I do firmly believe that dataloggers are intended to substitute netbook, and not viceversa. Having a computer (even a netbook) in the field immediately rises the problem of power availability, and then that of sturdiness. Dataloggers can be specifically designed to face the many difficulties of the natural environment, with a very low power consumption.

That said, I would advicde you to plan a bit better type and number of measurements you will want to deploy. Many sensor give a voltage as an output, but not all (some give out an alternate voltage, and your logger will have to be able to measure a frequency).

Another issue to consider is the number of "stations". Very often the soil has a high variablity, and you like to sample with an extende network of sensors/loggers. At that point, loggers should also be cheap...

If you will need just temperature and moisture (which still is a very difficult variable), you may wanto to have a look at Decagon Devices (http://www.decagon.com). They produce both sensors and loggers.

More sophysticated hardware (again, sensors and loggers) are thos by Campbell Scientific (http://www.campbellsci.com). Here, you will have higher flexibility and complexity, and the road open to logging everything else you may desire.

The soil moisture sensor by Campbell can be read also by small, cheap dataloggers like these: http://www.slsargent.com/  Actually, I do not know whether this producer is still alaive, but their loggers were interesting, since they could be buried in a waterproof box, and let them run for months on their own.

If you are just interested in soil temperature, you may also consider simple "buttons" which can store quite some data at regular fixed intervals. You can deploy tens of them... the only difficulty you will experience will be in retrieving them!

'Hope this helps,

Best,

Andrea

First of all I would like to raise a question, is the goal of your surveying is soil survey or any other goal? in anyhow the first important issue is the sampling I would like from you to be sure that this sample is represented the area of sample the other important thing is the storage of these samples until beginning the lab analysis because your survey including soil biota, I would like also to advise you to look at this literature. http://www.proprights.org/PDFs/workshop_2011/References/NRCS/SSIR_51.pdf

Hi Andres,

A replacement for a conventional data logger can be quite a simple smartphone (even without SIM card) or a netbook. However, a specified program is to be programmed to receive the data from the sensors and recorded.

The solution with the smartphone offering in Germany, the Firm UGT (http://www.ugt-online.de) to. I'm sure other companies also have the smart phone or netbook solution.

The setup of the experimental array is another question. The sensors for the sought-after parameters and measured depths must be adapted to your research question!

Best regards from Osnabrück/ Germany

I do firmly believe that dataloggers are intended to substitute netbook, and not viceversa. Having a computer (even a netbook) in the field immediately rises the problem of power availability, and then that of sturdiness. Dataloggers can be specifically designed to face the many difficulties of the natural environment, with a very low power consumption.

That said, I would advicde you to plan a bit better type and number of measurements you will want to deploy. Many sensor give a voltage as an output, but not all (some give out an alternate voltage, and your logger will have to be able to measure a frequency).

Another issue to consider is the number of "stations". Very often the soil has a high variablity, and you like to sample with an extende network of sensors/loggers. At that point, loggers should also be cheap...

If you will need just temperature and moisture (which still is a very difficult variable), you may wanto to have a look at Decagon Devices (http://www.decagon.com). They produce both sensors and loggers.

More sophysticated hardware (again, sensors and loggers) are thos by Campbell Scientific (http://www.campbellsci.com). Here, you will have higher flexibility and complexity, and the road open to logging everything else you may desire.

The soil moisture sensor by Campbell can be read also by small, cheap dataloggers like these: http://www.slsargent.com/  Actually, I do not know whether this producer is still alaive, but their loggers were interesting, since they could be buried in a waterproof box, and let them run for months on their own.

If you are just interested in soil temperature, you may also consider simple "buttons" which can store quite some data at regular fixed intervals. You can deploy tens of them... the only difficulty you will experience will be in retrieving them!

'Hope this helps,

Best,

Andrea

Getting an accurate measure of soil moisture is difficult.

The gold standard for soil moisture is Jack Stone's Neutron Probe. It's radioactive putting of Neutrons that are extremely difficult to sense and the probe is placed in tight fitting hole that need to be check each and every time with a dummy probe to be sure the live probe doesn't get stuck in the hole. A probe stuck in a hole is a nuclear incident.

I worked 3 soil moisture sensors in the 1990's for Biosystems and Ag Engineering at Oklahoma State. The one that measured the capacitance or phase shift at 50 MHz on 2 Copper bands around 1.5 inch Plexiglas rod work until the soil broke away in dry weather and didn't reestablish the same contact. It also took a very long time to calibrate. I made one that had a Gypsum block on a temperature sensor that had a predictable increases in temperature when it was engined. The method was measure the temperature of the Gypsum block, heat up for a few seconds then measure the time it took for the Gypsum block to cool down.  It was easy to calibrate but Jack Stone pointed out I was measuring the relative humidity of the soil not the moisture in the soil. It also broke away form dry soil.

