A recent project required me to connect a number of analog signals to a manufacturing floor data collection system. To do this I made a set of 4 connectors which I could but into the tool simply by separating existing connectors and inserting mine into the circuit. In my connector I replaced 1 wire with a 100 Ohm resistor to convert a 4-20ma signal to a voltage, along with wires and a third connector for the data collection system. While testing my connectors I measured the voltage out to the data collection system, 3 of the 4 measured .9V the 4th measured .5V. They should have been approximately equal, further investigation reveled that I had made a mistake by putting the 100 Ohm resistor in the wrong position in one of the connectors, it was on the far left it should have been on the right side. It was a easy fix to move the resistor. After the fix I proceeded to determine the slope and intercept of the line needed to convert the voltage to engineering units (in this case pressure). When I applied the equation to my measured voltages, they were wrong. Not just a little wrong but way wrong, my points were no where near the computed line! I finally used the line to compute a table of values across the range of input values. Something immediately jumped out at me. The voltage which returned the correct pressure was ~.5V. I had seen that number! That was the voltage returned by the “incorrectly” built connector. Further investigation reveled that indeed the correct current was on the 24V return line, not as specified in the manufacturer documentation on the 24V supply. It was my initial error which guided me to a correct solution, even thou it was simply not right according to the documentation I had. We later found a online copy of the sensors documentation which showed that the 4-20ma signal was in the 24V return line. Had I not made that initial mistake it is not clear how long it would have taken me to arrive at the root cause of my problems.