I am conducting an experiment on 6 samples at the same time, 6 thermistors are needed to monitor the samples' internal temperature, at the same time 4 Ultrasonic Proximity probes are needed ( to monitor water levels at 4 containers and record the elevation in each container with time) , in addition, relative humidity and air temperature in the lab are to be recorded with time, How can I cope with this setting ? Is there any way to connect these inputs to a data logger ? what kind of data logger I have to use ( 8 or 12 channels )?
Ahmad,
It all depends on the nature of the sensors.
Some of them are straight-forward.
* Thermistors
Provide them with a constant current, and measure the voltage developed across them. One channel per sensor, done!
* RH
Well. There are both analogue and digital hygrometers on the market. The HIH4000 (for example) is a fairly reliable analogue hygrometer. Provide it with constant voltage, log the output voltage.
One channel per sensor, done!
I2C sensors (we use some made by ENS: https://ams.com/ens210 ) are rather nice, but you have to develop your own PCB.
I've used standalone loggers from T&D before. Simple, robust. Not cheap.
http://www.tandd.com/product/index.html
* Ultrasonic sensors
There are so many ways that you might drive and sense these that it makes no sense to speak about logging them. Probably better off buying/renting them.
Are there better ways to record water levels?
Capacitive sensors, even some floats and a video camera (ie, dashcam) might be a fast/cheap solution.
For the T & RH logging an Arduino would suffice.
(depending on the accuracy you require)
For the level sensing I would think about how else to measure the height of a column of water.
Can you put a load transducer under the vessel and weigh it?
There are plenty of multichannel, rather low cost DAQ systems available,
e.g. https://www.dataq.com/data-acquisition/voltage/
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