Ametek Ortec 994 User manual

994
Dual Counter and Timer
•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 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. n 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. n
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 CCN M (Computer-Controlled
N M) 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 CCN M option includes A and B
counts, the preset value, and which counter is
being displayed. The CCN M 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 nput Polarity Jumpers on
the counter printed wiring board (PWB). The
negative input mode is designed to accept N M-
standard, fast-negative logic pulses with a fixed
threshold of –250 mV on a 50-input 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-input
impedance. To enhance 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. n
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 nterval
output of another ORTEC timer can perform this
function to synchronize the Model 994 counting
with the other timer. The nterval outputs on all
ORTEC timers provide nominally +5 V when
counting and <+0.5 V when counting is inhibited.
ndependent 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 N M bin with
power supply. For bins that do not contain a +6 V
supply, an nternal +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 ( n 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. n 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. t 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.
f the print loop option is used, the Dwell control is
disabled when the print loop controller is active and
controlling the dwell time.
994
Dual Counter and Timer
2

INPUT POLARITY JUMPERS Two jumpers located on
the printed wiring board (PWB) separately select the
desired input polarities for inputs n A and n B. P =
positive, N = negative.
A COUNTER/TIMER JUMPER Two-position jumper
located on the PWB. n the Counter position, Counter A
always counts and displays the events connected to n
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. f the Ext time base is selected,
Counter A will count and display the events from n A.
B COUNTER/TIMER JUMPER Two-position jumper
located on the PWB. n the Counter position, Counter B
always counts and displays the events from n B. n 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 n B.
GATE A (LIVE TIME/NORMAL) JUMPER Two-position
jumper mounted on the PWB. n the Normal position, the
signals from the rear-panel Gate A connector gate the
events from the n A connector. n 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 D P 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. n 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 to ground;
dc-coupled.
Negative Input Changing the nput Polarity Jumper
position on the counter board permits selection of the
N M-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 ; dc-
coupled. Minimum pulse width above threshold is 4 ns.
IN B dentical to n 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
N M-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 n 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 N M-
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 .
OVFL A Rear-panel output BNC connector provides a
N M-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. t 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. n 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.
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Dual Counter and Timer
3

ELECTRICAL AND MECHANICAL
POWER RE UIRED The basic Model 994 derives its power from a N M bin furnishing ±12 V and +6 V. For N M bins
that do not provide +6 V, an optional nternal +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 nternal +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 N M-standard double-width module, 6.90 X 22.13 cm (2.70 X 8.714 in.) front panel per DOE/ER-0457T.
Ordering nformation
Model Description
994 Basic module without plug-in options.
99X-1 RS-232-C nterface option (cable not included).
99X-4 nternal +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
Specifications subject to change
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