ORTEC 994 User manual
ORTEC ®
994
Dual Counter and Timer
The ORTEC Model 994 Dual Counter
and Timer incorporates two eight-
decade counters and a blind preset
timer. Considerable functional flexibility
is designed into the instrument,
allowing it to be configured for a variety
of measurement tasks. Typically, it can
be used as two counters recording
separate events under the control of
the preset blind timer. When continuous
readout of the time is needed, Counter
A can be diverted to count the time
while Counter B records external
events. This provides the function of a
counter and a displayed preset timer. In
some applications, the time taken to
count a preset number of events must
be measured. For this application,
Counter A, coupled with the preset
blind counter, can be used as a preset
counter while Counter B records the
time in 0.01-second intervals. In
measurements where it is important to
correct for the dead time of the
detector and its associated electronics,
the Gate A input can be switched to
also gate the time clock On and Off
with a 100-ns time resolution. A
positive logic signal that defines the
system live time is connected to the
Gate A input. This configuration
provides a live-time clock (Counter A)
and a counter (B).
Excellent flexibility in setting the preset
value is offered by the MN X 10P
selection. The M and N values provide
two-digit precision, while P selects the
decade. Presets can be chosen in the
ranges of 0.01 to 990,000 seconds,
0.01 to 990,000 minutes, or 1 to
99,000,000 counts.
The basic Model 994 includes an 8-
decade LED display that offers
instantaneous visual readout of the full
contents of Counter A or B, even in a
dimly lighted room. By adding field-
installable options, considerably
enhanced readout and control
capabilities can be incorporated.
The full power of CCNIM (Computer-
Controlled NIM) can be obtained by
adding the RS-232-C option. This plug-
in board allows computer control of all
functions normally selectable from the
front panel, including start and stop
count, readout, reset, setting the preset
value, selecting the displayed counter,
and selecting the desired time base. To
eliminate accidental operator
interference, the computer can disable
all front-panel controls in the Remote
mode. Computer readout with the
CCNIM option includes A and B
counts, the preset value, and which
counter is being displayed. The CCNIM
option can directly drive printers having
RS-232-C ports.
The inputs to Counters A and B are
individually selectable as either positive
or negative sensing inputs by changing
the Input Polarity Jumpers on the
counter printed wiring board (PWB).
The negative input mode is designed to
accept NIM-standard, fast-negative
logic pulses with a fixed threshold of
–250 mV on a 50- Ωinput impedance.
The negative inputs can handle
counting rates up to 100 MHz. The
positive input mode can accept
counting rates up to 25 MHz on a
1000- Ωinput impedance. To enhance
• Two 8-decade counters and a timer with the configuration flexibility to
serve a variety of measurement needs
• RS-232-C option provides CCNIM capability with full computer control
and readout
• Can directly drive printers having RS-232-C ports
• An 8-decade LED display provides instantaneous readout of the entire
counter capacity, even in dimly lighted rooms
• All commonly used controls are easily accessible on the front panel
• 100-MHz counting rate capability
• Preset time or counts set with the precision of a two-digit and
decade selection
• All options are field-installable
the flexibility of the positive input mode,
precision discriminators are included on
both counters. The discriminator
thresholds are variable over the range
from +100 mV to +9.5 V using front-
panel, 25-turn trimpots. The thresholds
can be adjusted to suit the amplitude of a
specific source of logic pulses or used as
precision integral discriminators on
analog pulses. For the latter application,
the TTL logic outputs of the
discriminators are provided as test points
on the front panel. These outputs can be
used to trigger an oscilloscope while
viewing the analog signal at the counter
input on the oscilloscope. The
oscilloscope trace will show the signals
that are being counted by the Model 994,
thus permitting a very selective
adjustment of the threshold.
All the commonly used functions are
conveniently accessible on the front
panel. Manual control of the Count, Stop,
and Reset functions is via three push-
buttons. The Gate LED is illuminated
when the Model 994 is enabled to count.
Selection of the 0.01 second, 0.01
minute, or external time base is made by
the Time Base push-button. In the
external mode, the preset counter counts
the events at the counter A input. The
Display push-button switches the display
to show the contents of Counter A, the
preset stop value, or the contents of
Counter B. To change the preset value,
the Preset mode must first be selected
with the Display push-button.
