Figure 1. GMP251 probe. GMP251 is a robust carbon dioxide (CO2) measurement probe for use in demanding applications such as life science incubators. Operating temperature range −40 ... +60 °C (−40 ... +140 °F). 1 M12 5-pin male connector. Must be connected to the M12 connector of the Probe Splitter M8/M12 accessory. 2 Ø 25 mm probe body. 2 Sensor protection filter. Do not attach from this area.