 modules. Normally everything works fine, but after a restart of a system there is a chance you get the maximum reading of an input (25 mA). After some resistance measurement's on the input I discovered that the module switches off his current measurement (shunt) resistor. Ofter some while the resistor is back online again, but we are certain that the sensor aren't giving this value so I started to dig in the module. Thanks to NI support we established the following:

The system resets, and the shunt resistor is disconnected
the sensors are increasing their outputs in attempt to deliver the correct current
The module comes back online, configures and puts the shunt resistor back in place
The sensor decreases its output, but sometimes (because the problem doesn't occur at all restarts) this happens not fast enough. This is on both the position sensor and the flow sensor.
The protection circuit (which is the one described in the paragraph about excitation protection) switches off the shunt resistor, because it detects to high power
The sensor increases again its output because it sees a high resistance

So to avoid this from happening, or to get everything going again the sensors should be disable giving the protection circuit the chance to recover and put the 30 ohm resistor back in place again. For us this means that we need to design this in the control system since all three locations are very remote.

With other modules (like the NI 9203) the resistor is never switched off. So with other applications we didn't take a reset circuit in account. So we ever implemented it this way, but should it normally be this way? So if you reset (software reset or hard reset) your system is it common to switch off your sensors, then reboot your system and after reboot enable your sensors again?

I know this isn't really a problem question, but I'm curious if it is just us who missed something.

Best regards,