Multichannel Systems PPS2 Manual - Manual (Page 20)

Peristaltic Pump Manual
18
3.2 Perfusion and Noise
Low frequency fluctuations in electrophysiological measurements can be caused by the
perfusion. Shortly switch off the pump to see whether the fluctuations disappear if the pump
is off. 50 Hz noise can also be caused by the perfusion, but is independent of the pump running
or not. Perfusion in and out should contain a piece of metal that can be connected to the
amplifiers ground to remove 50 Hz noise. The easiest way is to use a bend cannula for suction.
In the setup described above, both perfusion in- and outlet are already grounded via the MPHs.
The opening of the cannula should be positioned in a way that it always sucks air and liquid at
the same time, possibly resulting in a constant slurping noise. This prevents the fluid level from
going up and down, which also causes noise. See a suggested perfusion setup below.
Warning: The droplet isolators remove pulsation artifacts, but also cause a continuing flow
even some time after the pumps are stopped. To avoid flooding, please use hose clamps to
stop the flow. Do not forget to open the clamps when you restart the pump
.
If you experience low frequency noise from the perfusion, try to optimize the suction as
described above. Additionally, the droplet isolator chambers of the PPS2 interrupt the fluid
flow between pump and recording chamber, and thereby minimize the influence of the pump
head movement on the recordings.
50 Hz noise can be caused by the perfusion of by external noise sources. Remove perfusion in
and out from the bath. If the noise persists, check for external noise sources, like microscope
lamp, power supplies close by and so on. If the noise is caused by the perfusion, check the
grounding of the perfusion in and out. If the magnetic perfusion holders (MPH) from MCS
are used, make sure that there is an electrical contact between PH01, suction cannula, and
the metal plate in front of the MEA2100.
Perfusion Cannula PH01 with Magnetic Perfusion Holder MPH
All MEA amplifiers can be equipped with a magnetic stainless steel plate on top to enable
the use of magnets as perfusion holders. The magnetic perfusion holders MPH also connect
any attached metal cannula directly to the ground of the MEA recording system. The metal
ball holding the cannula allows an accurate positioning of the perfusion tips and a quick and
easy detachment of the perfusion by removing the ball from the magnetic base, if necessary.
The perfusion cannula PH01 with heating element and sensor and a temperature controller
TC01 or TC02 is able to heat the perfusion solution with an accuracy of 0.1 °C to any
temperature from room temperature up to a maximum of 50 °C.