Greisinger gtf 300 nicr ni standard measuring probe type k greisinger gtf 300 the greisinger gtf 300 is a type k wire probe mini thermocouple wire sensor for gases liquids and extremely small surfaces the sensor is supplied with 1m teflon insulated twisted wires terminated with a mini thermocouple plug greisinger gtf 300 type k wire probe mini thermocouple 65 to 300 deg