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4.2 ELECTRODES: A FEW IMPORTANT WORDS: You may have noticed that I have insisted particularly that you do not remove the electrode from the water while the meter/controller is in the on position. This is very important. It will prevent the electrode from becoming polarized. An electrode can become polarized in as little as 15 seconds if taken out of the water and held up in the air while the unit is plugged in. Should such happen, your electrode will become sluggish, and read inaccurately. You may even have to buy a new one. And at the price they are, you certainly want to avoid having to do so. Polarized electrodes can sometimes be regenerated. The procedure is not simple and success is not guaranteed. Always unplug the meter/controller before removing an electrode from the water. Always place the electrode in the water before plugging in the meter/controller, or switching it on. You must also clean your electrode regularly. More so if it is in an area where strong light is present. Algae will grow on the tip and on the semi-permeable membrane around the tip. They must be cleaned using a special pH electrode cleaning solution. Do not use home brews, or generic stuff, even if someone you know tells you over and over that they are safe and do the job. I have seen a lot of ruined electrodes that way. Buy the special cleaning solutions that are offered for sale by scientific supply houses, Route 4 Marine Technology, Thiel*Aqua*Tech and others. Make it part of your regular maintenance schedule. About every 3 to 4 weeks is average. Never let the tip of the electrode become dry. This will affect the accuracy of the probe and result in increased drift and an inaccurate reading. Drift is defined as an electrode that does not remain stable, even though the liquid in which it is immersed does. For example, if you immerse an electrode in a pH 8.0 calibrating solution, after a short while, if your electrode is accurate, the meter or controller will indicate a pH of 8.0. If, however, that reading does not remain stable, even though you have added nothing to the solution, your electrode is said to be drifting. Small drifting is unavoidable, e.g. 0.05 pH over 24 hours is not uncommon. If the drift is greater, your electrode is damaged and may need replacing. Mishandling the probe will exacerbate this drift. Never remove an electrode that is attached to a plugged-in meter or controller from the water. Never switch on a meter or controller before the electrode is already submersed. Doing so will greatly shorten the lifespan of an electrode. This is true for any kind of electrode: pH, redox, oxygen, ion elective and so on. Electrodes are highly sensitive. Protect your investment by cleaning them regularly. About $25.00 should get you the two cleaning solutions you will need. The placement, positioning that is, of an electrode is an important criterion in deciding the set points that will be used when installing a controller for pH or redox potential. It is also important in terms of how often the electrode may need to be cleaned. Electrode must always be in a location where good water flow exists over the sensing part of the probe. Such will ensure a more accurate reading. Here are some suggested locations and their relative merits: Cleaning as suggested already. 4.3 CALIBRATING ELECTRODES: The usual procedure to be followed to calibrate a pH meter or controller is as follows: Electrodes should be recalibrated after they have been cleaned with a pH or redox electrode cleaning solution. Always be careful not to damage the BNC jack at the end of the wire attached to the electrode. Do not get any water or salt on the BNC jack, this will short out the electrode, give a zero reading on the meter/controller, and may damage both. Be extremely careful not to nick the electrode cable. Do not run this same cable too close to an electric wire, interference may occur that will make your meter's reading jump around erratically. If your meter/controller acts in this manner, look first for electric wires that are either touching the electrode cable, or are very close to it. Do not touch your meter and/or electrode if you suspect that you are carrying static electricity. Touch a metal object first. Transferring static electricity to the meter can damage the circuits and other electronic parts, ruining the instrument. Because the glass tip of the electrode is extremely fragile, take great care not to hit it against the filter or aquarium. If it breaks your electrode needs to be replaced. Never clean your electrode with boiling or very hot water, except if the electrode you own has been certified for use at such high temperatures. Many types of electrodes for pH, redox potential and specific ion measurements are available through scientific supply houses. That is, too, where you will find the widest choice and the greatest variety of length, thickness, body materials, junctions, and so on. We have already indicated the names of some of the better known ones: Cole Parmer, Markson's, Extech, Omega, and so on. Brand names of electrodes can vary greatly, mainly because electrode manufacturers will let other companies relabel the electrode in their own names. Buy enough electrodes and companies such as Sensorex will put your own name on them, or let you affix the stickers yourself. Many electrodes sold in the hobby fit into this class. One can classify electrodes in 3 broad categories: general purpose inexpensive electrodes, medium quality more accurate electrodes, laboratory quality expensive to very expensive electrodes. A pH electrode, for instance, can cost as little as $39.00 to as much as $475.00 for a specialized Orion, Beckman or Hach brand one. Most of the ones sold in the hobby are in the lower price category, but because of intermediate mark-ups, they will end up costing you from $100.00 to $150.00 anyway. You may, however, still be getting an electrode that you can buy elsewhere for $50.00 or so (through the channels already mentioned). There are exceptions of course, some excellent ones are sold by at least two aquarium manufacturers. One electrode is German in origin (Tunze), the other one is English (TAT). The same applies to redox potential electrodes, both quality and cost price wise. To get a truly excellent electrode you will have to spend upwards of $175.00 when buying from a scientific supply house. Spending that amount when buying from a dealer in the hobby, does not guarantee that you will get excellent quality, except with the two exceptions mentioned. The main reason for this is that all products that are not intended for the hobby, e.g. electrodes, that are sold in pet stores, or through ads in the magazines (especially mail order), are offered to you at greatly marked-up prices. You could buy a better electrode, for less money, if you took the time to buy it from a scientific supply house. These remarks are not meant to discredit mail order places or pet stores, to the contrary, they are meant to explain the real facts of life. Because the market for electrodes, for example, is small in the hobby, those who buy them from manufacturers to resell them to you, only buy small quantities and cannot obtain large discounts. Not much more, usually, than 20 to 25 percent, if that. When such an item now goes through 2, or sometimes 3, intermediaries, you can be sure that after it has been marked up once or twice, it will cost more than what it originally was listed for as a retail price in the manufacturer's catalog. To give you an idea of the prices of some pH electrodes that you may want to consider here is a sampling taken from the 1989 catalog of Cole Parmer, page 510 and onwards: As already indicated a good electrode for use in reef tanks should be selected from the lower range of the medium cost type electrodes. Get either a really inexpensive electrode and replace it often, or buy a real good quality one, but not the top of the line.
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