VTI Instruments Corp.
22
EX1200-1538: Counter/Timer Operation
I
NPUTS
The EX1200-1538 counter has eight differential digital and eight analog input channels. The
digital input channels can receive ground-referenced TTL signals (+5 V maximum) and allow for
fast operating speeds.
Digital Input Channel
+5 V
Shielded Twisted Pair
GND
DIN_CH
x
GND
EX1200-1538
Front Panel
F
IGURE
3-2:
C
OUNTER
D
IGITAL
I
NPUT
C
HANNEL
C
ONNECTIVITY
Analog channels offer the threshold-level control and voltage compliance required to interface
real-world sensors and transducers. The analog inputs are positive and negative differential pairs
and receive differential voltage waveforms (up to ±48 V maximum). Analog input lines must be
connected to the device under test (DUT) as detailed in Figure 3-3.
Analog Input Channel
Shielded Twisted Pair/Channel
GND
AIN_CH
x
_P
AIN_CH
x
_N
EX1200-1538
Front Panel
±48 V
F
IGURE
3-3:
C
OUNTER
A
NALOG
I
NPUT
C
HANNEL
C
ONNECTIVITY
Input Coupling
AC/DC coupling is selectable on a per channel basis for analog inputs. In DC coupling mode, the
signal is passed “as is” without modification. DC coupling is suitable for most applications.
However, if the input signal contains a large, unpredictable DC offset, AC coupling mode may be
used. In this mode, each channel contains a series capacitor (0.47 µF) which helps block the DC
component from the input signal, while allowing the AC component of the signal to pass.
NOTE
The digital input channels are always DC coupled.
