Specifications

MEA-System Manual
20
3.5 Using the Additional Analog Inputs
The additional analog inputs A1, A2, A3 are intended for recording additional information from
external devices, for example, for recording patch clamp in parallel to the MEA recording, for
monitoring the temperature, or for recording voice. You could also use the analog inputs for
triggering the MC_Card, but please note that the digital inputs are intended for accepting TTL
pulses.
As the gain is generally completely different on the electrode inputs and on the additional analog
inputs, signals on the analog channels are recorded "as is", with no respect to the gain specified
in MC_Rack.
Recording Voice on Analog Inputs
Microphones do not generate enough voltage to directly connect them to the analog inputs. You
need to use some kind of amplifier that adapts the output voltage of the microphone to the input
voltage range of the MC_Card.
You can then use the MC_Rack Sound tool for replaying the recorded voice. Please see the
MC_Rack Manual for more information.
3.6 Digital Input / Output, System Synchronization
TTL stands for Transistor-Transistor Logic. A TTL pulse is defined as a digital signal for
communication between two devices. A voltage between 0 V and 0.8 V is considered as a logical
state of 0 (LOW), and a voltage between 2 V and 5 V means 1 (HIGH).
Warning: A voltage that is higher than +5 Volts or lower than 0 Volts, that is, a negative voltage,
applied to the digital input would destroy the MC_Card. Make sure that you apply only TTL pulses
(0–5 V) to the digital inputs.
Important: In the standard configurations of the MEA-System, only 3 BNC connectors are included
for the digital input bits 0 to 2. If you want to use more bits of the 16-bit input channel or the
16-bit output channel (as described in chapter Triggering other Instruments by the MC_Card), you
have to order a digital in / out extension separately. You can also upgrade your MEA-System with
the extension later. Please contact your local retailer for details.
3.6.1 Triggering the MC_Card and MC_Rack
The digital input accepts TTL pulses. This feature can be used for triggering the MC_Card and
MC_Rack, for example, for synchronizing stimulation and data acquisition.
For example, you can connect the Sync Out of a STG (stimulus generator) to one of the digital
input bits. If you use only one instrument for triggering, connect it to bit 0. In MC_Rack, add a
Trigger Detector to your virtual rack, and select the Digital Data D1 input stream as the
Trigger. Select the appropriate logical state (generally HIGH) for triggering. Mask all unused bits.
The standard settings of the Trigger Detector are for using bit 0.
Please see the documentation on the Recorder and on the Trigger Detector instrument and on
triggered data in the MC_Rack Help or Manual for more details.
Important: It is recommended to apply TTL pulses with a duration of a to at least 200 μs. Shorter
pulses may be ignored by the MC_Card. Please mask unused (not connected) digital input channels
in the MC_Rack program to ignore undefined states of the open inputs that can cause unwanted
trigger events. Please see the MC_Rack Manual for more details.