84
Relay Contacts and Event Inputs
10.1.4
High DC-Voltage Relay Ratings
Specification
Value
Arrangement
1 set of Form C (SPDT) contacts
Operate, release time
Approx. 10 ms, 5 ms
Rated voltage
250 Vac (300 Vdc)
Max switching voltage
400 Vac (300 Vdc)
Rated switching cur-
rent (resistive)
8 A at 250 Vac, 8 A at 30 Vdc
Max switching capacity
2,000 VA
Expected life
50,000 electrical cycles (100,000 typical)
Min. permissible load
10 mA, 5 Vdc
Table 10.2: Specifications
Figure 10.2: Switching Power
10.2
Event and 1 PPS Deviation Recording
10.2.1
Event Timing and Recording
When configured for event timing, the clock can provide one input channel with one hundred nanosecond
resolution. This channel is primarily used for synchronization via the RS-232 port with an external computer
or other type of device. It may also be used to time an external 5 V CMOS signal applied to one of the I/O
connectors; see Section 5.2.7 and 8.10.
Data for individual recorded events can be recalled by pressing the TIMING key, then ENTER at the
Event/Deviation menu, or through the Utility software. Data for each event will be retained until it is
retrieved using one of these two methods. Thus, if no event data points are retrieved, recording will be
suspended when the total number of of events in the buffer is full. As soon as data is retrieved for a recorded
event, its address (1 to 25) is made available for data corresponding to a new event.
Because of the method used in the event recording circuit, a minimum of 11 milliseconds must elapse
between one event (rising edge) and the next, in order to guarantee that the second event will be recorded.
If the second event occurs sooner than 11 milliseconds after the first, the second event may be ignored, but
the the time data for the first will still be recorded.
10.2.2
Event Timing Latency
Event data are recorded using a high-speed capture circuit operating with a 32 MHz time base. Latency
is limited by the interrupt processing speed of the clock’s microcontroller, which in turn depends on its
workload at the time the event is received. Since the workload varies from time to time, latency likewise
varies. However, response time will, in general, never be less than a few hundred microseconds nor greater
than 10 milliseconds.
10.2.3
1 PPS Deviation Measurement
The Channel A input can also be configured to display measured event times as 1 pulse-per-second (1
PPS) deviation measurements. The intended purpose of the deviation measurement function is to allow
comparison of an external 1 PPS signal to the clock’s internal 1 PPS signal. The clock determines the mean
time difference between the two signals, which can be displayed on the front panel or read via the RS-232
Interface.
