Voltage step down from 12V to 3V3 for cDAQ module
If you just want to measure the coil voltage to sense if the relay is on then a simple voltage divider will do the job.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A simple voltage divider will reduce the voltage to a level suitable for the cDAC input.

I'm not familiar with the cDAC module so this answer gives you the means of working out the voltage divider.

Assuming that R3, the input impedance of the cDAC input, is high (x 10) relative to R2 the voltage at INPUT will be given as the simple ratio \$ V_{IN} = V_S \frac {R2}{R1 + R2} \$, where \$ V_S \$ is the supply voltage. In the example of Figure 1 we get \$ V_{IN} = 12 \frac {12}{33 + 12} = 3.2 \; V\$. I think this is a bit low for a 5 V input but check this from the datasheets.