Off brand Ph probe
- Thread starter ludiNano
- Start date
Most meters and probes use a connection called BNC. Look for that. Optimally, you'll find a double junction, sealed probe, but others can be OK. I discuss such issues here:
Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm
A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm
Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm
A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm
JR's Reef
Premium Member
therealfatman
In Memoriam
The typical difference between the cheaper and the middle priced pH probes is often the length of the probe as the cheaper probes typically used with hobby grade pH meters and monitors are Ag/AgCl Gel type. The smaller/shorter the probe the less gel type Ag/AgCl electrolyte it contains. The less it contains the more often it will need to be replaced. For cheap probes the profit lies in volume of sells.
With the more expensive probs you have built in temperature capability and they are usually refillable not gel type and they can have more features not need for aquarium monitoring. There are probes that will give very quick readings but your then into price ranges of $250 - $450 per probe.
One way to look at it is that a good probe will work on cheap pH meters but cheap probes will seldom work on good meters.
With the more expensive probs you have built in temperature capability and they are usually refillable not gel type and they can have more features not need for aquarium monitoring. There are probes that will give very quick readings but your then into price ranges of $250 - $450 per probe.
One way to look at it is that a good probe will work on cheap pH meters but cheap probes will seldom work on good meters.
therealfatman
In Memoriam
If it is a double junction electrode it will not be cheap and it would very likely include the fact that it is a double junction electrode in an advertisement if it is a double junction probe as it increases its value and cost. Typically double junction electrodes are not used with the pH meters typically use in the aquarium trade. However the below describes the difference between a single and double junction electrode. Personnaly I would suggest that unlees you are seeking unnecesary information on Double junction electrodes you just skp down to the area in bold and read from there down.
In classical combined pH electrode reference electrode is separated from the external solution by the junction through which the electrolyte leaks. Lost electrolyte must be periodically refilled through the filling hole, which makes these electrodes inconvenient to use, especially in the field. Methods of slowing down the leak - like gelling of the electrolyte - have a side effect of shortening the lifetime of the electrode, as it is more prone to the changes in electrolyte composition due to contamination and diffusional leak of the ions. Contaminated gel can not be replaced, thus lifetime of gel electrode is rarely longer then several months.
To prolong lifetime of such electrodes double junction is sometimes used. In double junction electrodes additional chamber is introduced between reference electrode and external solution. Before contamination from the external solution can get to the reference electrode it must diffuse through not one junction, but two (hence the name). Additional chamber works as a buffer, slowing down the changes in the composition of the reference electrode electrolyte. Double junction electrodes can work longer, but they are more difficult to make, thus more expensive.
Typically what you will be dealing with in aquarium grade pH probes is either a standand single electrode pH probe or what is referred to as a comination pH electrode. Both are addressed below.
The most often used pH electrodes out side the aquarium trade are are glass electrodes so this artcles centers around glass body elecrodes but it asso applies to the plastic bodied electrodes. The typical model is made of glass tube ended with small glass bubble. The inside of the electrode is usually filled with a buffered solution of chlorides in which sa ilver wire covered with silver chloride is immersed. The pH of the internal solution varies - for example it can be 1.0 (0.1M HCl) or 7.0 (different buffers used by different producers).
The active part of the electrode is the glass bubble. While the tube has strong and thick walls, the bubble is made to be as thin as possible. The surface of the glass is protonated by both internal and external solution untill equilibrium is achieved. Both sides of the glass are charged by the adsorbed protons, this charge is responsible for potential difference. This potential in turn is described by the Nernst equation and is directly proportional to the pH difference between solutions on both sides of the glass.
The majority of pH electrodes available commercially are combination electrodes that have both a glass H+ ion sensitive electrode and additional reference electrode conveniently placed in one housing. For some specific applications separate pH electrodes and reference electrodes are still used - they allow higher precision needed sometimes for research purposes. In most cases combination electrodes are precise enough and much more convenient to use.
Construction of combination electrode is in large part defined by the processes that must take place when measuring pH. We need to measure difference of potentials between sides of glass in the glass electrode. To do so we need a closed circuit.
The circuit is closed through the solutions - internal and external - and the pH meter. However, for correct and stable results of measurements reference electrode must be isolated from the solution so that they will not crosscontaminate - and it is not an easy task to connect and isolate two solutions at the same time.
