High Level • Alarm Indicator • Programmable Alarm Setpoint and Timer
LA/04 level comparator provides variable setpoint, timeout. Signal exceeding setpoint for timeout period switches comparator to latched alarm state (ALARM), denoted by LED and relay state change. Timeout delay eliminates spurious, transient, alarm activation.
Input signal, assumed periodic, is applied to the setpoint amplifier, thence to the rms converter and comparator.
"RUN" Mode
By dialling set point, range 10/100% re 1 volt rms/pk. sine, input exceeding the setpoint switches the reference comparator and this initiates countdown of the preset counter.
Providing this condition persists, the counter will timeout and enter ALARM (denoted by LED illumination and relay contact changeover) which may be excited by activation of RESET, only provided that the input level has fallen below the setpoint. The ALARM state denergizes the relay, thus the LA/04 is failsafe.
"CAL" Mode
This eliminates the timeout delay and alarm latch, and may be linked to the RELAY INHIBIT input. Thus an immediate visual (LED) response to input exceeding the setpoint, with/without relay activation, allows verification of setpoint accuracy. Comparator hysteresis shows as setpoint directional variation, only a low/high transformation is valid.
Timeout
The timeout feature separates trend information from spurious transitory high signal levels, subject of unassociated environmental factors.
Timeout is unaffected by the differential between the signal and setpoint levels, and should not be confused with AC/DC converter ripple smoothing time constant. This latter introduces a variable delay approaching zero as the signal level approaches the setpoint.
Applications
Threshold detector activating diagnostic/corrective procedures re vibration/fatigue testing, machine vibration monitoring, with inherent, proven robustness to spurious activation by virtue of unique timeout feature
