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Fig. 8
Function time diagram with fault
4.7. Function test
For applications in 'low demand mode' with safety requirements an automatic function test should be carried
out with regular intervals. The test intervals can be seen in section 4.4.2.2 .
Both part systems, the sounder channel and the monitoring circuit, have separate power supply connections.
This means that a check of the function is possible and can be carried out as follows (time dependencies see
Fig. 7 and Fig. 8).
a) Switching on the monitoring power supply when the sounder channel is not activated, (can be omit-
ted depending on use if the monitoring is continuously connected to the supply)
b) Check whether the fault alarm relay has high-resistance >0.5s after switching on,
c) Switching on the sounder channel (sound is generated)
d) Check whether the fault alarm relay has switched after >0.2s (low-resistance)
e) Switching off the operational voltage of the sounder channel, the fault alarm relay must have fallen
away (high-resistance) after 2.5s at the latest
f) Switching off the monitoring (depending on use)
It is important for the system test that the change of the switch position of the alarm relay is detected de-
pending on the generation of the acoustic warning signal. With which distances a system test has to take
place is dependent on the eventual use in which the sounder is involved. The equipment specific check in-
tervals must be defined in the respective proof of safety.
The function test can be shortened if a tone without interrupted tones is used. Then time in point 5 can be
reduced to 0.3s.
It is required that a tone is selected at the DIP switch of the sounder or a tone is activated simultaneously
with the sounder from the 'external tone selection' option.
4.8. Process safety time
Conclusions for the required process safety time can be drawn depending on use according to the function
time diagrams. The reaction times for the generation of the acoustic warning signal and the switching status
of the alarm relay depending on the switching on and off time of the operational voltage (Fig. 7) and in the
case of a fault (despite demand, the warning signal is not generated, Fig. 8) are illustrated here.
With the connection of the operational voltage, the sounder generates an acoustic warning signal after 0.3s
at the latest and reports this via the alarm relay (output low-resistance). This means the 'generation of a
warning signal' safety function has been activated. Further explanations of the reaction times of the alarm
relay can be found in section 4.5.
Tone
Operating voltage
Sounder channel
Operating voltage
Monitoring circuit
Alarm output
Tone is not generated
Tone cancelled
* dependent on the tone
and cause of fault
