652u & 655u User’s Manual
989490
Connectors, Indicators, and Cables 3-1
Connectors, Indicators, and Cables
3
Front Panel (Analog) Connectors …… 3-1
Introduction …. 3-1
Analog Common …… 3-1
Current Source (IEPE) with Transducer Fault Detection ……. 3-1
Input Coupling …… 3-2
Anti-Aliasing …… 3-2
Analog Triggers …… 3-2
Rear Pannel Connectors and Indicators …… 3-3
External Power ……3-3
Digital I/O
(requires eZ-TOMAS)……
3-3
#6-32 Machine Screw (chassis to earth ground)…… 3-4
USB2.0 …… 3-4
LED Indicators …… 3-4
5 Channel TC / RTD Connector (655u only) …… 3-4
Front Panel (Analog) Connectors
Front Panel –
Aside from the model number, the 652u and 655u front panels look the same
Introduction
The front panel includes ten BNC connectors for voltage input. These are labeled CH1 through CH10. The front
panel also includes analog common. The IOtech 652u and 655u include circuitry for dynamic analog signal
conditioning. The circuitry typically interfaces with piezoelectric transducers that include, but are not limited to:
accelerometers, microphones, and force/pressure transducers; and non-piezoelectric transducers such as
tachometers and proximity probes.
Features of 652u and 655u dynamic signal conditioning circuits include:
o
current source for transducer biasing (IEPE)
o
detection of a transducer fault
o
AC or DC coupling
o
±40 V range
o
anti-aliasing filters: 3-pole low pass filter in hardware; programmable digital filtering via software
o
pseudo-differential inputs
o
support for TEDS (Transducer Electronic Data Sheet), requires eZ-Analyst
o
any analog input channel can serve as a tach input
o
tight channel-to-channel phase matching
o
signal parameters are independently controlled in software on a per channel basis
Analog Common
The BNC shells for the analog input channels have a 1k ohm resistance from the BNC shell to analog ground. The
BNC center-conductor is the signal HI and the BNC shell is the signal LO. Each BNC shell is connected to the
chassis ground through its own channel-dedicated 1 k
Ω
resistor. Consequently, the shell is not meant to be driven
more than ±8V from earth ground to BNC shell.
If the host computer is a desktop PC
, then the computer ground will likely connect to the AC power line ground.
If the host computer is a notebook PC
, then the computer ground could be: (a)
floating
, for example, when operating
on batteries, or (b)
connected to a vehicle ground
, for example, when using an automotive cigarette lighter adapter in
conjunction with the vehicle’s battery.
TIP: Additional measurement noise may be present when using earth grounded transducers.
For best results electrically isolate the input transducers from earth ground.
