Frequently, people who are not insiders in electrochemistry, and start to work in this field, are shocked by the mysterious variety of instruments and methods. Now, as many of our customers have very individual ideas, we do not want to anticipate anything. On the other hand, newcomers in this technique clearly need some hints, how to make a "working bench" out of the bundle of instruments available. You know that the method you want to use is an electrochemical one: If you have doubts how to solve your problem, or how to configure an instrumentation, be aware that we offer help: our free consultancy.
Don't hesitate to contact us:
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Phone |
+49 - 6403 - 609860 |
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Fax |
+49 - 6403 - 6098622 |
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info(at)bank-ic.de |
In the meantime, we try to answer some frequently asked questions.
A potentiostat also known as "Patch Clamp Amplifier" is a device used to keep a working electrode at desired potential with respect to a reference electrode. This is done by a current which is passed from the working electrode to a counter electrode. From a more electronic point of view, a potentiostat is a special kind of feed-back amplifier.
A galvanostat is a device used to control the electric current passing an electrode. Indeed, each potentiostat can act as galvanostat, depending on the manner to connect the cell. Many of our potentiostats however, can be switched from the potentiostatic to the galvanostatic mode without changing the cell connections.
A signal generator is an instrument generating voltages varying with time: ramps, triangles, pulses, staircases or whatsoever is wanted (another name is function generator, or, due to its special function, ramp generator, pulse generator and so on...). These voltages are used to control potentiostats or galvanostats in order to obtain current potential - curves, or current - time - curves, or potential - time - curves in an electrochemical cell. There are analogue signal generators and digitally controlled ones. We produce both types, according to different requirements with respect to smoothness of the signal, pulse shape accuracy or versatility.
A current sink is an electronic load which sinks the electric power from a source (whatsoever...) in a controlled manner. For many common purposes current sinks are one-quadrant amplifiers, i.e. the operate in one polarity of current and voltage only. In addition, most sinks cannot operate below a certain minimum voltage, typically 0.7 V. Our current sinks, however, operate in four quadrants down to 0 V.
A zero resistance ammeter (ZRA) is an ampere meter which has practically no internal resistance. They are valuable if e.g. galvanic currents are to be measured without producing a voltage drop across the ammeter. So, they are capable to measure extremely small currents down below the pA - range.
Usually, reference electrodes have high source resistances: some kOhms up to MOhms. If you use a common voltmeter with an internal resistance of some MOhms, appreciable potential errors may occur. Potential meters therefore have input resistances in the order of 100 GOhms or more.
The working electrode is that item at which an electrochemical reaction occurs, which shall be studied or simply forced. A reference electrode is an electrode which always has a constant electrical potential (you may also say voltage) with respect to the standard hydrogen electrode: This is the reference point for all electrochemical potentials. The counter electrode is an auxiliary electrode which shall not react, it is only used to source or sink currents to or from the working electrode, respectively.
A potentiostat, of course, is expected to keep the electric potential of an electrode at a desired value. The desired potential may vary with time. You want to measure the actual current required to achive the desired potential, and you want to know whether the actual potential is really the desired one. Instruments, who deserve the name potentiostat, will do that.
What makes the difference?
Potentiostats are fast feed-back amplifiers, where a unknown and variable load (the electrochemical cell) acts within the feedback loop. This implies that the system cell / amplifier may become prone to oscillations. Wenking potentiostats are stable against oscillations under any circumstances.
Any Wenking potentiostat can be operated manually. In addition, many Wenking potentiostats can be controlled by a personal computer.
There is a certain variety of principle designs. Wenking designed potentiostats based on four different principles - each one has its special properties, which should be regarded when planning to buy such an instrument. An introduction to these design principles and their properties is available on request.
Electrochemistry is not easy. Therefore, we make instruments for beginners, who need very simple instruments, and other instruments for specialists, who never have problems to operate very advanced devices. Both beginners and specialists profit from our ergonomic design studies, which make Wenking potentiostats easy to operate.
Electrochemical cells are prone to do undesired things. They pick up electric noise from the environment, and electrodes may have bad connections: Discussing problems with our customers, I found that Murphy's laws are most reliable in that field. Wenking potentiostats compete such cell errors, by a variety of alarms which show the user where to look for the weak point.
The physicist Hans Wenking designed the first potentiostat 1954 in Goettingen, Germany. His partner, Mr. Bank, commercialised Wenking's designs since 1959. Since that time Wenking has developed a variety of famous instruments.
Bank Elektronik -
Intelligent Controls GmbH
Hubertusstr. 38
D-35415 Pohlheim
Tel. +49 - 6403 - 60 98 60
Fax +49 - 6403 - 60 98 622
e-Mail: info [at] bank-ic.de
