994 CCNIM Quad 100-MHz Counter/Timer

 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 10^P is 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 IEEE-488 and the RS-232-C interface boards. 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. Z_in = 1000 W to 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. Z_in = 50 W; 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.

OUPUTS

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. Z_o ~30 W.

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.

INTERFACES

IEEE-488 When the IEEE-488 option board is plugged in, it furnishes a rear-panel, standard, IEEE-488 bus connector. This 24-pin, AMP CHAMP^TM female connector allows the Model 994 to be controlled from a computer via the IEEE-488 bus. The field-installable 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, which counter is being displayed, and the overflow status for both counters.

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.

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.

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