Using the IntelliLogger™
21
GPDI; G
ENERAL
P
URPOSE
D
IGITAL
I
NPUTS
The IntelliLogger System Base has four integral General Purpose Digital Inputs that can each be
user configured to accept input signals from one of the following types:
•
Event - detection of discrete or On/Off type inputs
•
Count - high speed pulse train counting
•
Frequency - sampled frequency of an input waveform
Configuration of the channels is performed via the HyperWare-II software in the building of a
Program Net. Program Net development is covered in detail in Chapter 4 (Icon Based
Programming) and in Appendix B (System Base Icon Reference) in the HyperWare-II manual.
Physical connection and signal interface is discussed in the following section.
GPDI I
NPUT
S
IGNAL
C
ONNECTIONS
The four digital inputs are labeled as DI_A, B, C and D on the front panel. Input signal pairs
(positive and negative) for each of these channels is made to the lower System Base terminal
strip. Terminals 7 to 14 accept signal inputs in pairs. The terminals marked with a minus ( - )
are common and connect directly to circuit ground.
CAUTION:
Note that a direct connection exists between the common (-) terminal
on all four of the GPDI inputs. For this reason, ensure that signals
supplied from different sources are at the same potential on the
negative lead.
When connecting to multiple event, counter or frequency signal
sources sharing a common ground or reference, ensure that the
source’s ground or reference is connected to the terminal strip
`common’ terminal to prevent shorting out of the source signal and
possible damage to the input.
S
HIELDING
In most applications, use of twisted pair leads is sufficient for GPDI Event and Counter
applications and the use of shielded cable for event, counter signals is not necessary due to
the input circuitry noise margins.
Frequency inputs are amplified by the IntelliLogger input circuitry. When applying low level
input signals (e.g. amplitudes less than ~500mV) in electrically noisy environments,
improvements in measurement quality may be seen by the use of shielded cable. In this
case, connect the cable shield to the IntelliLogger ChGnd terminal (top terminal strip, terminal
18). The cable shield should then be allowed to float (i.e. no connection made) at the signal
source end. Shielded cable use for frequency signals will also minimize cable to cable noise
cross-talk to sensitive analog inputs connected to other channels of the IntelliLogger.
GPDI E
VENT
I
NPUT
A
PPLICATION
Event inputs on the System Base allow for the recording of the state of an ON/OFF or
‘discrete’ type input. Configured as an Event input, a channel will accept a powered input
signal (ranging from 0 to a maximum of 30VDC) or a contact closure (dry contact) input.
♦
For powered input signals, the System Base Event function defines signals
less than 1VDC as a Low level and greater than 4VDC (30VDC max) as a
High level.