ELC-01MX User Manual
version 2.6
page 18
5.2 Headstage Bias Current Adjustment
Caution: It is important that this tuning procedure is performed ONLY after a warm-up period
of at least 30 minutes!
The ELC-01MX is equipped with a voltage-to-current converter with a very high output
impedance which is connected to the recording electrode. The zero current of this unit is tuned
with the BIAS current trim-pot (see #26 in Figure 5).
The tuning procedure should be performed regularly (about once a month) since the bias
current changes over time.
The tuning procedure is performed using high-value resistors and/or a cell model. It cannot be
performed with an electrode, since there are always unknown potentials involved (tip
potential, junction potentials).
❏
Disconnect all input signals (except the headstage). Put the holding current switch to
position 0 (#5, Figure 5). Set the operation mode to CC.
❏
Connect the P
EL
connector of the headstage to ground. If oscillations occur take a resistor
of a few k
Ω
and connect it to ground.
Note: This cannot be done with the cell model. Please use a wire to connect the input of
the BNC connector on the headstage to GND of the headstage. Do not use the shield of the
BNC connector since it is connected to driven shield.
❏
Tune the OFFSET to zero using the OFFSET control (#2, Figure 5).
Remember: The zero position of the OFFSET control is at 5!!
❏
Remove the wire and attach the cell model or a resistor with a value of about 10 M
Ω
across the same connection.
❏
The value displayed at the POTENTIAL DISPLAY is related to the BIAS current of the
headstage according to Ohm's Law. Cancel this voltage by tuning the headstage BIAS
current trim-pot (#27, Figure 5) until the POTENTIAL DISPLAY shows 000.
