Advanced Measurement Technology 273A, Руководство пользователя

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Model 273A Potentiostat/Galvanostat User’s Manual
(decrement) the potential in 1 mV steps or the current in 0.1% of Current Range steps. If one
of these keys is held down continuously, the steps increase to 10 mV or 1% of Current
Range, allowing a large change to be achieved quickly. The second way of changing the
parameter's value is to specify a specific value and enter it.
Example: To set E/I APPLIED to 1 V, key:
[E/I APPLIED] [1] [ENTER]
5.2.7. MODE Group
1. STABILITY versus SPEED: This subgrouping consists of two indicators and one key. One of
the two available modes, HIGH SPEED or HIGH STABILITY, will always be in effect and the
corresponding indicator will glow. The key is used to alternate between the two modes.
Stability/Speed selection is entirely independent of whether the instrument is operated as a
potentiostat or galvanostat.
The HIGH SPEED mode gives the fastest response (see specifications) in Potentiostat or
Galvanostat operation, but without guaranteed stability. Under the proper conditions with
certain cells, ringing almost always occurs and oscillations may occur. Cells having large
capacitance and low resistance are most likely to prove troublesome.
The HIGH STABILITY mode provides extreme stability at somewhat reduced speed (see
specifications). In this mode, stable operation is assured with virtually any cell. However, the
possibility always exists that with an unfamiliar cell configuration, or under extremely unusual
operating conditions, stability problems might occur. If oscillation does occur in the HIGH
STABILITY mode, it usually results from a high-resistance reference electrode. Even a
well-designed, low-impedance reference electrode can develop a high resistance if salts
precipitate in the junction.
2. OPERATING MODE: There are three basic operating modes, each with its own key and
indicator. One of the three modes will be in effect at all times as indicated by the associated
indicator. To transfer from the mode in effect to either of the other two modes, simply press
the target-mode key.
a. POTENTIOSTAT: In this mode the 273A controls the potential of the working electrode
with respect to the reference electrode. The potential at the counter electrode is driven to
the potential required (consistent with the ±100 V compliance of the Control Amplifier) to
establish the desired working electrode potential.
b. GALVANOSTAT: In this mode the 273A controls the cell current at the specified faction
of the selected Current Range (up to the maximum of two times the Current Range; one
times the range if 1 A is selected). The counter electrode is driven to the potential
required (consistent with the ±100 V compliance of the Control Amplifier) to establish the
desired cell current. No reference electrode is required, although one can be used to
monitor the potential, if desired.
c. MEASURE ONLY: The open-circuit cell potential is continuously monitored and
displayed in this mode. Neither the potential nor the current is controlled. The cell is
OFF, even if Cell ON has been previously selected with the Cell key. If an attempt is
made to turn the Cell ON while in the Measure Only mode, the message: CAN'T TURN
CELL ON IN MEASURE ONLY is displayed. See 5.2.9 for a discussion of the effect of a
voltage applied to the External Input on the signals routed to the electrochemical cell.
5.2.8. CELL Group
There are two keys and one indicator in this group. All three are associated with the internal
switches that provide the connection to the counter electrode (red clip lead). The CELL ENABLE
pushbutton has two positions, in (ON) and out (OFF). CELL ENABLE is a hard-wired, fail-safe