mpec SA380-IT, Руководство пользователя

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eventual steady state condition:
Typical response to measurement pulses
The SA380-IT configurable "measurement timeout" parameters place limits on how long the device will wait for the steady state to be
achieved prior to taking a measurement. This time may be exceeded if:
The system capacitance and resistance are too high.
Transient signals present in the measurement loop prevent a steady state being achieved.
Transient signals may be due to sudden monitored circuit voltage variation, or transient resistance to earth events. Unstable circuit voltage
may also prevent the steady state being achieved.
Measurement Procedure:
Fast Scan
Rapid response time is achieved by performing resistance to earth measurements at high speed.
The timer setting (see section xxxx) governs how quickly the SA380-IT attempts measurement of each circuit. By default this fast scan
value is set to 1000 ms, meaning that measurement is performed within 1 second for each monitored circuit, giving a maximum cycle
time of 5 seconds for a fully utilised SA380-IT device.
If the steady-state can not be achieved in the fast-scan period, offending circuits are scheduled for a periodic slow scan. These slow
scans allow accurate measurement of high-resistance-to-earth, capacitive circuits, albeit a at a slower speed.
Slow Scan
Circuits that can not achieve steady state during the fast-scan period are measured during the slow-scan period. The timer slow scan
parameter control this frequency. (See section xxxx). By default this value is set to 5 minutes. Once every five minutes a slow scan is
performed on circuits that have repeatedly failed fast-scan readings. The period of time that the SA380-IT can spend performing
slow-scans is limited to 50% of total measurement time of the entire SA380-IT device, assuring that the fast-scan process still has time
to run.
If the slow scan fails, The SA380-IT still attempts measurement and displays one of the following:
If resistance-to-earth is estimated to be >= 5 M, then 5 M is displayed and the slow-scan is deemed to have succeeded.
If resistance-to-earth is estimated to be < 5 M, then the estimated reading is displayed on the user-interface alongside the
message "Unstable" and the slow-scan is deemed to have failed.
Spot-Readings
The successful result of a fast or slow scan is known as a spot reading. For circuits with little capacitance / low resistance-to-earth then
a spot-reading will be taken once every 1 to 5 seconds. A circuit with high capacitance / resistance-to-earth may record a spot reading
once every 5 minutes.
The latest Spot-readings are displayed on the user interface. If a spot-reading crosses an alert boundary (see section xxx), then the
latest average and spot-reading messages are sent to the EAMS to alert the maintainer of the transient fault condition.
Average Readings
Successful spot-readings are also used to calculate the long-term-mean resistance to earth of a circuit. The snapshot timer setting
governs how frequently these average readings are reported to the EAMS. By default, this period is set to 1 hour
The average is reset when the following occurs: