By nature CO2 sensors require more current to operate than most loop powered devices.
In fact in a 4-20mA loop 0-4mA is all that is available to power devices before the measurement signal is compromised. Due to this fact CO2 sensors across the industry are three wire devices. Although sometimes a limitation, 3 wire systems also provide the ability to create voltage signals. Veris has employed this advantage by offering field selectability of 4-20mA, 0-5VDC or 0-10VDC analog outputs in a single device.