Subsequently, the Preset Select push-
button is used to choose M, N, or P for
adjustment. Changing the value of M, N,
or P is accomplished with the Preset
Advance push-button. The display
contains LED flags to indicate whether M,
N, or P has been selected, to warn when
overflows have occurred in Counter A or
Counter B, and to advise when the front-
panel controls are disabled by the
computer in the Remote mode. When the
Model 994 is used in the automatic
recycle mode, the Dwell knob adjusts the
dwell time of the display from 1 to 10
seconds.
The counting function of the entire
module can be disabled by holding the
Enable input below +1.5 V using an
external signal source. This condition also
turns Off the Gate LED. Open circuit or
>+3 V at the Enable input allows the
instrument to count, if the Count mode
has been activated. The Interval output of
another ORTEC timer can perform this
function to synchronize the Model 994
counting with the other timer. The Interval
outputs on all ORTEC timers provide
nominally +5 V when counting and
<+0.5 V when counting is inhibited.
Independent gating of the A and B
Counter inputs can be achieved with the
Gate A and Gate B inputs on the rear
panel. The interface connector for the
RS-232-C option is located on the rear
panel. Each counter has a rear-panel
output dedicated to signaling overflows.
Counting these overflows on another
counter extends the counting capacity of
the Model 994.
The Model 994 derives its power from the
±12 V and +6 V supplies in a standard
NIM bin with power supply. For bins that
do not contain a +6 V supply, an Internal
+6 V Supply option is available. This
option is field-installable and derives its
power from the 117 V ac lines in the bin.
Specifications
PERFORMANCE
COUNT CAPACITY 8 decades for counts
ranging from 0 to 99,999,999 in each of 2
counters.
MAXIMUM COUNTING RATE 100 MHz for
negative inputs, 25 MHz for positive inputs.
TIME BASE 10-MHz clock with minimum
preset or displayed intervals of 0.01 seconds
or 0.01 minutes. Synchronizing error is
nominally 100 ns. Also accepts an external
input from the Counter A input (In A) when the
Ext (External) mode is selected.
TIME BASE INACCURACY ≤±0.0025% over
the 0 to 50°C operating temperature range.
PRESET TIME/COUNTS The module stops
counting when the preset value MN X 10Pis
reached on the blind preset register. M and N
are digits ranging from 0 to 6. With the 0.01-
second time base, preset times from 0.01 to
990,000 seconds can be used. Preset times
from 0.01 to 990,000 minutes are available
using the 0.01-minute time base. In the Ext
time base mode preset counts in the range of
1 to 99,000,000 can be used.
POSITIVE INPUT DISCRIMINATOR
Threshold variable from +100 mV to +9.5 V
with a 25-turn trimpot.
PULSE PAIR RESOLUTION <10 ns for
negative inputs; <40 ns for positive inputs.
INDICATORS
COUNTER DISPLAY 8-digit, 7-segment LED
display with leading zero suppression. When
displaying time, 2 digits to the right of a
decimal point are included.
OVERFLOW INDICATORS LED indicators
labeled OVFL A and OVFL B illuminate when
the corresponding A or B Counter exceeds its
capacity of 8 decades. The indicator remains
on until a reset is generated.
M, N, AND P INDICATORS 3 LED indicators
aid in the selection of the preset value. When
the Preset display function is activated, the
Select push-button selects which of the 3
LEDs is illuminated. When one of these LEDs
is On, that digit of the preset value can be
incremented using the Advance push-button.
DISPLAY 3 LEDs labeled A, B, and Preset
indicate the information being displayed in the
counter display. Counter A, Counter B, or the
Preset value may be displayed by repeatedly
pressing the Display push-button until the
desired LED is illuminated.
TIME BASE 3 LEDs indicate the selected
time base source. By repeatedly pressing the
Time Base push-button, 0.01 Sec, 0.01 Min, or
the Ext mode can be chosen.
GATE A single LED indicates that the entire
instrument is enabled to count. For the Gate
LED to be illuminated, the module must be
placed in the Count mode (either manually or
via the interface option), the Enable input must
be above +3 V, and the preset stop condition
must not have been reached.
REMOTE A single LED labeled REM
indicates that the Model 994 is under
computer control, and all front-panel controls
are disabled. This mode is set by the
ENABLE_REMOTE command.
