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EX1200-1538: Counter/Timer Operation
21
C
OUNTER
/T
IMER
O
PERATION
O
VERVIEW
The EX1200-1538’s electronic counter can be used to measure many time and frequency domain
signal parameters for time-continuous waveforms and non-continuous (burst/pulse train)
waveforms. These parameters include:
1)
Frequency
2)
RPM
3)
Pulse width
4)
Counter/totalize functions
5)
Quadrature input
6)
Duty cycle
The EX1200-1538 counter mechanism uses reciprocal counting technique (always makes a period
measurement on the input signal). The benefit of the counting method is that it is based on an
internal clock, so errors are dependent on the clock and not external sources. Hence, for a
noiseless input signal and assuming negligible trigger and time base error, the resolution of the
reciprocal counter would also be independent of the input signal frequency.
Static Update
Dynamic Update
AIN_Ch_x (+)
Threshold
level DAC
Threshold Detector
Polarity
modifier
Slope
Selector
Electronic
Counter Logic
BPL_TRIG
Module Front
panel
Module
Backplane
MUX
DMM_Bus
Index (Z) pulses of quadrature encoder
GND
DIN_Ch_x
Hysteresis
level DAC
Coupling
selection
AC
DC
Normal/Active High
Inverted/Active Low
Raising Edge
Falling Edge
OV & OC
prot
Noise Filter
Analog / Digital Input
Channel selection
TCXO (Ref
Oscillator
– 50MHz)
Enable
Disable
QINDEX_x
OV & OC
prot
Noise Filter
DIO_CHx_P
+24V Ref
High Voltage
Transient
Protection
Direction Control
Solid-state switch
(when Output)
Opto Isolator
(when Input)
Digital Input
Digital Output
DIO Control
section
DAC Control
Section
Opto Isolation
Barrier
24mA Current
limiter
24V internal
power supply
(non-isolated)
AOUT_CHx_P
AOUT_CHx_N
DIO_CHx_N
Output Amplifier
Mode selection
±10V
±20mA
Analog Output
level control
(16 bit DAC)
Data Control &
FIFO buffer
(256,000
samples)
Scaled input voltage of “AIN_Ch_x”
GND_C
Chassis Ground
(Isolated)
TTL Discrete signal
Analog / Digital signal
Differential analog
Isolated unit (signal & power)
AOUT_GND_x
AIN_Ch_x (-)
Attenuation &
Protection
F to V/I
conversion
Frequency
Range
selection
Refresh
rate
Freq Max
Freq Min
D
y
n
a
m
ic
I
n
p
u
t
D
y
n
a
m
ic
I
n
p
u
t
Frequency to Voltage/current converter
F
IGURE
3-1:
C
OUNTER
B
LOCK
D
IAGRAM
