Spectrum Controls 140 MPM 204 00sc User Manual

Page 37

Meter Proving Module

Rate Mode, Bit 8

When this bit is reset to “0” the frequency detection circuit operates in “Instant” mode. Instant

mode times the period of a single input transition from one rising edge to the next rising edge of an
input signal. Instant measurements are fast, in that they calculate a frequency based on one cycle.
However the accuracy of the measurement degrades as the input clock frequency goes up to 50KHz,
and any jitter within one cycle will be measured.

When the frequency mode bit is set to a “1” the frequency detection circuit is in “Average”

mode. Average mode counts the number of input transitions over a 1 second interval and calculates
the input frequency averaged over the 1-second interval. The average mode is slow, in that it reports
updated frequency rates once per second. However this mode is accurate to +- 1 count over the full
range of measurement.

Meter Phase, Bit 7

When this bit is 0, it indicates the phase relationship between the applicable channel pair is 90

degrees. When it is set to 1, the phase relationship is 180 degrees. This information is important
when pulse fidelity is being monitored as the phase relationship is continuously monitored.

Reset Common Mode Counter

Reset Common Mode Counter, Bit 6

, Bit 6

This bit clears the common mode counter. The Cm counter counts the number of “common

mode” or simultaneous pulses detected when pulse fidelity is enabled. Simultaneous pulses are
caused by noise coupling in both channels. Normally, the pulses are 90 degrees out of phase.

Unused, Bits 5-2

Apply M to Rate, Bit 1

If this bit is set to 0 the M factor will be applied to the Rate data value. When set to one, the M

factor will be applied to the rate value.