TEC-B-01 User Manual
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version 1.1
page 14
If the headstage generates an output current, this current will cause a voltage deflection at a test
resistor. If this test resistor has a low resistance of only a few k
this voltage deflection is nearly zero,
and a possible reading at the digital display originates only from a possible offset of the electrode,
which can be cancelled using the (CURRENT ELECTRODE) OFFSET (#
11
) potentiometer.
Replacing the low resistance resistor by one of a much higher resistance may lead to another voltage
reading at the digital display. This voltage deflection then originates only from the BIAS output
current and is proportional to this output current according to Ohm’s law. Using the BIAS C
EL
(#
12
)
control the monitored voltage can be set to 0.
The tuning procedure is performed using high-value resistors or a cell model. It cannot be performed
with an electrode, since there are always unknown potentials involved (tip potential, junction
potentials etc.).
Warning
:
High voltage!
Always turn power off when working directly on the current headstage
output.
Put the holding current switch to position 0 (+ / 0 / - switch, #
7
). If you use a cell model, only the
C
EL
and GND connectors must be connected.
Set the MODE OF OPERATION switch to OFF.
Important
: The tuning procedure
must not
be done in VC mode!!
Connect the CURR.EL connector of the current headstage to ground. If parasitic oscillations occur
use a 10 k
resistor for grounding. If you use a cell model set the ON / GND switch to GND.
Switch the digital display (#
9
) to V
CEL
(potential output of the current electrode) using the
electrode selector (#
10
). Set the reading of the display to 0 using the potentiometer OFFSET (#
11
).
After tuning the current electrode potential OFFSET connect the cell model (see chapter 4.2). If
you do not use a cell model simulate an electrode by replacing the 10 k
resistor with a much
larger resistor (min. 5-10 M
).
The digital display (and the CURRENT ELECTRODE potential connector (C
EL
x10mV (#
18
))
now shows a voltage deflection that is related to the BIAS current of the headstage according to
Ohm's Law. Cancel this voltage by tuning the headstage BIAS C
EL
potentiometer (#
12
). The
current is 0 if the voltage deflection is 0.
Now the CURRENT OUTPUT (#
17
) and the CURRENT DISPLAY (#
9
) should also read 0.
