Signal Connection
Correct signal connection is one of the most important important steps to assure your application
system will send and receive data correctly. Since most data acquisition applications involve
voltage, correct signal connection prevents costly damage to your personal computer and
hardware devices. This chapter provides some useful information on signal connection in
different types of data acquisition applications.
3.1 Analog Input Connection
The PCL-812PG supports a 16 single-ended analog input configuration. The single-ended
configuration has only one signal wire for each channel. The voltage to be measured is the
voltage of this wire referred to the common ground. A signal source without a local ground is
also called a "floating source". It is fairly simple to connect a single ended channel to a floating
signal source. A standard wiring diagram is illustrated below:
3.2 Expanding Analog Inputs
You may expand any or all of the PCL-812PG A/D input channels through sub-multiplexers.
The PCLD-789 Amplifier and Multiplexer daughter board in the PC-LabCard series is
specifically designed for multiplexing applications. Each PCLD-789 can multiplex 16
differential inputs to one A/D input channel. Up to eight PCLD-789s can be cascaded to one
PCL-812PG providing a total of 128 channels. Complete operation information of using the
PCL-812PG with the PCLD-789 is covered in the PCLD-789 user's manual.
The PCLD-774 analog expansion board is designed to accommodate multiple external signal-
conditioning daughterboards, such as the PCLD-779, PCLD-789, PCLD-889. Featuring five sets
of on-board 20-pin header connectors, the PCLD-774 introduces a new star-type architecture that
allows cascading of multiple signal-conditioning daughterboards. The signal-attenuation and
current-loading problems of normal cascading are solved by this unique arrangement. For
information about these products, please contact your local PC-LabCard sales representative.
3.3 Analog Output Connection
PCL-812PG provides two D/A output channels. You may use the PCL-812PG's internallly
generated precision -5V and -10V reference to generate 0 to +5V and 0 to +10V D/A output
range. You may create other D/A output ranges through external references. The maximum
reference input range is +/- 10V and maximum output scaling is +/- 10V. The PCL-812PG
conector CN2 is used for D/A signals. Some important areas in D/A signal connections are input
reference, D/A outputs and analog ground. The PCL-812PG D/As should be be connected as
illustrated below:
Legend (Connector 2 pin number):
13 = D/A 1 D/A outputs
15 = D/A 2 D/A outputs
14 = Analog ground
16 = Analog ground
17 = V.REF1
19 = V.REF2
3.4 Digital Signal Connection
The PCL-812PG has 16 digital input and 16 digital output channels. The digital I/O levels are
TTL compatible. To transmit or receive digital signal to/from other TTL devices, the connection
is:
To receive an OPEN/SHORT signal from a switch or relay, a pull-up resistor must be added to
ensure he high level when open.
