I currently have an OpenLog Artemis setup built that was going to go on a test stand in our lab but those plans have changed and it is currently sitting idle and available. I am involved in a different project now and we are doing testing on liquid pressures through our machine. What type of interface board(s) will I need to use the OpenLog Artemis to read in-line pressure transducers? I appreciate any and all help.
Thanks!
The OLA is pre-programmed to interface with many SparkFun sensors out-of-the-box, and can also perform analog logging via pin 32 and serial logging on RX/13 OpenLog Artemis Hookup Guide - SparkFun Learn - what protocol would the transducer use?
That sensor (probably, we can’t see it all) has an amplifier built in to scale the output 4-20mA, proportionally, across the 0-150 psi rated input. The terminal pair simultaneously provides power/excitation while transmitting its measured value in the analog return current. The terms to research are current sinking vs current sourcing sensors.
This allows for more easily installed sensors (2 vs 3 wires), some provision for primitive remote troubleshooting. Those are advantages in the factory but not a desirable on the bench or learning environment where a signal generating sourcing sensor is more easily experimented and demonstrated.
A 150 Ohm, 1% tolerance (or better) resistor in series with the sensor ground lead will scale the 4-20 mA output current to the voltage range of 0.6 to 3.0 V, which is convenient to read with a microprocessor ADC.
For the Artemis use a 100 Ohm, 1% or better resistor, as the ADC maximum input voltage is 2.0V.
Alternatively you can buy 4-20 mA to digital interface modules.