There was a third test going on that used an array of thermocouples at different depths in the ground and the readings were to be calibrated with weekly Neutron Probe surnames. On of the batteries failed and it only recoded day while the sun shown on the solos panel. I think that method hold promise but it would take 5 years to get a good calibration. OK for a farmer as the accuracy gets better each year. It is hard for an academic unless they have time to do it all themselves to make sure its down the same every time.

The farmer that farms my wife's irrigated place in West Texas dives a steel rod in the ground, digs with a shovel and uses his expertise to tell when to water. Of all the methods his is as good as any I have tried but the Neutron probe.

We spent a good deal of money and time and didn't publish a paper on any of them.

If I had to choose one today I would use Time Domain Reflectometry if I didn't have access to Neutron probes. If I needed accuracy I would take two samples and weigh them on the spot. Then dry one in the lap and raise the other one to field capacity by adding water then letting stabilize  in a 100% humidly camber. Then weigh them again. If I had historical density of samples that were taken a field capacity and in a drouth I could come awfully close.

For soil temperature any sensor that works with the instantiation and the method you use. A calibrated string of two or three Silicon diodes or transistors as diodes would do fine as will any senor that doesn't heat up much when read and had twice the precision you need.

Good Luck

Gordon

A number of sensors are available for use with dataloggers to measure soil moisture in terms of volumetric water content - I have used CS616 sensors from Campbell Scientific and also have used 10HS and other sensors from Onset (using Campbell dataloggers or onset hobo dataloggers).  These are both tdr based sensors.  Temperature sensors are also available for use with these dataloggers.  The Onset - HOBO dataloggers with their "plug-and-play" sensors are by far the easiest to use, and less expensive (if you are purchasing sensors), but the Campbell dataloggers and some of their sensors are more rugged and reliable, in my experience.  (I have had CS616 sensors run for multiple years without problems).

You should also check out the delta T theta probe (which could be used as a portable device with a digital readout), and the delta-t profile probe (which is a portable tdr based unit, that uses installed tubes for probe insertion).  I have used theta probes in the past for some studies where we just wanted to compare locations at one or a few points in time.

Campbell, Onset and others have standard thermistor based soil temperature sensors that run with their dataloggers.  I have used thermocouples that we make in our lab, as well.  However these are really only useful if you need large numbers of temperature sensors, since you do need to have a thermistor installed near the wiring panel of a Campbell datalogger as a "reference".   You could also use a portable digital soil thermometer to take instantaneous readings if you do not need to log data or longer time periods, and if you can collect measurements within a short time period.

Check out the websites for Onset, Campbell Scientific, Delta-T, Decagon Devices and others for sensors and dataloggers.

Are you looking to take one-off measurements or ongoing monitoring?

I am using Decagon devices (TDRs, matric potential probes and temperature probes) at several depths in conjunction with Campbel Scientific dataloggers. While the initial installation is a little demanding, the reliability of the equipment over time has been outstanding. Campbell Sci provided excellent customer support as regards the programming of my equipment.

Also, as Philip mentioned, many datalogger/sensors have a plug-and-play capacity that makes installation easier. Keep in mind the demands placed on in-situ devices; my dataloggers are stored in Campbell Sci loggerboxes and powered via solar panel. These are attached to a steel post. A hedge cutter struck these and ripped both loggerbox and panel off the post, which was mangled by the blades. The equipment was totally unharmed and I lost no measurements or power!

You can't always predict these sort of occurences when conducting fieldwork, so from personal experience I would certainly recomend dataloggers and a sturdy loggerbox!

Here are a couple of additional ideas. Sometime it comes down to numbers of samples (number of sample locations as well as number of samples per location).  In research I have done on short grass rangeland (at CSU) for soil temperatures you could use a datalogger called an ibutton (Maxium) which is quite low cost ~$20-$50 per logger. The up side is the low cost so you can monitor a lot of locations and depths for a relative low cost. The downside is the loggers are self contained and you have to leave the logger in place for the duration (It'll store nearly a years worth of data) of the experiment before retreving the data.

Soil water status is more difficult and costly, in addition to suggestions from others, take a look a Time Domain Transmissometry  ( TDT) (Acclima).

Lastly we have started building our own loggers for specialty applications with various collectors (Temp, solar etc.) take a look at Arduino on the Web. Again cost vs time vs data always have to be in balance.

Visit http://www.ugt-online.de/en/products/soil-science.html