995 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.

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.

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.

DISPLAY Two LEDs labeled A and B indicate the information being displayed in the counter display. Counter A or Counter B value may be displayed by repeatedly pressing the Display push-button until the desired LED is illuminated.

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), and the Enable input must be above +3 V.

REMOTE A single LED labeled REM indicates that the Model 995 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 for presentation in the 8-decade display. Repeatedly pushing the button cycles the selection through the two choices as indicated by the A and B LEDs.

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. 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.

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.

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.

INPUTS

IN A

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  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.

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; <+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

GATE B Rear-panel BNC connector accepts NIM-standard, slow-positive logic signals to control the counting in Counter B. A level >+3V 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

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 that 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 female connector allows the Model 995 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, and selecting the displayed counter. In the Remote mode, the computer can disable all front-panel controls. Computer readout includes: A and B counts, 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, and selecting the displayed counter. In the Remote mode, the computer can disable all front-panel controls. Computer readout includes: A and B counts and which counter is being displayed.

ELECTRICAL AND MECHANICAL

POWER REQUIRED The basic Model 995 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.

ORDERING INFORMATION