This removes the observer from the whole process and allows a completely objective record of any activity to be recorded. We started in the mid 1980's with an Acorn BBC micro. This allows four sensors to be connected with only a simple interface circuit and I wrote some data logging software. We usually used three temperature sensors and one light sensor. The temperature sensors are cheap and reliable thermistors and the light sensor is a photoresistive device.
Current equipment is a bit more advance.
It uses a Viglen 486 laptop computer with a Pico Technology analogue to digital converter unit. This allows 11 sensors and data is recorded using Picolog software. This equipment has been deployed at a number sites over the years. The problem is always that you need the ghost or poltergeist to cooperate and perform for you and the equipment. We have had many puzzling effects.