Programmable Safety Controller SCR P
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Bypassing a safeguarding device should not be confused with
muting
, which is a temporary, automatic suspension of the
safeguarding function of a safeguarding device during a non-hazardous portion of the machine cycle. Muting allows for
material to be manually or automatically fed into a machine or process without issuing a stop command. Another term
commonly confused with bypassing is
blanking
, which desensitizes a portion of the sensing field of an optical safeguarding
device, such as disabling one or more beams of a safety light curtain so that a specific beam break is ignored.
6.4.12 Adjustable Valve Monitoring (AVM) Function
The Adjustable Valve (Device) Monitoring (AVM) function is similar in function to One-Channel External Device
Monitoring (1-channel EDM, see
External Device Monitoring (EDM)
on p. 44). The AVM function monitors the state of the
device(s) that are controlled by the safety output to which the function is mapped. When the safety output turns Off, the
AVM input must be high/On (+24 V dc applied) before the AVM timer expires or a lockout will occur. The AVM input must
also be high/On when the safety output attempts to turn On or a lockout will occur.
Adjustable Valve
Monitoring
SO1
AVM
Closed
Open
50 ms
to
5 sec.
Adjustable Valve Monitoring AVM is a way to check the operation of dual channel valves. The force
guided N.C. monitoring contacts of the
valves are used as an input to detect a “stuck on” fault
condition and will prevent the safety controller outputs from turning On.
Note:
50 ms to 5 s time period is adjustable in 50 ms intervals (default is 50 ms).
Figure 10: Timing logic
—AVM Function
The Adjustable Valve (Device) Monitoring function is useful for dynamically monitoring devices under the control of the
safety output that may become slow, stick, or fail in an energized state or position, and whose operation needs to be
verified after a Stop signal occurs. Example applications include single- or dual-solenoid valves controlling clutch/brake
mechanisms, and position sensors that monitor the home position of a linear actuator.
Synchronization or checking a maximum differential timing between two or more devices, such as dual valves, may be
achieved by mapping multiple AVM functions to one safety output and configuring the AVM timer to the same values. Any
number of AVM inputs can be mapped to one safety output. An input signal can be generated by a hard/relay contact or a
solid-state PNP output.
Don’t Care
Don’t Care
