Function
13
The signalling sequence at the control input X10, illustrated in the preceding diagram, results in a
self test as a reset and subsequent calibration. The self test includes a test of the supply voltage
before and after zero point measurement. If the supply voltage is outside the tolerance, calibration
will be repeated.
Reset
For activating the reset function, a LOW level is to be applied across the control input X10 for at least
530 ms. The residual current measurement remains active during the time T1. After T1 has elapsed,
the residual current value measured at the time t2 is stored by the residual current monitoring
module . From the time T1 has elapsed until the time residual current measurement is restarted
(when T9 has elapsed), residual current measurement is inactive.
Calibration
A calibration is carried out when T1 has elapsed and a control impulse (HIGH for 50…100 μs) is
applied at the control input X10.
Calibration starts within 10…11 ms (T3). The RCMB disables the open collector switching output X12
(HIGH) and carries out an offset measurement. The DC component of a residual current, still flowing,
results in an incorrect calibration.
The calibration process approx. takes 4.6 s (T4). Once the calibration process is complete, the
switching output X12 (LOW) will be enabled.
Test current supply
After calibration the test winding is supplied with current for 2 s. The measured values resulting from
the two test currents will be provided proportionally at X1 and the corresponding switching states
are applied to X1(details page 8).
Repeating calibration
Once the test winding is supplied with current (X12 = LOW), calibration can be repeated as often as
required by applying a new control impulse at X10.
Staring residual current measurement
The residual current monitoring module starts residual current measurement when a HIGH level is
applied at X10 for at least 5 ms (T9).
The residual current measured at the time t2 remains stored until the measurement is restarted.
