Each ADInstruments front-end amplifier must be connected to a PowerLab via both the I2C and BNC connections in order to function.
The PowerLab controls front-ends through an expansion connector called the I2C bus. Many front-ends can be added to the system by connecting the I2C sockets in a simple daisy-chain structure (that is, connecting the output I2C on the first amplifier to the input I2C on the second) The PowerLab provides control and low voltage power to front-ends through the I2C bus so, in general, no separate power supply is required. In addition, each front-end requires a separate connection to one or more analog input channel(s) of the PowerLab. External signals are acquired through the PowerLab analog inputs and amplified before being digitized by the PowerLab. The digitized signal is transmitted to the computer using a fast USB connection. Once connected, the features of the front-end are combined with the appropriate features of the PowerLab (for example, range and filtering options) and are presented as a single set of software controls.
Note: The Stimulator front-ends differ from other front-ends in two respects:
1. Since they need to produce a reasonably high voltage and current, the Stimulator front-ends require a power supply in addition to the power provided by the I2C bus.
2. As they produce voltage output for stimulation, they are connected to a positive analog output socket (or analog output 1 depending on the model) of the PowerLab as a source for timing and producing pulses.
Connecting Front-Ends to the PowerLab
1. Ensure that the PowerLab is turned off. Failure to do this may damage the PowerLab, the front-end, or both.
2. The BNC socket labelled Signal Output on the back panel of the front-end provides the signal output to connect to an analog input socket on the front of the PowerLab. A BNCto-BNC cable is supplied for this connection. If necessary, use a BNC to DIN smart adapter [MLAC22] to connect the BNC cable to your PowerLab’s input. If you have an older PowerLab that has differential (rather than single-ended) inputs, the front-end must connect to a positive input.
3. Connect the I2C output of the PowerLab to the I2C input of the front-end using the I2C cable provided.
4. To connect multiple amplifiers, you can daisy chain the I2C outputs and inputs as shown. The BNC connections will stay the same, with Signal Output BNC connected to an input on the front of the PowerLab.
5. Upon turning on the PowerLab
and starting the LabChart
Software, the indicator lights on the front of the amplifiers should flash and then return to a solid green.