I suppose you could do that but why go thru all that hassle? Wife and I picked up what is link below. Monitored our frig/freezer temps while traveling all day. Temps don't high enough to bother running propane or generator. But, I did have to buy some fancy batteries for the sensor to work in freezer, didn't work off regular batteries. That is in instructions but sort of hidden.
Wireless remote readout up front with us and fridge/freezer sensors 50 feet behind RV no problem. And cheaper than running generator.
https://www.acurite.com/digital-freezer-refrigerator-thermometer-with-temperature-alarms-00986.htmlor
https://www.youtube.com/watch?v=l5UJB3hU4OsWhat ever your comfortable with. Every year we bring home a 1/2 steer from family farm other side of state and run generator for chest type freezer in the bed of pickup as it takes us a week to get home via camping and visiting other family along the way.