What is the purpose of the "Conversion Delay Jumpers" on the rear of the module?

Conversion Time for each of the modules is 7.2us. This time can be extended using the "Conversion Delay" jumpers on the rear of the module.

In ALL these modules (7164, 7166, 7167, 7186* and 7187), digitization may be delayed by an amount from 0 to 16us in 62.5ns increments using the "Conversion Delay" jumpers at the rear of the module. This will allow a greater acceptance window for CLEAR signals if needed. Once digitization begins, you will not be able to clear or access the module until the conversion cycle has been completed.

The 7.2 us Conversion Time starts at either the leading or trailing edge as shown in the following chart.  It includes the internal 600ns or 750ns delay mentioned below.

ADC 7164
Conversion starts 600ns after the trailing edge of the Gate signal.
QDC 7166, 7167
Conversion starts 750ns after the trailing edge of the Gate signal
TDC 7186, 7187
Conversion starts 750ns after the leading edge of the COMMON pulse
for the 7186, and 750ns after the trailing edge of the Gate pulse for the 7187

The 600ns and 750ns delay before starting the Conversions is for settling time and also allows time to accept fast clear signals.


It is recommended to delay digitization for the 7186 TDC when using COMMON START mode above 100ns full scale.  This prevents the module from beginning the Conversion Cycle to early.  It allows settling time and a few hundred nanoseconds for a fast clear acceptance window.
Example: If the module is set for 2us Full Scale with no additional delay, after 750ns from the Common Pulse (START), digitization begins. The module switches to "Hold" mode before Full Scale is reached therefore the highest reading you could get is around 750ns instead of 2us, This would also happen in channels with no stop pulses. The Manual shows the minimum recommended delays for the various Full Scale ranges when used in COMMON START mode. The chart is repeated here.  Note: The COMMON STOP mode does not require this.

100 nsec
200 nsec
125 nsec
400 nsec
312.5 nsec
800 nsec
750 nsec
1 usec
937.5 nsec
2 usec
1937.5 nsec
4 usec
3937.5 nsec
8 usec
7937.5 nsec
Other ranges
> (Range - 100 nsec)

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