CONTROLS
DISPLAY Push-button selects the contents of
Counter A or B, or the Preset value for
presentation in the 8-decade display.
Repeatedly pushing the button cycles the
selection through the three choices as
indicated by the A, B, and Preset LEDs.
SELECT Push-button chooses the M, N, or P
digit in the display of the preset value. Pushing
the button advances the selection through the
three choices as indicated by the illuminated
LED. The Select push-button operates only if
the Preset mode has been selected by the
Display push button.
ADVANCE Push-button increments the preset
digit selected by the Select push-button once
each time the Advance button is depressed.
The M and N digit ranges are both 0 to 9. The
P digit range is from 0 to 6. The Advance
push-button operates only if the Preset mode
has been selected by the Display push-button.
TIME BASE Each push on this button
advances the selection one step through the
three time base choices of 0.01 Sec, 0.01 Min,
and Ext to determine the time base source for
the preset register.
STOP This push-button stops all sections of
the instrument from counting.
RESET Depressing this button resets both
counters to zero counts and turns Off both
overflow indicators. It also clears any counts
accumulated in the blind preset counter, but
does not change the selected preset value.
When power is turned On to the Module, a
Reset is automatically generated.
COUNT Pushing this button enables the
counting condition for the entire instrument,
providing the Enable input is not held below
+1.5 V and the preset value has not been
reached.
THRESH ADJUST (A and B) Front-panel
mounted, 25-turn trimpots to adjust the
positive input thresholds for Counters A and B.
The range is from +100 mV to +9.5 V. Adjacent
test points provide the TTL logic signal outputs
from the discriminators to facilitate adjustment
using an oscilloscope.
DWELL A one-turn potentiometer on the front
panel with an On/Off switch at the fully
counterclockwise position. Adjusts the display
dwell time over the nominal range from 1 to 10
seconds. When the instrument is in the
Recycle mode, dwell time occurs after the
preset value has been reached. Turning the
switch Off at the fully counterclockwise
position selects the Single Cycle mode. If the
print loop option is used, the Dwell control is
disabled when the print loop controller is active
and controlling the dwell time.
INPUT POLARITY JUMPERS Two jumpers
located on the printed wiring board (PWB)
separately select the desired input polarities
for inputs In A and In B. P = positive, N =
negative.
A COUNTER/TIMER JUMPER Two-position
jumper located on the PWB. In the Counter
position, Counter A always counts and
displays the events connected to In A. When
set to the Timer position, Counter A counts
and displays the time if either the 0.01-Sec or
the 0.01-Min time base is selected. If the Ext
time base is selected, Counter A will count
and display the events from In A.
B COUNTER/TIMER JUMPER Two-position
jumper located on the PWB. In the Counter
position, Counter B always counts and
displays the events from In B. In the Timer
position with the Ext time base selected,
Counter B counts and displays the time in
0.01-second intervals. With either a 0.01-Sec
or 0.01-Min time base selected, Counter B
counts and displays the events from In B.
GATE A (LIVE TIME/NORMAL) JUMPER
Two-position jumper mounted on the PWB. In
the Normal position, the signals from the rear-
panel Gate A connector gate the events from
the In A connector. In the Live Time position,
the signals from the Gate A connector gate the
10-MHz clock to form a live-time clock.
1 CYCLE/RECYCLE Selection of either the 1
Cycle or the Recycle mode can be made via
an 8-pin DIP switch on the RS-232-C interface
board. The Recycle mode can be used when
the computer is able to respond with a data
transfer when the Model 994 reaches the
preset value. Upon reaching preset, the Model
994 latches its data into a buffer, resets the
counters, and starts the next counting interval.
This process takes ~50 µs. The computer
reads the data in the buffer before the next
counting interval ends. In the 1 Cycle mode,
the Model 994 simply stops counting and waits
for further commands when the preset value is
reached.
INPUTS
IN A Use of this input is affected by the A
Counter/Timer Jumper.
Positive Input Front-panel BNC connector for
Counter A accepts positive unipolar signals;
minimum width above threshold, 20 ns at a
50% duty cycle. The threshold is adjustable
from +100 mV to +9.5 V via a front-panel 25-
turn trimpot. Zin = 1000 Ωto ground; dc-
coupled.
