73A-541 - Tektronix Frequency Counters

The 73A-541 universal digitizing counter (UDC) module with time tag memory is a printed circuit board assembly for use in a card cage conforming to the VXIbus specification, such as the 73A-021 used in the CDS 73A IAC system.
The 73A-541 provides two channels that can measure signals in the sub-Hertz to 10 MHz frequency range.

The 73A-541 module incorporates both a universal timer/counter and a digitizing counter into a single instrument, operating in either of two modes

• The timer/counter mode includes the measurement functions associated with a traditional universal counter
• The digitizing counter mode using time tag memory has two real-time and two post-processing sub-modes.In this mode, an input signal can be analyzed on a cycle-to-cycle basis by storing the absolute time of each successive transition of the input waveform in a 28-bit by 2048-word memory

The 73A-541 module offers several different ways to contol the duration of the measurement cycle (or gate duration).For frequency and event-count functions in the timer/counter mode, or when using the digitizing counter mode using time tag memory, the measurement cycle can be controlled by one of the following

• A specified number of A or B events
• A specified amount of time, from 1 µs to 427 seconds
• Direct program control
• An external gate

For averaging functions, the measurement cycle can be specified as the number of occurences to average.The measurement cycle itself can be triggered either under program control or by an external trigger.

• Input channels: Two
• Functions
  • Counter/timer mode: Frequency, period, pulse width, time interval, event count, duty cycle, period average, pulse width average, time interval average, duty cycle average
  • Digitizing counter mode: Frequency, period, pulse width, time interval, event count, duty cycle
• Input characteristics
  • Input impedance: 1 MΩ, 30 pF, or 50 Ω, program selectable
  • Input coupling: DC or AC, program selectable
  • Attenuator: X1 or X3, program selectable
  • Channel input: Separate or common A to B, program selectable
• Dynamic range
  • 1 MΩ: X1 - 100 mV to 7 Vrms; X3 - 300 mV to 21 Vrms
  • 50 Ω: X1 - 100 mV to 7 Vrms; X3 - 300 mV to 7 Vrms
• Trigger-level range: X1, +2.54 to -2.56 Vdc; X3, +7.62 to -7.68 Vdc
• Gate time range: 1 µs to 427 s; 2 events to 4 x 10⁹ events of input A or B, programmable start/stop; or external TTL control
• Timer/counter mode
  • Frequency range: 0.0025 Hz to 10 MHz
  • Period range: 0 to 25 s
  • Pulse width range: 100 ns to 25 s
  • Interval A to B, B to A range: 0 ns to 25 s
  • Event count range: 0 to 4 x 10⁹ counts
• Digitizing counter mode
  • Time range: 0 to 25 s
  • Number of events individually time identified: 2047 identified 100 ns time intervals that contain either a positive or negative slope transition of channel A, or a positive or negative slope transition of channel B, or a coincident occurrence of any of the preceding
  • Time base (option 010) frequency: 10 MHz
• VSIbus compatibility: Fully compatible with the VXIbus specification for message-based instruments with the Halt switch in the ON position
• VXI device type: VXI message based instrument, VMEbus slave, revision 1.2
• VXI protocol: Word serial
• VXI card size: C size, one slot wide