Multichannel Systems MEA1060-Inv-BC Manual - Manual (Page 29)

Operating the MEA Amplifier
25
DC offset correction
The internal baseline restore routine of the preamplifier restores the offset to the ground level,
that is, to zero. This has to be a slow process. If the routine corrected too fast, slow signals would
be eliminated as well.
All electrodes on an array have different DC offsets at the beginning of an experiment. The
DC offsets are amplified by the preamplifier, and the amplified output signal of the preamplifier
is likely to exceed the input range of the following filter amplifier. In order to eliminate this
DC offset, a so-called baseline restorer is integrated in the preamplifier. For signals in the usual
measurement range, the baseline restore routine acts like a high pass filter with a very low
cut-off frequency of roughly 0.01 Hz, but unnaturally high signals like stimulus artifacts are
limited to a negligible value.
Due to the low cut-off frequency, the baseline restorer takes some time to stabilize after
switching on the amplifier or after replacing the MEA. One to two minutes are quite normal.
During this time, the filter amplifier input will be overloaded and you will see only a straight
line with very low noise. This is considered a normal behavior and should not trouble you.
Please wait until the baseline restore routine has been completed.
When replacing a MEA, the stabilizing time can be greatly reduced by connecting all electrodes
to ground during the opening of the amplifier and change of the MEA. The connection to ground
results in lower electrode offsets. Therefore, you should always use the Change MEA command
when replacing a MEA. See also the chapters First Tests and Tutorial, General Performance / Noise
Level and Operating the MEA Amplifier, Mounting the MEA Probe.
5.2 Temperature Control
The biological sample is cultured directly on the MEA. You can record without needing an
incubator, because a heating element is integrated into the amplifier and the perfusion cannula
and are both controlled by a Temperature Controller (Temperature Controller and perfusion
cannula with heating element and sensor are either included in the MEA-System or can be
ordered separately). You have several options regarding the culture chamber, such as a
semipermeable seal that guarantees stable environmental conditions.
For using the integrated heating element of the MEA amplifier, connect it with the black cable
to the Temperature Controller. The heating is active, but the cooling is passive. Therefore,
the minimum temperature is limited by the room temperature. Please refer to the Temperature
Controller manual for more information.
Important: Please make sure that you have selected the appropriate PID coefficients for the
amplifier type (for inverted or upright microscopes) in use.