Negative Input Changing the Input Polarity
Jumper position on the counter board permits
selection of the NIM-standard fast-negative
logic input which is designed to accept –600 to
–1800 mV pulses with a fixed discriminator
threshold of –250 mV. Zin = 50 Ω; dc-coupled.
Minimum pulse width above threshold is 4 ns.
IN B Identical to In A except that it feeds
Counter B. Use of this input is affected by the
B Counter/Timer Jumper.
ENABLE Front-panel BNC input connector
accepts NIM-standard, slow-positive logic
pulses to control the counting condition of the
entire module. A level of >+3 V or open circuit
allows counting provided the instrument is in
the Count mode and has not reached the
preset value; <+1.5 V inhibits counting. The
driving source must be capable of sinking
5 mA of positive current during inhibit; input
protected to +25 V.
GATE A Rear-panel BNC input connector is
identical to the Gate B input with the following
exception. With the Gate A jumper on the
PWB set to the Normal position, the Gate A
input controls counting of the In A events in
Counter A. By moving the PWB Gate A jumper
to the Live Time position, the Gate A input also
controls the 10-MHz clock to form a live-time
clock with a 100-ns resolution. A level >+3 V or
an open circuit allows counting of the clock. A
level <+1.5 V is used to inhibit counting of the
clock during dead-time intervals.
GATE B Rear-panel BNC connector accepts
NIM-standard, slow-positive logic signals to
control the counting in Counter B. A level
>+3 V or open circuit allows counting; <+1.5 V
inhibits counting; input protected to +25 V. The
driving source must be capable of sinking
5 mA of positive current during inhibit.
OUTPUTS
INTERVAL Front-panel output BNC connector
furnishes a positive level during the counting
interval. The level is nominally +5 V when
counting is enabled and <+0.5 V when
counting is disabled. Zo~30 Ω.
OVFL A Rear-panel output BNC connector
provides a NIM-standard, slow-positive logic
signal each time Counter A overflows its 8-
decade capacity. The signal has a nominal
amplitude of +5 V; width ~20 µs.
OVFL B Rear-panel output identical to OVFL A
except it monitors overflows from Counter B.
INTERFACE
SERIAL When the RS-232-C option board is
plugged in, it furnishes a rear-panel, 25-pin,
male, D connector containing all signals for
standard RS-232-C communications. It also
contains connections for 20-mA current loop
communications. The field-installable RS-232-
C option provides computer control of the
following functions: Count, Stop, Reset,
Remote, setting the preset value, selecting the
displayed counter, and selecting the desired
time base. In the Remote mode, the computer
can disable all front-panel controls. Computer
readout includes: A and B counts, the preset
value, and which counter is being displayed.
994
Dual Counter and Timer
ELECTRICAL AND MECHANICAL
POWER REQUIRED The basic Model 994 derives its power from a NIM bin furnishing ±12 V and
+6 V. For NIM bins that do not provide +6 V, an optional Internal +6 V Supply is available. This
option is field-installable and draws its power from the 117 V ac lines in the bin. With the Internal
+6 V Supply installed, the power requirements are shown in column 4 and not required in column
3.
Internal
Bin Supplied +6 V Supply
+12 V –12 V +6 V 117 V ac
Basic Model 994 35 mA 115 mA 1300 mA 110 mA
Model 994 plus RS-232-C option 54 mA 130 mA 1800 mA 145 mA
WEIGHT
Net 2.4 kg (5.2 lb).
Shipping 3.7 kg (8.2 lb).
DIMENSIONS NIM-standard double-width module, 6.90 X 22.13 cm (2.70 X 8.714 in.) front panel
per DOE/ER-0457T.
Ordering Information
Model Description
994 Basic module without plug-in options.
99X-1 RS-232-C Interface option (cable not included).
99X-4 Internal +6 V Supply option.
C-75 Female-to-female RS-232-C null modem cable (3-meter length).
C-80 Male-to-female RS-232-C extension cable (3-meter length).
994
Dual Counter and Timer
801 South Illinois Ave., Oak Ridge, TN 37831-0895 U.S.A.
For International Office Locations, Visit Our Website
www.ortec-online.com
Specifications subject to change
012810
ORTEC
®
