我建立了DIY电导探针冰川下的测量。不幸的是我的传感器在~ 100 m的冰,所以我没有能够恢复他们检查校准,但出于同样的原因,我采取多个测量减少校准漂移,因为我无法珍惜他们。到目前为止,他们已经产生合理的数据2 +年,但我还没检查校准。但是我可以分享我的测试结果和研究以产生一个稳定的传感器。(有两个主要类型的电导率测量][1]:第一个是电位的方法。这是最常见的一个,和措施电导率通过创建两个或两个以上的电极之间的电流嵌入式在中测量。第二种类型是归纳方法,是磁场槽中,并通过变化测量电导率诱导效应,磁场在线圈。[![在这里输入图像描述][2]][2](图片取自[骑士][3])电感探针接触,因此,最稳定的。然而,他们更复杂的构建和不工作与电导率很低(< 100 /厘米)。 Glacier water is often in that very low conductivity range, something that, in addition to the higher complexity made me choose the potentiometric method (you can see a bit of my attempts to put together an induction sensor in [this forum][4]). For potentiometric probes, oxidation, deposition of salts or others chemicals can change the calibration parameters. This would be enhanced when direct current is used, as that will create acids in the water that will quickly corrode the probe. To reduce that problem, probes of inert materials are used, like platinum, gold or graphite (more common in DIY projects due to its lower cost). But to reduce deposition of chemical compounds in the probes you still need to avoid direct currents and use high-frequency alternating currents with zero mean, otherwise if there is a net current towards one electrode, you will accumulate acids or ions there that can degrade or coat the electrode and change its properties (i.e. change the calibration). [![enter image description here][5]][5] The picture above shows an example of an electric signal that can be generated using a false ground and the PWM output of an Arduino board. The setup could be as follows: [![enter image description here][6]][6] Where R1 and R2 have in general to be equal to ensure a signal with zero mean, and the value have to be chosen depending of the range of conductivity values you want to measure and the resolution. If you want to cover a wide range (pure cave water to marine water), you will have very low resolution (un less you use a AD converter with more resolution than the 10-bits provided by Arduino boards). Alternatively you can have multiple sensors each one optimized for a different range. For probes meant to be deployed outside of lab conditions, concentric electrodes are recommended, otherwise natural currents going trough the ground/water can affect the measurements. The setup I used is this one: [![enter image description here][7]][7] Where a central graphite electrode is surrounded by a ring of graphite electrodes. As you can't solder to graphite, I used conductive epoxy to glue it to a piece of plumbing copper tube modified with legs so it can be solder to a PCB. It looks like this: [![enter image description here][8]][8] Many comercial setups use three or four electrodes. I don't understand all the advantages of those sensors. In some cases they are just multiple sensors each one calibrated for a specific range. I've also seen three concentric electrodes. I haven't do the math, but my suspicion is that they measure the current in two independent electrodes with different surface area. Then, you can model and calculate the resistivity of the layer of deposits/corrosion that covers the electrodes and compensate your reading accordingly, reducing the calibration drift issues. [1]: https://en.wikipedia.org/wiki/Electrical_conductivity_meter [2]: https://i.stack.imgur.com/Dvtpi.png [3]: http://www.knightequip.com/ump.html [4]: https://forums.adafruit.com/viewtopic.php?f=19&t=54274 [5]: https://i.stack.imgur.com/RUhl3.png [6]: https://i.stack.imgur.com/m2rBl.png [7]: https://i.stack.imgur.com/6MHBQ.jpg [8]: https://i.stack.imgur.com/d6zrU.png