Most dehumidifiers/humidifiers have a built in humidity sensor. Simply set it to a given value and it will work to keep the humidity at a certain spot.
More important is the capability of dehumidifier than fancy controllers. If you are dehumidifying the lung room you will need some serious power on it to keep the moisture of the air going inside of the tent at bay.
I would not use a dehumidifier inside of the tent as it tends to create a microclimate.