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The Cell LED does not indicate a dangerous condition when it is lighted. The voltages
output by the Interface 1000 are generally considered to be safe. Still, you should avoid
touching the cell leads when the cell is on.
If you need to make changes to your cell leads, you normally do so between experiments, when the Cell LED is
off and the potentiostat is inactive.
In a typical experimental sequence, the Cell LED will be off between experiments and during any open circuit
potential measurements. It will glow yellow whenever the cell is polarized.
Overload LED
The Overload LED is located just below the Cell LED.
The Overload LED is normally unlighted. When it glows red, this indicates that some circuit in the Interface
1000 has exceeded its normal operating limit. Conditions that generate Overloads include:
The absolute value of the differential electrometer output voltage (the difference in voltage between
•
the Working and Reference leads) exceeds 10 volts. This condition is known as an E Overload.
The control amplifier has lost control of the cell. The absolute value of the cell current may be trying to
•
exceed ±1 amp, or the absolute value of the counter electrode voltage may be trying to exceed
±22 volts. Either condition will be called a Control Overload.
The absolute value of the cell current has exceeded full scale on the current range presently in use.
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This condition is known as an I Overload.
Transient (temporary) overloads during an experiment in which the cell voltage or current is being stepped or
swept are often normal. In most cases, they do not indicate a system or instrument malfunction.
Consider the case of an infinitely fast voltage step into a perfect capacitor. In theory, charging the capacitor
requires an infinite current. The current spike seen at each step in a stepped voltage waveform can easily light
the Overload LED. The current spike will normally decay to near zero before the actual current and voltage
readings are taken.
Overload indications when the cell is being connected or disconnected are common and usually do not
indicate a problem. Overloads can also be seen when one of the cell leads is disconnected from the other cell
leads, even though the cell is off. Again, this does not indicate a problem.
A steadily glowing Overload LED during an experiment most likely indicates a problem is occurring. Possible
causes include:
One of the cell leads is disconnected (this is the most common cause),
•
a gas bubble in the cell is blocking one of the electrodes,
•
the potentiostat could be oscillating (see Chapter 7).
•
As described above, a glowing red Overload LED does not necessarily indicate a system
malfunction. The Overload LED can light when one or more cell leads are disconnected,
without indicating a problem with the system. The Overload LED can often light
momentarily during a swept or stepped experiment. The only Overload LED indication
that definitely points towards a problem is a continuously glowing Overload LED during
an experiment.
Personalization Label Area
The right side of the Interface 1000 front panel has a clear area in its plastic overlay. A paper label behind this
area allows for a custom appearance. This is especially important when the instrument is in a multiple
potentiostat system.
Chapter 5 -- Panel Indicators and Connectors--Front Panel
Note
Note
5 - 3
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