Options - Option 23 COMTRADE Sample Rate Generator

Summary Information

Provides a GPS-synchronized sampling signal at rates of 200 PPS to 192 kPPS, as defined in IEEE Standard C37.111-1991. Available on the Models 1084, 1088.

Full Description

COMTRADE Sample Rate Generator, as installed on rear of chassis.

The Arbiter Systems^®, Inc. GPS Satellite-Controlled Clock, equipped with the COMTRADE Sample Rate Generator, generates any one of the 48 standard sampling rates for waveform digitization in 50 Hz or 60 Hz systems as defined in IEEE Standard C37.111-1991, Data Exchange (COMTRADE) for Power Systems. Standard COMTRADE Sampling Rates are listed in Tables 1 and 2.

The selected sample rate is available as a 5 V CMOS-level square wave in both normal (rising edge of clock synchronous with 1 PPS) and complemented (falling edge of clock synchronous with 1 PPS) polarities. The sampling pulse is synchronized to within ± 50 ns of 1 PPS, and has sample-to-sample jitter less than 1 ns.

Principles of Operation

The assembly generates sampling signals which are precisely locked to 1 PPS-GPS by phase locking a precision voltage-controlled crystal oscillator (VCXO) to the internal 1 kPPS signal present in the clock. This VCXO output signal is then divided down to obtain the desired sampling rate. Synchronization logic is also provided, to ensure that the output divider is synchronized to 1 PPS-GPS. By using a precision VCXO, pulse-to-pulse sampling jitter is held to an absolute minimum, and is specified not to exceed 1 ns rms. The output signals have a 50 % duty cycle (square wave).

Other Features

This assembly includes four configurable BNC outputs, which are in addition to those available for the standard model clock. Either normal or complemented-polarity COMTRADE sampling frequency signals may be made available at each of these additional outputs. Furthermore, any output not configured for a COMTRADE sampling rate output can be used as a general-purpose configurable output, and can deliver any of the standard signals that are available in the clock.

Comtrade Sample Rate Generator Specifications

Table 1. Sample Rates, f LCM = 384 x f base Samples/Cycle fs for 60 Hz fs for 50 Hz 384 23040 19200 192 11520 9600 128 7680 6400 96 5760 4800 64 3840 3200 48 2880 2400 32 1920 1600 24 1440 1200 16 960 800 12 720 600 8 480 400 6 360 300 4 240 200

Table 2. Sample Rates, f LCM = 3200 x f base Samples/Cycle fs for 60 Hz fs for 50 Hz 3200 192000 160000 1600 96000 80000 800 48000 40000 640 38400 32000 400 24000 20000 320 19200 16000 200 12000 10000 160 9600 8000 128 7680 6400 100 6000 5000 80 4800 4000 64 3840 3200 50 3000 2500 40 2400 2000 32 1920 1600 20 1200 1000 16 960 800 10 600 500 8 480 400 4 240 200

Specifications

Performance:

• Accuracy: ± 50 ns from 1 PPS, maximum, (- 10 ns, typical)
• Jitter: 1 ns rms, maximum pulse to pulse (guaranteed by design, not production tested)

Outputs:

• Connectors Four, BNC 50-ohm, configurable
• Signals
  • Normal Polarity COMTRADE Sample Rate, 50 % Duty Cycle
  • Complemented COMTRADE Sample Rate, 50 % Duty Cycle
  • All Other Signals Available in 1088B or 1084A/B/C Clocks

Drive Capability:

• Digital 5 V CMOS Buffer, 50 Ohms Impedance
• Analog Opamp Buffer, 600 Ohms Impedance

 

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