Connection is made through a small hole in the electrode body. This hole is blocked by porous membrane, or ceramic (asbestous in older models) Fiberwick. Internal solution flows very slowly through the junction, thus such electrodes are called flowing electrodes. To slow down the leaking, in gel electrodes internal solution is gelled.
To put it in a nut shell what as a aquarium keeper you would normally be looking for is typically called a combination pH probe or electrode that has the proper connector type needed for your pH meter. Most newer pH meters have the push and turn BN or BNC connector. Tyipcally the difference between the cheaper pH probe lies in the physical dimensions of the probe. The smaller diameter probes use less material and hold less gel and are cheaper to ship, but as they hold less gel they do not last as long. There are also Triode electrodes that will make it capable for some pH meters to read the temperture of the sample water while obtaining the pH reading.
When advertisement refer to fiber junctions they are referring to the wick as describe above.
In classical combined pH electrode reference electrode is separated from the external solution by the junction through which the electrolyte leaks. Lost electrolyte must be periodically refilled through the filling hole, which makes these electrodes inconvenient to use, especially in the field. Methods of slowing down the leak - like gelling of the electrolyte - have a side effect of shortening the lifetime of the electrode, as it is more prone to the changes in electrolyte composition due to contamination and diffusional leak of the ions. Contaminated gel can not be replaced, thus lifetime of gel electrode is rarely longer then several months.
To prolong lifetime of such electrodes double junction is sometimes used. In double junction electrodes additional chamber is introduced between reference electrode and external solution. Before contamination from the external solution can get to the reference electrode it must diffuse through not one junction, but two (hence the name). Additional chamber works as a buffer, slowing down the changes in the composition of the reference electrode electrolyte. Double junction electrodes can work longer, but they are more difficult to make, thus more expensive.
Typically what you will be dealing with in aquarium grade pH probes is either a standand single electrode pH probe or what is referred to as a comination pH electrode. Both are addressed below.
The most often used pH electrodes out side the aquarium trade are are glass electrodes so this artcles centers around glass body elecrodes but it asso applies to the plastic bodied electrodes. The typical model is made of glass tube ended with small glass bubble. The inside of the electrode is usually filled with a buffered solution of chlorides in which sa ilver wire covered with silver chloride is immersed. The pH of the internal solution varies - for example it can be 1.0 (0.1M HCl) or 7.0 (different buffers used by different producers).
The active part of the electrode is the glass bubble. While the tube has strong and thick walls, the bubble is made to be as thin as possible. The surface of the glass is protonated by both internal and external solution untill equilibrium is achieved. Both sides of the glass are charged by the adsorbed protons, this charge is responsible for potential difference. This potential in turn is described by the Nernst equation and is directly proportional to the pH difference between solutions on both sides of the glass.
The majority of pH electrodes available commercially are combination electrodes that have both a glass H+ ion sensitive electrode and additional reference electrode conveniently placed in one housing. For some specific applications separate pH electrodes and reference electrodes are still used - they allow higher precision needed sometimes for research purposes. In most cases combination electrodes are precise enough and much more convenient to use.
Construction of combination electrode is in large part defined by the processes that must take place when measuring pH. We need to measure difference of potentials between sides of glass in the glass electrode. To do so we need a closed circuit.
The circuit is closed through the solutions - internal and external - and the pH meter. However, for correct and stable results of measurements reference electrode must be isolated from the solution so that they will not crosscontaminate - and it is not an easy task to connect and isolate two solutions at the same time.
Connection is made through a small hole in the electrode body. This hole is blocked by porous membrane, or ceramic (asbestous in older models) Fiberwick. Internal solution flows very slowly through the junction, thus such electrodes are called flowing electrodes. To slow down the leaking, in gel electrodes internal solution is gelled.
To put it in a nut shell what as a aquarium keeper you would normally be looking for is typically called a combination pH probe or electrode that has the proper connector type needed for your pH meter. Most newer pH meters have the push and turn BN or BNC connector. Tyipcally the difference between the cheaper pH probe lies in the physical dimensions of the probe. The smaller diameter probes use less material and hold less gel and are cheaper to ship, but as they hold less gel they do not last as long. There are also Triode electrodes that will make it capable for some pH meters to read the temperture of the sample water while obtaining the pH reading.
When advertisement refer to fiber junctions they are referring to the wick as describe above.
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