NOTE
After successful teach-in (Teach), the value should be adjusted to suit the application
conditions. Since all variations should be considered in this value, both a teach-in
under good conditions and a teach-in under challenging conditions should be per‐
formed. The value can then be better estimated. After that, it is useful to multiply the
determined value by 80% for a maximum allowed aging.
Function
Description
VMA switching thresh‐
old (signal level warn‐
ing)
•
The
VMA (Signal level warning)
switching threshold can be used to
manually set the level warning threshold or signal level switching
point for the
VMA (Signal level warning)
switching mode in the form of
a signal level within the value range of 0 to 65535.
•
The Teach function can be used to teach in the level warning
threshold or the signal level switching point for the
VMA (Signal level
warning)
switching mode based on the reflective properties of a
reference object.
Since the signal level is not expressed as a standardized unit, but
instead corresponds to a device-specific value, it is advisable to deter‐
mine and define the level warning threshold for each application
based on test measurements. There is no switching hysteresis func‐
tion in the
VMA (Signal level warning)
switching mode. This is because
both the level warning threshold and time-dependent behavior of the
signal level curve vary from one application to the next. In light of
these facts, it is also advisable to use external and specific or time-
dependent filtering of the signal level warning in the control system in
addition to the output of the signal level warning.
Switching behavior
With the “Q1 output behavior” setting, you can manually select
whether the signal level warning output is
Active high
or
Active low
.
Example VMA (signal level warning) parameterization for Q1:
1.
Connect to the device and switch to the
Outputs settings
page in SOPAS ET.
2.
Set the Q1 switching function to
VMA (Signal level warning)
.
3.
Set the Q1 output behavior according to the desired function:
Active low
4.
Position the reference object in front of the device and perform a
Teach
.
5.
Position a “bad” reference object in front of the device and perform a
Teach
.
6.
Determine and enter the
VMA (Signal level warning)
switching threshold based on the
Teach results.
7.
Transfer parameters the device using the “Write all parameters” button.
8.
Check whether the function works appropriately for the configured parameters!
7
COMMISSIONING AND CONFIGURATION
36
O P E R A T I N G I N S T R U C T I O N S | DT35S
8027663//2022-08-04 | SICK
Subject to change without notice