Measuring and control equipment. Hygrometers, thermometers, hygrostats, thermostats, sensors, all control of the growing space, ph meters (mostly without probes, new ones must be purchased), ec meters, ph & ec regulators, etc. etc.) Don't be afraid to buy old ph or ec meters, ec meters do not deteriorate with age and for ph you just need to buy a new probe for the old device. An ideal alternative if you want to try out watering regulation according to these devices and you don't want to buy expensive measuring devices.