The Behringer ECM-8000 has a lot of response variability between units, so unless you get your specimen characterized, you could get very inaccurate measurements. A surprising value is the Dayton Audio EMM-6. It only costs around 60 USD (or less if you find a sale) but comes with its own calibration file (you submit the serial number on their web site and download the info). Users have commented that the build quality is similar to the ECM-8000 with the bonus of being predictable. All of these mikes require an XLR jack, and phantom power in the preamp.