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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