Measurement of current consumption on MC3 Vref

Kevin 6 years ago in Master modules / MC3 updated by Gustav Widén (System support) 6 years ago 1

Is there a way of detecting how much current draw there is on the VREF supply on an MC3?

I have experimented with a SIL2 pressure transducer connected to an MD4 (don't have an MC3 to hand) and noticed that disconnecting the -VREF and leaving +5V supply and VIN signal wires connected to the controller will generate 2500mV signal into the MD4 VIN. This is not desirable as it simulates a pressure in the system which is not true. I can only imagine its how the internal electronic circuit is manufactured inside the transducer causing the false signal, but its not unique to one manufacture of pressure transducer. The current consumption of the sensor drops from 6mA to zero when the -VE is removed, wondered if this would be a good way to detect disconnected -VREF connection?

Aside from the method above or monitoring for a sudden change in VIN signal within the software, can anyone suggest any other solution to this issue?

The VREF is monitored for voltage and over current, but the MC3 does not have a measurement of output current on the VREF.

An alternative to consider would be to use two separate pressure transducers (e.g IQAN-SP500), each with its own -VREF connection, so that loss of ground to one of them can be detected by cross monitoring.

For the pressure transducer you are experimenting with right now, is this giving you two output signals, and if so, are both connected? I don't know what sensor you are using, but it could be that both outputs must have a connection to ground via a pull-down resistor for it to handle the loss of ground. (That is the case for LC6-H1 handle loss of ground)